From 89ee24fcd868fccf2be90744d9ad81c68674408d Mon Sep 17 00:00:00 2001
From: oscarlvp <oscarlvp@gmail.com>
Date: Sun, 16 Jul 2023 12:36:23 +0200
Subject: [PATCH] Static analysis, code style refactoring, method mathing
 refactoring

---
 README.md                                     |  10 +-
 configuration/pmd-rules.xml                   |  14 +
 configuration/style.xml                       | 380 ++++++++++++++++
 docs/examples/commons-cli/issues/index.html   |   2 +-
 ....commons.cli.AmbiguousOptionException.html |  26 +-
 .../org.apache.commons.cli.DefaultParser.html |  20 +-
 .../issues/org.apache.commons.cli.Option.html |  26 +-
 docs/output-format.md                         |   8 +-
 docs/performance-comparison.md                |  46 +-
 pom.xml                                       |  62 ++-
 src/docgen/README.md                          |  18 +-
 .../descartes/DescartesEngineFactory.java     | 101 +++--
 .../descartes/DescartesMutater.java           |  95 ++--
 .../descartes/DescartesMutationEngine.java    |  72 +--
 .../descartes/annotations/DoNotMutate.java    |   3 +-
 .../descartes/annotations/Operator.java       |   5 +-
 .../codemanipulation/BaseClassVisitor.java    |  52 ++-
 .../codemanipulation/BaseMethodVisitor.java   |  15 +-
 .../codemanipulation/ElementInfo.java         |  53 ++-
 .../codemanipulation/LineCounter.java         |  91 ++--
 .../codemanipulation/MethodInfo.java          |  85 ++--
 .../MethodRewritingVisitor.java               |  89 +---
 .../MutationClassAdapter.java                 |  61 ++-
 .../codemanipulation/MutationPointFinder.java | 153 ++++---
 .../descartes/codemanipulation/TypeInfo.java  |  88 ++--
 .../AvoidNullInNotNullFilter.java             |  23 +-
 .../AvoidNullInNotNullFilterFactory.java      |  30 +-
 .../interceptors/MutationFilter.java          |  56 +--
 .../interceptors/SkipDoNotMutateFilter.java   |  86 ++--
 .../SkipDoNotMutateFilterFactory.java         |  28 +-
 .../interceptors/SkipShortMethodsFilter.java  |  51 ++-
 .../SkipShortMethodsFilterFactory.java        |  45 +-
 .../stopmethods/InstructionMatchers.java      |  97 ++++
 .../stopmethods/MethodMatcher.java            |  54 +++
 .../stopmethods/StopMethodInterceptor.java    |  22 +-
 .../stopmethods/StopMethodMatcher.java        |  58 ---
 .../StopMethodMatcherInterceptorFactory.java  | 128 +++---
 .../stopmethods/StopMethodMatchers.java       | 274 +++++------
 .../ArgumentPropagationOperator.java          |  27 +-
 .../operators/ConstantMutationOperator.java   | 149 +++---
 .../operators/EmptyArrayMutationOperator.java |  35 +-
 .../operators/InvalidOperatorException.java   |  13 +-
 .../descartes/operators/MutationOperator.java |  98 ++--
 .../NewInstanceMutationOperator.java          | 168 ++++---
 .../operators/NullMutationOperator.java       |  22 +-
 .../operators/OptionalMutationOperator.java   |  33 +-
 .../operators/ThisMutationOperator.java       |  18 +-
 .../operators/VoidMutationOperator.java       |  18 +-
 .../operators/parsing/LiteralParser.java      | 283 ++++++------
 .../descartes/operators/parsing/Token.java    |  52 ++-
 .../operators/parsing/TokenType.java          | 145 +++---
 .../reporting/IssuesReportFactory.java        |  30 +-
 .../reporting/IssuesReportListener.java       | 196 ++++----
 .../reporting/JSONReportFactory.java          |  25 --
 .../reporting/JSONReportListener.java         | 110 -----
 .../descartes/reporting/JSONWriter.java       | 209 ---------
 .../reporting/JsonReportFactory.java          |  25 ++
 .../reporting/JsonReportListener.java         | 105 +++++
 .../descartes/reporting/JsonWriter.java       | 235 ++++++++++
 .../reporting/MethodTestingFactory.java       |  22 +-
 .../reporting/MethodTestingListener.java      | 158 ++++---
 .../models/MethodClassification.java          |  27 +-
 .../reporting/models/MethodRecord.java        | 349 +++++++-------
 .../eu/stamp_project/utils/Converter.java     | 111 ++---
 .../eu/stamp_project/utils/TypeHelper.java    | 116 ++---
 .../java/eu/stamp_project/utils/Utils.java    |  10 +-
 ...mutationtest.MutationResultListenerFactory |   2 +-
 .../descartes/IntegrationTest.java            | 190 ++++----
 .../AvoidNullInNotNullFilterTest.java         |  73 ++-
 .../interceptors/MutationFilterTest.java      |  25 +-
 .../SkipDoNotMutateFilterTest.java            |  95 ++--
 .../SkipShortMethodsFilterTest.java           |  44 +-
 .../DelegateMethodMatcherTest.java            |  57 ++-
 .../stopmethods/DeprecatedClassTest.java      |  45 +-
 .../stopmethods/EmptyArrayMatcherTest.java    |  54 ++-
 .../EmptyVoidMethodMatcherTest.java           |  25 +-
 .../stopmethods/EnumMethodMatcherTest.java    |  40 +-
 .../HashcodeMethodMatcherTest.java            |  41 +-
 .../IsKotlinGeneratedSetterMatcherTest.java   |  28 +-
 .../stopmethods/MethodMatcherTest.java        |  97 ++--
 .../ReturnConstantMatcherTest.java            |  62 ++-
 .../stopmethods/ReturnsNullMatcherTest.java   |  36 +-
 .../ReturnsParameterMethodMatcherTest.java    |  41 +-
 .../ReturnsThisMethodMatcherTest.java         |  27 +-
 .../stopmethods/SimpleGetterMatcherTest.java  |  59 ++-
 .../stopmethods/SimpleSetterMatcherTest.java  |  58 ++-
 .../ToStringMethodMatcherTest.java            |  40 +-
 .../ArgumentPropagationOperatorTest.java      |  95 ++--
 .../ConstantMutationOperatorTest.java         | 147 +++---
 .../EmptyArrayMutationOperatorTest.java       | 103 +++--
 .../operators/MutationOperatorTest.java       |  95 ++--
 .../NewInstanceMutationOperatorTest.java      |  85 ++--
 .../operators/NullMutationOperatorTest.java   | 108 ++---
 .../OptionalMutationOperatorTest.java         |  95 ++--
 .../operators/ParameterlessOperatorTest.java  |  95 ++--
 .../operators/ThisMutationOperatorTest.java   | 107 ++---
 .../operators/VoidMutationOperatorTest.java   | 100 +++--
 .../descartes/operators/VoidWrapperTest.java  | 107 ++---
 .../operators/parsing/LiteralParserTest.java  | 193 ++++----
 .../descartes/reporting/JSONWriterTest.java   | 184 ++++----
 .../reporting/models/MethodRecordTest.java    | 206 ++++-----
 .../eu/stamp_project/test/Assertions.java     |  56 ++-
 .../test/MethodStreamBuilder.java             |  89 ++--
 .../eu/stamp_project/test/TestValues.java     |  76 ++--
 .../java/eu/stamp_project/test/Utils.java     |  34 +-
 .../test/input/AbstractClass.java             |  12 +-
 .../stamp_project/test/input/Calculator.java  | 223 +++++----
 .../test/input/DeprecatedClass.java           |   7 +-
 .../eu/stamp_project/test/input/Fluent.java   |  53 ++-
 .../eu/stamp_project/test/input/Index.java    |  22 +-
 .../stamp_project/test/input/Interface.java   |   3 +-
 .../test/input/NativeMethodClass.java         |   2 +-
 .../eu/stamp_project/test/input/Numbers.java  |  12 +-
 .../test/input/Parameterless.java             | 187 ++++----
 .../stamp_project/test/input/SideEffect.java  |  15 +-
 .../input/SkipFalseMutationOnAllButOne.java   |  11 +-
 .../test/input/SkipMutationOnMethod.java      |  10 +-
 .../test/input/SkipMutationTarget.java        |  10 +-
 .../stamp_project/test/input/StopMethods.java | 425 ++++++++++--------
 119 files changed, 5033 insertions(+), 4389 deletions(-)
 create mode 100644 configuration/pmd-rules.xml
 create mode 100644 configuration/style.xml
 create mode 100644 src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/InstructionMatchers.java
 create mode 100644 src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/MethodMatcher.java
 delete mode 100644 src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatcher.java
 delete mode 100644 src/main/java/eu/stamp_project/descartes/reporting/JSONReportFactory.java
 delete mode 100644 src/main/java/eu/stamp_project/descartes/reporting/JSONReportListener.java
 delete mode 100644 src/main/java/eu/stamp_project/descartes/reporting/JSONWriter.java
 create mode 100644 src/main/java/eu/stamp_project/descartes/reporting/JsonReportFactory.java
 create mode 100644 src/main/java/eu/stamp_project/descartes/reporting/JsonReportListener.java
 create mode 100644 src/main/java/eu/stamp_project/descartes/reporting/JsonWriter.java

diff --git a/README.md b/README.md
index c658e48..1f7c7b5 100644
--- a/README.md
+++ b/README.md
@@ -37,7 +37,7 @@ cd my-project-under-test
 mvn clean package org.pitest:pitest-maven:mutationCoverage
 ```
 
-All options from PIT can be used. For more details check the [the PIT documentation](https://pitest.org/quickstart/maven/). 
+All options from PIT can be used. For more details check [the PIT documentation](https://pitest.org/quickstart/maven/). 
 
 Check ["Running Descartes on your project"](#running-descartes-on-your-project) for additional Descartes configuration options. 
 
@@ -65,7 +65,7 @@ If you use a multi-module project take a look at [PitMP](https://github.com/STAM
 ### Mutation testing
 Mutation testing allows you to verify if your test suite can detect possible bugs.
 The technique works by introducing small changes or faults into the original program. These modified versions are called **mutants**.
-A good test suite should able to detect or *kill* a mutant. That is, at least one test case should fail when the test suite is executed with the mutant. 
+A good test suite should be able to detect or *kill* a mutant. That is, at least one test case should fail when the test suite is executed with the mutant. 
 [Read more](https://en.wikipedia.org/wiki/Mutation_testing).
 Traditional mutation testing works at the instruction level, e.g., replacing ">" by "<=", so the number of generated mutants is huge, as the time required to check the entire test suite.
 That's why the authors of [Will my tests tell me if I break this code?](http://dl.acm.org/citation.cfm?doid=2896941.2896944) proposed an *Extreme Mutation* strategy, which works at the method level.
@@ -399,7 +399,7 @@ PIT reporting extensions work with Descartes and include `XML`, `CSV` and `HTML`
 Descartes also provides three new reporting extensions:
   - a general reporting extension supporting `JSON` files. It works also with **Gregor**, the default mutation engine for PIT. To use just set `JSON` as report format for PIT.
   - a reporting extension designed for Descartes that generates a JSON file with information about pseudo and partially tested methods. To use just set `METHOD` as report format for PIT.
-  - Descartes can generate a human readable report containing only the list of methods with testing issues by using the `ISSUES` format.
+  - Descartes can generate a human-readable report containing only the list of methods with testing issues by using the `ISSUES` format.
  
 Examples of these reporting extensions for [Apache Commons-CLI](https://github.com/apache/commons-cli/tree/b9ccc94008c78a59695f0c77ebe4ecf284370956) can be checked [here](docs/examples/commons-cli).
 
@@ -498,7 +498,7 @@ To configure the stop methods under consideration Descartes provides a `STOP_MET
 This feature is enabled by default. The parameter `exclude` can be used to prevent certain methods to be treated as stop methods and bring them back to the analysis. This parameter can take any of the following values:
 
 
-|`exclude`        | Method description                                                                     | Example                                                                                          |
+| `exclude`       | Method description                                                                     | Example                                                                                          |
 |-----------------|----------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------|
 | `empty`         | `void` methods with no instruction.                                                    | `public void m() {}`                                                                             |
 | `enum`          | Methods generated by the compiler to support enum types (`values` and `valueOf`).      |                                                                                                  |
@@ -553,7 +553,7 @@ The feature can be completely disabled:
 As said before, there are several reporting options provided by Descartes:
 - `JSON` for a general mutation testing report using that file format. It can be used with **Gregor**.
 - `METHODS` that produces a `methods.json` file with the list of all methods analyzed and categorized according to the mutation testing result.
-- `ISSUES` a human readable report containing only the methods with testing issues.
+- `ISSUES` a human-readable report containing only the methods with testing issues.
 
 They can be configured and combined as regular PIT report formats:
 
diff --git a/configuration/pmd-rules.xml b/configuration/pmd-rules.xml
new file mode 100644
index 0000000..4e63b26
--- /dev/null
+++ b/configuration/pmd-rules.xml
@@ -0,0 +1,14 @@
+<?xml version="1.0" ?>
+<ruleset name="Descartes Coding Rules"
+         xmlns="http://pmd.sourceforge.net/ruleset/2.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 https://pmd.sourceforge.io/ruleset_2_0_0.xsd">
+
+    <description>
+        Rules enforcing an accepted set of coding styles and best practices taken from PMD predefined rules.
+        This file customizes some of the rules to avoid false positives.
+    </description>
+
+    <rule ref="category/java/bestpractices.xml" />
+
+</ruleset>
diff --git a/configuration/style.xml b/configuration/style.xml
new file mode 100644
index 0000000..58e25d9
--- /dev/null
+++ b/configuration/style.xml
@@ -0,0 +1,380 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC
+        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+        "https://checkstyle.org/dtds/configuration_1_3.dtd">
+
+<!--
+    Copied and modified from the Google Java Style checks available at
+    https://raw.githubusercontent.com/checkstyle/checkstyle/master/src/main/resources/google_checks.xml
+    Original authors and comments are kept.
+    Main changes:
+        - Remove the style relative to the pattern of the package names as it contradicts the eu.stamp_project
+          package.
+        -
+-->
+
+<!--
+    Checkstyle configuration that checks the Google coding conventions from Google Java Style
+    that can be found at https://google.github.io/styleguide/javaguide.html
+
+    Checkstyle is very configurable. Be sure to read the documentation at
+    http://checkstyle.org (or in your downloaded distribution).
+
+    To completely disable a check, just comment it out or delete it from the file.
+    To suppress certain violations please review suppression filters.
+
+    Authors: Max Vetrenko, Ruslan Diachenko, Roman Ivanov.
+ -->
+
+<module name="Checker">
+    <module name="SuppressWarningsFilter"/>
+
+    <property name="charset" value="UTF-8"/>
+
+    <property name="severity" value="warning"/>
+
+    <property name="fileExtensions" value="java, properties, xml"/>
+    <!-- Excludes all 'module-info.java' files              -->
+    <!-- See https://checkstyle.org/filefilters/index.html -->
+    <module name="BeforeExecutionExclusionFileFilter">
+        <property name="fileNamePattern" value="module\-info\.java$"/>
+    </module>
+    <!-- https://checkstyle.org/filters/suppressionfilter.html -->
+    <module name="SuppressionFilter">
+        <property name="file" value="${org.checkstyle.google.suppressionfilter.config}"
+                  default="checkstyle-suppressions.xml" />
+        <property name="optional" value="true"/>
+    </module>
+
+    <!-- Checks for whitespace                               -->
+    <!-- See http://checkstyle.org/checks/whitespace/index.html -->
+    <module name="FileTabCharacter">
+        <property name="eachLine" value="true"/>
+    </module>
+
+    <module name="LineLength">
+        <property name="fileExtensions" value="java"/>
+        <property name="max" value="100"/>
+        <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
+    </module>
+
+    <module name="TreeWalker">
+        <module name="OuterTypeFilename"/>
+        <module name="IllegalTokenText">
+            <property name="tokens" value="STRING_LITERAL, CHAR_LITERAL"/>
+            <property name="format"
+                      value="\\u00(09|0(a|A)|0(c|C)|0(d|D)|22|27|5(C|c))|\\(0(10|11|12|14|15|42|47)|134)"/>
+            <property name="message"
+                      value="Consider using special escape sequence instead of octal value or Unicode escaped value."/>
+        </module>
+        <module name="AvoidEscapedUnicodeCharacters">
+            <property name="allowEscapesForControlCharacters" value="true"/>
+            <property name="allowByTailComment" value="true"/>
+            <property name="allowNonPrintableEscapes" value="true"/>
+        </module>
+<!--        <module name="AvoidStarImport"/>-->
+        <module name="OneTopLevelClass"/>
+        <module name="NoLineWrap">
+            <property name="tokens" value="PACKAGE_DEF, IMPORT, STATIC_IMPORT"/>
+        </module>
+        <module name="EmptyBlock">
+            <property name="option" value="TEXT"/>
+            <property name="tokens"
+                      value="LITERAL_TRY, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, LITERAL_SWITCH"/>
+        </module>
+        <module name="NeedBraces">
+            <property name="tokens"
+                      value="LITERAL_DO, LITERAL_ELSE, LITERAL_FOR, LITERAL_IF, LITERAL_WHILE"/>
+        </module>
+        <module name="LeftCurly">
+            <property name="tokens"
+                      value="ANNOTATION_DEF, CLASS_DEF, CTOR_DEF, ENUM_CONSTANT_DEF, ENUM_DEF,
+                    INTERFACE_DEF, LAMBDA, LITERAL_CASE, LITERAL_CATCH, LITERAL_DEFAULT,
+                    LITERAL_DO, LITERAL_ELSE, LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF,
+                    LITERAL_SWITCH, LITERAL_SYNCHRONIZED, LITERAL_TRY, LITERAL_WHILE, METHOD_DEF,
+                    OBJBLOCK, STATIC_INIT, RECORD_DEF, COMPACT_CTOR_DEF"/>
+        </module>
+        <module name="RightCurly">
+            <property name="id" value="RightCurlySame"/>
+            <property name="tokens"
+                      value="LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE,
+                    LITERAL_DO"/>
+        </module>
+        <module name="RightCurly">
+            <property name="id" value="RightCurlyAlone"/>
+            <property name="option" value="alone"/>
+            <property name="tokens"
+                      value="CLASS_DEF, METHOD_DEF, CTOR_DEF, LITERAL_FOR, LITERAL_WHILE, STATIC_INIT,
+                    INSTANCE_INIT, ANNOTATION_DEF, ENUM_DEF, INTERFACE_DEF, RECORD_DEF,
+                    COMPACT_CTOR_DEF"/>
+        </module>
+        <module name="SuppressionXpathSingleFilter">
+            <!-- suppresion is required till https://github.com/checkstyle/checkstyle/issues/7541 -->
+            <property name="id" value="RightCurlyAlone"/>
+            <property name="query" value="//RCURLY[parent::SLIST[count(./*)=1]
+                                     or preceding-sibling::*[last()][self::LCURLY]]"/>
+        </module>
+        <module name="WhitespaceAround">
+            <property name="allowEmptyConstructors" value="true"/>
+            <property name="allowEmptyLambdas" value="true"/>
+            <property name="allowEmptyMethods" value="true"/>
+            <property name="allowEmptyTypes" value="true"/>
+            <property name="allowEmptyLoops" value="true"/>
+            <property name="ignoreEnhancedForColon" value="false"/>
+            <property name="tokens"
+                      value="ASSIGN, BAND, BAND_ASSIGN, BOR, BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR,
+                    BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN, DO_WHILE, EQUAL, GE, GT, LAMBDA, LAND,
+                    LCURLY, LE, LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE, LITERAL_FINALLY,
+                    LITERAL_FOR, LITERAL_IF, LITERAL_RETURN, LITERAL_SWITCH, LITERAL_SYNCHRONIZED,
+                    LITERAL_TRY, LITERAL_WHILE, LOR, LT, MINUS, MINUS_ASSIGN, MOD, MOD_ASSIGN,
+                    NOT_EQUAL, PLUS, PLUS_ASSIGN, QUESTION, RCURLY, SL, SLIST, SL_ASSIGN, SR,
+                    SR_ASSIGN, STAR, STAR_ASSIGN, LITERAL_ASSERT, TYPE_EXTENSION_AND"/>
+            <message key="ws.notFollowed"
+                     value="WhitespaceAround: ''{0}'' is not followed by whitespace. Empty blocks
+               may only be represented as '{}' when not part of a multi-block statement (4.1.3)"/>
+            <message key="ws.notPreceded"
+                     value="WhitespaceAround: ''{0}'' is not preceded with whitespace."/>
+        </module>
+        <module name="OneStatementPerLine"/>
+        <module name="MultipleVariableDeclarations"/>
+        <module name="ArrayTypeStyle"/>
+        <module name="MissingSwitchDefault"/>
+        <module name="FallThrough"/>
+        <module name="UpperEll"/>
+        <module name="ModifierOrder"/>
+        <module name="EmptyLineSeparator">
+            <property name="tokens"
+                      value="PACKAGE_DEF, IMPORT, STATIC_IMPORT, CLASS_DEF, INTERFACE_DEF, ENUM_DEF,
+                    STATIC_INIT, INSTANCE_INIT, METHOD_DEF, CTOR_DEF, VARIABLE_DEF, RECORD_DEF,
+                    COMPACT_CTOR_DEF"/>
+            <property name="allowNoEmptyLineBetweenFields" value="true"/>
+        </module>
+        <module name="SeparatorWrap">
+            <property name="id" value="SeparatorWrapDot"/>
+            <property name="tokens" value="DOT"/>
+            <property name="option" value="nl"/>
+        </module>
+        <module name="SeparatorWrap">
+            <property name="id" value="SeparatorWrapComma"/>
+            <property name="tokens" value="COMMA"/>
+            <property name="option" value="EOL"/>
+        </module>
+        <module name="SeparatorWrap">
+            <!-- ELLIPSIS is EOL until https://github.com/google/styleguide/issues/259 -->
+            <property name="id" value="SeparatorWrapEllipsis"/>
+            <property name="tokens" value="ELLIPSIS"/>
+            <property name="option" value="EOL"/>
+        </module>
+        <module name="SeparatorWrap">
+            <!-- ARRAY_DECLARATOR is EOL until https://github.com/google/styleguide/issues/258 -->
+            <property name="id" value="SeparatorWrapArrayDeclarator"/>
+            <property name="tokens" value="ARRAY_DECLARATOR"/>
+            <property name="option" value="EOL"/>
+        </module>
+        <module name="SeparatorWrap">
+            <property name="id" value="SeparatorWrapMethodRef"/>
+            <property name="tokens" value="METHOD_REF"/>
+            <property name="option" value="nl"/>
+        </module>
+        <module name="TypeName">
+            <property name="tokens" value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF,
+                    ANNOTATION_DEF, RECORD_DEF"/>
+            <message key="name.invalidPattern"
+                     value="Type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="MemberName">
+            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9]*$"/>
+            <message key="name.invalidPattern"
+                     value="Member name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="ParameterName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
+            <message key="name.invalidPattern"
+                     value="Parameter name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="LambdaParameterName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
+            <message key="name.invalidPattern"
+                     value="Lambda parameter name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="CatchParameterName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
+            <message key="name.invalidPattern"
+                     value="Catch parameter name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="LocalVariableName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
+            <message key="name.invalidPattern"
+                     value="Local variable name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="PatternVariableName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
+            <message key="name.invalidPattern"
+                     value="Pattern variable name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="ClassTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <message key="name.invalidPattern"
+                     value="Class type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="RecordComponentName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
+            <message key="name.invalidPattern"
+                     value="Record component name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="RecordTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <message key="name.invalidPattern"
+                     value="Record type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="MethodTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <message key="name.invalidPattern"
+                     value="Method type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="InterfaceTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <message key="name.invalidPattern"
+                     value="Interface type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="NoFinalizer"/>
+        <module name="GenericWhitespace">
+            <message key="ws.followed"
+                     value="GenericWhitespace ''{0}'' is followed by whitespace."/>
+            <message key="ws.preceded"
+                     value="GenericWhitespace ''{0}'' is preceded with whitespace."/>
+            <message key="ws.illegalFollow"
+                     value="GenericWhitespace ''{0}'' should followed by whitespace."/>
+            <message key="ws.notPreceded"
+                     value="GenericWhitespace ''{0}'' is not preceded with whitespace."/>
+        </module>
+        <module name="Indentation">
+            <property name="basicOffset" value="2"/>
+            <property name="braceAdjustment" value="2"/>
+            <property name="caseIndent" value="2"/>
+            <property name="throwsIndent" value="4"/>
+            <property name="lineWrappingIndentation" value="4"/>
+            <property name="arrayInitIndent" value="2"/>
+        </module>
+        <module name="AbbreviationAsWordInName">
+            <property name="ignoreFinal" value="false"/>
+            <property name="allowedAbbreviationLength" value="0"/>
+            <property name="tokens"
+                      value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, ANNOTATION_DEF, ANNOTATION_FIELD_DEF,
+                    PARAMETER_DEF, VARIABLE_DEF, METHOD_DEF, PATTERN_VARIABLE_DEF, RECORD_DEF,
+                    RECORD_COMPONENT_DEF"/>
+        </module>
+        <module name="NoWhitespaceBeforeCaseDefaultColon"/>
+        <module name="OverloadMethodsDeclarationOrder"/>
+        <module name="VariableDeclarationUsageDistance"/>
+        <module name="CustomImportOrder">
+            <property name="sortImportsInGroupAlphabetically" value="true"/>
+            <property name="separateLineBetweenGroups" value="true"/>
+            <property name="customImportOrderRules" value="STATIC###THIRD_PARTY_PACKAGE"/>
+            <property name="tokens" value="IMPORT, STATIC_IMPORT, PACKAGE_DEF"/>
+        </module>
+        <module name="MethodParamPad">
+            <property name="tokens"
+                      value="CTOR_DEF, LITERAL_NEW, METHOD_CALL, METHOD_DEF,
+                    SUPER_CTOR_CALL, ENUM_CONSTANT_DEF, RECORD_DEF"/>
+        </module>
+        <module name="NoWhitespaceBefore">
+            <property name="tokens"
+                      value="COMMA, SEMI, POST_INC, POST_DEC, DOT,
+                    LABELED_STAT, METHOD_REF"/>
+            <property name="allowLineBreaks" value="true"/>
+        </module>
+        <module name="ParenPad">
+            <property name="tokens"
+                      value="ANNOTATION, ANNOTATION_FIELD_DEF, CTOR_CALL, CTOR_DEF, DOT, ENUM_CONSTANT_DEF,
+                    EXPR, LITERAL_CATCH, LITERAL_DO, LITERAL_FOR, LITERAL_IF, LITERAL_NEW,
+                    LITERAL_SWITCH, LITERAL_SYNCHRONIZED, LITERAL_WHILE, METHOD_CALL,
+                    METHOD_DEF, QUESTION, RESOURCE_SPECIFICATION, SUPER_CTOR_CALL, LAMBDA,
+                    RECORD_DEF"/>
+        </module>
+        <module name="OperatorWrap">
+            <property name="option" value="NL"/>
+            <property name="tokens"
+                      value="BAND, BOR, BSR, BXOR, DIV, EQUAL, GE, GT, LAND, LE, LITERAL_INSTANCEOF, LOR,
+                    LT, MINUS, MOD, NOT_EQUAL, PLUS, QUESTION, SL, SR, STAR, METHOD_REF,
+                    TYPE_EXTENSION_AND "/>
+        </module>
+        <module name="AnnotationLocation">
+            <property name="id" value="AnnotationLocationMostCases"/>
+            <property name="tokens"
+                      value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF,
+                      RECORD_DEF, COMPACT_CTOR_DEF"/>
+        </module>
+        <module name="AnnotationLocation">
+            <property name="id" value="AnnotationLocationVariables"/>
+            <property name="tokens" value="VARIABLE_DEF"/>
+            <property name="allowSamelineMultipleAnnotations" value="true"/>
+        </module>
+        <module name="NonEmptyAtclauseDescription"/>
+        <module name="InvalidJavadocPosition"/>
+        <module name="JavadocTagContinuationIndentation"/>
+        <module name="SummaryJavadoc">
+            <property name="forbiddenSummaryFragments"
+                      value="^@return the *|^This method returns |^A [{]@code [a-zA-Z0-9]+[}]( is a )"/>
+        </module>
+        <module name="JavadocParagraph"/>
+        <module name="RequireEmptyLineBeforeBlockTagGroup"/>
+        <module name="AtclauseOrder">
+            <property name="tagOrder" value="@param, @return, @throws, @deprecated"/>
+            <property name="target"
+                      value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF, VARIABLE_DEF"/>
+        </module>
+        <module name="JavadocMethod">
+            <property name="accessModifiers" value="public"/>
+            <property name="allowMissingParamTags" value="true"/>
+            <property name="allowMissingReturnTag" value="true"/>
+            <property name="allowedAnnotations" value="Override, Test"/>
+            <property name="tokens" value="METHOD_DEF, CTOR_DEF, ANNOTATION_FIELD_DEF, COMPACT_CTOR_DEF"/>
+        </module>
+<!--        <module name="MissingJavadocMethod">-->
+<!--            <property name="scope" value="public"/>-->
+<!--            <property name="minLineCount" value="2"/>-->
+<!--            <property name="allowedAnnotations" value="Override, Test"/>-->
+<!--            <property name="tokens" value="METHOD_DEF, CTOR_DEF, ANNOTATION_FIELD_DEF,-->
+<!--                                   COMPACT_CTOR_DEF"/>-->
+<!--        </module>-->
+<!--        <module name="MissingJavadocType">-->
+<!--            <property name="scope" value="protected"/>-->
+<!--            <property name="tokens"-->
+<!--                      value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF,-->
+<!--                      RECORD_DEF, ANNOTATION_DEF"/>-->
+<!--            <property name="excludeScope" value="nothing"/>-->
+<!--        </module>-->
+        <module name="MethodName">
+            <property name="format" value="^[a-z][a-z0-9]\w*$"/>
+            <message key="name.invalidPattern"
+                     value="Method name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="SingleLineJavadoc"/>
+        <module name="EmptyCatchBlock">
+            <property name="exceptionVariableName" value="expected"/>
+        </module>
+        <module name="CommentsIndentation">
+            <property name="tokens" value="SINGLE_LINE_COMMENT, BLOCK_COMMENT_BEGIN"/>
+        </module>
+        <!-- https://checkstyle.org/filters/suppressionxpathfilter.html -->
+        <module name="SuppressionXpathFilter">
+            <property name="file" value="${org.checkstyle.google.suppressionxpathfilter.config}"
+                      default="checkstyle-xpath-suppressions.xml" />
+            <property name="optional" value="true"/>
+        </module>
+        <module name="SuppressWarningsHolder" />
+        <module name="SuppressionCommentFilter">
+            <property name="offCommentFormat" value="CHECKSTYLE.OFF\: ([\w\|]+)" />
+            <property name="onCommentFormat" value="CHECKSTYLE.ON\: ([\w\|]+)" />
+            <property name="checkFormat" value="$1" />
+        </module>
+        <module name="SuppressWithNearbyCommentFilter">
+            <property name="commentFormat" value="CHECKSTYLE.SUPPRESS\: ([\w\|]+)"/>
+            <!-- $1 refers to the first match group in the regex defined in commentFormat -->
+            <property name="checkFormat" value="$1"/>
+            <!-- The check is suppressed in the next line of code after the comment -->
+            <property name="influenceFormat" value="1"/>
+        </module>
+    </module>
+</module>
\ No newline at end of file
diff --git a/docs/examples/commons-cli/issues/index.html b/docs/examples/commons-cli/issues/index.html
index 9626a80..76e20be 100644
--- a/docs/examples/commons-cli/issues/index.html
+++ b/docs/examples/commons-cli/issues/index.html
@@ -1,4 +1,4 @@
-<html>
+<html lang="en">
   <head>
     <title>Testing issues report</title>
     <style>
diff --git a/docs/examples/commons-cli/issues/org.apache.commons.cli.AmbiguousOptionException.html b/docs/examples/commons-cli/issues/org.apache.commons.cli.AmbiguousOptionException.html
index 816d209..1405e35 100644
--- a/docs/examples/commons-cli/issues/org.apache.commons.cli.AmbiguousOptionException.html
+++ b/docs/examples/commons-cli/issues/org.apache.commons.cli.AmbiguousOptionException.html
@@ -1,5 +1,5 @@
 
-<html>
+<html lang="en">
   <head>
     <title>org.apache.commons.cli.AmbiguousOptionException</title>
     <style>
@@ -47,18 +47,18 @@ <h2 class="method-name">createMessage(java.lang.String, java.util.Collection)</h
             <div class="explanation">
                 <p>The body of this method has been replaced by:</p>
               <ul class="transformation-list">
-    <li class="transformation">
-                <span class="code-snippet">return "A";<span>
-  </li>
-    <li class="transformation">
-                <span class="code-snippet">return "";<span>
-  </li>
-    <li class="transformation">
-                <span class="code-snippet">return null;<span>
-  </li>
-  </ul>
-              <p>Yet, no test case detected any of those changes.</p>
-                  </div>
+                  <li class="transformation">
+                      <span class="code-snippet">return "A";</span>
+                  </li>
+                  <li class="transformation">
+                      <span class="code-snippet">return "";</span>
+                  </li>
+                  <li class="transformation">
+                      <span class="code-snippet">return null;</span>
+                  </li>
+              </ul>
+                <p>Yet, no test case detected any of those changes.</p>
+            </div>
             <div class="test-relation">
               The following test cases execute the method:
               <ul>
diff --git a/docs/examples/commons-cli/issues/org.apache.commons.cli.DefaultParser.html b/docs/examples/commons-cli/issues/org.apache.commons.cli.DefaultParser.html
index cc9f907..18fe1b0 100644
--- a/docs/examples/commons-cli/issues/org.apache.commons.cli.DefaultParser.html
+++ b/docs/examples/commons-cli/issues/org.apache.commons.cli.DefaultParser.html
@@ -1,5 +1,5 @@
 
-<html>
+<html lang="en">
   <head>
     <title>org.apache.commons.cli.DefaultParser</title>
     <style>
@@ -47,19 +47,19 @@ <h2 class="method-name">isLongOption(java.lang.String)</h2>
             <div class="explanation">
                 <p>The body of this method has been replaced by:</p>
               <ul class="transformation-list">
-    <li class="transformation">
-                <span class="code-snippet">return false;<span>
-  </li>
-  </ul>
+                  <li class="transformation">
+                      <span class="code-snippet">return false;</span>
+                  </li>
+              </ul>
               <p>Yet, no test case detected any of those changes.</p>
                   <p>However, when the body of the method is replaced by:</p>
               <ul class="transformation-list">
-    <li class="transformation">
-                <span class="code-snippet">return true;<span>
-  </li>
-  </ul>
+                  <li class="transformation">
+                      <span class="code-snippet">return true;</span>
+                  </li>
+              </ul>
               <p>The test suite fails.</p>
-                  </div>
+            </div>
             <div class="test-relation">
               The following test cases execute the method:
               <ul>
diff --git a/docs/examples/commons-cli/issues/org.apache.commons.cli.Option.html b/docs/examples/commons-cli/issues/org.apache.commons.cli.Option.html
index b11d985..e990750 100644
--- a/docs/examples/commons-cli/issues/org.apache.commons.cli.Option.html
+++ b/docs/examples/commons-cli/issues/org.apache.commons.cli.Option.html
@@ -1,5 +1,5 @@
 
-<html>
+<html lang="en">
   <head>
     <title>org.apache.commons.cli.Option</title>
     <style>
@@ -47,19 +47,19 @@ <h2 class="method-name">hasValueSeparator()</h2>
             <div class="explanation">
                 <p>The body of this method has been replaced by:</p>
               <ul class="transformation-list">
-    <li class="transformation">
-                <span class="code-snippet">return true;<span>
-  </li>
-  </ul>
-              <p>Yet, no test case detected any of those changes.</p>
+                    <li class="transformation">
+                          <span class="code-snippet">return true;</span>
+                    </li>
+              </ul>
+                  <p>Yet, no test case detected any of those changes.</p>
                   <p>However, when the body of the method is replaced by:</p>
-              <ul class="transformation-list">
-    <li class="transformation">
-                <span class="code-snippet">return false;<span>
-  </li>
-  </ul>
-              <p>The test suite fails.</p>
-                  </div>
+                  <ul class="transformation-list">
+                        <li class="transformation">
+                              <span class="code-snippet">return false;</span>
+                        </li>
+                  </ul>
+                  <p>The test suite fails.</p>
+            </div>
             <div class="test-relation">
               The following test cases execute the method:
               <ul>
diff --git a/docs/output-format.md b/docs/output-format.md
index 1e1125f..d3125d2 100644
--- a/docs/output-format.md
+++ b/docs/output-format.md
@@ -2,7 +2,7 @@
 
 Descartes includes its own output formats which are focused on *pseudo*
 and *partially-tested* methods.
-These formats can used by specifying `METHODS` and/or `ISSUES` in the
+These formats can be used by specifying `METHODS` and/or `ISSUES` in the
 PITest `outputFormats` parameter.
 
 `METHODS` produces a `JSON` file with the following structure:
@@ -65,10 +65,10 @@ PITest `outputFormats` parameter.
 }
 ```
 
-The `methods` list contains an entry for every methods that was part of the analysis. For each method there is information about its metadata, its testing classification (*tested*, *partially-tested*, *pseudo-tested*, *not-covered*), which mutations were detected and which not, all tests covering the method and there is also a list of entries for every mutation performed with more information.
+The `methods` list contains an entry for every method that was part of the analysis. For each method there is information about its metadata, its testing classification (*tested*, *partially-tested*, *pseudo-tested*, *not-covered*), which mutations were detected and which not, all tests covering the method and there is also a list of entries for every mutation performed with more information.
 
-A method is said to be *not-covered* if it is not covered by the test suite. It is said to be *pseudo-tested* if it is covered by the test suite, yet no extreme mutation applied to the method was detected by any test case. A method is said to be *partially-tested* if t has mixed results: some mutations were detected and others were not. Finally, a method is classified as *tested* if all extreme transformations are detected by the test suite.
+A method is said to be *not-covered* if it is not covered by the test suite. It is said to be *pseudo-tested* if it is covered by the test suite, yet no extreme mutation applied to the method was detected by any test case. A method is said to be *partially-tested* if it has mixed results: some mutations were detected and others were not. Finally, a method is classified as *tested* if all extreme transformations are detected by the test suite.
 
 Examples of files with this format can be checked [here](examples/commons-cli/methods.json) and also [here](examples/jsoup.json). These were obtained from actual open-source projects.
 
-The `ISSUES` output format contains this same information but it is rendered as an `HTML` document with human-readable descriptions. An example can be checked [here](examples/commons-cli/issues/).
+The `ISSUES` output format contains this same information, but it is rendered as an `HTML` document with human-readable descriptions. An example can be checked [here](examples/commons-cli/issues/).
diff --git a/docs/performance-comparison.md b/docs/performance-comparison.md
index 1700887..458a2f8 100644
--- a/docs/performance-comparison.md
+++ b/docs/performance-comparison.md
@@ -3,7 +3,7 @@
 We have compared the performance of Descartes and Gregor, which is the
 default mutation engine for PITest. The table below shows the execution
 time and number of mutants created by both engines in a set of
-open source projects. In all cases Descartes created much less mutants
+open source projects. In all cases Descartes created fewer mutants
 and employed much less time.
 
 Nevertheless, the results given by Descartes are coarse-grained compared
@@ -14,26 +14,26 @@ the worst tested methods in a project.
 |                                                                         | Descartes |         | Gregor   |         |
 |-------------------------------------------------------------------------|-----------|---------|----------|---------|
 | Project                                                                 | Time      | Mutants | Time     | Mutants |
-| [authzforce](https://github.com/authzforce/core.git)                    | 0:08:00   |    626  |  1:23:50 |    7296 |
-| [aws-sdk-java](https://github.com/aws/aws-sdk-java)                     | 1:32:23   | 161758  |  6:11:22 | 2141689 |
-| [commons-cli](https://github.com/apache/commons-cli)                    | 0:00:13   |    271  |  0:01:26 |    2560 |
-| [commons-codec](https://github.com/apache/commons-codec)                | 0:02:02   |    979  |  0:07:57 |    9233 |
-| [commons-collections](https://github.com/apache/commons-collections)     | 0:01:41   |   3558  |  0:05:41 |   20394 |
-| [commons-io](https://github.com/apache/commons-io)                      | 0:02:16   |   1164  |  0:12:48 |    8809 |
-| [commons-lang](https://github.com/apache/commons-lang)                  | 0:02:07   |   3872  |  0:21:02 |   30361 |
-| [flink-core](https://github.com/apache/flink/tree/master/flink-core)    | 0:14:04   |   4935  |  2:29:45 |   43619 |
-| [gson](https://github.com/google/gson)                                  | 0:01:08   |    848  |  0:05:34 |    7353 |
-| [imagej-common](https://github.com/imagej/imagej-common)                | 0:08:07   |   1947  |  0:29:09 |   15592 |
-| [jaxen](https://github.com/jaxen-xpath/jaxen)                           | 0:01:31   |   1252  |  0:24:40 |   12210 |
-| [jfreechart](https://github.com/jfree/jfreechart)                       | 0:05:48   |   7210  |  0:41:28 |   89592 |
-| [jgit](https://github.com/eclipse/jgit)                                 | 1:30:08   |   7152  | 16:02:03 |   78316 |
-| [joda-time](https://github.com/JodaOrg/joda-time)                       | 0:03:39   |   4525  |  0:16:32 |   31233 |
-| [jopt-simple](https://github.com/jopt-simple/jopt-simple)               | 0:00:37   |    412  |  0:01:36 |    2271 |
-| [jsoup](https://github.com/jhy/jsoup)                                   | 0:02:43   |   1566  |  0:12:49 |   14054 |
-| [sat4j-core](https://github.com/apache/pdfbox)                          | 0:53:09   |   2304  | 10:55:50 |   17163 |
-| [pdfbox](https://gitlab.ow2.org/sat4j/sat4j/tree/master/org.sat4j.core) | 0:44:07   |   7559  |  6:20:25 |   79763 |
-| [scifio](https://github.com/scifio/scifio)                              | 0:24:14   |   3627  |  3:12:11 |   62768 |
-| [spoon](https://github.com/INRIA/spoon)                                 | 2:24:55   |   4713  | 56:47:57 |   43916 |
-| [urbanairship](https://github.com/urbanairship/java-library)            | 0:07:25   |   3082  |  0:11:31 |   17345 |
-| [xwiki-rendering](https://github.com/xwiki/xwiki-rendering)             | 0:10:56   |   5534  |  2:07:19 |  112605 |
+| [authzforce](https://github.com/authzforce/core.git)                    | 0:08:00   | 626     | 1:23:50  | 7296    |
+| [aws-sdk-java](https://github.com/aws/aws-sdk-java)                     | 1:32:23   | 161758  | 6:11:22  | 2141689 |
+| [commons-cli](https://github.com/apache/commons-cli)                    | 0:00:13   | 271     | 0:01:26  | 2560    |
+| [commons-codec](https://github.com/apache/commons-codec)                | 0:02:02   | 979     | 0:07:57  | 9233    |
+| [commons-collections](https://github.com/apache/commons-collections)    | 0:01:41   | 3558    | 0:05:41  | 20394   |
+| [commons-io](https://github.com/apache/commons-io)                      | 0:02:16   | 1164    | 0:12:48  | 8809    |
+| [commons-lang](https://github.com/apache/commons-lang)                  | 0:02:07   | 3872    | 0:21:02  | 30361   |
+| [flink-core](https://github.com/apache/flink/tree/master/flink-core)    | 0:14:04   | 4935    | 2:29:45  | 43619   |
+| [gson](https://github.com/google/gson)                                  | 0:01:08   | 848     | 0:05:34  | 7353    |
+| [imagej-common](https://github.com/imagej/imagej-common)                | 0:08:07   | 1947    | 0:29:09  | 15592   |
+| [jaxen](https://github.com/jaxen-xpath/jaxen)                           | 0:01:31   | 1252    | 0:24:40  | 12210   |
+| [jfreechart](https://github.com/jfree/jfreechart)                       | 0:05:48   | 7210    | 0:41:28  | 89592   |
+| [jgit](https://github.com/eclipse/jgit)                                 | 1:30:08   | 7152    | 16:02:03 | 78316   |
+| [joda-time](https://github.com/JodaOrg/joda-time)                       | 0:03:39   | 4525    | 0:16:32  | 31233   |
+| [jopt-simple](https://github.com/jopt-simple/jopt-simple)               | 0:00:37   | 412     | 0:01:36  | 2271    |
+| [jsoup](https://github.com/jhy/jsoup)                                   | 0:02:43   | 1566    | 0:12:49  | 14054   |
+| [sat4j-core](https://github.com/apache/pdfbox)                          | 0:53:09   | 2304    | 10:55:50 | 17163   |
+| [pdfbox](https://gitlab.ow2.org/sat4j/sat4j/tree/master/org.sat4j.core) | 0:44:07   | 7559    | 6:20:25  | 79763   |
+| [scifio](https://github.com/scifio/scifio)                              | 0:24:14   | 3627    | 3:12:11  | 62768   |
+| [spoon](https://github.com/INRIA/spoon)                                 | 2:24:55   | 4713    | 56:47:57 | 43916   |
+| [urbanairship](https://github.com/urbanairship/java-library)            | 0:07:25   | 3082    | 0:11:31  | 17345   |
+| [xwiki-rendering](https://github.com/xwiki/xwiki-rendering)             | 0:10:56   | 5534    | 2:07:19  | 112605  |
 
diff --git a/pom.xml b/pom.xml
index 9833540..e658477 100644
--- a/pom.xml
+++ b/pom.xml
@@ -4,7 +4,7 @@
 
     <groupId>eu.stamp-project</groupId>
     <artifactId>descartes</artifactId>
-    <version>1.3.3-SNAPSHOT</version>
+    <version>1.3.3</version>
     <packaging>jar</packaging>
 
     <name>descartes</name>
@@ -38,7 +38,7 @@
         <connection>scm:git:git://github.com:STAMP-project/pitest-descartes.git</connection>
         <developerConnection>scm:git:git@github.com:STAMP-project/pitest-descartes.git</developerConnection>
         <url>https://github.com/STAMP-project/pitest-descartes</url>
-      <tag>HEAD</tag>
+      <tag>descartes-1.3.3</tag>
   </scm>
 
     <distributionManagement>
@@ -74,6 +74,14 @@
             <scope>provided</scope>
         </dependency>
 
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>3.12.0</version>
+            <!-- Provided by PIT -->
+            <scope>provided</scope>
+        </dependency>
+
         <dependency>
             <groupId>org.apache.velocity</groupId>
             <artifactId>velocity</artifactId>
@@ -97,7 +105,6 @@
 
     <build>
         <plugins>
-
             <!-- Generate code from jFlex files -->
             <plugin>
                 <groupId>de.jflex</groupId>
@@ -123,6 +130,55 @@
                 </configuration>
             </plugin>
 
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-checkstyle-plugin</artifactId>
+                <version>3.2.2</version>
+                <configuration>
+                    <failOnViolation>true</failOnViolation>
+                    <violationSeverity>warning</violationSeverity>
+                    <configLocation>./configuration/style.xml</configLocation>
+                    <outputEncoding>UTF-8</outputEncoding>
+                    <linkXRef>false</linkXRef>
+                </configuration>
+                <executions>
+                    <execution>
+                        <phase>verify</phase>
+                        <goals><goal>check</goal></goals>
+                    </execution>
+                </executions>
+            </plugin>
+
+            <plugin>
+                <groupId>com.spotify.fmt</groupId>
+                <artifactId>fmt-maven-plugin</artifactId>
+                <version>2.20</version>
+            </plugin>
+
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-pmd-plugin</artifactId>
+                <version>3.17.0</version>
+                <configuration>
+                    <failOnViolation>true</failOnViolation>
+                    <printFailingErrors>true</printFailingErrors>
+                    <rulesets>
+                        <ruleset>
+                            ./configuration/pmd-rules.xml
+                        </ruleset>
+                    </rulesets>
+                </configuration>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>
+                                check
+                            </goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+
             <!-- Testing -->
             <plugin>
                 <artifactId>maven-surefire-plugin</artifactId>
diff --git a/src/docgen/README.md b/src/docgen/README.md
index 7a93a3f..a448e19 100644
--- a/src/docgen/README.md
+++ b/src/docgen/README.md
@@ -37,7 +37,7 @@ cd my-project-under-test
 mvn clean package org.pitest:pitest-maven:mutationCoverage
 ```
 
-All options from PIT can be used. For more details check the [the PIT documentation](https://pitest.org/quickstart/maven/). 
+All options from PIT can be used. For more details check [the PIT documentation](https://pitest.org/quickstart/maven/). 
 
 Check ["Running Descartes on your project"](#running-descartes-on-your-project) for additional Descartes configuration options. 
 
@@ -65,7 +65,7 @@ If you use a multi-module project take a look at [PitMP](https://github.com/STAM
 ### Mutation testing
 Mutation testing allows you to verify if your test suite can detect possible bugs.
 The technique works by introducing small changes or faults into the original program. These modified versions are called **mutants**.
-A good test suite should able to detect or *kill* a mutant. That is, at least one test case should fail when the test suite is executed with the mutant. 
+A good test suite should be able to detect or *kill* a mutant. That is, at least one test case should fail when the test suite is executed with the mutant. 
 [Read more](https://en.wikipedia.org/wiki/Mutation_testing).
 Traditional mutation testing works at the instruction level, e.g., replacing ">" by "<=", so the number of generated mutants is huge, as the time required to check the entire test suite.
 That's why the authors of [Will my tests tell me if I break this code?](http://dl.acm.org/citation.cfm?doid=2896941.2896944) proposed an *Extreme Mutation* strategy, which works at the method level.
@@ -112,7 +112,7 @@ This operator accepts a method with a reference return type and replaces all ins
 with `return null`. For example, using the following class as input:
 ```Java
 class A {
-    public A clone() {
+    public A create() {
         return new A();
     }
 }
@@ -121,7 +121,7 @@ this operator will generate:
 
 ```Java
 class A {
-    public A clone() {
+    public A create() {
         return null;
     }
 }
@@ -349,7 +349,7 @@ For example, in the following fragment of code, the method `m` will not be mutat
 ```Java
 class A {
     @DoNotMutate
-    public void m() {...}
+    public void m() {/* ... */}
 }
 ```
 
@@ -358,7 +358,7 @@ All methods in a class annotated with `@DoNotMutate` will be avoided as well. Fo
 ```Java
 @DoNotMutate
 class A {
-    public void m() {...}
+    public void m() {/* ... */}
 }
 ```
 
@@ -399,7 +399,7 @@ PIT reporting extensions work with Descartes and include `XML`, `CSV` and `HTML`
 Descartes also provides three new reporting extensions:
   - a general reporting extension supporting `JSON` files. It works also with **Gregor**, the default mutation engine for PIT. To use just set `JSON` as report format for PIT.
   - a reporting extension designed for Descartes that generates a JSON file with information about pseudo and partially tested methods. To use just set `METHOD` as report format for PIT.
-  - Descartes can generate a human readable report containing only the list of methods with testing issues by using the `ISSUES` format.
+  - Descartes can generate a human-readable report containing only the list of methods with testing issues by using the `ISSUES` format.
  
 Examples of these reporting extensions for [Apache Commons-CLI](https://github.com/apache/commons-cli/tree/b9ccc94008c78a59695f0c77ebe4ecf284370956) can be checked [here](docs/examples/commons-cli).
 
@@ -498,7 +498,7 @@ To configure the stop methods under consideration Descartes provides a `STOP_MET
 This feature is enabled by default. The parameter `exclude` can be used to prevent certain methods to be treated as stop methods and bring them back to the analysis. This parameter can take any of the following values:
 
 
-|`exclude`        | Method description                                                                     | Example                                                                                          |
+| `exclude`       | Method description                                                                     | Example                                                                                          |
 |-----------------|----------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------|
 | `empty`         | `void` methods with no instruction.                                                    | `public void m() {}`                                                                             |
 | `enum`          | Methods generated by the compiler to support enum types (`values` and `valueOf`).      |                                                                                                  |
@@ -553,7 +553,7 @@ The feature can be completely disabled:
 As said before, there are several reporting options provided by Descartes:
 - `JSON` for a general mutation testing report using that file format. It can be used with **Gregor**.
 - `METHODS` that produces a `methods.json` file with the list of all methods analyzed and categorized according to the mutation testing result.
-- `ISSUES` a human readable report containing only the methods with testing issues.
+- `ISSUES` a human-readable report containing only the methods with testing issues.
 
 They can be configured and combined as regular PIT report formats:
 
diff --git a/src/main/java/eu/stamp_project/descartes/DescartesEngineFactory.java b/src/main/java/eu/stamp_project/descartes/DescartesEngineFactory.java
index bde9659..6836382 100644
--- a/src/main/java/eu/stamp_project/descartes/DescartesEngineFactory.java
+++ b/src/main/java/eu/stamp_project/descartes/DescartesEngineFactory.java
@@ -2,67 +2,70 @@
 
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
 import eu.stamp_project.descartes.operators.MutationOperator;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
 import org.pitest.functional.prelude.Prelude;
 import org.pitest.mutationtest.EngineArguments;
 import org.pitest.mutationtest.MutationEngineFactory;
 import org.pitest.mutationtest.engine.MutationEngine;
 import org.pitest.util.Glob;
 
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.function.Predicate;
-import java.util.stream.Collectors;
-
+public class DescartesEngineFactory implements MutationEngineFactory {
 
-public class DescartesEngineFactory implements MutationEngineFactory{
-
-
-    @Override
-    public MutationEngine createEngine(EngineArguments engineArguments) {
-
-        Collection<String> operators = engineArguments.mutators();
-        if(operators == null || operators.isEmpty())
-            operators = getDefaultOperators();
-
-        return createEngine(
-                globsToPredicate(engineArguments.excludedMethods()),
-                operators.stream()
-                        .map(MutationOperator::fromID)
-                        .collect(Collectors.toList()));
+  @Override
+  public MutationEngine createEngine(final EngineArguments engineArguments) {
+    Collection<String> operators = engineArguments.mutators();
+    if (operators == null || operators.isEmpty()) {
+      operators = getDefaultOperators();
     }
+    return createEngine(
+        globsToPredicate(engineArguments.excludedMethods()),
+        operators.stream().map(MutationOperator::fromIdentifier).collect(Collectors.toList()));
+  }
 
-    public MutationEngine createEngine(Predicate<MethodInfo> excludedMethods,
-                                       Collection<MutationOperator> operators) {
-        return new DescartesMutationEngine(excludedMethods, operators);
-    }
+  public MutationEngine createEngine(
+      final Predicate<MethodInfo> excludedMethods, final Collection<MutationOperator> operators) {
 
-    public static Collection<String> getDefaultOperators() {
-        return Arrays.asList(
-                "void",
-                "null",
-                "empty",
-                "true", "false",
-                "0", "1",
-                "(short)0", "(short)1",
-                "(byte)0", "(byte)1",
-                "0L", "1L",
-                "0.0", "1.0",
-                "0.0f", "1.0f",
-                "'\\40'", "'A'",
-                "\"\"", "\"A\"");
-    }
+    return new DescartesMutationEngine(excludedMethods, operators);
+  }
 
+  public static Collection<String> getDefaultOperators() {
+    return Arrays.asList(
+        "void",
+        "null",
+        "empty",
+        "true",
+        "false",
+        "0",
+        "1",
+        "(short)0",
+        "(short)1",
+        "(byte)0",
+        "(byte)1",
+        "0L",
+        "1L",
+        "0.0",
+        "1.0",
+        "0.0f",
+        "1.0f",
+        "'\\40'",
+        "'A'",
+        "\"\"",
+        "\"A\"");
+  }
 
-    public static Predicate<MethodInfo> globsToPredicate(Collection<String> globs) {
-        Predicate<String> excludedNames = Prelude.or(Glob.toGlobPredicates(globs));
-        return (method) -> excludedNames.test(method.getName());
-    }
+  public static Predicate<MethodInfo> globsToPredicate(final Collection<String> globs) {
+    Predicate<String> excludedNames = Prelude.or(Glob.toGlobPredicates(globs));
+    return (method) -> excludedNames.test(method.getName());
+  }
 
-    public String name() {
-        return "descartes";
-    }
+  public String name() {
+    return "descartes";
+  }
 
-    public String description() {
-        return "Extreme mutation engine";
-    }
+  public String description() {
+    return "Extreme mutation engine";
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/DescartesMutater.java b/src/main/java/eu/stamp_project/descartes/DescartesMutater.java
index d6e4803..166ae22 100644
--- a/src/main/java/eu/stamp_project/descartes/DescartesMutater.java
+++ b/src/main/java/eu/stamp_project/descartes/DescartesMutater.java
@@ -1,10 +1,11 @@
-
 package eu.stamp_project.descartes;
 
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
 import eu.stamp_project.descartes.codemanipulation.MutationClassAdapter;
 import eu.stamp_project.descartes.codemanipulation.MutationPointFinder;
 import eu.stamp_project.descartes.operators.MutationOperator;
+import java.util.*;
+import java.util.function.Predicate;
 import org.pitest.classinfo.ClassByteArraySource;
 import org.pitest.classinfo.ClassName;
 import org.pitest.mutationtest.engine.Mutant;
@@ -14,52 +15,66 @@
 import org.pitest.reloc.asm.ClassReader;
 import org.pitest.reloc.asm.ClassWriter;
 
-import java.util.*;
-import java.util.function.Predicate;
-
 public class DescartesMutater implements Mutater {
 
+  private final ClassByteArraySource byteSource;
+  private final Predicate<MethodInfo> excludedMethods;
+  private final Collection<MutationOperator> operators;
 
-    private final ClassByteArraySource byteSource;
-    private final Predicate<MethodInfo> excludedMethods;
-    private final Collection<MutationOperator> operators;
-
+  public DescartesMutater(
+      final ClassByteArraySource byteSource,
+      final Predicate<MethodInfo> excludedMethods,
+      final Collection<MutationOperator> operators) {
+    Objects.requireNonNull(byteSource, "Source to inspect for mutations can not be null");
+    this.byteSource = byteSource;
 
-    public DescartesMutater(final ClassByteArraySource byteSource, Predicate<MethodInfo> excludedMethods, Collection<MutationOperator> operators) {
-        Objects.requireNonNull(byteSource, "Source to inspect for mutations can not be null");
-        this.byteSource = byteSource;
+    Objects.requireNonNull(excludedMethods, "Predicate for excluded methods can not be null");
+    this.excludedMethods = excludedMethods;
 
-        Objects.requireNonNull(excludedMethods, "Predicate for excluded methods can not be null");
-        this.excludedMethods = excludedMethods;
+    Objects.requireNonNull(operators, "Collection of mutation operators can not be null");
+    this.operators = operators;
+  }
 
-        Objects.requireNonNull(operators, "Collection of mutation operators can not be null");
-        this.operators = operators;
+  public List<MutationDetails> findMutations(final ClassName classToMutate) {
+    Optional<byte[]> classBytes = byteSource.getBytes(classToMutate.asInternalName());
+    if (!classBytes.isPresent()) {
+      return Collections.emptyList();
     }
+    MutationPointFinder finder = new MutationPointFinder(excludedMethods, operators);
+    ClassReader reader = new ClassReader(classBytes.get());
+    return finder.findMutationPoints(classToMutate, reader);
+  }
 
-    public List<MutationDetails> findMutations(final ClassName classToMutate) {
-        Optional<byte[]> classBytes = byteSource.getBytes(classToMutate.asInternalName());
-        if(!classBytes.isPresent())
-            return Collections.emptyList();
-        MutationPointFinder finder = new MutationPointFinder(excludedMethods, operators);
-        ClassReader reader = new ClassReader(classBytes.get());
-        return finder.findMutationPoints(classToMutate, reader);
-    }
-
-    private byte[] createMutant(MutationIdentifier mID) {
-        Optional<byte[]> bytes = byteSource.getBytes(mID.getClassName().asJavaName()); //So does the original PIT
-        ClassReader reader = new ClassReader(bytes.orElseThrow(
-                () -> new IllegalArgumentException("Class " + mID.getClassName().asJavaName() + " not found in the binary source")));
-        ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
-        MutationClassAdapter adapter = new MutationClassAdapter(mID, writer);
-        reader.accept(adapter, 0);
-        return writer.toByteArray();
-    }
-
-    public Mutant getMutation(MutationIdentifier mID) {
-        // We can return a default MutationDetails object as PIT uses the precomputed details for the process.
-        // Given this it would be better to have this method receive the MutationDetails instance instead of the MutationIdentifier.
-        return new Mutant(new MutationDetails(mID, "", "", 0, 0), createMutant(mID));
-    }
+  private byte[] createMutant(MutationIdentifier mutationIdentifier) {
+    Optional<byte[]> bytes =
+        // As the original PITest code does
+        byteSource.getBytes(mutationIdentifier.getClassName().asJavaName());
+    ClassReader reader =
+        new ClassReader(
+            bytes.orElseThrow(
+                () ->
+                    new IllegalArgumentException(
+                        "Class "
+                            + mutationIdentifier.getClassName().asJavaName()
+                            + " not found in the binary source")));
+    ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
+    MutationClassAdapter adapter = new MutationClassAdapter(mutationIdentifier, writer);
+    reader.accept(adapter, 0);
+    return writer.toByteArray();
+  }
 
+  public Mutant getMutation(final MutationIdentifier mutationIdentifier) {
+    // We can return a default MutationDetails object as PIT uses the precomputed details for the
+    // process.
+    // Given this it would be better to have this method receive the MutationDetails instance
+    // instead of the MutationIdentifier.
+    return new Mutant(
+        new MutationDetails(
+            mutationIdentifier,
+            "",
+            "",
+            0,
+            0),
+        createMutant(mutationIdentifier));
+  }
 }
-
diff --git a/src/main/java/eu/stamp_project/descartes/DescartesMutationEngine.java b/src/main/java/eu/stamp_project/descartes/DescartesMutationEngine.java
index 67c6795..3a753df 100644
--- a/src/main/java/eu/stamp_project/descartes/DescartesMutationEngine.java
+++ b/src/main/java/eu/stamp_project/descartes/DescartesMutationEngine.java
@@ -2,57 +2,59 @@
 
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
 import eu.stamp_project.descartes.operators.MutationOperator;
-import org.pitest.classinfo.ClassByteArraySource;
-import org.pitest.mutationtest.engine.Mutater;
-import org.pitest.mutationtest.engine.MutationEngine;
-
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Objects;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
+import org.pitest.classinfo.ClassByteArraySource;
+import org.pitest.mutationtest.engine.Mutater;
+import org.pitest.mutationtest.engine.MutationEngine;
 
+public class DescartesMutationEngine implements MutationEngine {
 
-public class DescartesMutationEngine implements  MutationEngine {
-
-    private final Predicate<MethodInfo> excludedMethods;
+  private final Predicate<MethodInfo> excludedMethods;
 
-    private final Collection<MutationOperator> operators;
+  private final Collection<MutationOperator> operators;
 
-    public DescartesMutationEngine(Collection<MutationOperator> operators) {
-        this(m -> false, operators);
-    }
+  public DescartesMutationEngine(final Collection<MutationOperator> operators) {
+    this(m -> false, operators);
+  }
 
-    public DescartesMutationEngine(MutationOperator... operators) {
-        this(Arrays.<MutationOperator>asList(operators));
-    }
+  public DescartesMutationEngine(final MutationOperator... operators) {
+    this(Arrays.asList(operators));
+  }
 
-    public DescartesMutationEngine(Predicate<MethodInfo> excludedMethods, MutationOperator...operators) {
-        this(excludedMethods, Arrays.<MutationOperator>asList(operators));
-    }
+  public DescartesMutationEngine(
+      final Predicate<MethodInfo> excludedMethods, final MutationOperator... operators) {
+    this(excludedMethods, Arrays.asList(operators));
+  }
 
-    public DescartesMutationEngine(Predicate<MethodInfo> excludedMethods, Collection<MutationOperator> operators) {
-        Objects.requireNonNull(excludedMethods, "Excluded methods predicate can not be null");
-        this.excludedMethods = excludedMethods;
+  public DescartesMutationEngine(
+      final Predicate<MethodInfo> excludedMethods, final Collection<MutationOperator> operators) {
+    Objects.requireNonNull(excludedMethods, "Excluded methods predicate can not be null");
+    this.excludedMethods = excludedMethods;
 
-        Objects.requireNonNull(operators, "Collection of mutation operators can not be null");
-        this.operators = operators;
-    }
+    Objects.requireNonNull(operators, "Collection of mutation operators can not be null");
+    this.operators = operators;
+  }
 
-    public Mutater createMutator(final ClassByteArraySource byteSource) {
+  public Mutater createMutator(final ClassByteArraySource byteSource) {
 
-        return new DescartesMutater(byteSource, excludedMethods, operators);
-    }
+    return new DescartesMutater(byteSource, excludedMethods, operators);
+  }
 
-    public Collection<String> getMutatorNames() {
-       return operators.stream().map(MutationOperator::getIdentifier).collect(Collectors.toList());
-    }
+  public Collection<String> getMutatorNames() {
+    return operators.stream().map(MutationOperator::getIdentifier).collect(Collectors.toList());
+  }
 
-    @Override
-    public String toString() {
-        return "DescartesMutationEngine"; //TODO: Add more details here
-    }
+  @Override
+  public String toString() {
+    return "DescartesMutationEngine";
+  }
 
-    @Override
-    public String getName() { return "descartes"; }
+  @Override
+  public String getName() {
+    return "descartes";
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/annotations/DoNotMutate.java b/src/main/java/eu/stamp_project/descartes/annotations/DoNotMutate.java
index d9a05c9..0870c3a 100644
--- a/src/main/java/eu/stamp_project/descartes/annotations/DoNotMutate.java
+++ b/src/main/java/eu/stamp_project/descartes/annotations/DoNotMutate.java
@@ -1,9 +1,10 @@
 package eu.stamp_project.descartes.annotations;
 
 import static java.lang.annotation.ElementType.*;
+
 import java.lang.annotation.Target;
 
 @Target({METHOD, TYPE})
 public @interface DoNotMutate {
-    String[] operators() default {};
+  String[] operators() default {};
 }
diff --git a/src/main/java/eu/stamp_project/descartes/annotations/Operator.java b/src/main/java/eu/stamp_project/descartes/annotations/Operator.java
index d59089f..11ad055 100644
--- a/src/main/java/eu/stamp_project/descartes/annotations/Operator.java
+++ b/src/main/java/eu/stamp_project/descartes/annotations/Operator.java
@@ -8,6 +8,7 @@
 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.TYPE)
 public @interface Operator {
-    String identifier();
-    String description();
+  String identifier();
+
+  String description();
 }
diff --git a/src/main/java/eu/stamp_project/descartes/codemanipulation/BaseClassVisitor.java b/src/main/java/eu/stamp_project/descartes/codemanipulation/BaseClassVisitor.java
index b3b3c41..9aeef59 100644
--- a/src/main/java/eu/stamp_project/descartes/codemanipulation/BaseClassVisitor.java
+++ b/src/main/java/eu/stamp_project/descartes/codemanipulation/BaseClassVisitor.java
@@ -1,25 +1,43 @@
 package eu.stamp_project.descartes.codemanipulation;
 
 import static org.pitest.bytecode.ASMVersion.ASM_VERSION;
+
 import org.pitest.reloc.asm.ClassVisitor;
 
 public class BaseClassVisitor extends ClassVisitor {
 
-    public BaseClassVisitor() { super(ASM_VERSION); }
-
-    public BaseClassVisitor(ClassVisitor classVisitor) { super(ASM_VERSION, classVisitor); }
-
-    private TypeInfo classInfo;
-
-    public TypeInfo getClassInfo() { return classInfo; }
-
-    public MethodInfo createMethodInfo(int access, String name, String desc, String signature, String[] exceptions) {
-        return new MethodInfo(classInfo, access, name, desc, signature, exceptions);
-    }
-
-    @Override
-    public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
-        classInfo = new TypeInfo(version, access, name, signature, superName, interfaces);
-        super.visit(version, access, name, signature, superName, interfaces);
-    }
+  public BaseClassVisitor() {
+    super(ASM_VERSION);
+  }
+
+  public BaseClassVisitor(final ClassVisitor classVisitor) {
+    super(ASM_VERSION, classVisitor);
+  }
+
+  private TypeInfo classInfo;
+
+  public TypeInfo getClassInfo() {
+    return classInfo;
+  }
+
+  public MethodInfo createMethodInfo(
+      final int access,
+      final String name,
+      final String desc,
+      final String signature,
+      final String[] exceptions) {
+    return new MethodInfo(classInfo, access, name, desc, signature, exceptions);
+  }
+
+  @Override
+  public void visit(
+      int version,
+      int access,
+      String name,
+      String signature,
+      String superName,
+      String[] interfaces) {
+    classInfo = new TypeInfo(version, access, name, signature, superName, interfaces);
+    super.visit(version, access, name, signature, superName, interfaces);
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/codemanipulation/BaseMethodVisitor.java b/src/main/java/eu/stamp_project/descartes/codemanipulation/BaseMethodVisitor.java
index 2f39da2..2279d5e 100644
--- a/src/main/java/eu/stamp_project/descartes/codemanipulation/BaseMethodVisitor.java
+++ b/src/main/java/eu/stamp_project/descartes/codemanipulation/BaseMethodVisitor.java
@@ -1,14 +1,15 @@
 package eu.stamp_project.descartes.codemanipulation;
 
-import org.pitest.reloc.asm.MethodVisitor;
 import static org.pitest.bytecode.ASMVersion.ASM_VERSION;
 
+import org.pitest.reloc.asm.MethodVisitor;
+
 public abstract class BaseMethodVisitor extends MethodVisitor {
-    public BaseMethodVisitor() {
-        super(ASM_VERSION);
-    }
+  public BaseMethodVisitor() {
+    super(ASM_VERSION);
+  }
 
-    public BaseMethodVisitor(MethodVisitor methodVisitor) {
-        super(ASM_VERSION, methodVisitor);
-    }
+  public BaseMethodVisitor(MethodVisitor methodVisitor) {
+    super(ASM_VERSION, methodVisitor);
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/codemanipulation/ElementInfo.java b/src/main/java/eu/stamp_project/descartes/codemanipulation/ElementInfo.java
index eb99a17..c8a9e24 100644
--- a/src/main/java/eu/stamp_project/descartes/codemanipulation/ElementInfo.java
+++ b/src/main/java/eu/stamp_project/descartes/codemanipulation/ElementInfo.java
@@ -1,37 +1,50 @@
 package eu.stamp_project.descartes.codemanipulation;
 
-import org.pitest.reloc.asm.Opcodes;
-import org.pitest.reloc.asm.Type;
-
 import java.util.Set;
 import java.util.stream.Stream;
+import org.pitest.reloc.asm.Opcodes;
+import org.pitest.reloc.asm.Type;
 
 public abstract class ElementInfo {
 
-    protected int access;
-    protected String name;
-    protected String signature;
+  protected final int access;
+  protected final String name;
+  protected final String signature;
 
-    public ElementInfo(int access, String name, String signature) {
-        this.access = access;
-        this.name = name; //TODO: validate
-        this.signature = signature;
-    }
+  public ElementInfo(int access, String name, String signature) {
+    this.access = access;
+    this.name = name;
+    this.signature = signature;
+  }
 
-    public String getName() { return name; }
+  public String getName() {
+    return name;
+  }
 
-    public String getSignature() { return signature; }
+  public String getSignature() {
+    return signature;
+  }
 
-    public boolean hasFlag(int flag) { return (access & flag) != 0; }
+  public boolean hasFlag(int flag) {
+    return (access & flag) != 0;
+  }
 
-    protected Type[] toTypes(String[] typeNames) {
-        if(typeNames == null || typeNames.length == 0) return new Type[0];
-        return Stream.of(typeNames).map(Type::getObjectType).toArray(Type[]::new);
+  protected Type[] toTypes(String[] typeNames) {
+    if (typeNames == null || typeNames.length == 0) {
+      return new Type[0];
     }
+    return Stream.of(typeNames).map(Type::getObjectType).toArray(Type[]::new);
+  }
 
-    protected Set<Type> toTypeSet(String[] typeNames) { return Set.of(toTypes(typeNames)); }
+  protected Set<Type> toTypeSet(String[] typeNames) {
+    return Set.of(toTypes(typeNames));
+  }
 
-    public boolean isStatic() { return hasFlag(Opcodes.ACC_STATIC); }
+  public boolean isStatic() {
+    return hasFlag(Opcodes.ACC_STATIC);
+  }
 
-    public boolean isAbstract() { return hasFlag(Opcodes.ACC_ABSTRACT); }
+  public boolean isAbstract() {
+    return hasFlag(Opcodes.ACC_ABSTRACT);
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/codemanipulation/LineCounter.java b/src/main/java/eu/stamp_project/descartes/codemanipulation/LineCounter.java
index 5848552..1d89fc8 100644
--- a/src/main/java/eu/stamp_project/descartes/codemanipulation/LineCounter.java
+++ b/src/main/java/eu/stamp_project/descartes/codemanipulation/LineCounter.java
@@ -6,59 +6,66 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
-public class LineCounter {
+public final class LineCounter {
 
-    private int firstLine;
-    private int lastLine;
+  private int firstLine;
+  private int lastLine;
 
-    public LineCounter() { reset(); }
+  public LineCounter() {
+    reset();
+  }
 
-    public void reset() {
-        firstLine = Integer.MAX_VALUE;
-        lastLine = Integer.MIN_VALUE;
-    }
+  public void reset() {
+    firstLine = Integer.MAX_VALUE;
+    lastLine = Integer.MIN_VALUE;
+  }
 
-    public void registerLine(int line) {
-        firstLine = Math.min(firstLine, line);
-        lastLine = Math.max(lastLine, line);
-    }
+  public void registerLine(int line) {
+    firstLine = Math.min(firstLine, line);
+    lastLine = Math.max(lastLine, line);
+  }
 
-    public boolean empty() { return firstLine > lastLine; }
+  public boolean empty() {
+    return firstLine > lastLine;
+  }
 
-    public int getCount() {
-        if (empty())
-            return 0;
-        return lastLine - firstLine + 1;
+  public int getCount() {
+    if (empty()) {
+      return 0;
     }
+    return lastLine - firstLine + 1;
+  }
 
-    public int getFirstLine() {
-        ensureNotEmpty();
-        return firstLine;
-    }
+  public int getFirstLine() {
+    ensureNotEmpty();
+    return firstLine;
+  }
 
-    public int getLastLine() {
-        ensureNotEmpty();
-        return lastLine;
-    }
+  public int getLastLine() {
+    ensureNotEmpty();
+    return lastLine;
+  }
 
-    public Collection<Integer> getShiftedRange() {
-        if(empty())
-            return Collections.emptyList();
-        //NOTE: MutationDetails has the following two methods:
-        //  getFirstIndex() { return this.id.getFirstIndex(); }
-        // which returns the first index included in the identifier
-        //  getInstructionIndex() { return getFirstIndex() - 1; }
-        //  which is used mostly for filters
-        // Returning 0 as the first index results in an index out of bound exception in the filters
-        // that's why I return 1 here. Anyways, it is really hard to create a method covered in the
-        // first bytecode instruction (0) and not the second one (1).
-        // Here, the first index is the one that really counts as all tests will execute it and this
-        // will determine the coverage.
-        return IntStream.rangeClosed(1, lastLine - firstLine + 1).boxed().collect(Collectors.toList());
+  public Collection<Integer> getShiftedRange() {
+    if (empty()) {
+      return Collections.emptyList();
     }
+    // NOTE: MutationDetails has the following two methods:
+    //  getFirstIndex() { return this.id.getFirstIndex(); }
+    // which returns the first index included in the identifier
+    //  getInstructionIndex() { return getFirstIndex() - 1; }
+    // which is used mostly for filters
+    // Returning 0 as the first index results in an index out of bound exception in the filters
+    // that's why I return 1 here. In any case it is really hard to create a method covered in the
+    // first bytecode instruction (0) and not the second one (1).
+    // Here the first index is the one that really counts as all tests will execute it and this
+    // will determine the coverage.
+    return IntStream.rangeClosed(1, lastLine - firstLine + 1).boxed().collect(Collectors.toList());
+  }
 
-    private void ensureNotEmpty() {
-      if (empty())
-            throw new NoSuchElementException("Attempt to grab a line from an empty interval");
+  private void ensureNotEmpty() {
+    if (empty()) {
+      throw new NoSuchElementException("Attempt to grab a line from an empty interval");
     }
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/codemanipulation/MethodInfo.java b/src/main/java/eu/stamp_project/descartes/codemanipulation/MethodInfo.java
index cc1a93a..12fee7d 100644
--- a/src/main/java/eu/stamp_project/descartes/codemanipulation/MethodInfo.java
+++ b/src/main/java/eu/stamp_project/descartes/codemanipulation/MethodInfo.java
@@ -1,55 +1,70 @@
 package eu.stamp_project.descartes.codemanipulation;
 
-import org.pitest.reloc.asm.Opcodes;
-import org.pitest.reloc.asm.Type;
-
 import java.lang.reflect.Method;
 import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
+import org.pitest.reloc.asm.Opcodes;
+import org.pitest.reloc.asm.Type;
 
 public class MethodInfo extends ElementInfo {
 
-    private final Type returnType;
-    private final List<Type> argumentTypes;
-    private final Set<Type> exceptions;
-    private final TypeInfo owner;
-    private final String descriptor;
-
-    public MethodInfo(Method method) {
-        //TODO: Validate
-        super(method.getModifiers(), method.getName(), method.toGenericString()); //TODO: to Generic string?
-        Type methodType = Type.getType(method);
-        owner = new TypeInfo(method.getDeclaringClass());
-        descriptor = methodType.getDescriptor();
-        returnType = methodType.getReturnType();
-        argumentTypes = List.of(methodType.getArgumentTypes());
-        exceptions =   Stream.of(method.getExceptionTypes()).map(Type::getType).collect(Collectors.toSet());
-    }
+  private final Type returnType;
+  private final List<Type> argumentTypes;
+  private final Set<Type> exceptions;
+  private final TypeInfo owner;
+  private final String descriptor;
 
-    public MethodInfo(TypeInfo owner, int access, String name, String desc, String signature, String[] exceptions) {
-        super(access, name, signature);
-        //TODO: Validate
-        this.owner = owner;
-        descriptor = desc;
-        returnType = Type.getReturnType(desc);
-        argumentTypes = List.of(Type.getArgumentTypes(desc));
-        this.exceptions = toTypeSet(exceptions);
-    }
+  public MethodInfo(Method method) {
+    super(
+        method.getModifiers(),
+        method.getName(),
+        method.toGenericString());
+    Type methodType = Type.getType(method);
+    owner = new TypeInfo(method.getDeclaringClass());
+    descriptor = methodType.getDescriptor();
+    returnType = methodType.getReturnType();
+    argumentTypes = List.of(methodType.getArgumentTypes());
+    exceptions =
+        Stream.of(method.getExceptionTypes()).map(Type::getType).collect(Collectors.toSet());
+  }
 
-    public Type getReturnType() { return returnType; }
+  public MethodInfo(
+      TypeInfo owner, int access, String name, String desc, String signature, String[] exceptions) {
+    super(access, name, signature);
+    this.owner = owner;
+    descriptor = desc;
+    returnType = Type.getReturnType(desc);
+    argumentTypes = List.of(Type.getArgumentTypes(desc));
+    this.exceptions = toTypeSet(exceptions);
+  }
 
-    public List<Type> getArgumentTypes() { return argumentTypes; }
+  public Type getReturnType() {
+    return returnType;
+  }
 
-    public Set<Type> getExceptions() { return exceptions; }
+  public List<Type> getArgumentTypes() {
+    return argumentTypes;
+  }
 
-    public TypeInfo getOwner() { return owner; }
+  public Set<Type> getExceptions() {
+    return exceptions;
+  }
 
-    public String getDescriptor() { return descriptor; }
+  public TypeInfo getOwner() {
+    return owner;
+  }
 
-    public boolean isConstructor() { return name.equals("<init>"); }
+  public String getDescriptor() {
+    return descriptor;
+  }
 
-    public boolean hasNoCode() { return hasFlag(Opcodes.ACC_NATIVE | Opcodes.ACC_ABSTRACT); }
+  public boolean isConstructor() {
+    return name.equals("<init>");
+  }
 
+  public boolean hasNoCode() {
+    return hasFlag(Opcodes.ACC_NATIVE | Opcodes.ACC_ABSTRACT);
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/codemanipulation/MethodRewritingVisitor.java b/src/main/java/eu/stamp_project/descartes/codemanipulation/MethodRewritingVisitor.java
index f91c9a5..5817bc0 100644
--- a/src/main/java/eu/stamp_project/descartes/codemanipulation/MethodRewritingVisitor.java
+++ b/src/main/java/eu/stamp_project/descartes/codemanipulation/MethodRewritingVisitor.java
@@ -4,86 +4,15 @@
 
 public abstract class MethodRewritingVisitor extends BaseMethodVisitor {
 
-    public MethodRewritingVisitor(MethodVisitor mv) {super(mv);}
+  public MethodRewritingVisitor(MethodVisitor mv) {
+    super(mv);
+  }
 
-    @Override
-    public void visitCode() {
-        generateCode();
-        mv.visitMaxs(0, 0);
-    }
-
-    protected abstract void generateCode();
-
-    @Override
-    public void visitFrame(int type, int numLocal, Object[] local, int numStack, Object[] stack) { }
-
-    @Override
-    public void visitFieldInsn(int opcode, String owner, String name, String descriptor) { }
-
-    @Override
-    public void visitIincInsn(int var, int increment) { }
-
-    @Override
-    public void visitInsn(int opcode) { }
-
-    @Override
-    public void visitIntInsn(int opcode, int operand) { }
-
-    @Override
-    public void visitInvokeDynamicInsn(String name, String descriptor, Handle bootstrapMethodHandle, Object... bootstrapMethodArguments) { }
-
-    @Override
-    public void visitJumpInsn(int opcode, Label label) { }
-
-    @Override
-    public void visitLdcInsn(Object value) { }
-
-    @Override
-    public void visitLookupSwitchInsn(Label dflt, int[] keys, Label[] labels) { }
-
-    @Override
-    public void visitMethodInsn(int opcode, String owner, String name, String descriptor, boolean isInterface) { }
-
-    @Override
-    public void visitMultiANewArrayInsn(String descriptor, int numDimensions) { }
-
-    @Override
-    public void visitTableSwitchInsn(int min, int max, Label dflt, Label... labels) { }
-
-    @Override
-    public void visitTypeInsn(int opcode, String type) { }
-
-    @Override
-    public void visitVarInsn(int opcode, int var) { }
-
-    @Override
-    public void visitLabel(Label label) { }
-
-    @Override
-    public AnnotationVisitor visitInsnAnnotation(int typeRef, TypePath typePath, String descriptor, boolean visible) {
-        return null;
-    }
-
-    @Override
-    public void visitTryCatchBlock(Label start, Label end, Label handler, String type) { }
-
-    @Override
-    public AnnotationVisitor visitTryCatchAnnotation(int typeRef, TypePath typePath, String descriptor, boolean visible) {
-        return null;
-    }
-
-    @Override
-    public void visitLocalVariable(String name, String descriptor, String signature, Label start, Label end, int index) { }
-
-    @Override
-    public AnnotationVisitor visitLocalVariableAnnotation(int typeRef, TypePath typePath, Label[] start, Label[] end, int[] index, String descriptor, boolean visible) {
-        return null;
-    }
-
-    @Override
-    public void visitLineNumber(int line, Label start) { }
-
-    @Override
-    public void visitMaxs(int maxStack, int maxLocals) { }
+  @Override
+  public void visitCode() {
+    generateCode();
+    mv.visitMaxs(0, 0);
+  }
 
+  protected abstract void generateCode();
 }
diff --git a/src/main/java/eu/stamp_project/descartes/codemanipulation/MutationClassAdapter.java b/src/main/java/eu/stamp_project/descartes/codemanipulation/MutationClassAdapter.java
index dad890b..d9143b2 100644
--- a/src/main/java/eu/stamp_project/descartes/codemanipulation/MutationClassAdapter.java
+++ b/src/main/java/eu/stamp_project/descartes/codemanipulation/MutationClassAdapter.java
@@ -5,40 +5,39 @@
 import org.pitest.mutationtest.engine.MutationIdentifier;
 import org.pitest.reloc.asm.ClassVisitor;
 import org.pitest.reloc.asm.MethodVisitor;
-import org.pitest.reloc.asm.Type;
 import org.pitest.reloc.asm.commons.GeneratorAdapter;
-import org.pitest.reloc.asm.commons.Method;
 
 public class MutationClassAdapter extends BaseClassVisitor {
 
-    private final MutationIdentifier mutation;
-
-    public MutationClassAdapter(MutationIdentifier mutation, ClassVisitor cv) {
-        super(cv);
-        this.mutation = mutation;
-    }
-
-    private boolean shouldNotTarget(MethodInfo method) {
-        Location location = mutation.getLocation();
-        return !location.getMethodDesc().equals(method.getDescriptor()) || !location.getMethodName().equals(method.getName());
-    }
-
-    @Override
-    public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
-
-        MethodVisitor methodVisitor = cv.visitMethod(access, name, desc, signature, exceptions);
-        MethodInfo method = createMethodInfo(access, name, desc, signature, exceptions);
-        if(shouldNotTarget(method))
-            return methodVisitor;
-
-        final MutationOperator operator = MutationOperator.fromID(mutation.getMutator());
-
-        return new MethodRewritingVisitor(methodVisitor) {
-            @Override
-            protected void generateCode() {
-                GeneratorAdapter adapter = new GeneratorAdapter(mv, method.access, method.name, method.getDescriptor());
-                operator.writeMutant(method, adapter);
-            }
-        };
+  private final MutationIdentifier mutation;
+
+  public MutationClassAdapter(MutationIdentifier mutation, ClassVisitor cv) {
+    super(cv);
+    this.mutation = mutation;
+  }
+
+  private boolean shouldNotTarget(MethodInfo method) {
+    Location location = mutation.getLocation();
+    return !location.getMethodDesc().equals(method.getDescriptor())
+        || !location.getMethodName().equals(method.getName());
+  }
+
+  @Override
+  public MethodVisitor visitMethod(
+      int access, String name, String desc, String signature, String[] exceptions) {
+    MethodVisitor methodVisitor = cv.visitMethod(access, name, desc, signature, exceptions);
+    MethodInfo method = createMethodInfo(access, name, desc, signature, exceptions);
+    if (shouldNotTarget(method)) {
+      return methodVisitor;
     }
+    final MutationOperator operator = MutationOperator.fromIdentifier(mutation.getMutator());
+    return new MethodRewritingVisitor(methodVisitor) {
+      @Override
+      protected void generateCode() {
+        GeneratorAdapter adapter =
+            new GeneratorAdapter(mv, method.access, method.name, method.getDescriptor());
+        operator.writeMutant(method, adapter);
+      }
+    };
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/codemanipulation/MutationPointFinder.java b/src/main/java/eu/stamp_project/descartes/codemanipulation/MutationPointFinder.java
index 814e971..20cfb2f 100644
--- a/src/main/java/eu/stamp_project/descartes/codemanipulation/MutationPointFinder.java
+++ b/src/main/java/eu/stamp_project/descartes/codemanipulation/MutationPointFinder.java
@@ -1,6 +1,9 @@
 package eu.stamp_project.descartes.codemanipulation;
 
 import eu.stamp_project.descartes.operators.MutationOperator;
+import java.util.*;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
 import org.pitest.classinfo.ClassName;
 import org.pitest.mutationtest.engine.Location;
 import org.pitest.mutationtest.engine.MutationDetails;
@@ -9,96 +12,100 @@
 import org.pitest.reloc.asm.Label;
 import org.pitest.reloc.asm.MethodVisitor;
 
-import java.util.*;
-import java.util.function.Predicate;
-import java.util.stream.Collectors;
-
 public class MutationPointFinder extends BaseClassVisitor {
 
-    private final Predicate<MethodInfo> excludedMethods;
-    private final Collection<MutationOperator> operators;
-    private List<MutationDetails> mutationPoints;
-    private  ClassName className;
-    private String source = null;
-
+  private final Predicate<MethodInfo> excludedMethods;
+  private final Collection<MutationOperator> operators;
+  private List<MutationDetails> mutationPoints;
+  private ClassName className;
+  private String source;
 
-    public MutationPointFinder(MutationOperator... operators) {
-        this((method) -> false, List.of(operators));
-    }
+  public MutationPointFinder(MutationOperator... operators) {
+    this((method) -> false, List.of(operators));
+  }
 
-    public MutationPointFinder(Predicate<MethodInfo> excludedMethods, Collection<MutationOperator> operators) {
-        super();
+  public MutationPointFinder(
+      Predicate<MethodInfo> excludedMethods, Collection<MutationOperator> operators) {
+    super();
 
-        Objects.requireNonNull(excludedMethods, "Excluded methods predicate must not be null");
-        this.excludedMethods = excludedMethods;
+    Objects.requireNonNull(excludedMethods, "Excluded methods predicate must not be null");
+    this.excludedMethods = excludedMethods;
 
-        Objects.requireNonNull(operators, "Collection of mutation operators can not be null");
-        if(operators.isEmpty()) {
-            throw new IllegalArgumentException("Collection of mutation operators can not be empty");
-        }
-        this.operators = operators;
+    Objects.requireNonNull(operators, "Collection of mutation operators can not be null");
+    if (operators.isEmpty()) {
+      throw new IllegalArgumentException("Collection of mutation operators can not be empty");
     }
-
-    public List<MutationDetails> findMutationPoints(ClassName className, ClassReader reader) {
-        Objects.requireNonNull(className, "Class name must not be null for mutation finding");
-        this.className = className;
-        mutationPoints = new ArrayList<>();
-        reader.accept(this, 0);
-        return mutationPoints;
+    this.operators = operators;
+  }
+
+  public List<MutationDetails> findMutationPoints(ClassName className, ClassReader reader) {
+    Objects.requireNonNull(className, "Class name must not be null for mutation finding");
+    this.className = className;
+    mutationPoints = new ArrayList<>();
+    reader.accept(this, 0);
+    return mutationPoints;
+  }
+
+  @Override
+  public void visitSource(String source, String debug) {
+    this.source = source;
+  }
+
+  private boolean canNotMutate(MethodInfo method) {
+    // Can not mutate abstract, native methods or constructors or excluded methods
+    return method.hasNoCode() || method.isConstructor() || excludedMethods.test(method);
+  }
+
+  private Set<MutationOperator> getOperatorsFor(MethodInfo method) {
+    return operators.stream().filter(op -> op.canMutate(method)).collect(Collectors.toSet());
+  }
+
+  @Override
+  public MethodVisitor visitMethod(
+      int access, String name, String desc, String signature, String[] exceptions) {
+
+    MethodInfo method = createMethodInfo(access, name, desc, signature, exceptions);
+    if (canNotMutate(method)) {
+      return null;
     }
 
-
-    @Override
-    public void visitSource(String source, String debug) { this.source = source; }
-
-    private boolean canNotMutate(MethodInfo method) {
-        // Can not mutate abstract, native methods or constructors or excluded methods
-        return method.hasNoCode() || method.isConstructor() || excludedMethods.test(method);
-    }
-
-    private Set<MutationOperator> getOperatorsFor(MethodInfo method) {
-        return operators.stream().filter(op -> op.canMutate(method)).collect(Collectors.toSet());
+    final Set<MutationOperator> selectedOperators = getOperatorsFor(method);
+    if (selectedOperators.isEmpty()) {
+      return null;
     }
 
-    @Override
-    public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
+    return new BaseMethodVisitor() {
+      final LineCounter counter = new LineCounter();
 
-        MethodInfo method = createMethodInfo(access, name, desc, signature, exceptions);
-        if(canNotMutate(method)) {
-            return null;
-        }
+      @Override
+      public void visitLineNumber(int line, Label start) {
+        counter.registerLine(line);
+      }
 
-        final Set<MutationOperator> selectedOperators = getOperatorsFor(method);
-        if(selectedOperators.isEmpty()) {
-            return null;
+      @Override
+      public void visitEnd() {
+        if (!counter.empty()) {
+          registerMutations(method, selectedOperators, counter);
         }
-
-        return new BaseMethodVisitor() {
-            final LineCounter counter = new LineCounter();
-
-            @Override
-            public void visitLineNumber(int line, Label start) { counter.registerLine(line); }
-
-            @Override
-            public void visitEnd() {
-                if (!counter.empty())
-                    registerMutations(method, selectedOperators, counter);
-            }
-        };
-    }
-
-    private void registerMutations(MethodInfo method, Set<MutationOperator> operators, LineCounter lines) {
-        Location location = new Location(className, method.getName(), method.getDescriptor());
-        Collection<Integer> indexes = lines.getShiftedRange();
-        mutationPoints.addAll(
-                operators.stream().map(op -> new MutationDetails(
+      }
+    };
+  }
+
+  private void registerMutations(
+      MethodInfo method, Set<MutationOperator> operators, LineCounter lines) {
+    Location location = new Location(className, method.getName(), method.getDescriptor());
+    Collection<Integer> indexes = lines.getShiftedRange();
+    mutationPoints.addAll(
+        operators.stream()
+            .map(
+                op ->
+                    new MutationDetails(
                         new MutationIdentifier(location, indexes, op.getIdentifier()),
                         source,
                         op.getDescription(),
                         lines.getFirstLine(),
                         0 // Top basic block
-                )).collect(Collectors.toSet())
-        );
-    }
+                        ))
+            .collect(Collectors.toSet()));
+  }
 }
-
diff --git a/src/main/java/eu/stamp_project/descartes/codemanipulation/TypeInfo.java b/src/main/java/eu/stamp_project/descartes/codemanipulation/TypeInfo.java
index 86af0a7..c224788 100644
--- a/src/main/java/eu/stamp_project/descartes/codemanipulation/TypeInfo.java
+++ b/src/main/java/eu/stamp_project/descartes/codemanipulation/TypeInfo.java
@@ -1,48 +1,58 @@
 package eu.stamp_project.descartes.codemanipulation;
 
-import org.pitest.reloc.asm.Type;
-
 import java.util.Set;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
+import org.pitest.reloc.asm.Type;
 
 public class TypeInfo extends ElementInfo {
 
-    public static final int UNKNOWN_VERSION = -1;
-
-    private final int version;
-
-    private final Type type;
-    private final Type superType;
-    private final Set<Type> interfaces;
-
-    public TypeInfo(Class<?> type) {
-        super(type.getModifiers(), Type.getType(type).getInternalName(), type.toGenericString());
-        version = UNKNOWN_VERSION;
-        this.type = Type.getType(type);
-        superType = Type.getType(type.getSuperclass());
-        interfaces = Stream.of(type.getInterfaces()).map(Type::getType).collect(Collectors.toSet());
-    }
-
-    public TypeInfo(int version, int access, String name, String signature, String superName, String[] interfaces) {
-        super(access, name, signature);
-        this.version = version;
-        type = Type.getObjectType(name);
-        superType = Type.getObjectType(superName);
-        this.interfaces = toTypeSet(interfaces);
-    }
-
-    public int getVersion() { return version; }
-
-    public Type getSuperType() {  return superType; }
-
-    public Set<Type> getInterfaces() { return interfaces; }
-
-    public boolean canBeAssignedTo(Type other) {
-        return type.equals(other)
-                || superType.equals(other)
-                || interfaces.contains(other)
-                || other.equals(Type.getType(Object.class));
-    }
-
+  public static final int UNKNOWN_VERSION = -1;
+
+  private final int version;
+
+  private final Type type;
+  private final Type superType;
+  private final Set<Type> interfaces;
+
+  public TypeInfo(Class<?> type) {
+    super(type.getModifiers(), Type.getType(type).getInternalName(), type.toGenericString());
+    version = UNKNOWN_VERSION;
+    this.type = Type.getType(type);
+    superType = Type.getType(type.getSuperclass());
+    interfaces = Stream.of(type.getInterfaces()).map(Type::getType).collect(Collectors.toSet());
+  }
+
+  public TypeInfo(
+      int version,
+      int access,
+      String name,
+      String signature,
+      String superName,
+      String[] interfaces) {
+    super(access, name, signature);
+    this.version = version;
+    type = Type.getObjectType(name);
+    superType = Type.getObjectType(superName);
+    this.interfaces = toTypeSet(interfaces);
+  }
+
+  public int getVersion() {
+    return version;
+  }
+
+  public Type getSuperType() {
+    return superType;
+  }
+
+  public Set<Type> getInterfaces() {
+    return interfaces;
+  }
+
+  public boolean canBeAssignedTo(Type other) {
+    return type.equals(other)
+        || superType.equals(other)
+        || interfaces.contains(other)
+        || other.equals(Type.getType(Object.class));
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilter.java b/src/main/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilter.java
index ab09421..6d914e5 100644
--- a/src/main/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilter.java
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilter.java
@@ -1,23 +1,18 @@
 package eu.stamp_project.descartes.interceptors;
 
+import java.util.Optional;
 import org.pitest.bytecode.analysis.MethodTree;
-import org.pitest.mutationtest.engine.Mutater;
 import org.pitest.mutationtest.engine.MutationDetails;
 
-import java.util.Collection;
-import java.util.Optional;
-import java.util.stream.Collectors;
-
 public class AvoidNullInNotNullFilter extends MutationFilter {
 
-    public boolean allows(MutationDetails details) {
-        Optional<MethodTree> method = getMethod(details);
-        return !details.getMutator().equals("null") || (method.isPresent() && canBeNull(method.get()));
-    }
+  public boolean allows(MutationDetails details) {
+    Optional<MethodTree> method = getMethod(details);
+    return !details.getMutator().equals("null") || (method.isPresent() && canBeNull(method.get()));
+  }
 
-    private boolean canBeNull(MethodTree method) {
-        return method.annotations()
-                .stream()
-                .noneMatch(annotation -> annotation.desc.equals("Lorg/jetbrains/annotations/NotNull;"));
-    }
+  private boolean canBeNull(MethodTree method) {
+    return method.annotations().stream()
+        .noneMatch(annotation -> annotation.desc.equals("Lorg/jetbrains/annotations/NotNull;"));
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilterFactory.java b/src/main/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilterFactory.java
index fccc506..0bf66fc 100644
--- a/src/main/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilterFactory.java
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilterFactory.java
@@ -7,23 +7,21 @@
 
 public class AvoidNullInNotNullFilterFactory implements MutationInterceptorFactory {
 
-    private final static String DESCRIPTION = "Avoids null mutation in non-nullable methods, as marked by the Kotlin compiler";
+  private static final String DESCRIPTION =
+      "Avoids null mutation in non-nullable methods, as marked by the Kotlin compiler";
 
-    @Override
-    public MutationInterceptor createInterceptor(InterceptorParameters interceptorParameters) {
-        return new AvoidNullInNotNullFilter();
-    }
+  @Override
+  public MutationInterceptor createInterceptor(InterceptorParameters interceptorParameters) {
+    return new AvoidNullInNotNullFilter();
+  }
 
-    @Override
-    public Feature provides() {
-        return Feature.named("AVOID_NULL")
-                .withDescription(DESCRIPTION)
-                .withOnByDefault(true);
-    }
-
-    @Override
-    public String description() {
-        return DESCRIPTION;
-    }
+  @Override
+  public Feature provides() {
+    return Feature.named("AVOID_NULL").withDescription(DESCRIPTION).withOnByDefault(true);
+  }
 
+  @Override
+  public String description() {
+    return DESCRIPTION;
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/MutationFilter.java b/src/main/java/eu/stamp_project/descartes/interceptors/MutationFilter.java
index 3710287..0968846 100644
--- a/src/main/java/eu/stamp_project/descartes/interceptors/MutationFilter.java
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/MutationFilter.java
@@ -1,5 +1,8 @@
 package eu.stamp_project.descartes.interceptors;
 
+import java.util.Collection;
+import java.util.Optional;
+import java.util.stream.Collectors;
 import org.pitest.bytecode.analysis.ClassTree;
 import org.pitest.bytecode.analysis.MethodTree;
 import org.pitest.mutationtest.build.InterceptorType;
@@ -7,41 +10,38 @@
 import org.pitest.mutationtest.engine.Mutater;
 import org.pitest.mutationtest.engine.MutationDetails;
 
-import java.util.Collection;
-import java.util.Optional;
-import java.util.stream.Collectors;
-
 public abstract class MutationFilter implements MutationInterceptor {
 
-    private ClassTree classTree;
+  private ClassTree classTree;
 
-    @Override
-    public InterceptorType type() {
-        return InterceptorType.FILTER;
-    }
+  @Override
+  public InterceptorType type() {
+    return InterceptorType.FILTER;
+  }
 
-    @Override
-    public void begin(ClassTree classTree) {
-        this.classTree = classTree;
-    }
+  @Override
+  public void begin(ClassTree classTree) {
+    this.classTree = classTree;
+  }
 
-    public Optional<MethodTree> getMethod(MutationDetails details) {
-        return classTree.method(details.getId().getLocation());
-    }
+  public Optional<MethodTree> getMethod(MutationDetails details) {
+    return classTree.method(details.getId().getLocation());
+  }
 
-    public ClassTree getCurrentClass() {
-        return classTree;
-    }
+  public ClassTree getCurrentClass() {
+    return classTree;
+  }
 
-    @Override
-    public void end() {
-        classTree = null;
-    }
+  @Override
+  public void end() {
+    classTree = null;
+  }
 
-    @Override
-    public Collection<MutationDetails> intercept(Collection<MutationDetails> collection, Mutater mutater) {
-        return collection.stream().filter(this::allows).collect(Collectors.toList());
-    }
+  @Override
+  public Collection<MutationDetails> intercept(
+      Collection<MutationDetails> collection, Mutater mutater) {
+    return collection.stream().filter(this::allows).collect(Collectors.toList());
+  }
 
-    public abstract boolean allows(MutationDetails details);
+  public abstract boolean allows(MutationDetails details);
 }
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilter.java b/src/main/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilter.java
index f69d964..a3f0a98 100644
--- a/src/main/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilter.java
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilter.java
@@ -1,60 +1,60 @@
 package eu.stamp_project.descartes.interceptors;
 
+import java.util.*;
 import org.objectweb.asm.tree.AnnotationNode;
 import org.pitest.bytecode.analysis.ClassTree;
 import org.pitest.bytecode.analysis.MethodTree;
 import org.pitest.mutationtest.engine.MutationDetails;
 import org.pitest.reloc.asm.Type;
 
-import java.util.*;
-
 public class SkipDoNotMutateFilter extends MutationFilter {
 
-    @Override
-    public boolean allows(MutationDetails details) {
-        Optional<MethodTree> method = getMethod(details);
-        return method.isPresent() && mayMutate(method.get(), getCurrentClass(), details.getMutator());
-    }
+  @Override
+  public boolean allows(MutationDetails details) {
+    Optional<MethodTree> method = getMethod(details);
+    return method.isPresent() && mayMutate(method.get(), getCurrentClass(), details.getMutator());
+  }
 
-    private boolean mayMutate(MethodTree method, ClassTree owner, String mutator) {
-        Optional<AnnotationNode> doNotMutateAnnotation = getDoNotMutateAnnotation(method.annotations());
-        if(doNotMutateAnnotation.isPresent()){
-            return isMutationAllowed(doNotMutateAnnotation.get(), mutator);
-        }
-        doNotMutateAnnotation = getDoNotMutateAnnotation(owner.annotations());
-        return !doNotMutateAnnotation.isPresent() || isMutationAllowed(doNotMutateAnnotation.get(), mutator);
+  private boolean mayMutate(MethodTree method, ClassTree owner, String mutator) {
+    Optional<AnnotationNode> doNotMutateAnnotation = getDoNotMutateAnnotation(method.annotations());
+    if (doNotMutateAnnotation.isPresent()) {
+      return isMutationAllowed(doNotMutateAnnotation.get(), mutator);
     }
-
-    private Optional<AnnotationNode> getDoNotMutateAnnotation(List<AnnotationNode> annotations) {
-        return annotations.stream().filter(
-                annotation -> Type.getType(annotation.desc).getClassName().endsWith(".DoNotMutate")
-        ).findFirst();
+    doNotMutateAnnotation = getDoNotMutateAnnotation(owner.annotations());
+    return !doNotMutateAnnotation.isPresent()
+        || isMutationAllowed(doNotMutateAnnotation.get(), mutator);
+  }
+
+  private Optional<AnnotationNode> getDoNotMutateAnnotation(List<AnnotationNode> annotations) {
+    return annotations.stream()
+        .filter(annotation -> Type.getType(annotation.desc).getClassName().endsWith(".DoNotMutate"))
+        .findFirst();
+  }
+
+  private boolean isMutationAllowed(AnnotationNode annotation, String mutator) {
+    Set<String> explicitlyForbiddenMutators = forbiddenMutators(annotation);
+    return !explicitlyForbiddenMutators.isEmpty() && !explicitlyForbiddenMutators.contains(mutator);
+  }
+
+  private Set<String> forbiddenMutators(AnnotationNode annotation) {
+    List<Object> values = annotation.values;
+    if (values == null || values.size() < 2) {
+      return Collections.emptySet();
     }
-
-    private boolean isMutationAllowed(AnnotationNode annotation, String mutator) {
-        Set<String> explicitlyForbiddenMutators = forbiddenMutators(annotation);
-        return !explicitlyForbiddenMutators.isEmpty() && !explicitlyForbiddenMutators.contains(mutator);
+    // We only look at the first parameter
+    Object parameter = values.get(1);
+    if (parameter instanceof String) {
+      return Set.of((String) parameter);
     }
-
-    private Set<String> forbiddenMutators(AnnotationNode annotation) {
-        List<Object> values = annotation.values;
-        if(values == null || values.size() < 2) {
-            return Collections.emptySet();
-        }
-        // We only look at the first parameter
-        Object parameter = values.get(1);
-        if(parameter instanceof String) {
-            return Set.of((String)parameter);
-        }
-        if(parameter instanceof List) {
-            HashSet<String> result = new HashSet<>();
-            for(Object val : (List<?>) parameter) {
-                if(val instanceof String) {
-                    result.add((String)val);
-                }
-            }
-            return result;
+    if (parameter instanceof List) {
+      HashSet<String> result = new HashSet<>();
+      for (Object val : (List<?>) parameter) {
+        if (val instanceof String) {
+          result.add((String) val);
         }
-        return Collections.emptySet();
+      }
+      return result;
     }
+    return Collections.emptySet();
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilterFactory.java b/src/main/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilterFactory.java
index 45067dd..df6a10c 100644
--- a/src/main/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilterFactory.java
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilterFactory.java
@@ -7,20 +7,22 @@
 
 public class SkipDoNotMutateFilterFactory implements MutationInterceptorFactory {
 
-    private static final String DESCRIPTION = "Skips any method annotated with an annotation whose simple name is DoNotMutate or declared in a class likewise annotated.";
+  private static final String DESCRIPTION =
+      "Skips any method having an annotation whose simple name is DoNotMutate "
+          + "or any method declared in a class with such annotation.";
 
-    @Override
-    public MutationInterceptor createInterceptor(InterceptorParameters interceptorParameters) {
-        return new SkipDoNotMutateFilter();
-    }
+  @Override
+  public MutationInterceptor createInterceptor(InterceptorParameters interceptorParameters) {
+    return new SkipDoNotMutateFilter();
+  }
 
-    @Override
-    public Feature provides() {
-        return Feature.named("DO_NOT_MUTATE").withDescription(DESCRIPTION).withOnByDefault(true);
-    }
+  @Override
+  public Feature provides() {
+    return Feature.named("DO_NOT_MUTATE").withDescription(DESCRIPTION).withOnByDefault(true);
+  }
 
-    @Override
-    public String description() {
-        return DESCRIPTION;
-    }
+  @Override
+  public String description() {
+    return DESCRIPTION;
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilter.java b/src/main/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilter.java
index f453075..77a3e59 100644
--- a/src/main/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilter.java
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilter.java
@@ -1,36 +1,41 @@
 package eu.stamp_project.descartes.interceptors;
 
+import static org.pitest.bytecode.ASMVersion.ASM_VERSION;
+
 import eu.stamp_project.descartes.codemanipulation.LineCounter;
+import java.util.Optional;
 import org.objectweb.asm.MethodVisitor;
 import org.pitest.bytecode.analysis.MethodTree;
 import org.pitest.mutationtest.engine.MutationDetails;
 
-import java.util.Optional;
-
-import static org.pitest.bytecode.ASMVersion.ASM_VERSION;
-
 public class SkipShortMethodsFilter extends MutationFilter {
 
-    private final int threshold;
-
-    public SkipShortMethodsFilter(int threshold) {
-        this.threshold = threshold;
-    }
+  private final int threshold;
 
-    @Override
-    public boolean allows(MutationDetails details) {
-        Optional<MethodTree> method = getMethod(details);
-        if(!method.isPresent())
-            return false;
-        LineCounter counter = new LineCounter();
+  public SkipShortMethodsFilter(int threshold) {
+    this.threshold = threshold;
+  }
 
-        //For some reason this MethodNode is using ASM's packages instead of the relocated PIT ASM's API
-        method.get().rawNode().accept(new MethodVisitor(ASM_VERSION) {
-            @Override
-            public void visitLineNumber(int line, org.objectweb.asm.Label start) {
-                counter.registerLine(line);
-            }
-        });
-        return counter.getCount() >= threshold;
+  @Override
+  public boolean allows(MutationDetails details) {
+    Optional<MethodTree> method = getMethod(details);
+    if (!method.isPresent()) {
+      return false;
     }
+    LineCounter counter = new LineCounter();
+
+    // For some reason this MethodNode is using ASM's packages instead of the relocated PIT ASM's
+    // API
+    method
+        .get()
+        .rawNode()
+        .accept(
+            new MethodVisitor(ASM_VERSION) {
+              @Override
+              public void visitLineNumber(int line, org.objectweb.asm.Label start) {
+                counter.registerLine(line);
+              }
+            });
+    return counter.getCount() >= threshold;
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilterFactory.java b/src/main/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilterFactory.java
index 4a681c7..540a33e 100644
--- a/src/main/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilterFactory.java
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilterFactory.java
@@ -1,35 +1,38 @@
 package eu.stamp_project.descartes.interceptors;
 
+import java.util.Optional;
 import org.pitest.mutationtest.build.InterceptorParameters;
 import org.pitest.mutationtest.build.MutationInterceptor;
 import org.pitest.mutationtest.build.MutationInterceptorFactory;
 import org.pitest.plugin.Feature;
 import org.pitest.plugin.FeatureParameter;
 
-import java.util.Optional;
-
 public class SkipShortMethodsFilterFactory implements MutationInterceptorFactory {
 
-    protected static final int DEFAULT_THRESHOLD = 5;
-    private static final String DESCRIPTION = "Skips any method shorter than a given number of lines. Default threshold is " + DEFAULT_THRESHOLD;
-    private static final FeatureParameter LINES = FeatureParameter.named("lines").withDescription("Threshold for the size of the methods in lines.");
+  protected static final int DEFAULT_THRESHOLD = 5;
+  private static final String DESCRIPTION =
+      "Skips any method shorter than a given number of lines. Default threshold is "
+          + DEFAULT_THRESHOLD;
+  private static final FeatureParameter LINES =
+      FeatureParameter.named("lines")
+          .withDescription("Threshold for the size of the methods in lines.");
 
-    @Override
-    public MutationInterceptor createInterceptor(InterceptorParameters interceptorParameters) {
-        Optional<Integer> lines = interceptorParameters.getInteger(LINES);
-        return new SkipShortMethodsFilter(lines.orElse(DEFAULT_THRESHOLD));
-    }
+  @Override
+  public MutationInterceptor createInterceptor(InterceptorParameters interceptorParameters) {
+    Optional<Integer> lines = interceptorParameters.getInteger(LINES);
+    return new SkipShortMethodsFilter(lines.orElse(DEFAULT_THRESHOLD));
+  }
 
-    @Override
-    public Feature provides() {
-        return Feature.named("SKIP_SHORT")
-                .withDescription(DESCRIPTION)
-                .withOnByDefault(false)
-                .withParameter(LINES);
-    }
+  @Override
+  public Feature provides() {
+    return Feature.named("SKIP_SHORT")
+        .withDescription(DESCRIPTION)
+        .withOnByDefault(false)
+        .withParameter(LINES);
+  }
 
-    @Override
-    public String description() {
-        return DESCRIPTION;
-    }
+  @Override
+  public String description() {
+    return DESCRIPTION;
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/InstructionMatchers.java b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/InstructionMatchers.java
new file mode 100644
index 0000000..e98a201
--- /dev/null
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/InstructionMatchers.java
@@ -0,0 +1,97 @@
+package eu.stamp_project.descartes.interceptors.stopmethods;
+
+import static org.pitest.bytecode.analysis.InstructionMatchers.opCode;
+import static org.pitest.sequence.Result.result;
+
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.AbstractInsnNode;
+import org.objectweb.asm.tree.MethodInsnNode;
+import org.objectweb.asm.tree.VarInsnNode;
+import org.pitest.sequence.Match;
+import org.pitest.sequence.Result;
+
+public final class InstructionMatchers {
+
+  private InstructionMatchers() {}
+
+  private static Match<AbstractInsnNode> opCodeBetween(int lower, int upper) {
+    return (c, abstractInsnNode) -> {
+      int opcode = abstractInsnNode.getOpcode();
+      return result(opcode >= lower && opcode <= upper, c);
+    };
+  }
+
+  private static Match<AbstractInsnNode> isLoadWithVar(int var) {
+    return (context, instruction) -> {
+      if (!(instruction instanceof VarInsnNode)) {
+        return result(false, context);
+      }
+      VarInsnNode node = (VarInsnNode) instruction;
+      return result(node.getOpcode() == Opcodes.ALOAD && node.var == var, context);
+    };
+  }
+
+
+  public static final Match<AbstractInsnNode> RETURN = opCode(Opcodes.RETURN);
+  public static final Match<AbstractInsnNode> ARETURN = opCode(Opcodes.ARETURN);
+  public static final Match<AbstractInsnNode> ALOAD = opCode(Opcodes.ALOAD);
+  public static final Match<AbstractInsnNode> ILOAD = opCode(Opcodes.ILOAD);
+  public static final Match<AbstractInsnNode> ICONST_0 = opCode(Opcodes.ICONST_0);
+  public static final Match<AbstractInsnNode> GETSTATIC = opCode(Opcodes.GETSTATIC);
+  public static final Match<AbstractInsnNode> PUTSTATIC = opCode(Opcodes.PUTSTATIC);
+  public static final Match<AbstractInsnNode> GETFIELD = opCode(Opcodes.GETFIELD);
+  public static final Match<AbstractInsnNode> PUTFIELD = opCode(Opcodes.PUTFIELD);
+  public static final Match<AbstractInsnNode> NEWARRAY = opCode(Opcodes.NEWARRAY);
+  public static final Match<AbstractInsnNode> ANEWARRAY = opCode(Opcodes.ANEWARRAY);
+  public static final Match<AbstractInsnNode> ACONST_NULL = opCode(Opcodes.ACONST_NULL);
+  public static final Match<AbstractInsnNode> LDC = opCode(Opcodes.LDC);
+  public static final Match<AbstractInsnNode> INVOKESTATIC = opCode(Opcodes.INVOKESTATIC);
+
+  public static final Match<AbstractInsnNode> XRETURN
+      = opCodeBetween(Opcodes.IRETURN, Opcodes.RETURN);
+
+  public static final Match<AbstractInsnNode> XLOAD
+      = opCodeBetween(Opcodes.ILOAD, Opcodes.ALOAD);
+
+  public static final Match<AbstractInsnNode> XLOAD_N
+      = opCodeBetween(21, 45);
+  public static final Match<AbstractInsnNode> ANY_CONSTANT_PUSH
+      = opCodeBetween(Opcodes.ACONST_NULL, 20);
+
+  public static final Match<AbstractInsnNode> LOAD_THIS = isLoadWithVar(0);
+  public static final Match<AbstractInsnNode> LOAD_FIRST_PARAMETER = isLoadWithVar(1);
+
+  public static final Match<AbstractInsnNode> LOAD_ANY_PARAMETER
+      = (context, instruction) ->
+      Result.result(
+          instruction instanceof VarInsnNode && ((VarInsnNode) instruction).var > 0,
+          context
+      );
+
+  public static final Match<AbstractInsnNode> ANY_INVOKE_WITH_RECEIVER
+      = (context, instructionNode) -> {
+        int opcode = instructionNode.getOpcode();
+        return Result.result(
+            opcode == Opcodes.INVOKEVIRTUAL
+                || opcode == Opcodes.INVOKESPECIAL
+                || opcode == Opcodes.INVOKEINTERFACE,
+            context
+        );
+      };
+
+  public static final Match<AbstractInsnNode> KOTLIN_CHECK_PARAMETER_IS_NOT_NULL =
+      (context, instruction) -> {
+        if (!(instruction instanceof MethodInsnNode)) {
+          return result(false, context);
+        }
+        MethodInsnNode node = (MethodInsnNode) instruction;
+        return result(
+            node.getOpcode() == Opcodes.INVOKESTATIC
+                && node.name.equals("checkParameterIsNotNull")
+                && node.owner.equals("kotlin/jvm/internal/Intrinsics")
+                && node.desc.equals("(Ljava/lang/Object;Ljava/lang/String;)V"),
+            context);
+      };
+
+}
+
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/MethodMatcher.java b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/MethodMatcher.java
new file mode 100644
index 0000000..d22e5e0
--- /dev/null
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/MethodMatcher.java
@@ -0,0 +1,54 @@
+package eu.stamp_project.descartes.interceptors.stopmethods;
+
+import static org.pitest.bytecode.analysis.InstructionMatchers.isA;
+
+import java.util.Collection;
+import org.objectweb.asm.tree.*;
+import org.pitest.bytecode.analysis.ClassTree;
+import org.pitest.bytecode.analysis.MethodTree;
+import org.pitest.sequence.QueryParams;
+import org.pitest.sequence.SequenceMatcher;
+import org.pitest.sequence.SequenceQuery;
+
+@FunctionalInterface
+public interface MethodMatcher {
+
+  // MethodTree does not contain a reference to ClassTree.
+  // Some matchers require the class context to classify the method
+  boolean matches(ClassTree classTree, MethodTree methodTree);
+
+  static boolean matchesNameDesc(MethodTree methodTree, String name, String desc) {
+    MethodNode node = methodTree.rawNode();
+    return node.name.equals(name) && node.desc.equals(desc);
+  }
+
+  static boolean matchesAccess(ClassTree classTree, int access) {
+    return (classTree.rawNode().access & access) != 0;
+  }
+
+  static boolean matchesAccess(MethodTree methodTree, int access) {
+    return (methodTree.rawNode().access & access) != 0;
+  }
+
+  static MethodMatcher matcherForNameAndDesc(String name, String desc) {
+    return (classTree, methodTree) -> matchesNameDesc(methodTree, name, desc);
+  }
+
+  static MethodMatcher matcherForAccess(int access) {
+    return (classTree, methodTree) -> matchesAccess(methodTree, access);
+  }
+
+  static MethodMatcher matcherForBodyWithPattern(SequenceQuery<AbstractInsnNode> body) {
+    final SequenceMatcher<AbstractInsnNode> matcher =
+        body.compile(
+            QueryParams.<AbstractInsnNode>params()
+                .withIgnores(
+                    isA(LabelNode.class).or(isA(FrameNode.class)).or(isA(LineNumberNode.class))));
+    return (classTree, methodTree) -> matcher.matches(methodTree.instructions());
+  }
+
+  static MethodMatcher matcherForAnyOf(Collection<MethodMatcher> matchers) {
+    return (classTree, methodTree) ->
+        matchers.stream().anyMatch(matcher -> matcher.matches(classTree, methodTree));
+  }
+}
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodInterceptor.java b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodInterceptor.java
index 16aae89..e5bf8ab 100644
--- a/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodInterceptor.java
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodInterceptor.java
@@ -1,23 +1,21 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
 import eu.stamp_project.descartes.interceptors.MutationFilter;
+import java.util.Optional;
 import org.pitest.bytecode.analysis.MethodTree;
 import org.pitest.mutationtest.engine.MutationDetails;
 
-import java.util.Optional;
-
 public class StopMethodInterceptor extends MutationFilter {
 
-    private final StopMethodMatcher matcher;
-
-    public StopMethodInterceptor(StopMethodMatcher matcher) {
-        this.matcher = matcher;
-    }
+  private final MethodMatcher matcher;
 
-    @Override
-    public boolean allows(MutationDetails details) {
-        Optional<MethodTree> methodTree = getMethod(details);
-        return methodTree.isPresent() && !matcher.matches(getCurrentClass(), methodTree.get());
-    }
+  public StopMethodInterceptor(MethodMatcher matcher) {
+    this.matcher = matcher;
+  }
 
+  @Override
+  public boolean allows(MutationDetails details) {
+    Optional<MethodTree> methodTree = getMethod(details);
+    return methodTree.isPresent() && !matcher.matches(getCurrentClass(), methodTree.get());
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatcher.java b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatcher.java
deleted file mode 100644
index 1445814..0000000
--- a/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatcher.java
+++ /dev/null
@@ -1,58 +0,0 @@
-package eu.stamp_project.descartes.interceptors.stopmethods;
-
-import org.objectweb.asm.tree.*;
-import org.pitest.bytecode.analysis.ClassTree;
-import org.pitest.bytecode.analysis.MethodTree;
-import org.pitest.sequence.QueryParams;
-import org.pitest.sequence.SequenceMatcher;
-import org.pitest.sequence.SequenceQuery;
-
-import java.util.Collection;
-
-import static org.pitest.bytecode.analysis.InstructionMatchers.isA;
-
-@FunctionalInterface
-public interface StopMethodMatcher {
-
-    //MethodTree does not contain a reference to ClassTree.
-    //Some matchers require the class context to classify the method
-    boolean matches(ClassTree classTree, MethodTree methodTree);
-
-    static boolean matchesNameDesc(MethodTree methodTree, String name, String desc) {
-        MethodNode node = methodTree.rawNode();
-        return node.name.equals(name) && node.desc.equals(desc);
-    }
-
-    static boolean matchesAccess(ClassTree classTree, int access) {
-        return (classTree.rawNode().access & access) != 0;
-    }
-
-    static boolean matchesAccess(MethodTree methodTree, int access) {
-        return (methodTree.rawNode().access & access) != 0;
-    }
-
-    static StopMethodMatcher forNameDesc(String name, String desc) {
-        return (classTree, methodTree) -> matchesNameDesc(methodTree, name, desc);
-    }
-
-    static StopMethodMatcher forAccess(int access) {
-        return (classTree, methodTree) -> matchesAccess(methodTree, access);
-    }
-
-    static StopMethodMatcher forBody(SequenceQuery<AbstractInsnNode> body) {
-        final SequenceMatcher<AbstractInsnNode> matcher =
-                body.compile(
-                        QueryParams.<AbstractInsnNode>params()
-                        .withIgnores(
-                                isA(LabelNode.class)
-                                        .or(isA(FrameNode.class))
-                                        .or(isA(LineNumberNode.class)))
-                );
-        return (classTree, methodTree) -> matcher.matches(methodTree.instructions());
-    }
-
-    static  StopMethodMatcher any(Collection<StopMethodMatcher> matchers) {
-        return (classTree, methodTree) ->
-                matchers.stream().anyMatch(matcher -> matcher.matches(classTree, methodTree));
-    }
-}
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatcherInterceptorFactory.java b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatcherInterceptorFactory.java
index db96e730..8b34bcc 100644
--- a/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatcherInterceptorFactory.java
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatcherInterceptorFactory.java
@@ -1,83 +1,73 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
-import org.pitest.mutationtest.build.InterceptorParameters;
-import org.pitest.mutationtest.build.MutationInterceptor;
-import org.pitest.mutationtest.build.MutationInterceptorFactory;
-import org.pitest.plugin.Feature;
-import org.pitest.plugin.FeatureParameter;
+import static eu.stamp_project.descartes.interceptors.stopmethods.StopMethodMatchers.*;
 
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.stream.Collectors;
-
-import static eu.stamp_project.descartes.interceptors.stopmethods.StopMethodMatchers.*;
+import org.pitest.mutationtest.build.InterceptorParameters;
+import org.pitest.mutationtest.build.MutationInterceptor;
+import org.pitest.mutationtest.build.MutationInterceptorFactory;
+import org.pitest.plugin.Feature;
+import org.pitest.plugin.FeatureParameter;
 
 public class StopMethodMatcherInterceptorFactory implements MutationInterceptorFactory {
 
-    private final FeatureParameter EXCEPT;
-
-    private final Map<String, StopMethodMatcher> availableMatchers;
-
-    public StopMethodMatcherInterceptorFactory() {
-
-        availableMatchers = new HashMap<>();
-        availableMatchers.put("empty", isEmptyVoid());
-        availableMatchers.put("enum", isEnumGenerated());
-        availableMatchers.put("to_string", isToString());
-        availableMatchers.put("hash_code", isHashCode());
-        availableMatchers.put("deprecated", isDeprecated());
-        availableMatchers.put("synthetic", isSynthetic());
-        availableMatchers.put("getter", isSimpleGetter());
-        availableMatchers.put("setter", isSimpleSetter());
-        availableMatchers.put("constant", returnsAConstant());
-        availableMatchers.put("delegate", isDelegate());
-        availableMatchers.put("clinit", isStaticInitializer());
-        availableMatchers.put("empty_array", returnsAnEmptyArray());
-        availableMatchers.put("null_return", returnsNull());
-        availableMatchers.put("return_this", returnsThis());
-        availableMatchers.put("return_param", returnsAParameter());
-        availableMatchers.put("kotlin_setter", isKotlinGeneratedSetter());
-
-
-        String description = "Allows to reinsert some stop methods into the analysis. Possible values are: ";
-        description += String.join(", ", availableMatchers.keySet());
-        EXCEPT = FeatureParameter.named("except").withDescription(description);
-    }
-
-    @Override
-    public MutationInterceptor createInterceptor(InterceptorParameters interceptorParameters) {
-        Set<String> matchers = availableMatchers.keySet();
-        List<String> exclusions = interceptorParameters.getList(EXCEPT);
-        if(exclusions != null) {
-            exclusions.forEach(matchers::remove);
-        }
-
-        return new StopMethodInterceptor(
-                StopMethodMatcher.any(
-                        matchers.stream()
-                                .map(availableMatchers::get)
-                                .collect(Collectors.toList())
-                )
-        );
-
-    }
-
-    @Override
-    public Feature provides() {
-        return Feature
-                .named("STOP_METHODS")
-                .withOnByDefault(true)
-                .withDescription("Filters out mutations in methods that are generally of no interest")
-                .withParameter(EXCEPT);
-
+  private final FeatureParameter exceptParameter;
+
+  private final Map<String, MethodMatcher> availableMatchers;
+
+  public StopMethodMatcherInterceptorFactory() {
+
+    availableMatchers = new HashMap<>();
+    availableMatchers.put("empty", IS_EMPTY_VOID);
+    availableMatchers.put("enum", IS_ENUM_GENERATED);
+    availableMatchers.put("to_string", IS_TO_STRING);
+    availableMatchers.put("hash_code", IS_HASH_CODE);
+    availableMatchers.put("deprecated", IS_DEPRECATED);
+    availableMatchers.put("synthetic", IS_SYNTEHTIC);
+    availableMatchers.put("getter", IS_SIMPLE_GETTER);
+    availableMatchers.put("setter", IS_SIMPLE_SETTER);
+    availableMatchers.put("constant", RETURNS_CONSTANT);
+    availableMatchers.put("delegate", IS_DELEGATE);
+    availableMatchers.put("clinit", IS_STATIC_INITIALIZER);
+    availableMatchers.put("empty_array", RETURNS_EMPTY_ARRAY);
+    availableMatchers.put("null_return", RETURNS_NULL);
+    availableMatchers.put("return_this", RETURNS_THIS);
+    availableMatchers.put("return_param", RETURNS_PARAMETER);
+    availableMatchers.put("kotlin_setter", IS_KOTLIN_GENERATED_SETTER);
+
+    String description =
+        "Allows to reinsert some stop methods into the analysis. Possible values are: ";
+    description += String.join(", ", availableMatchers.keySet());
+    exceptParameter = FeatureParameter.named("except").withDescription(description);
+  }
+
+  @Override
+  public MutationInterceptor createInterceptor(InterceptorParameters interceptorParameters) {
+    Set<String> matchers = availableMatchers.keySet();
+    List<String> exclusions = interceptorParameters.getList(exceptParameter);
+    if (exclusions != null) {
+      exclusions.forEach(matchers::remove);
     }
 
-    @Override
-    public String description() {
-        return "Stop methods filter";
-    }
-
-
+    return new StopMethodInterceptor(
+        MethodMatcher.matcherForAnyOf(
+            matchers.stream().map(availableMatchers::get).collect(Collectors.toList())));
+  }
+
+  @Override
+  public Feature provides() {
+    return Feature.named("STOP_METHODS")
+        .withOnByDefault(true)
+        .withDescription("Filters out mutations in methods that are generally of no interest")
+        .withParameter(exceptParameter);
+  }
+
+  @Override
+  public String description() {
+    return "Stop methods filter";
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatchers.java b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatchers.java
index a14d31f..afd79a7 100644
--- a/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatchers.java
+++ b/src/main/java/eu/stamp_project/descartes/interceptors/stopmethods/StopMethodMatchers.java
@@ -1,179 +1,109 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
-import org.objectweb.asm.tree.*;
-import org.pitest.sequence.Match;
-import org.pitest.sequence.SequenceQuery;
-
-import static eu.stamp_project.descartes.interceptors.stopmethods.StopMethodMatcher.*;
-import static org.objectweb.asm.Opcodes.*;
-import static org.pitest.bytecode.analysis.InstructionMatchers.opCode;
+import static eu.stamp_project.descartes.interceptors.stopmethods.InstructionMatchers.*;
 import static org.pitest.sequence.QueryStart.match;
-import static org.pitest.sequence.Result.result;
-
-public class StopMethodMatchers {
-
-    private StopMethodMatchers() { }
-
-    static StopMethodMatcher isEnumGenerated() {
-        return ((classTree, methodTree) -> {
-            ClassNode classNode = classTree.rawNode();
-            //Inside enum declaration
-            if(!classNode.superName.equals("java/lang/Enum"))
-                return false;
-            //Static
-            MethodNode methodNode = methodTree.rawNode();
-            if((methodNode.access & ACC_STATIC) == 0) //Both methods are static, if it is not a static method, then false
-                return false;
-            String returnTypeDescription = "L" + classNode.name + ";";
-            // Class valueOf(String) or  Class[] values()
-            return matchesNameDesc(methodTree,"valueOf", "(Ljava/lang/String;)" + returnTypeDescription)
-                    || matchesNameDesc(methodTree, "values", "()[" + returnTypeDescription)
-                    // Compatibility with other JDKs
-                    || matchesNameDesc(methodTree, "$values", "()[" + returnTypeDescription);
-        });
-    }
-
-    static  StopMethodMatcher isToString() {
-        return forNameDesc("toString", "()Ljava/lang/String;");
-    }
-
-    static StopMethodMatcher isHashCode() {
-        return forNameDesc("hashCode", "()I");
-    }
-
-    static StopMethodMatcher isDeprecated() {
-        return (classTree, methodTree) ->
-                matchesAccess(classTree, ACC_DEPRECATED) || matchesAccess(methodTree, ACC_DEPRECATED);
-    }
-
-    static StopMethodMatcher isEmptyVoid() {
-        return forBody(match(opCode(RETURN)));
-    }
-
-    static StopMethodMatcher isSynthetic() {
-        return (classTree, methodTree) -> methodTree.isSynthetic() && !methodTree.rawNode().name.startsWith("lambda$");
-    }
-
-    static Match<AbstractInsnNode> opCodeBetween(int lower, int upper) {
-        return (c, abstractInsnNode) -> {
-            int opcode = abstractInsnNode.getOpcode();
-            return result(opcode >= lower && opcode <= upper, c);
-        };
-    }
-
-    static StopMethodMatcher isSimpleGetter() {
-        return forBody(
-                (match(opCode(GETSTATIC))
-                        .or(match(opCode(ALOAD)).then(opCode(GETFIELD))))
-                    .then(opCodeBetween(IRETURN, RETURN))
-        );
-    }
-
-    static StopMethodMatcher isSimpleSetter() {
-        // ( (ALOAD [ILOAD..ALOAD] PUTFIELD) | (ILOAD PUTSTATIC) ) (RETURN | ALOAD ARETURN)
-        return forBody(
-                (
-                        (
-                                match(opCode(ALOAD)).then(opCodeBetween(ILOAD, ALOAD)).then(opCode(PUTFIELD))
-                        ).or(match(opCode(ILOAD)).then(opCode(PUTSTATIC)))
-                ).then(
-                        match(opCode(RETURN)).or(match(opCode(ALOAD)).then(opCode(ARETURN))))
-        );
 
-    }
-
-    static StopMethodMatcher returnsAConstant() {
-        return forBody(match(opCodeBetween(1, 20)).then(opCodeBetween(IRETURN, RETURN)));
-    }
-
-    static StopMethodMatcher isDelegate() {
-
-        SequenceQuery<AbstractInsnNode> paramMatch = match(opCodeBetween(21, 45));
-        Match<AbstractInsnNode> returnOpcode = opCodeBetween(IRETURN, RETURN);
-        Match<AbstractInsnNode> anyInvoke = (context, instructionNode) -> {
-            int opcode = instructionNode.getOpcode();
-            return result(opcode == INVOKEVIRTUAL || opcode == INVOKESPECIAL || opcode == INVOKEINTERFACE, context);
-        };
-
-        return forBody((
-                        match(opCode(ALOAD).or(opCode(GETSTATIC)))
-                        .or(match(opCode(ALOAD)).then(opCode(GETFIELD))) //Target on the stack
-                        .zeroOrMore(paramMatch) // Param loop
-                        .then(anyInvoke)
-                        .then(returnOpcode))
-                .or(paramMatch.zeroOrMore(paramMatch).then(opCode(INVOKESTATIC)).then(returnOpcode))
-                .or(match(opCode(INVOKESTATIC)).then(returnOpcode)) //Not expressive enough to match zeroOrMore form the beginning
-        );
-    }
-
-    static StopMethodMatcher isStaticInitializer() {
-        return forNameDesc("<clinit>", "()V");
-    }
-
-    static StopMethodMatcher returnsAnEmptyArray() {
-        return forBody(
-                match(opCode(ICONST_0))
-                        .then(opCode(NEWARRAY).or(opCode(ANEWARRAY)))
-                        .then(opCode(ARETURN))
-        );
-    }
-
-    static StopMethodMatcher returnsNull() {
-        return forBody(
-          match(opCode(ACONST_NULL))
-          .then(opCode(ARETURN)));
-    }
-
-    static StopMethodMatcher returnsThis() {
-        Match<AbstractInsnNode> ALOAD_0 = (context, instruction) ->
-                result((instruction instanceof VarInsnNode) && ((VarInsnNode) instruction).var == 0, context)
-        ;
-        return forBody(match(ALOAD_0).then(opCode(ARETURN)));
-    }
-
-    static StopMethodMatcher returnsAParameter() {
-        // ALOAD_X (DRETURN | FRETURN | IRETURN | LRETURN | ARETURN)
-        Match<AbstractInsnNode> ALOAD_X = (context, instruction) ->
-                result(instruction instanceof VarInsnNode && ((VarInsnNode) instruction).var > 0, context)
-        ;
-        return forBody(match(ALOAD_X).then(opCodeBetween(IRETURN, ARETURN)));
-    }
-
-    static Match<AbstractInsnNode> aload(int var) {
-        return (context, instruction) -> {
-            if(!(instruction instanceof VarInsnNode)) {
-                return result(false, context);
-            }
-            VarInsnNode node = (VarInsnNode) instruction;
-            return result(node.getOpcode() == ALOAD && node.var == var, context);
-        };
-    }
-
-    static StopMethodMatcher isKotlinGeneratedSetter() {
-        Match<AbstractInsnNode> ALOAD_1 = aload(1);
-        Match<AbstractInsnNode> INVOKE_CHECK = (context, instruction) -> {
-            if(!(instruction instanceof MethodInsnNode)) {
-                return result(false, context);
-            }
-            MethodInsnNode node = (MethodInsnNode) instruction;
-            return result(
-                    node.getOpcode() == INVOKESTATIC &&
-                    node.name.equals("checkParameterIsNotNull") &&
-                    node.owner.equals("kotlin/jvm/internal/Intrinsics") &&
-                    node.desc.equals("(Ljava/lang/Object;Ljava/lang/String;)V"),
-                    context
-            );
-        };
-
-        return forBody(
-                match(ALOAD_1)
-                        .then(opCode(LDC))
-                        .then(INVOKE_CHECK)
-                        .then(aload(0))
-                        .then(ALOAD_1)
-                        .then(opCode(PUTFIELD))
-                        .then(opCode(RETURN))
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.tree.MethodNode;
+
+public final class StopMethodMatchers {
+
+  private StopMethodMatchers() {}
+
+  public static final MethodMatcher IS_STATIC_INITIALIZER
+      = MethodMatcher.matcherForNameAndDesc("<clinit>", "()V");
+
+  public static final MethodMatcher IS_HASH_CODE
+      = MethodMatcher.matcherForNameAndDesc("hashCode", "()I");
+
+  public static final MethodMatcher IS_TO_STRING
+      = MethodMatcher.matcherForNameAndDesc("toString", "()Ljava/lang/String;");
+
+  public static final MethodMatcher IS_DEPRECATED
+      = (classTree, methodTree) ->
+        MethodMatcher.matchesAccess(classTree, Opcodes.ACC_DEPRECATED)
+            || MethodMatcher.matchesAccess(methodTree, Opcodes.ACC_DEPRECATED)
+      ;
+
+  public static final MethodMatcher IS_SYNTEHTIC
+      = (classTree, methodTree) ->
+        methodTree.isSynthetic() && !methodTree.rawNode().name.startsWith("lambda$");
+
+  public static final MethodMatcher IS_EMPTY_VOID
+      = MethodMatcher.matcherForBodyWithPattern(match(RETURN));
+
+  public static final MethodMatcher RETURNS_NULL
+      = MethodMatcher.matcherForBodyWithPattern(match(ACONST_NULL).then(ARETURN));
+
+  public static final MethodMatcher RETURNS_THIS
+      = MethodMatcher.matcherForBodyWithPattern(match(LOAD_THIS).then(ARETURN));
+
+  // ALOAD_X (DRETURN | FRETURN | IRETURN | LRETURN | ARETURN)
+  public static final MethodMatcher RETURNS_PARAMETER
+      = MethodMatcher.matcherForBodyWithPattern(match(LOAD_ANY_PARAMETER).then(XRETURN));
+
+  public static final MethodMatcher RETURNS_CONSTANT
+      = MethodMatcher.matcherForBodyWithPattern(match(ANY_CONSTANT_PUSH).then(XRETURN));
+
+
+  public static final MethodMatcher IS_SIMPLE_GETTER
+      = MethodMatcher.matcherForBodyWithPattern(
+        (match(GETSTATIC).or(match(ALOAD).then(GETFIELD))).then(XRETURN));
+
+  public static final MethodMatcher RETURNS_EMPTY_ARRAY
+      = MethodMatcher.matcherForBodyWithPattern(
+        match(ICONST_0).then(NEWARRAY.or(ANEWARRAY)).then(ARETURN));
+
+  // ( (ALOAD [ILOAD..ALOAD] PUTFIELD) | (ILOAD PUTSTATIC) ) (RETURN | ALOAD ARETURN)
+  public static final MethodMatcher IS_SIMPLE_SETTER
+      = MethodMatcher.matcherForBodyWithPattern(
+        ((match(ALOAD).then(XLOAD).then(PUTFIELD))
+                .or(match(ILOAD).then(PUTSTATIC)))
+            .then(match(RETURN).or(match(ALOAD).then(ARETURN))));
+
+  public static final MethodMatcher IS_KOTLIN_GENERATED_SETTER
+      = MethodMatcher.matcherForBodyWithPattern(
+          match(LOAD_FIRST_PARAMETER)
+            .then(LDC)
+            .then(KOTLIN_CHECK_PARAMETER_IS_NOT_NULL)
+            .then(LOAD_THIS)
+            .then(LOAD_FIRST_PARAMETER)
+            .then(PUTFIELD)
+            .then(RETURN));
+
+  public static final MethodMatcher IS_DELEGATE
+      = MethodMatcher.matcherForBodyWithPattern((match(ALOAD.or(GETSTATIC))
+                .or(match(ALOAD).then(GETFIELD)) // Target on the stack
+                .zeroOrMore(match(XLOAD_N)) // Param loop
+                .then(ANY_INVOKE_WITH_RECEIVER)
+                .then(XRETURN))
+            .or(match(XLOAD_N).zeroOrMore(match(XLOAD_N)).then(INVOKESTATIC).then(XRETURN))
+            .or(
+                match(INVOKESTATIC)
+                    .then(XRETURN)) // Not expressive enough to match zeroOrMore form the beginning
         );
-    }
 
+  public static final MethodMatcher IS_ENUM_GENERATED
+      = (classTree, methodTree) -> {
+        ClassNode classNode = classTree.rawNode();
+        // Inside enum declaration
+        if (!classNode.superName.equals("java/lang/Enum")) {
+          return false;
+        }
+        // Static
+        MethodNode methodNode = methodTree.rawNode();
+        if ((methodNode.access & Opcodes.ACC_STATIC) == 0) {
+          // Both methods are static, if it is not a static method, then false
+          return false;
+        }
+        String returnTypeDescription = "L" + classNode.name + ";";
+        // Class valueOf(String) or  Class[] values()
+        return MethodMatcher.matchesNameDesc(
+            methodTree, "valueOf", "(Ljava/lang/String;)" + returnTypeDescription)
+            || MethodMatcher.matchesNameDesc(methodTree, "values", "()[" + returnTypeDescription)
+            // Compatibility with other JDKs
+            || MethodMatcher.matchesNameDesc(
+            methodTree, "$values", "()[" + returnTypeDescription);
+      };
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/ArgumentPropagationOperator.java b/src/main/java/eu/stamp_project/descartes/operators/ArgumentPropagationOperator.java
index 0de301d..a0f7c34 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/ArgumentPropagationOperator.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/ArgumentPropagationOperator.java
@@ -4,18 +4,21 @@
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
 import org.pitest.reloc.asm.commons.GeneratorAdapter;
 
-@Operator(identifier = "argument", description = "Method is rewritten so it only returns the first argument whose " +
-        "type is equal to the return type")
+@Operator(
+    identifier = "argument",
+    description =
+        "Method is rewritten so it only returns the first argument whose "
+            + "type is equal to the return type")
 public class ArgumentPropagationOperator extends MutationOperator {
-    @Override
-    public boolean canMutate(MethodInfo method) {
-        return method.getArgumentTypes().contains(method.getReturnType());
-    }
+  @Override
+  public boolean canMutate(MethodInfo method) {
+    return method.getArgumentTypes().contains(method.getReturnType());
+  }
 
-    @Override
-    protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
-        int index = method.getArgumentTypes().indexOf(method.getReturnType());
-        generator.loadArg(index);
-        generator.returnValue();
-    }
+  @Override
+  protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
+    int index = method.getArgumentTypes().indexOf(method.getReturnType());
+    generator.loadArg(index);
+    generator.returnValue();
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/ConstantMutationOperator.java b/src/main/java/eu/stamp_project/descartes/operators/ConstantMutationOperator.java
index 65259f2..b955407 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/ConstantMutationOperator.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/ConstantMutationOperator.java
@@ -2,95 +2,100 @@
 
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
 import eu.stamp_project.utils.TypeHelper;
-import org.pitest.reloc.asm.Opcodes;
 import org.pitest.reloc.asm.Type;
 import org.pitest.reloc.asm.commons.GeneratorAdapter;
 import org.pitest.reloc.asm.commons.Method;
 
 /**
- * A mutation operator that replaces the method body by a return instruction whose result is the given constant
+ * A mutation operator that replaces the method body by a return instruction whose result is the
+ * given constant.
  */
 public class ConstantMutationOperator extends MutationOperator {
 
-    private final Object constant;
-    private final String id;
-
-    /**
-     * Builds an instance of the operator given a constant value to be used in the return statement.
-     *
-     * @param id The identifier for the instance of the operator. It does not have to coincide with the constant value.
-     * @param constant The constant value to be used
-     */
-    public ConstantMutationOperator(String id, Object constant) {
-        // We actually need the identifier to be able to distinguish the operator.
-        // Besides, there could be a scenario in which two different operators can produce the same constant.
-        if(!TypeHelper.isConstantType(constant.getClass()))
-            throw new IllegalArgumentException();
-        this.constant = constant;
-        this.id = id;
+  private final Object constant;
+  private final String id;
 
+  /**
+   * Builds an instance of the operator given a constant value to be used in the return statement.
+   *
+   * @param id The identifier for the instance of the operator. It does not have to coincide with
+   *     the constant value.
+   * @param constant The constant value to be used
+   */
+  public ConstantMutationOperator(String id, Object constant) {
+    // We actually need the identifier to be able to distinguish the operator.
+    // Besides, there could be a scenario in which two different operators can produce the same
+    // constant.
+    final Class<?> constantType = constant.getClass();
+    if (!TypeHelper.isConstantType(constantType)) {
+      throw new IllegalArgumentException(
+          "Given object of type " + constantType.getName() + " is not a constant");
     }
+    this.constant = constant;
+    this.id = id;
+  }
 
-    /**
-     * Give access to the constant value used by the operator
-     *
-     * @return The constant value used to build the operator instance
-     */
-    public Object getConstant() { return constant; }
-
-    /**
-     * Returns a value indicating whether the operator can transform the given method.
-     * In this case, checks if the return type of the method is the same as the type of the constant value.
-     *
-     * @param method Method to be tested by the operator
-     * @return A boolean value indicating if the return type and the constant value type are the same
-     */
-    @Override
-    public boolean canMutate(MethodInfo method) {
-        Type methodType = method.getReturnType();
-        int typeSort = methodType.getSort();
-        Type constantType = Type.getType(constant.getClass());
-
-        if(typeSort == Type.ARRAY || typeSort == Type.METHOD)
-            return false;
-
-        if(typeSort == Type.OBJECT)
-            return constantType.equals(methodType);
+  /**
+   * Gives access to the constant value used by the operator.
+   *
+   * @return The constant value used to build the operator instance
+   */
+  public Object getConstant() {
+    return constant;
+  }
 
-        return methodType.equals(constantType) ||
-                methodType.equals(wrapperType());
+  /**
+   * Returns a value indicating whether the operator can transform the given method. In this case,
+   * checks if the return type of the method is the same as the type of the constant value.
+   *
+   * @param method Method to be tested by the operator
+   * @return A boolean value indicating if the return type and the constant value type are the same
+   */
+  @Override
+  public boolean canMutate(MethodInfo method) {
+    Type methodType = method.getReturnType();
+    int typeSort = methodType.getSort();
+    Type constantType = Type.getType(constant.getClass());
+    if (typeSort == Type.ARRAY || typeSort == Type.METHOD) {
+      return false;
     }
-
-    /**
-     * Generates the code associated with the mutation.
-     * @param method Method to which the mutation should be applied
-     * @param mv MethodVisitor in charge of code generation.
-     */
-    @Override
-    protected void generateCode(MethodInfo method, GeneratorAdapter mv) {
-        mv.visitLdcInsn(constant);
-        Type returnType = method.getReturnType();
-        Type constantType = Type.getType(constant.getClass());
-        if(constant.getClass() != String.class && returnType.equals(constantType)) {
-            String descriptor = String.format("(%s)L%s;", wrapperType().getInternalName(), returnType.getInternalName());
-            Method valueOfMethod = new Method("valueOf", descriptor);
-            mv.invokeStatic(returnType, valueOfMethod);
-        }
-        mv.returnValue();
+    if (typeSort == Type.OBJECT) {
+      return constantType.equals(methodType);
     }
+    return methodType.equals(constantType) || methodType.equals(wrapperType());
+  }
 
-    private Type wrapperType() {
-        return Type.getType(TypeHelper.unwrap(constant.getClass()));
+  /**
+   * Generates the code associated with the mutation.
+   *
+   * @param method Method to which the mutation should be applied
+   * @param mv MethodVisitor in charge of code generation.
+   */
+  @Override
+  protected void generateCode(MethodInfo method, GeneratorAdapter mv) {
+    mv.visitLdcInsn(constant);
+    Type returnType = method.getReturnType();
+    Type constantType = Type.getType(constant.getClass());
+    if (constant.getClass() != String.class && returnType.equals(constantType)) {
+      String descriptor =
+          String.format("(%s)L%s;", wrapperType().getInternalName(), returnType.getInternalName());
+      Method valueOfMethod = new Method("valueOf", descriptor);
+      mv.invokeStatic(returnType, valueOfMethod);
     }
+    mv.returnValue();
+  }
 
-    @Override
-    public String getIdentifier() {
-        return id;
-    }
+  private Type wrapperType() {
+    return Type.getType(TypeHelper.unwrap(constant.getClass()));
+  }
 
-    @Override
-    public String getDescription() {
-        return "All method instructions replaced by: return " + id;
-    }
+  @Override
+  public String getIdentifier() {
+    return id;
+  }
 
+  @Override
+  public String getDescription() {
+    return "All method instructions replaced by: return " + id;
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/EmptyArrayMutationOperator.java b/src/main/java/eu/stamp_project/descartes/operators/EmptyArrayMutationOperator.java
index f67bf62..f71dbc7 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/EmptyArrayMutationOperator.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/EmptyArrayMutationOperator.java
@@ -5,24 +5,27 @@
 import org.pitest.reloc.asm.Type;
 import org.pitest.reloc.asm.commons.GeneratorAdapter;
 
-@Operator(identifier = "empty", description = "Method body replaced by instructions that returns an empty array of the corresponding type")
+@Operator(
+    identifier = "empty",
+    description =
+        "Method body is modified to return an empty array of the corresponding type")
 public class EmptyArrayMutationOperator extends MutationOperator {
 
-    @Override
-    public boolean canMutate(MethodInfo method) {
-        return method.getReturnType().getSort() == Type.ARRAY;
-    }
+  @Override
+  public boolean canMutate(MethodInfo method) {
+    return method.getReturnType().getSort() == Type.ARRAY;
+  }
 
-    @Override
-    protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
-        Type arrayType = method.getReturnType();
-        for (int i = arrayType.getDimensions(); i > 0; i--) {
-            generator.push(0);
-        }
-        //Removing the first [ results in the element type for a one-dimensional array
-        // or an array with one dimension less for multi-arrays
-        Type lowerDimensionType = Type.getType(arrayType.getDescriptor().substring(1));
-        generator.newArray(lowerDimensionType);
-        generator.returnValue();
+  @Override
+  protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
+    Type arrayType = method.getReturnType();
+    for (int i = arrayType.getDimensions(); i > 0; i--) {
+      generator.push(0);
     }
+    // Removing the first [ results in the element type for a one-dimensional array
+    // or an array with one dimension less for multi-arrays
+    Type lowerDimensionType = Type.getType(arrayType.getDescriptor().substring(1));
+    generator.newArray(lowerDimensionType);
+    generator.returnValue();
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/InvalidOperatorException.java b/src/main/java/eu/stamp_project/descartes/operators/InvalidOperatorException.java
index 1d4c548..42a47a3 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/InvalidOperatorException.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/InvalidOperatorException.java
@@ -1,13 +1,12 @@
 package eu.stamp_project.descartes.operators;
 
-
 public class InvalidOperatorException extends RuntimeException {
 
-    public InvalidOperatorException(String message, Throwable cause) {
-        super(message, cause);
-    }
+  public InvalidOperatorException(String message, Throwable cause) {
+    super(message, cause);
+  }
 
-    public InvalidOperatorException(String message) {
-        super(message);
-    }
+  public InvalidOperatorException(String message) {
+    super(message);
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/MutationOperator.java b/src/main/java/eu/stamp_project/descartes/operators/MutationOperator.java
index 3e4feb2..20087e4 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/MutationOperator.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/MutationOperator.java
@@ -3,66 +3,72 @@
 import eu.stamp_project.descartes.annotations.Operator;
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
 import eu.stamp_project.descartes.operators.parsing.LiteralParser;
-import org.pitest.reloc.asm.commons.GeneratorAdapter;
-
 import java.lang.reflect.InvocationTargetException;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
+import org.pitest.reloc.asm.commons.GeneratorAdapter;
 
 public abstract class MutationOperator {
 
-    public abstract boolean canMutate(MethodInfo method);
+  public abstract boolean canMutate(MethodInfo method);
 
-    public void writeMutant(MethodInfo method, GeneratorAdapter code) {
-        if(!canMutate(method)) {
-            throw new IllegalArgumentException("Operator " + getIdentifier() + " can not mutate method " + method.getDescriptor());
-        }
-        generateCode(method, code);
+  public void writeMutant(MethodInfo method, GeneratorAdapter code) {
+    if (!canMutate(method)) {
+      throw new IllegalArgumentException(
+          "Operator " + getIdentifier() + " can not mutate method " + method.getDescriptor());
     }
+    generateCode(method, code);
+  }
 
-    protected abstract void generateCode(MethodInfo method, GeneratorAdapter generator);
+  protected abstract void generateCode(MethodInfo method, GeneratorAdapter generator);
 
-    public String getIdentifier() {
-        return getClass().getAnnotation(Operator.class).identifier();
-    }
+  public String getIdentifier() {
+    return getClass().getAnnotation(Operator.class).identifier();
+  }
 
-    public String getDescription() {
-        return getClass().getAnnotation(Operator.class).description();
-    }
+  public String getDescription() {
+    return getClass().getAnnotation(Operator.class).description();
+  }
 
-    public static MutationOperator fromID(String id) {
-        id = id.trim();
-        if(ID_2_CLASS.containsKey(id)) {
-            Class<?> operatorClass = ID_2_CLASS.get(id);
-            try {
-                return (MutationOperator) operatorClass.getConstructor().newInstance();
-            } catch (InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException exc) {
-                throw new AssertionError("Could not invoke default constructor for class " + operatorClass.getName(), exc);
-            }
-        }
-        LiteralParser parser = new LiteralParser();
-        LiteralParser.Result result = parser.parse(id);
-        if(result.hasError()) {
-            throw new InvalidOperatorException("Provided identifier \"" + id + "\" is not a valid mutation operator identidier.");
-        }
-        return new ConstantMutationOperator(id, result.getValue());
+  public static MutationOperator fromIdentifier(final String id) {
+    final String trimmedId = id.trim();
+    if (ID_2_CLASS.containsKey(trimmedId)) {
+      Class<?> operatorClass = ID_2_CLASS.get(trimmedId);
+      try {
+        return (MutationOperator) operatorClass.getConstructor().newInstance();
+      } catch (InstantiationException
+          | IllegalAccessException
+          | InvocationTargetException
+          | NoSuchMethodException exc) {
+        throw new AssertionError(
+            "Could not invoke default constructor for class " + operatorClass.getName(), exc);
+      }
+    }
+    LiteralParser parser = new LiteralParser();
+    LiteralParser.Result result = parser.parse(trimmedId);
+    if (result.hasError()) {
+      throw new InvalidOperatorException(
+          "Provided identifier \"" + trimmedId + "\" is not a valid mutation operator identidier.");
     }
+    return new ConstantMutationOperator(trimmedId, result.getValue());
+  }
 
-    private final static Class<?>[] PARAMETERLESS_OPERATORS =  {
-            EmptyArrayMutationOperator.class,
-            NewInstanceMutationOperator.class,
-            NullMutationOperator.class,
-            OptionalMutationOperator.class,
-            VoidMutationOperator.class,
-            ArgumentPropagationOperator.class,
-            ThisMutationOperator.class
-    };
+  private static final Class<?>[] PARAMETERLESS_OPERATORS = {
+    EmptyArrayMutationOperator.class,
+    NewInstanceMutationOperator.class,
+    NullMutationOperator.class,
+    OptionalMutationOperator.class,
+    VoidMutationOperator.class,
+    ArgumentPropagationOperator.class,
+    ThisMutationOperator.class
+  };
 
-    private final static Map<String, Class<?>> ID_2_CLASS;
-    static {
-        ID_2_CLASS = new HashMap<>(PARAMETERLESS_OPERATORS.length);
-        Arrays.stream(PARAMETERLESS_OPERATORS).forEach(opc ->
-                ID_2_CLASS.put(opc.getAnnotation(Operator.class).identifier(), opc));
-    }
+  private static final Map<String, Class<?>> ID_2_CLASS;
+
+  static {
+    ID_2_CLASS = new HashMap<>(PARAMETERLESS_OPERATORS.length);
+    Arrays.stream(PARAMETERLESS_OPERATORS)
+        .forEach(opc -> ID_2_CLASS.put(opc.getAnnotation(Operator.class).identifier(), opc));
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/NewInstanceMutationOperator.java b/src/main/java/eu/stamp_project/descartes/operators/NewInstanceMutationOperator.java
index 64286e7..c67cc64 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/NewInstanceMutationOperator.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/NewInstanceMutationOperator.java
@@ -1,111 +1,105 @@
 package eu.stamp_project.descartes.operators;
 
-import java.lang.reflect.Constructor;
-import java.lang.reflect.Modifier;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Map;
-import java.util.Queue;
-import java.util.Set;
-
 import eu.stamp_project.descartes.annotations.Operator;
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Modifier;
+import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
 import org.pitest.reloc.asm.Opcodes;
 import org.pitest.reloc.asm.Type;
 import org.pitest.reloc.asm.commons.GeneratorAdapter;
 
 /**
- * Replaces the method body with a return statement, which generates an instance of the specified return type.
- * <br>
- * This is currently working for classes with parameterless constructors and a few well-known Java interfaces.
+ * Replaces the method body with a return statement, which generates an instance of the specified
+ * return type. <br>
+ * This is currently working for classes with parameterless constructors and a few well-known Java
+ * interfaces.
  */
-@Operator(identifier = "new", description = "Method body replaced by instructions to return an instance of the class using a constructor with no parameters")
+@Operator(
+    identifier = "new",
+    description =
+        "Method body replaced by instructions to return an instance "
+            + "of the class using a constructor with no parameters")
 public class NewInstanceMutationOperator extends MutationOperator {
 
-    private static final Map<Class<?>, Class<?>> ALTERNATIVE_RETURN_CLASS_BY_TYPE = new HashMap<>();
-
-    static {
-        ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(Collection.class, ArrayList.class);
-        ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(Iterable.class, ArrayList.class);
-        ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(List.class, ArrayList.class);
-        ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(Queue.class, LinkedList.class);
-        ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(Set.class, HashSet.class);
-        ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(Map.class, HashMap.class);
-    }
-
-    /**
-     * Returns a value indicating whether the operator can transform the given method.
-     */
-    @Override
-    public boolean canMutate(MethodInfo method) {
-        try {
-            Class<?> returnClass = getAppropriateReturnClass(method);
-
-            if(returnClass.equals(String.class)
-                    || !belongsToJavaPackages(returnClass)
-                    || Modifier.isAbstract(returnClass.getModifiers())) {
-                return false;
-            }
-            for (Constructor<?> publicConstructor : returnClass.getConstructors()) {
-                if (publicConstructor.getParameters().length == 0) {
-                    return true;
-                }
-            }
-            return false;
-        }
-        catch (ClassNotFoundException e) {
-            return false;
+  private static final Map<Class<?>, Class<?>> ALTERNATIVE_RETURN_CLASS_BY_TYPE =
+      new ConcurrentHashMap<>();
+
+  static {
+    ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(Collection.class, ArrayList.class);
+    ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(Iterable.class, ArrayList.class);
+    ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(List.class, ArrayList.class);
+    ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(Queue.class, LinkedList.class);
+    ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(Set.class, HashSet.class);
+    ALTERNATIVE_RETURN_CLASS_BY_TYPE.put(Map.class, HashMap.class);
+  }
+
+  /** Returns a value indicating whether the operator can transform the given method. */
+  @Override
+  public boolean canMutate(MethodInfo method) {
+    try {
+      Class<?> returnClass = getAppropriateReturnClass(method);
+
+      if (returnClass.equals(String.class)
+          || !belongsToJavaPackages(returnClass)
+          || Modifier.isAbstract(returnClass.getModifiers())) {
+        return false;
+      }
+      for (Constructor<?> publicConstructor : returnClass.getConstructors()) {
+        if (publicConstructor.getParameters().length == 0) {
+          return true;
         }
+      }
+      return false;
+    } catch (ClassNotFoundException e) {
+      return false;
     }
+  }
 
-    private boolean belongsToJavaPackages(Class<?> aClass) {
-        Package classPackage = aClass.getPackage();
-        if (classPackage == null) {
-            return false;
-        }
-        String[] nameParts = classPackage.getName().split("\\.");
-        return nameParts.length >= 1 && nameParts[0].equals("java");
+  private boolean belongsToJavaPackages(Class<?> givenClass) {
+    Package classPackage = givenClass.getPackage();
+    if (classPackage == null) {
+      return false;
     }
-
-    /**
-     * Returns the specified class or a class which is assignable from this class.
-     */
-    protected static Class<?> getAppropriateReturnClass(MethodInfo method) throws ClassNotFoundException {
-        return getAppropriateReturnClass(method.getReturnType().getClassName());
+    String[] nameParts = classPackage.getName().split("\\.");
+    return nameParts.length >= 1 && nameParts[0].equals("java");
+  }
+
+  /** Returns the specified class or a class which is assignable from this class. */
+  protected static Class<?> getAppropriateReturnClass(MethodInfo method)
+      throws ClassNotFoundException {
+    return getAppropriateReturnClass(method.getReturnType().getClassName());
+  }
+
+  /** Returns the specified class or a class which is assignable from this class. */
+  protected static Class<?> getAppropriateReturnClass(String className)
+      throws ClassNotFoundException {
+    Class<?> originalClass = Class.forName(className);
+
+    if (ALTERNATIVE_RETURN_CLASS_BY_TYPE.containsKey(originalClass)) {
+      return ALTERNATIVE_RETURN_CLASS_BY_TYPE.get(originalClass);
     }
 
-    /**
-     * Returns the specified class or a class which is assignable from this class.
-     */
-    protected static Class<?> getAppropriateReturnClass(String className) throws ClassNotFoundException {
-        Class<?> originalClass = Class.forName(className);
+    return originalClass;
+  }
 
-        if (ALTERNATIVE_RETURN_CLASS_BY_TYPE.containsKey(originalClass)) {
-            return ALTERNATIVE_RETURN_CLASS_BY_TYPE.get(originalClass);
-        }
+  @Override
+  protected void generateCode(MethodInfo method, GeneratorAdapter mv) {
+    Class<?> appropriateReturnClass = null;
 
-        return originalClass;
+    try {
+      appropriateReturnClass = getAppropriateReturnClass(method);
+    } catch (ClassNotFoundException e) {
+      throw new IllegalStateException(e);
     }
 
-    @Override
-    protected void generateCode(MethodInfo method, GeneratorAdapter mv) {
-        Class<?> appropriateReturnClass = null;
+    Type appropriateReturnType = Type.getType(appropriateReturnClass);
 
-        try {
-            appropriateReturnClass = getAppropriateReturnClass(method);
-        } catch (ClassNotFoundException e) {
-            throw new IllegalStateException(e);
-        }
-
-        Type appropriateReturnType = Type.getType(appropriateReturnClass);
-
-        mv.visitTypeInsn(Opcodes.NEW, appropriateReturnType.getInternalName());
-        mv.visitInsn(Opcodes.DUP);
-        mv.visitMethodInsn(Opcodes.INVOKESPECIAL, appropriateReturnType.getInternalName(), "<init>", "()V", false);
-        mv.visitInsn(Opcodes.ARETURN);
-    }
+    mv.visitTypeInsn(Opcodes.NEW, appropriateReturnType.getInternalName());
+    mv.visitInsn(Opcodes.DUP);
+    mv.visitMethodInsn(
+        Opcodes.INVOKESPECIAL, appropriateReturnType.getInternalName(), "<init>", "()V", false);
+    mv.visitInsn(Opcodes.ARETURN);
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/NullMutationOperator.java b/src/main/java/eu/stamp_project/descartes/operators/NullMutationOperator.java
index 46737c8..2201efc 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/NullMutationOperator.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/NullMutationOperator.java
@@ -6,17 +6,17 @@
 import org.pitest.reloc.asm.commons.GeneratorAdapter;
 
 @Operator(identifier = "null", description = "All method instructions replaced by: return null;")
-public class NullMutationOperator extends MutationOperator{
+public class NullMutationOperator extends MutationOperator {
 
-    @Override
-    public boolean canMutate(MethodInfo method) {
-        int target = method.getReturnType().getSort();
-        return  target == Type.OBJECT || target == Type.ARRAY;
-    }
+  @Override
+  public boolean canMutate(MethodInfo method) {
+    int target = method.getReturnType().getSort();
+    return target == Type.OBJECT || target == Type.ARRAY;
+  }
 
-    @Override
-    protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
-        generator.push((Type)null);
-        generator.returnValue();
-    }
+  @Override
+  protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
+    generator.push((Type) null);
+    generator.returnValue();
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/OptionalMutationOperator.java b/src/main/java/eu/stamp_project/descartes/operators/OptionalMutationOperator.java
index 338d9d4..2f54091 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/OptionalMutationOperator.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/OptionalMutationOperator.java
@@ -1,28 +1,29 @@
 package eu.stamp_project.descartes.operators;
 
+import static org.pitest.reloc.asm.Type.getType;
+
 import eu.stamp_project.descartes.annotations.Operator;
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
+import java.util.Optional;
 import org.pitest.reloc.asm.Type;
 import org.pitest.reloc.asm.commons.GeneratorAdapter;
 import org.pitest.reloc.asm.commons.Method;
 
-import java.util.Optional;
-
-import static org.pitest.reloc.asm.Type.getType;
-
-@Operator(identifier = "optional", description = "All method instructions replaced by: return Optional.empty();")
+@Operator(
+    identifier = "optional",
+    description = "All method instructions replaced by: return Optional.empty();")
 public class OptionalMutationOperator extends MutationOperator {
 
-    @Override
-    public boolean canMutate(MethodInfo method) {
-        return method.getReturnType().equals(getType(Optional.class));
-    }
+  @Override
+  public boolean canMutate(MethodInfo method) {
+    return method.getReturnType().equals(getType(Optional.class));
+  }
 
-    @Override
-    protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
-        Type optionalType = Type.getType(Optional.class);
-        Method emptyMethod = new Method("empty", "()L" + optionalType.getInternalName() + ";");
-        generator.invokeStatic(optionalType, emptyMethod);
-        generator.returnValue();
-    }
+  @Override
+  protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
+    Type optionalType = Type.getType(Optional.class);
+    Method emptyMethod = new Method("empty", "()L" + optionalType.getInternalName() + ";");
+    generator.invokeStatic(optionalType, emptyMethod);
+    generator.returnValue();
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/ThisMutationOperator.java b/src/main/java/eu/stamp_project/descartes/operators/ThisMutationOperator.java
index d284b78..ca745ed 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/ThisMutationOperator.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/ThisMutationOperator.java
@@ -6,14 +6,14 @@
 
 @Operator(identifier = "this", description = "Replaces the method by return this;")
 public class ThisMutationOperator extends MutationOperator {
-    @Override
-    public boolean canMutate(MethodInfo method) {
-        return !method.isStatic() && method.getOwner().canBeAssignedTo(method.getReturnType());
-    }
+  @Override
+  public boolean canMutate(MethodInfo method) {
+    return !method.isStatic() && method.getOwner().canBeAssignedTo(method.getReturnType());
+  }
 
-    @Override
-    protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
-        generator.loadThis();
-        generator.returnValue();
-    }
+  @Override
+  protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
+    generator.loadThis();
+    generator.returnValue();
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/VoidMutationOperator.java b/src/main/java/eu/stamp_project/descartes/operators/VoidMutationOperator.java
index 74d3b47..b262a55 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/VoidMutationOperator.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/VoidMutationOperator.java
@@ -8,15 +8,13 @@
 @Operator(identifier = "void", description = "Removed all instructions in the method")
 public final class VoidMutationOperator extends MutationOperator {
 
-    @Override
-    public boolean canMutate(MethodInfo method) {
-        //TODO: Detect methods that contain only calls to logging classes or System.out --> this should be done in an interceptor
-        return !method.isConstructor() && method.getReturnType().equals(Type.VOID_TYPE);
-    }
-
-    @Override
-    protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
-        generator.returnValue();
-    }
+  @Override
+  public boolean canMutate(MethodInfo method) {
+    return !method.isConstructor() && method.getReturnType().equals(Type.VOID_TYPE);
+  }
 
+  @Override
+  protected void generateCode(MethodInfo method, GeneratorAdapter generator) {
+    generator.returnValue();
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/parsing/LiteralParser.java b/src/main/java/eu/stamp_project/descartes/operators/parsing/LiteralParser.java
index f503006..5807cfd 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/parsing/LiteralParser.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/parsing/LiteralParser.java
@@ -1,160 +1,187 @@
 package eu.stamp_project.descartes.operators.parsing;
 
+import static eu.stamp_project.descartes.operators.parsing.TokenType.BOOLEAN_LITERAL;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.CHAR_LITERAL;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.END_OF_FILE;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.INTEGRAL_LITERAL;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.LEFT_PARENTHESIS;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.MINUS_SIGN;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.NUMERIC_LITERAL;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.RIGHT_PARENTHESIS;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.STRING_LITERAL;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.TYPE_IDENTIFIER;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.getNumericType;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.getRadix;
+import static eu.stamp_project.descartes.operators.parsing.TokenType.typeToLiteral;
+import static java.util.Objects.requireNonNull;
+import static org.apache.commons.lang3.StringUtils.isBlank;
+
 import java.io.IOException;
 import java.io.StringReader;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.NoSuchElementException;
 
-import static eu.stamp_project.descartes.operators.parsing.TokenType.*;
-import static java.util.Objects.requireNonNull;
-
 public class LiteralParser {
 
-    public static class Result {
-
-        private final Object value;
-        private final String error;
-
-        private Result(Object value, String error) { this.value = value; this.error = error;  }
-
-        public static Result ok(Object value) {
-            requireNonNull(value, "Value can not be null in successful parsing result");
-            return new Result(value, null);
-        }
-
-        public static Result error(String error) {
-            if(isNullOrBlank(error))
-                throw new IllegalArgumentException("Resulting error message can not be null, empty or blank.");
-            return new Result(null, error);
-        }
+  public static class Result {
 
-        public boolean hasError() { return error != null; }
+    private final Object value;
+    private final String error;
 
-        public Object getValue() {
-            if(hasError())
-                throw new NoSuchElementException("Parsing resulted in error. No value was produced.");
-            return value;
-        }
+    private Result(Object value, String error) {
+      this.value = value;
+      this.error = error;
+    }
 
-        public String getError() {
-            return hasError()?error:null;
-        }
+    public static Result ok(Object value) {
+      requireNonNull(value, "Value can not be null in successful parsing result");
+      return new Result(value, null);
     }
 
-    private Token lookahead;
-
-    private LiteralLexer lexer;
-
-    public Result parse(String line) {
-        if(isNullOrBlank(line))
-            return Result.error("Input is null or blank");
-        try {
-
-            lexer = new LiteralLexer(new StringReader(line));
-
-            Result result = null;
-
-            next();
-
-            if (lookahead.is(CHAR_LITERAL)) {
-                result = Result.ok(lookahead.getLexeme().charAt(0));
-            } else if (lookahead.is(STRING_LITERAL)) {
-                result = Result.ok(lookahead.getLexeme());
-            } else if (lookahead.is(BOOLEAN_LITERAL)) {
-                result = Result.ok(Boolean.valueOf(lookahead.getLexeme()));
-            } else if (lookahead.is(NUMERIC_LITERAL)) {
-                result = Result.ok(tokenToNumber(lookahead));
-            } else if (lookahead.is(MINUS_SIGN)) {
-                result = negativeNumericLiteral();
-            } else if (lookahead.is(LEFT_PARENTHESIS)) {
-                result = byteOrShortLiteral();
-            }
-            if(result == null) {
-                return Result.error("Invalid literal notation");
-            }
-            if (!result.hasError()) {
-                next();
-                if (!lookahead.is(END_OF_FILE)) {
-                    result = Result.error("End of line expected.");
-                }
-            }
-            return result;
-        }
-        catch (Exception exc) {
-             return Result.error("Unexpected exception " + exc);
-        }
+    public static Result error(String error) {
+      if (isBlank(error)) {
+        throw new IllegalArgumentException(
+            "Resulting error message can not be null, empty or blank.");
+      }
+      return new Result(null, error);
     }
 
-    private Result negativeNumericLiteral() throws IOException {
-        next();
-        if(lookahead.is(NUMERIC_LITERAL)) {
-            return Result.ok(tokenToNumber(new Token(lookahead.getType(), "-" + lookahead.getLexeme())));
-        }
-        return Result.error("Expecting numeric literal after minus sign.");
+    public boolean hasError() {
+      return error != null;
     }
 
-    private Result byteOrShortLiteral() throws IOException {
-        next();
-        if(!lookahead.is(TYPE_IDENTIFIER)) {
-            return Result.error("Expecting type names byte or short, got: " + lookahead.getLexeme());
-        }
-        int resultType = lookahead.getType();
-        String prefix = "";
-        next();
-        if(!lookahead.is(RIGHT_PARENTHESIS)) {
-            return Result.error("Expecting right parenthesis, got: " + lookahead.getLexeme());
-        }
-        next();
-        if(lookahead.is(MINUS_SIGN)) {
-            prefix = "-";
-            next();
-        }
-        if(!lookahead.is(INTEGRAL_LITERAL)){
-            return Result.error("Expecting an integral literal, got: " + lookahead.getLexeme());
-        }
+    public Object getValue() {
+      if (hasError()) {
+        throw new NoSuchElementException("Parsing resulted in error. No value was produced.");
+      }
+      return value;
+    }
 
-        return Result.ok(tokenToNumber(new Token( typeToLiteral(resultType) | getRadix(lookahead.getType()) , prefix + lookahead.getLexeme())));
+    public String getError() {
+      return hasError() ? error : null;
     }
+  }
 
-    public void next() throws IOException { lookahead = lexer.nextToken(); }
+  private Token lookahead;
 
+  private LiteralLexer lexer;
 
-    private Object tokenToNumber(Token token) {
-        Class<?> numericType = getNumericType(token.getType());
-        if(token.is(INTEGRAL_LITERAL)) {
-            return integerValueOf(numericType, token.getLexeme(), getRadix(token.getType()));
-        }
-        return valueOf(numericType, token.getLexeme());
+  public Result parse(String line) {
+    if (isBlank(line)) {
+      return Result.error("Input is null or blank");
     }
-
-    private Object valueOf(Class<?> type, String value) {
-        try {
-            Method method = type.getDeclaredMethod("valueOf", String.class);
-            return method.invoke(null, value);
-        }
-        catch (NoSuchMethodException | IllegalAccessException exc) {
-            throw new AssertionError("Class " + type.getName() + " expected to have an accessible valueOf(String) method");
-        }
-        catch (InvocationTargetException exc) {
-            throw new IllegalArgumentException("Error while obtaining value of type " + type.getName() + " from string " + value, exc);
+    try {
+      lexer = new LiteralLexer(new StringReader(line));
+      Result result = null;
+      next();
+      if (lookahead.is(CHAR_LITERAL)) {
+        result = Result.ok(lookahead.getLexeme().charAt(0));
+      } else if (lookahead.is(STRING_LITERAL)) {
+        result = Result.ok(lookahead.getLexeme());
+      } else if (lookahead.is(BOOLEAN_LITERAL)) {
+        result = Result.ok(Boolean.valueOf(lookahead.getLexeme()));
+      } else if (lookahead.is(NUMERIC_LITERAL)) {
+        result = Result.ok(tokenToNumber(lookahead));
+      } else if (lookahead.is(MINUS_SIGN)) {
+        result = negativeNumericLiteral();
+      } else if (lookahead.is(LEFT_PARENTHESIS)) {
+        result = byteOrShortLiteral();
+      }
+      if (result == null) {
+        return Result.error("Invalid literal notation");
+      }
+      if (!result.hasError()) {
+        next();
+        if (!lookahead.is(END_OF_FILE)) {
+          result = Result.error("End of line expected.");
         }
+      }
+      return result;
+    } catch (Exception exc) {
+      return Result.error("Unexpected exception " + exc);
     }
+  }
 
-    private Object integerValueOf(Class<?> type, String value, int radix) {
-        try {
-            Method method = type.getDeclaredMethod("valueOf", String.class, int.class);
-            return method.invoke(null, value, radix);
-        }
-        catch (NoSuchMethodException | IllegalAccessException exc) {
-            throw new AssertionError("Class " + type.getName() + " expected to have an accessible valueOf(String, int) method");
-        }
-        catch (InvocationTargetException exc) {
-            throw new IllegalArgumentException("Error while obtaining value of type " + type.getName() + " from string " + value + " using radix " + radix, exc);
-        }
+  private Result negativeNumericLiteral() throws IOException {
+    next();
+    if (lookahead.is(NUMERIC_LITERAL)) {
+      return Result.ok(tokenToNumber(new Token(lookahead.getType(), "-" + lookahead.getLexeme())));
+    }
+    return Result.error("Expecting numeric literal after minus sign.");
+  }
+
+  @SuppressWarnings("checkstyle:variabledeclarationusagedistance")
+  private Result byteOrShortLiteral() throws IOException {
+    next();
+    if (!lookahead.is(TYPE_IDENTIFIER)) {
+      return Result.error("Expecting type names byte or short, got: " + lookahead.getLexeme());
+    }
+    int resultType = lookahead.getType();
+    String prefix = "";
+    next();
+    if (!lookahead.is(RIGHT_PARENTHESIS)) {
+      return Result.error("Expecting right parenthesis, got: " + lookahead.getLexeme());
+    }
+    next();
+    if (lookahead.is(MINUS_SIGN)) {
+      prefix = "-";
+      next();
+    }
+    if (!lookahead.is(INTEGRAL_LITERAL)) {
+      return Result.error("Expecting an integral literal, got: " + lookahead.getLexeme());
     }
 
-    private static boolean isNullOrBlank(String str) {
-        return str == null || str.trim().isEmpty();
+    return Result.ok(
+        tokenToNumber(
+            new Token(
+                typeToLiteral(resultType) | getRadix(lookahead.getType()),
+                prefix + lookahead.getLexeme())));
+  }
+
+  public void next() throws IOException {
+    lookahead = lexer.nextToken();
+  }
+
+  private Object tokenToNumber(Token token) {
+    Class<?> numericType = getNumericType(token.getType());
+    if (token.is(INTEGRAL_LITERAL)) {
+      return integerValueOf(numericType, token.getLexeme(), getRadix(token.getType()));
+    }
+    return valueOf(numericType, token.getLexeme());
+  }
+
+  private Object valueOf(Class<?> type, String value) {
+    try {
+      Method method = type.getDeclaredMethod("valueOf", String.class);
+      return method.invoke(null, value);
+    } catch (NoSuchMethodException | IllegalAccessException exc) {
+      throw new AssertionError(
+          "Class " + type.getName() + " expected to have an accessible valueOf(String) method");
+    } catch (InvocationTargetException exc) {
+      throw new IllegalArgumentException(
+          "Error while obtaining value of type " + type.getName() + " from string " + value, exc);
+    }
+  }
+
+  private Object integerValueOf(Class<?> type, String value, int radix) {
+    try {
+      Method method = type.getDeclaredMethod("valueOf", String.class, int.class);
+      return method.invoke(null, value, radix);
+    } catch (NoSuchMethodException | IllegalAccessException exc) {
+      throw new AssertionError(
+          "Class "
+              + type.getName()
+              + " expected to have an accessible valueOf(String, int) method");
+    } catch (InvocationTargetException exc) {
+      throw new IllegalArgumentException(
+          "Error while obtaining value of type "
+              + type.getName()
+              + " from string "
+              + value
+              + " using radix "
+              + radix,
+          exc);
     }
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/parsing/Token.java b/src/main/java/eu/stamp_project/descartes/operators/parsing/Token.java
index 3b201e0..5970e3a 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/parsing/Token.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/parsing/Token.java
@@ -1,29 +1,33 @@
 package eu.stamp_project.descartes.operators.parsing;
 
-
 class Token {
 
-    public static final Token FALSE = new Token(TokenType.FALSE, "false");
-    public static final Token TRUE = new Token(TokenType.TRUE, "true");
-    public static final Token BYTE = new Token(TokenType.BYTE_TYPE, "byte");
-    public static final Token SHORT = new Token(TokenType.SHORT_TYPE, "short");
-    public static final Token LPAR = new Token(TokenType.LEFT_PARENTHESIS, "(");
-    public static final Token RPAR = new Token(TokenType.RIGHT_PARENTHESIS, ")");
-    public static final Token MINUS = new Token(TokenType.MINUS_SIGN, "-");
-    public static final Token EOF = new Token(TokenType.END_OF_FILE, "<END OF INPUT>");
-
-    private final int type;
-    private final String lexeme;
-
-    public Token(int type, String lexeme) {
-        this.type = type;
-        this.lexeme = lexeme;
-    }
-
-    public int getType() { return type; }
-
-    public String getLexeme() { return lexeme; }
-
-    public boolean is(int tokenType) { return TokenType.is(type, tokenType);  }
-
+  public static final Token FALSE = new Token(TokenType.FALSE, "false");
+  public static final Token TRUE = new Token(TokenType.TRUE, "true");
+  public static final Token BYTE = new Token(TokenType.BYTE_TYPE, "byte");
+  public static final Token SHORT = new Token(TokenType.SHORT_TYPE, "short");
+  public static final Token LPAR = new Token(TokenType.LEFT_PARENTHESIS, "(");
+  public static final Token RPAR = new Token(TokenType.RIGHT_PARENTHESIS, ")");
+  public static final Token MINUS = new Token(TokenType.MINUS_SIGN, "-");
+  public static final Token EOF = new Token(TokenType.END_OF_FILE, "<END OF INPUT>");
+
+  private final int type;
+  private final String lexeme;
+
+  public Token(int type, String lexeme) {
+    this.type = type;
+    this.lexeme = lexeme;
+  }
+
+  public int getType() {
+    return type;
+  }
+
+  public String getLexeme() {
+    return lexeme;
+  }
+
+  public boolean is(int tokenType) {
+    return TokenType.is(type, tokenType);
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/operators/parsing/TokenType.java b/src/main/java/eu/stamp_project/descartes/operators/parsing/TokenType.java
index 8bc45c3..9a53ea7 100644
--- a/src/main/java/eu/stamp_project/descartes/operators/parsing/TokenType.java
+++ b/src/main/java/eu/stamp_project/descartes/operators/parsing/TokenType.java
@@ -1,94 +1,101 @@
 package eu.stamp_project.descartes.operators.parsing;
 
+final class TokenType {
 
-class TokenType {
+  public static final int SYMBOL = (1 << 16);
+  public static final int MINUS_SIGN = SYMBOL | 1;
+  public static final int LEFT_PARENTHESIS = SYMBOL | 2;
+  public static final int RIGHT_PARENTHESIS = SYMBOL | 4;
 
-    public static final int SYMBOL = (1 << 16);
-    public static final int MINUS_SIGN = SYMBOL | 1;
-    public static final int LEFT_PARENTHESIS = SYMBOL | 2;
-    public static final int RIGHT_PARENTHESIS = SYMBOL | 4;
+  public static final int TYPE_IDENTIFIER = (2 << 16);
+  public static final int BYTE_TYPE = TYPE_IDENTIFIER | 1;
+  public static final int SHORT_TYPE = TYPE_IDENTIFIER | 2;
 
-    public static final int TYPE_IDENTIFIER = (2 << 16);
-    public static final int BYTE_TYPE = TYPE_IDENTIFIER | 1;
-    public static final int SHORT_TYPE = TYPE_IDENTIFIER | 2;
+  public static final int LITERAL = (4 << 16);
 
-    public static final int LITERAL = (4 << 16);
+  public static final int CHAR_LITERAL = LITERAL | (1 << 12);
+  public static final int STRING_LITERAL = LITERAL | (2 << 12);
 
-    public static final int CHAR_LITERAL    = LITERAL | (1 << 12);
-    public static final int STRING_LITERAL  = LITERAL | (2 << 12);
+  public static final int BOOLEAN_LITERAL = LITERAL | (4 << 12);
+  public static final int FALSE = BOOLEAN_LITERAL | 1;
+  public static final int TRUE = BOOLEAN_LITERAL | 2;
 
-    public static final int BOOLEAN_LITERAL = LITERAL | (4 << 12);
-    public static final int FALSE = BOOLEAN_LITERAL | 1;
-    public static final int TRUE  = BOOLEAN_LITERAL | 2;
+  public static final int NUMERIC_LITERAL = LITERAL | 8 << 12;
 
-    public static final int NUMERIC_LITERAL = LITERAL | 8 << 12;
+  public static final int FLOAT_LITERAL = NUMERIC_LITERAL | (1 << 9);
+  public static final int DOUBLE_LITERAL = NUMERIC_LITERAL | (2 << 9);
 
-    public static final int FLOAT_LITERAL   = NUMERIC_LITERAL | (1 << 9);
-    public static final int DOUBLE_LITERAL  = NUMERIC_LITERAL | (2 << 9);
+  public static final int INTEGRAL_LITERAL = NUMERIC_LITERAL | (4 << 9);
 
-    public static final int INTEGRAL_LITERAL = NUMERIC_LITERAL | (4 << 9);
+  public static final int BYTE_LITERAL = INTEGRAL_LITERAL | (1 << 5);
+  public static final int BYTE_BIN_LITERAL = BYTE_LITERAL | 2;
+  public static final int BYTE_OCT_LITERAL = BYTE_LITERAL | 8;
+  public static final int BYTE_DEC_LITERAL = BYTE_LITERAL | 10;
+  public static final int BYTE_HEX_LITERAL = BYTE_LITERAL | 16;
 
-    public static final int BYTE_LITERAL        = INTEGRAL_LITERAL | (1 << 5);
-    public static final int BYTE_BIN_LITERAL    = BYTE_LITERAL | 2;
-    public static final int BYTE_OCT_LITERAL    = BYTE_LITERAL | 8;
-    public static final int BYTE_DEC_LITERAL    = BYTE_LITERAL | 10;
-    public static final int BYTE_HEX_LITERAL    = BYTE_LITERAL | 16;
+  public static final int SHORT_LITERAL = INTEGRAL_LITERAL | (2 << 5);
+  public static final int SHORT_BIN_LITERAL = SHORT_LITERAL | 2;
+  public static final int SHORT_OCT_LITERAL = SHORT_LITERAL | 8;
+  public static final int SHORT_DEC_LITERAL = SHORT_LITERAL | 10;
+  public static final int SHORT_HEX_LITERAL = SHORT_LITERAL | 16;
 
-    public static final int SHORT_LITERAL       = INTEGRAL_LITERAL | (2 << 5);
-    public static final int SHORT_BIN_LITERAL   = SHORT_LITERAL | 2;
-    public static final int SHORT_OCT_LITERAL   = SHORT_LITERAL | 8;
-    public static final int SHORT_DEC_LITERAL   = SHORT_LITERAL | 10;
-    public static final int SHORT_HEX_LITERAL   = SHORT_LITERAL | 16;
+  public static final int INTEGER_LITERAL = INTEGRAL_LITERAL | (4 << 5);
+  public static final int INTEGER_BIN_LITERAL = INTEGER_LITERAL | 2;
+  public static final int INTEGER_OCT_LITERAL = INTEGER_LITERAL | 8;
+  public static final int INTEGER_DEC_LITERAL = INTEGER_LITERAL | 10;
+  public static final int INTEGER_HEX_LITERAL = INTEGER_LITERAL | 16;
 
-    public static final int INTEGER_LITERAL = INTEGRAL_LITERAL | (4 << 5);
-    public static final int INTEGER_BIN_LITERAL = INTEGER_LITERAL | 2;
-    public static final int INTEGER_OCT_LITERAL = INTEGER_LITERAL | 8;
-    public static final int INTEGER_DEC_LITERAL = INTEGER_LITERAL | 10;
-    public static final int INTEGER_HEX_LITERAL = INTEGER_LITERAL | 16;
+  public static final int LONG_LITERAL = INTEGRAL_LITERAL | (8 << 5);
+  public static final int LONG_BIN_LITERAL = LONG_LITERAL | 2;
+  public static final int LONG_OCT_LITERAL = LONG_LITERAL | 8;
+  public static final int LONG_DEC_LITERAL = LONG_LITERAL | 10;
+  public static final int LONG_HEX_LITERAL = LONG_LITERAL | 16;
 
-    public static final int LONG_LITERAL    = INTEGRAL_LITERAL | (8 << 5);
-    public static final int LONG_BIN_LITERAL    = LONG_LITERAL | 2;
-    public static final int LONG_OCT_LITERAL    = LONG_LITERAL | 8;
-    public static final int LONG_DEC_LITERAL    = LONG_LITERAL | 10;
-    public static final int LONG_HEX_LITERAL    = LONG_LITERAL | 16;
+  public static final int END_OF_FILE = 16 << 16;
 
-    public static final int END_OF_FILE = 16 << 16;
+  private TokenType() {}
 
-    private TokenType() {}
+  public static boolean is(int token, int category) {
+    return (token & category) == category;
+  }
 
-    public static boolean is(int token, int category) {
-        return (token & category) == category;
+  public static int typeToLiteral(int tokenType) {
+    if (is(tokenType, SHORT_TYPE)) {
+      return SHORT_LITERAL;
     }
-
-    public static int typeToLiteral(int tokenType) {
-        if(is(tokenType, SHORT_TYPE))
-            return SHORT_LITERAL;
-        if(is(tokenType, BYTE_TYPE))
-            return BYTE_LITERAL;
-        throw new IllegalArgumentException("Expecting type identifier token types");
+    if (is(tokenType, BYTE_TYPE)) {
+      return BYTE_LITERAL;
     }
+    throw new IllegalArgumentException("Expecting type identifier token types");
+  }
 
-    public static Class<?> getNumericType(int tokenType) {
-        if (is(tokenType, BYTE_TYPE) || is(tokenType, BYTE_LITERAL))
-            return Byte.class;
-        if (is(tokenType, SHORT_TYPE) || is(tokenType, SHORT_LITERAL))
-            return Short.class;
-        if (is(tokenType, INTEGER_LITERAL))
-            return Integer.class;
-        if (is(tokenType, LONG_LITERAL))
-            return Long.class;
-        if (is(tokenType, FLOAT_LITERAL))
-            return Float.class;
-        if (is(tokenType, DOUBLE_LITERAL))
-            return Double.class;
-        throw new IllegalArgumentException("Token type must represent a numeric literal or a type identifier");
+  public static Class<?> getNumericType(int tokenType) {
+    if (is(tokenType, BYTE_TYPE) || is(tokenType, BYTE_LITERAL)) {
+      return Byte.class;
     }
-
-    public static int getRadix(int tokenType) {
-        if(!is(tokenType, INTEGRAL_LITERAL))
-            throw new IllegalArgumentException("Only integral literals have radix");
-        return tokenType & 31;
+    if (is(tokenType, SHORT_TYPE) || is(tokenType, SHORT_LITERAL)) {
+      return Short.class;
+    }
+    if (is(tokenType, INTEGER_LITERAL)) {
+      return Integer.class;
+    }
+    if (is(tokenType, LONG_LITERAL)) {
+      return Long.class;
     }
+    if (is(tokenType, FLOAT_LITERAL)) {
+      return Float.class;
+    }
+    if (is(tokenType, DOUBLE_LITERAL)) {
+      return Double.class;
+    }
+    throw new IllegalArgumentException(
+        "Token type must represent a numeric literal or a type identifier");
+  }
 
+  public static int getRadix(int tokenType) {
+    if (!is(tokenType, INTEGRAL_LITERAL)) {
+      throw new IllegalArgumentException("Only integral literals have radix");
+    }
+    return tokenType & 31;
+  }
 }
-
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/IssuesReportFactory.java b/src/main/java/eu/stamp_project/descartes/reporting/IssuesReportFactory.java
index ef41dcb..ed28788 100644
--- a/src/main/java/eu/stamp_project/descartes/reporting/IssuesReportFactory.java
+++ b/src/main/java/eu/stamp_project/descartes/reporting/IssuesReportFactory.java
@@ -1,26 +1,24 @@
 package eu.stamp_project.descartes.reporting;
 
+import java.util.Properties;
 import org.pitest.mutationtest.ListenerArguments;
 import org.pitest.mutationtest.MutationResultListener;
 import org.pitest.mutationtest.MutationResultListenerFactory;
 
-
-
-import java.util.Properties;
-
 public class IssuesReportFactory implements MutationResultListenerFactory {
-    @Override
-    public MutationResultListener getListener(Properties properties, ListenerArguments listenerArguments) {
-        return new IssuesReportListener(listenerArguments);
-    }
+  @Override
+  public MutationResultListener getListener(
+      Properties properties, ListenerArguments listenerArguments) {
+    return new IssuesReportListener(listenerArguments);
+  }
 
-    @Override
-    public String name() {
-        return "ISSUES";
-    }
+  @Override
+  public String name() {
+    return "ISSUES";
+  }
 
-    @Override
-    public String description() {
-        return "Pseudo and partially-tested methods HTML report";
-    }
+  @Override
+  public String description() {
+    return "Pseudo and partially-tested methods HTML report";
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/IssuesReportListener.java b/src/main/java/eu/stamp_project/descartes/reporting/IssuesReportListener.java
index 980ebd4..23b8cbd 100644
--- a/src/main/java/eu/stamp_project/descartes/reporting/IssuesReportListener.java
+++ b/src/main/java/eu/stamp_project/descartes/reporting/IssuesReportListener.java
@@ -1,6 +1,12 @@
 package eu.stamp_project.descartes.reporting;
 
 import eu.stamp_project.descartes.reporting.models.MethodRecord;
+import java.io.IOException;
+import java.io.Writer;
+import java.nio.file.Paths;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.List;
 import org.apache.velocity.Template;
 import org.apache.velocity.VelocityContext;
 import org.apache.velocity.app.VelocityEngine;
@@ -11,122 +17,122 @@
 import org.pitest.mutationtest.MutationResultListener;
 import org.pitest.util.Unchecked;
 
-import java.io.IOException;
-import java.io.Writer;
-import java.nio.file.Paths;
-import java.time.Duration;
-import java.util.ArrayList;
-import java.util.List;
-
 public class IssuesReportListener implements MutationResultListener {
 
-    private final ListenerArguments arguments;
+  private final ListenerArguments arguments;
 
-    private Template methodResportTemplate;
-    private Template indexTemplate;
+  private Template methodResportTemplate;
+  private Template indexTemplate;
 
-    private List<ClassIssues> findings;
+  private List<ClassIssues> findings;
 
-    public IssuesReportListener(final ListenerArguments arguments) {
-        this.arguments = arguments;
-    }
-
-    @Override
-    public void runStart() {
-        VelocityEngine engine = new VelocityEngine();
-        engine.setProperty(RuntimeConstants.RESOURCE_LOADER, "classpath");
-        engine.setProperty("classpath.resource.loader.class", ClasspathResourceLoader.class.getName());
-        engine.init();
+  public IssuesReportListener(final ListenerArguments arguments) {
+    this.arguments = arguments;
+  }
 
-        methodResportTemplate = engine.getTemplate("templates/method-report.vm", "UTF-8");
-        indexTemplate = engine.getTemplate("templates/index-report.vm", "UTF-8");
+  @Override
+  public void runStart() {
+    VelocityEngine engine = new VelocityEngine();
+    engine.setProperty(RuntimeConstants.RESOURCE_LOADER, "classpath");
+    engine.setProperty("classpath.resource.loader.class", ClasspathResourceLoader.class.getName());
+    engine.init();
 
-        findings = new ArrayList<>();
-    }
+    methodResportTemplate = engine.getTemplate("templates/method-report.vm", "UTF-8");
+    indexTemplate = engine.getTemplate("templates/index-report.vm", "UTF-8");
 
-    private Writer createFile(String path) {
-        String filePath = Paths.get("issues", path).toString();
-        return arguments.getOutputStrategy().createWriterForFile(filePath);
-    }
+    findings = new ArrayList<>();
+  }
 
-    @Override
-    public void handleMutationResult(ClassMutationResults classMutationResults) {
+  private Writer createFile(String path) {
+    String filePath = Paths.get("issues", path).toString();
+    return arguments.getOutputStrategy().createWriterForFile(filePath);
+  }
 
-        MethodRecord[] issues = MethodRecord.getRecords(classMutationResults)
-                .filter(MethodRecord::hasIssues)
-                .toArray(MethodRecord[]::new);
+  @Override
+  public void handleMutationResult(ClassMutationResults classMutationResults) {
 
-        if (issues.length == 0) {
-            return;
-        }
+    MethodRecord[] issues =
+        MethodRecord.getRecords(classMutationResults)
+            .filter(MethodRecord::hasIssues)
+            .toArray(MethodRecord[]::new);
 
-        String className = classMutationResults.getMutatedClass().asJavaName();
-        VelocityContext context = new VelocityContext();
-        context.put("className", className);
-        context.put("issues", issues);
+    if (issues.length == 0) {
+      return;
+    }
 
-        try (Writer writer = createFile(className + ".html")) {
-            methodResportTemplate.merge(context, writer);
-        } catch (IOException exc) {
-            throw Unchecked.translateCheckedException("Could not write file for class: " + className, exc);
-        }
+    String className = classMutationResults.getMutatedClass().asJavaName();
+    VelocityContext context = new VelocityContext();
+    context.put("className", className);
+    context.put("issues", issues);
 
-        findings.add(new ClassIssues(className, issues.length));
+    try (Writer writer = createFile(className + ".html")) {
+      methodResportTemplate.merge(context, writer);
+    } catch (IOException exc) {
+      throw Unchecked.translateCheckedException(
+          "Could not write file for class: " + className, exc);
     }
 
-    private String getStringTime() {
-        //TODO: Is there a way to have this code in the template?
-
-        Duration elapsed = Duration.ofMillis(System.currentTimeMillis() - arguments.getStartTime());
-        String[] units = {"day", "hour", "minute", "second"};
-        long[] parts = { elapsed.toDays(), elapsed.toHours() % 24, elapsed.toMinutes() % 60, elapsed.getSeconds() % 60};
-        StringBuilder result = new StringBuilder();
-        for(int i=0; i < parts.length; i++) {
-            if(parts[i] == 0) continue;
-            result.append(parts[i]).append(" ").append(units[i]);
-            if(parts[i] > 1)
-                result.append("s");
-            result.append(" ");
-        }
-        if(result.length() == 0)
-            return "less than one second";
-        return result.substring(0, result.length() - 1);
+    findings.add(new ClassIssues(className, issues.length));
+  }
+
+  private String getStringTime() {
+    Duration elapsed = Duration.ofMillis(System.currentTimeMillis() - arguments.getStartTime());
+    String[] units = {"day", "hour", "minute", "second"};
+    long[] parts = {
+      elapsed.toDays(), elapsed.toHours() % 24, elapsed.toMinutes() % 60, elapsed.getSeconds() % 60
+    };
+    StringBuilder result = new StringBuilder();
+    for (int i = 0; i < parts.length; i++) {
+      if (parts[i] == 0) {
+        continue;
+      }
+      result.append(parts[i]).append(' ').append(units[i]);
+      if (parts[i] > 1) {
+        result.append('s');
+      }
+      result.append(' ');
     }
-
-    @Override
-    public void runEnd() {
-
-        VelocityContext context = new VelocityContext();
-        context.put("duration", getStringTime());
-        context.put("total", findings.stream().mapToInt(ClassIssues::getIssues).sum()); // Is there a way to put this code into the template??
-        context.put("findings", findings);
-        context.put("operators", arguments.getEngine().getMutatorNames());
-
-        try (Writer writer = createFile("index.html")) {
-            indexTemplate.merge(context, writer);
-        }
-        catch (IOException exc) {
-           throw Unchecked.translateCheckedException("Could not write report index file", exc);
-        }
-
+    if (result.length() == 0) {
+      return "less than one second";
     }
+    return result.substring(0, result.length() - 1);
+  }
+
+  @Override
+  public void runEnd() {
+
+    VelocityContext context = new VelocityContext();
+    context.put("duration", getStringTime());
+    context.put(
+        "total",
+        findings.stream()
+            .mapToInt(ClassIssues::getIssues)
+            .sum()); // Is there a way to put this code into the template??
+    context.put("findings", findings);
+    context.put("operators", arguments.getEngine().getMutatorNames());
+
+    try (Writer writer = createFile("index.html")) {
+      indexTemplate.merge(context, writer);
+    } catch (IOException exc) {
+      throw Unchecked.translateCheckedException("Could not write report index file", exc);
+    }
+  }
 
-    public static class ClassIssues {
-        private final String className;
-        private final int issues;
-
-        public ClassIssues(String className, int issues) {
-            this.className = className;
-            this.issues = issues;
-        }
+  public static class ClassIssues {
+    private final String className;
+    private final int issues;
 
-        public String getClassName() {
-            return className;
-        }
+    public ClassIssues(String className, int issues) {
+      this.className = className;
+      this.issues = issues;
+    }
 
-        public int getIssues() {
-            return issues;
-        }
+    public String getClassName() {
+      return className;
     }
 
+    public int getIssues() {
+      return issues;
+    }
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/JSONReportFactory.java b/src/main/java/eu/stamp_project/descartes/reporting/JSONReportFactory.java
deleted file mode 100644
index 48dbf78..0000000
--- a/src/main/java/eu/stamp_project/descartes/reporting/JSONReportFactory.java
+++ /dev/null
@@ -1,25 +0,0 @@
-package eu.stamp_project.descartes.reporting;
-
-import org.pitest.mutationtest.ListenerArguments;
-import org.pitest.mutationtest.MutationResultListener;
-import org.pitest.mutationtest.MutationResultListenerFactory;
-
-import java.util.Properties;
-
-public class JSONReportFactory implements MutationResultListenerFactory {
-
-    public MutationResultListener getListener(Properties properties, ListenerArguments listenerArguments) {
-        return new JSONReportListener(
-                listenerArguments.getStartTime(),
-                listenerArguments.getEngine().getMutatorNames(),
-                listenerArguments.getOutputStrategy());
-    }
-
-    public String name() {
-        return "JSON";
-    }
-
-    public String description() {
-        return "JSON report plugin";
-    }
-}
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/JSONReportListener.java b/src/main/java/eu/stamp_project/descartes/reporting/JSONReportListener.java
deleted file mode 100644
index 1489a44..0000000
--- a/src/main/java/eu/stamp_project/descartes/reporting/JSONReportListener.java
+++ /dev/null
@@ -1,110 +0,0 @@
-package eu.stamp_project.descartes.reporting;
-
-import org.pitest.coverage.TestInfo;
-
-import org.pitest.mutationtest.*;
-import org.pitest.mutationtest.engine.MutationDetails;
-import org.pitest.util.ResultOutputStrategy;
-import org.pitest.util.Unchecked;
-
-import java.io.IOException;
-import java.util.Collection;
-import java.util.stream.Collectors;
-
-
-public class JSONReportListener implements MutationResultListener{
-
-    private ResultOutputStrategy strategy;
-    private Collection<String> mutators;
-    private long startTime;
-
-    private JSONWriter report;
-
-    public JSONReportListener(final long startTime, final Collection<String> mutators, final ResultOutputStrategy strategy) {
-        this.strategy = strategy;
-        this.startTime = startTime;
-        this.mutators = mutators;
-    }
-
-    public void runStart() {
-        try {
-            report = new JSONWriter(strategy.createWriterForFile("mutations.json"));
-            report.beginObject();
-            report.beginListAttribute("mutators");
-            for (String mutator :
-                    mutators) {
-                report.write(mutator);
-            }
-            report.endList();
-            report.beginListAttribute("mutations");
-        }catch(IOException exc) {
-            throw Unchecked.translateCheckedException(exc);
-        }
-    }
-
-
-    public void handleMutationResult(ClassMutationResults classMutationResults) {
-        try {
-
-            for (MutationResult result : classMutationResults.getMutations()) {
-
-                MutationDetails details = result.getDetails();
-                DetectionStatus status = result.getStatus();
-
-                MutationStatusTestPair pair = result.getStatusTestPair();
-                String method = details.getMethod();
-                String methodDescription = details.getId().getLocation().getMethodDesc();
-
-                report.beginObject();
-                report.writeAttribute("detected", status.isDetected());
-                report.writeAttribute("status", status.name());
-                report.writeAttribute("mutator", details.getMutator());
-                report.writeAttribute("line", details.getLineNumber());
-
-                report.beginAttribute("blocks");
-                report.beginList();
-                for (Integer block : details.getBlocks()) {
-                    report.write(block);
-                }
-                report.endList();
-
-                report.writeAttribute("file", details.getFilename());
-                report.writeAttribute("index", details.getFirstIndex()); // Saving only the first index
-
-                report.beginObjectAttribute("method");
-                report.writeAttribute("name", method);
-                report.writeAttribute("description", methodDescription);
-                report.writeAttribute("class", details.getClassName().getNameWithoutPackage().asJavaName());
-                report.writeAttribute("package", details.getClassName().getPackage().asJavaName());
-                report.endObject();
-
-                report.beginObjectAttribute("tests");
-                report.writeAttribute("run", result.getNumberOfTestsRun());
-
-                report.writeStringListAttribute("ordered",
-                        details.getTestsInOrder().stream().map(TestInfo::getName).collect(Collectors.toList()));
-
-                report.writeStringListAttribute("killing", pair.getKillingTests());
-                report.writeStringListAttribute("succeeding", pair.getSucceedingTests());
-
-                report.endObject();
-
-                report.endObject();
-            }
-        } catch (IOException exc) {
-            throw Unchecked.translateCheckedException(exc);
-        }
-    }
-
-    public void runEnd() {
-        try {
-            report.endList();
-            report.writeAttribute("time", System.currentTimeMillis() - startTime);
-            report.endObject();
-            report.close();
-        }catch(IOException exc) {
-            throw Unchecked.translateCheckedException(exc);
-        }
-    }
-
-}
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/JSONWriter.java b/src/main/java/eu/stamp_project/descartes/reporting/JSONWriter.java
deleted file mode 100644
index 6759eb1..0000000
--- a/src/main/java/eu/stamp_project/descartes/reporting/JSONWriter.java
+++ /dev/null
@@ -1,209 +0,0 @@
-package eu.stamp_project.descartes.reporting;
-
-
-import java.io.IOException;
-import java.io.StringWriter;
-import java.io.Writer;
-import java.util.Collection;
-import java.util.Stack;
-
-enum WriterState {
-    Initial, EmptyObject, Object, EmptyList, List, Value, Final
-}
-
-
-public class JSONWriter {
-    Writer out;
-    Stack<WriterState> memory;
-    WriterState state;
-
-    public JSONWriter(Writer out) {
-        this.out = out;
-        state = WriterState.Initial;
-        memory = new Stack<WriterState>();
-    }
-
-    public void beginObject() throws IOException {
-        beginStructure();
-        state = WriterState.EmptyObject;
-        out.write('{');
-    }
-
-    public void beginObjectAttribute(String key) throws IOException {
-        beginAttribute(key); beginObject();
-    }
-
-    public void endObject() throws IOException {
-        if(state != WriterState.EmptyObject && state != WriterState.Object)
-            throw new IllegalStateException("Object not started");
-        out.write('}');
-        endStructure();
-    }
-
-    private void beginStructure() throws IOException {
-        switch(state) {
-            case EmptyObject: //Illegal states
-            case Object:
-            case Final:
-                throw new IllegalStateException("Cant' start an object in the current state");
-            case Initial: //Initial object or list
-                memory.push(WriterState.Final);
-                break;
-            case List: //The new object or list is placed inside another list which already has some elements
-                out.write(',');
-            case EmptyList: //The new object or list is placed inside another list which has no other elements
-                memory.push(WriterState.List);
-                break;
-            default: // The object or list is placed as value of an attribute
-                memory.push(state);
-        }
-        //This is one case in which I guess the switch is better than other alternatives
-        //Here it is sort of replacing a follow lookup in a LL(1) parser
-        //The entire code of beginList and beginObject could be placed here adding some parameters
-        //but I think this won't help readability
-    }
-
-    private void endStructure() {
-        state = memory.pop();
-        if(state == WriterState.Value)
-            state = memory.pop();
-    }
-
-    public void beginList() throws IOException {
-        beginStructure();
-        state = WriterState.EmptyList;
-        out.write('[');
-    }
-
-    public void beginListAttribute(String key) throws IOException {
-        beginAttribute(key); beginList();
-    }
-
-    public void endList() throws IOException {
-        if(state != WriterState.EmptyList && state != WriterState.List)
-            throw new IllegalStateException("List not started");
-        out.write(']');
-        endStructure();
-    }
-
-    public void writeStringList(Collection<String> values) throws IOException {
-        beginList();
-
-        for(String value : values) {
-            write(value);
-        }
-
-        endList();
-    }
-
-    public void writeStringListAttribute(String key, Collection<String> values) throws IOException {
-        beginAttribute(key); writeStringList(values);
-    }
-
-    public void beginAttribute(String key) throws IOException {
-        if(state != WriterState.Object && state != WriterState.EmptyObject)
-            throw new IllegalStateException("Attributes can only be added to objects");
-        if(state == WriterState.Object)
-            out.write(',');
-        memory.push(WriterState.Object);
-        state = WriterState.Value;
-        out.write(String.format("\"%1$s\":", escapeString(key)));
-    }
-
-    public void writeAttribute(String key, int value) throws IOException {
-        beginAttribute(key); write(value);
-    }
-
-    public void writeAttribute(String key, long value) throws IOException {
-        beginAttribute(key); write(value);
-    }
-
-    public void writeAttribute(String key, boolean value) throws IOException {
-        beginAttribute(key); write(value);
-    }
-
-    public void writeAttribute(String key, String value) throws IOException {
-        beginAttribute(key); write(value);
-    }
-
-    private void writeValue(String value) throws IOException {
-        if(state != WriterState.List && state != WriterState.EmptyList && state != WriterState.Value)
-            throw new IllegalStateException("Can't place a value in current context");
-        if(state == WriterState.List)
-            out.write(',');
-        if(state == WriterState.EmptyList)
-            state = WriterState.List;
-        out.write(value);
-        if(state == WriterState.Value)
-            state = memory.pop();
-    }
-
-    public void write(String value) throws IOException {
-        if(value == null) {
-            writeValue("null");
-        }
-        else {
-            writeValue(String.format("\"%1$s\"", escapeString(value)));
-        }
-    }
-
-    public void write(int value) throws IOException {
-        writeValue(String.valueOf(value));
-    }
-
-    public void write(long value) throws IOException {
-        writeValue(String.valueOf(value));
-    }
-
-    public void write(boolean value) throws IOException {
-        writeValue(String.valueOf(value).toLowerCase());
-    }
-
-    public void close() throws IOException {
-        if(state != WriterState.Final)
-            throw new IllegalStateException("JSON structure isn't finished");
-        out.close();
-    }
-
-    public static String escapeString(String value) {
-        StringWriter result = new StringWriter(value.length());
-        for(int i=0; i< value.length(); i++) {
-            char c = value.charAt(i);
-            String toWrite = null;
-            if(c < 128) {
-                toWrite = ESCAPE_SEQUENCES[c];
-            }
-            else if(c == '\u2028') {
-                toWrite = "\\u2028";
-            }
-            else if(c == '\u2029') {
-                toWrite = "\\u2028";
-            }
-            if(toWrite == null)
-                result.write(c);
-            else
-                result.write(toWrite);
-        }
-        return result.getBuffer().toString();
-    }
-
-    private final static String[] ESCAPE_SEQUENCES;
-    static {
-        //Adapted from GSON Library
-        //https://github.com/google/gson/blob/master/gson/src/main/java/com/google/gson/stream/JsonWriter.java
-
-        ESCAPE_SEQUENCES = new String[128];
-        for(int i=0; i <= 31; i++)
-            ESCAPE_SEQUENCES[i] = String.format("\\u%04x", i);
-
-        ESCAPE_SEQUENCES['"'] = "\\\"";
-        ESCAPE_SEQUENCES['\\'] = "\\\\";
-        ESCAPE_SEQUENCES['\t'] = "\\t";
-        ESCAPE_SEQUENCES['\b'] = "\\b";
-        ESCAPE_SEQUENCES['\n'] = "\\n";
-        ESCAPE_SEQUENCES['\r'] = "\\r";
-        ESCAPE_SEQUENCES['\f'] = "\\f";
-
-    }
-
-}
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/JsonReportFactory.java b/src/main/java/eu/stamp_project/descartes/reporting/JsonReportFactory.java
new file mode 100644
index 0000000..14d3e84
--- /dev/null
+++ b/src/main/java/eu/stamp_project/descartes/reporting/JsonReportFactory.java
@@ -0,0 +1,25 @@
+package eu.stamp_project.descartes.reporting;
+
+import java.util.Properties;
+import org.pitest.mutationtest.ListenerArguments;
+import org.pitest.mutationtest.MutationResultListener;
+import org.pitest.mutationtest.MutationResultListenerFactory;
+
+public class JsonReportFactory implements MutationResultListenerFactory {
+
+  public MutationResultListener getListener(
+      Properties properties, ListenerArguments listenerArguments) {
+    return new JsonReportListener(
+        listenerArguments.getStartTime(),
+        listenerArguments.getEngine().getMutatorNames(),
+        listenerArguments.getOutputStrategy());
+  }
+
+  public String name() {
+    return "JSON";
+  }
+
+  public String description() {
+    return "JSON report plugin";
+  }
+}
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/JsonReportListener.java b/src/main/java/eu/stamp_project/descartes/reporting/JsonReportListener.java
new file mode 100644
index 0000000..c150006
--- /dev/null
+++ b/src/main/java/eu/stamp_project/descartes/reporting/JsonReportListener.java
@@ -0,0 +1,105 @@
+package eu.stamp_project.descartes.reporting;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.stream.Collectors;
+import org.pitest.coverage.TestInfo;
+import org.pitest.mutationtest.*;
+import org.pitest.mutationtest.engine.MutationDetails;
+import org.pitest.util.ResultOutputStrategy;
+import org.pitest.util.Unchecked;
+
+public class JsonReportListener implements MutationResultListener {
+
+  private final ResultOutputStrategy strategy;
+  private final Collection<String> mutators;
+  private final long startTime;
+
+  private JsonWriter report;
+
+  public JsonReportListener(
+      final long startTime,
+      final Collection<String> mutators,
+      final ResultOutputStrategy strategy) {
+    this.strategy = strategy;
+    this.startTime = startTime;
+    this.mutators = mutators;
+  }
+
+  public void runStart() {
+    try {
+      report = new JsonWriter(strategy.createWriterForFile("mutations.json"));
+      report.beginObject();
+      report.beginListAttribute("mutators");
+      for (String mutator : mutators) {
+        report.write(mutator);
+      }
+      report.endList();
+      report.beginListAttribute("mutations");
+    } catch (IOException exc) {
+      throw Unchecked.translateCheckedException(exc);
+    }
+  }
+
+  public void handleMutationResult(ClassMutationResults classMutationResults) {
+    try {
+
+      for (MutationResult result : classMutationResults.getMutations()) {
+
+        MutationDetails details = result.getDetails();
+        DetectionStatus status = result.getStatus();
+
+        report.beginObject();
+        report.writeAttribute("detected", status.isDetected());
+        report.writeAttribute("status", status.name());
+        report.writeAttribute("mutator", details.getMutator());
+        report.writeAttribute("line", details.getLineNumber());
+
+        report.beginAttribute("blocks");
+        report.beginList();
+        for (Integer block : details.getBlocks()) {
+          report.write(block);
+        }
+        report.endList();
+
+        report.writeAttribute("file", details.getFilename());
+        report.writeAttribute("index", details.getFirstIndex()); // Saving only the first index
+
+        report.beginObjectAttribute("method");
+        report.writeAttribute("name", details.getMethod());
+        report.writeAttribute("description", details.getId().getLocation().getMethodDesc());
+        report.writeAttribute("class", details.getClassName().getNameWithoutPackage().asJavaName());
+        report.writeAttribute("package", details.getClassName().getPackage().asJavaName());
+        report.endObject();
+
+        report.beginObjectAttribute("tests");
+        report.writeAttribute("run", result.getNumberOfTestsRun());
+
+        report.writeStringListAttribute(
+            "ordered",
+            details.getTestsInOrder().stream().map(TestInfo::getName).collect(Collectors.toList()));
+
+        MutationStatusTestPair pair = result.getStatusTestPair();
+        report.writeStringListAttribute("killing", pair.getKillingTests());
+        report.writeStringListAttribute("succeeding", pair.getSucceedingTests());
+
+        report.endObject();
+
+        report.endObject();
+      }
+    } catch (IOException exc) {
+      throw Unchecked.translateCheckedException(exc);
+    }
+  }
+
+  public void runEnd() {
+    try {
+      report.endList();
+      report.writeAttribute("time", System.currentTimeMillis() - startTime);
+      report.endObject();
+      report.close();
+    } catch (IOException exc) {
+      throw Unchecked.translateCheckedException(exc);
+    }
+  }
+}
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/JsonWriter.java b/src/main/java/eu/stamp_project/descartes/reporting/JsonWriter.java
new file mode 100644
index 0000000..e27cea5
--- /dev/null
+++ b/src/main/java/eu/stamp_project/descartes/reporting/JsonWriter.java
@@ -0,0 +1,235 @@
+package eu.stamp_project.descartes.reporting;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.io.Writer;
+import java.util.Collection;
+import java.util.Stack;
+
+
+public class JsonWriter {
+
+  enum WriterState {
+    INITIAL,
+    EMPTY_OBJECT,
+    OBJECT,
+    EMPTY_LIST,
+    LIST,
+    VALUE,
+    FINAL
+  }
+
+  Writer out;
+  Stack<WriterState> memory;
+  WriterState state;
+
+  public JsonWriter(Writer out) {
+    this.out = out;
+    state = WriterState.INITIAL;
+    memory = new Stack<>();
+  }
+
+  public void beginObject() throws IOException {
+    beginStructure();
+    state = WriterState.EMPTY_OBJECT;
+    out.write('{');
+  }
+
+  public void beginObjectAttribute(String key) throws IOException {
+    beginAttribute(key);
+    beginObject();
+  }
+
+  public void endObject() throws IOException {
+    if (state != WriterState.EMPTY_OBJECT && state != WriterState.OBJECT) {
+      throw new IllegalStateException("Object not started");
+    }
+    out.write('}');
+    endStructure();
+  }
+
+  @SuppressWarnings("checkstyle:fallthrough")
+  private void beginStructure() throws IOException {
+    switch (state) {
+      case EMPTY_OBJECT: // Illegal states
+      case OBJECT:
+      case FINAL:
+        throw new IllegalStateException("Cant' start an object in the current state");
+      case INITIAL: // Initial object or list
+        memory.push(WriterState.FINAL);
+        break;
+      case LIST:
+        // The new object or list is placed inside another list
+        // which already has some elements
+        out.write(',');
+      case EMPTY_LIST:
+        // The new object or list is placed inside another list
+        // which has no other elements
+        memory.push(WriterState.LIST);
+        break;
+      default: // The object or list is placed as value of an attribute
+        memory.push(state);
+    }
+    // This is one case in which I guess the switch is better than other alternatives
+    // Here it is sort of replacing a follow lookup in a LL(1) parser
+    // The entire code of beginList and beginObject could be placed here adding some parameters
+    // ,but I think this won't help readability
+  }
+
+  private void endStructure() {
+    state = memory.pop();
+    if (state == WriterState.VALUE) {
+      state = memory.pop();
+    }
+  }
+
+  public void beginList() throws IOException {
+    beginStructure();
+    state = WriterState.EMPTY_LIST;
+    out.write('[');
+  }
+
+  public void beginListAttribute(String key) throws IOException {
+    beginAttribute(key);
+    beginList();
+  }
+
+  public void endList() throws IOException {
+    if (state != WriterState.EMPTY_LIST && state != WriterState.LIST) {
+      throw new IllegalStateException("List not started");
+    }
+    out.write(']');
+    endStructure();
+  }
+
+  public void writeStringList(Collection<String> values) throws IOException {
+    beginList();
+    for (String value : values) {
+      write(value);
+    }
+    endList();
+  }
+
+  public void writeStringListAttribute(String key, Collection<String> values) throws IOException {
+    beginAttribute(key);
+    writeStringList(values);
+  }
+
+  public void beginAttribute(String key) throws IOException {
+    if (state != WriterState.OBJECT && state != WriterState.EMPTY_OBJECT) {
+      throw new IllegalStateException("Attributes can only be added to objects");
+    }
+    if (state == WriterState.OBJECT) {
+      out.write(',');
+    }
+    memory.push(WriterState.OBJECT);
+    state = WriterState.VALUE;
+    out.write(String.format("\"%1$s\":", escapeString(key)));
+  }
+
+  public void writeAttribute(String key, int value) throws IOException {
+    beginAttribute(key);
+    write(value);
+  }
+
+  public void writeAttribute(String key, long value) throws IOException {
+    beginAttribute(key);
+    write(value);
+  }
+
+  public void writeAttribute(String key, boolean value) throws IOException {
+    beginAttribute(key);
+    write(value);
+  }
+
+  public void writeAttribute(String key, String value) throws IOException {
+    beginAttribute(key);
+    write(value);
+  }
+
+  private void writeValue(String value) throws IOException {
+    if (state != WriterState.LIST
+        && state != WriterState.EMPTY_LIST
+        && state != WriterState.VALUE) {
+      throw new IllegalStateException("Can't place a value in current context");
+    }
+    if (state == WriterState.LIST) {
+      out.write(',');
+    }
+    if (state == WriterState.EMPTY_LIST) {
+      state = WriterState.LIST;
+    }
+    out.write(value);
+    if (state == WriterState.VALUE) {
+      state = memory.pop();
+    }
+  }
+
+  public void write(String value) throws IOException {
+    if (value == null) {
+      writeValue("null");
+    } else {
+      writeValue(String.format("\"%1$s\"", escapeString(value)));
+    }
+  }
+
+  public void write(int value) throws IOException {
+    writeValue(String.valueOf(value));
+  }
+
+  public void write(long value) throws IOException {
+    writeValue(String.valueOf(value));
+  }
+
+  public void write(boolean value) throws IOException {
+    writeValue(String.valueOf(value).toLowerCase());
+  }
+
+  public void close() throws IOException {
+    if (state != WriterState.FINAL) {
+      throw new IllegalStateException("JSON structure isn't finished");
+    }
+    out.close();
+  }
+
+  public static String escapeString(String value) {
+    StringWriter result = new StringWriter(value.length());
+    for (int i = 0; i < value.length(); i++) {
+      char c = value.charAt(i);
+      String toWrite = null;
+      if (c < 128) {
+        toWrite = ESCAPE_SEQUENCES[c];
+      } else if (c == '\u2028') {
+        toWrite = "\\u2028";
+      } else if (c == '\u2029') {
+        toWrite = "\\u2028";
+      }
+      if (toWrite == null) {
+        result.write(c);
+      } else {
+        result.write(toWrite);
+      }
+    }
+    return result.getBuffer().toString();
+  }
+
+  private static final String[] ESCAPE_SEQUENCES;
+
+  static {
+    // Adapted from GSON Library
+    // https://github.com/google/gson/blob/master/gson/src/main/java/com/google/gson/stream/JsonWriter.java
+
+    ESCAPE_SEQUENCES = new String[128];
+    for (int i = 0; i <= 31; i++) {
+      ESCAPE_SEQUENCES[i] = String.format("\\u%04x", i);
+    }
+
+    ESCAPE_SEQUENCES['"'] = "\\\"";
+    ESCAPE_SEQUENCES['\\'] = "\\\\";
+    ESCAPE_SEQUENCES['\t'] = "\\t";
+    ESCAPE_SEQUENCES['\b'] = "\\b";
+    ESCAPE_SEQUENCES['\n'] = "\\n";
+    ESCAPE_SEQUENCES['\r'] = "\\r";
+    ESCAPE_SEQUENCES['\f'] = "\\f";
+  }
+}
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/MethodTestingFactory.java b/src/main/java/eu/stamp_project/descartes/reporting/MethodTestingFactory.java
index c00d064..c676cd7 100644
--- a/src/main/java/eu/stamp_project/descartes/reporting/MethodTestingFactory.java
+++ b/src/main/java/eu/stamp_project/descartes/reporting/MethodTestingFactory.java
@@ -1,23 +1,21 @@
 package eu.stamp_project.descartes.reporting;
 
+import java.util.Properties;
 import org.pitest.mutationtest.ListenerArguments;
 import org.pitest.mutationtest.MutationResultListener;
 import org.pitest.mutationtest.MutationResultListenerFactory;
 
-import java.util.Properties;
-
 public class MethodTestingFactory implements MutationResultListenerFactory {
 
+  public MutationResultListener getListener(Properties props, ListenerArguments args) {
+    return new MethodTestingListener(args);
+  }
 
-    public MutationResultListener getListener(Properties props, ListenerArguments args) {
-        return new MethodTestingListener(args);
-    }
-
-    public String name() {
-        return "METHODS";
-    }
+  public String name() {
+    return "METHODS";
+  }
 
-    public String description() {
-        return "Pseudo and partially-tested methods JSON report";
-    }
+  public String description() {
+    return "Pseudo and partially-tested methods JSON report";
+  }
 }
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/MethodTestingListener.java b/src/main/java/eu/stamp_project/descartes/reporting/MethodTestingListener.java
index f542d3d..28e7097 100644
--- a/src/main/java/eu/stamp_project/descartes/reporting/MethodTestingListener.java
+++ b/src/main/java/eu/stamp_project/descartes/reporting/MethodTestingListener.java
@@ -1,121 +1,117 @@
 package eu.stamp_project.descartes.reporting;
 
 import eu.stamp_project.descartes.reporting.models.MethodRecord;
-import org.pitest.coverage.TestInfo;
-import org.pitest.mutationtest.*;
-
-import org.pitest.util.Unchecked;
-
 import java.io.IOException;
 import java.util.*;
 import java.util.stream.Collectors;
+import org.pitest.coverage.TestInfo;
+import org.pitest.mutationtest.*;
+import org.pitest.util.Unchecked;
 
 public class MethodTestingListener implements MutationResultListener {
 
-    public MethodTestingListener(final ListenerArguments args) {
-        this.args = args;
-    }
-
-    private final ListenerArguments args;
+  public MethodTestingListener(final ListenerArguments args) {
+    this.args = args;
+  }
 
-    public ListenerArguments getArguments() { return args; }
+  private final ListenerArguments args;
 
-    private JSONWriter report;
+  public ListenerArguments getArguments() {
+    return args;
+  }
 
-    public void runStart() {
-        try {
-            report = new JSONWriter(args.getOutputStrategy().createWriterForFile("methods.json"));
-            report.beginObject();
+  private JsonWriter report;
 
-            report.beginListAttribute("methods");
+  public void runStart() {
+    try {
+      report = new JsonWriter(args.getOutputStrategy().createWriterForFile("methods.json"));
+      report.beginObject();
 
-        }catch(IOException exc) {
-            throw Unchecked.translateCheckedException(exc);
-        }
-    }
+      report.beginListAttribute("methods");
 
-    public void handleMutationResult(ClassMutationResults results) {
-            MethodRecord.getRecords(results).forEach(this::writeMethod);
+    } catch (IOException exc) {
+      throw Unchecked.translateCheckedException(exc);
     }
+  }
 
-    private Collection<String> getMutators(Collection<MutationResult> mutations) {
-        return mutations.stream().map(mutation -> mutation.getDetails().getMutator()).collect(Collectors.toList());
-    }
+  public void handleMutationResult(ClassMutationResults results) {
+    MethodRecord.getRecords(results).forEach(this::writeMethod);
+  }
 
-    private void writeMethod(MethodRecord method) {
-        try {
+  private Collection<String> getMutators(Collection<MutationResult> mutations) {
+    return mutations.stream()
+        .map(mutation -> mutation.getDetails().getMutator())
+        .collect(Collectors.toList());
+  }
 
-            report.beginObject();
+  private void writeMethod(MethodRecord method) {
+    try {
 
-            report.writeAttribute("name", method.getName());
-            report.writeAttribute("description", method.getDesc());
-            report.writeAttribute("class", method.getClassName());
-            report.writeAttribute("package", method.getPackageName());
-            report.writeAttribute("file-name", method.getFileName());
-            report.writeAttribute("line-number", method.getLineNumber());
+      report.beginObject();
 
+      report.writeAttribute("name", method.getName());
+      report.writeAttribute("description", method.getDesc());
+      report.writeAttribute("class", method.getClassName());
+      report.writeAttribute("package", method.getPackageName());
+      report.writeAttribute("file-name", method.getFileName());
+      report.writeAttribute("line-number", method.getLineNumber());
 
-            report.writeAttribute("classification", method.getClassification().toString());
-            report.writeStringListAttribute("detected", getMutators(method.getDetectedMutations()));
-            report.writeStringListAttribute("not-detected", getMutators(method.getUndetectedMutations()));
+      report.writeAttribute("classification", method.getClassification().toString());
+      report.writeStringListAttribute("detected", getMutators(method.getDetectedMutations()));
+      report.writeStringListAttribute("not-detected", getMutators(method.getUndetectedMutations()));
 
+      report.writeStringListAttribute(
+          "tests", method.getTests().stream().map(TestInfo::getName).collect(Collectors.toList()));
 
-            report.writeStringListAttribute(
-                    "tests",
-                    method.getTests().stream()
-                            .map(TestInfo::getName).collect(Collectors.toList()));
-
-            report.beginListAttribute("mutations");
-            method.getMutations().forEach(this::writeMutationDetails);
-            report.endList();
-
-            report.endObject();
-        }
-        catch (IOException exc) {
-            throw Unchecked.translateCheckedException(exc);
-        }
+      report.beginListAttribute("mutations");
+      method.getMutations().forEach(this::writeMutationDetails);
+      report.endList();
 
+      report.endObject();
+    } catch (IOException exc) {
+      throw Unchecked.translateCheckedException(exc);
     }
+  }
 
-    private void writeMutationDetails(MutationResult mutation) {
-        try {
+  private void writeMutationDetails(MutationResult mutation) {
+    try {
 
-            report.beginObject();
+      report.beginObject();
 
-                report.writeAttribute("status", mutation.getStatus().name());
-                report.writeAttribute("mutator", mutation.getDetails().getMutator());
-                report.writeAttribute("tests-run", mutation.getNumberOfTestsRun());
+      report.writeAttribute("status", mutation.getStatus().name());
+      report.writeAttribute("mutator", mutation.getDetails().getMutator());
+      report.writeAttribute("tests-run", mutation.getNumberOfTestsRun());
 
-                report.writeStringListAttribute("tests",
-                    mutation.getDetails().getTestsInOrder().stream().map(TestInfo::getName).collect(Collectors.toList()));
+      report.writeStringListAttribute(
+          "tests",
+          mutation.getDetails().getTestsInOrder().stream()
+              .map(TestInfo::getName)
+              .collect(Collectors.toList()));
 
-                report.writeStringListAttribute("killing-tests", mutation.getKillingTests());
-                report.writeStringListAttribute("succeeding-tests", mutation.getSucceedingTests());
+      report.writeStringListAttribute("killing-tests", mutation.getKillingTests());
+      report.writeStringListAttribute("succeeding-tests", mutation.getSucceedingTests());
 
-            report.endObject();
-        }
-        catch (IOException exc) {
-            throw Unchecked.translateCheckedException(exc);
-        }
+      report.endObject();
+    } catch (IOException exc) {
+      throw Unchecked.translateCheckedException(exc);
     }
+  }
 
-    public void runEnd() {
-        try {
+  public void runEnd() {
+    try {
 
-            report.endList();
+      report.endList();
 
-            report.beginObjectAttribute("analysis");
-            report.writeAttribute("time", System.currentTimeMillis() - args.getStartTime());
-            report.writeStringListAttribute("mutators", args.getEngine().getMutatorNames());
-            report.endObject();
+      report.beginObjectAttribute("analysis");
+      report.writeAttribute("time", System.currentTimeMillis() - args.getStartTime());
+      report.writeStringListAttribute("mutators", args.getEngine().getMutatorNames());
+      report.endObject();
 
-            report.endObject();
-            report.close();
+      report.endObject();
+      report.close();
 
-        }
-        catch(IOException exc) {
-            throw Unchecked.translateCheckedException(exc);
-        }
+    } catch (IOException exc) {
+      throw Unchecked.translateCheckedException(exc);
     }
+  }
 }
-
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/models/MethodClassification.java b/src/main/java/eu/stamp_project/descartes/reporting/models/MethodClassification.java
index 0984e99..ed39808 100644
--- a/src/main/java/eu/stamp_project/descartes/reporting/models/MethodClassification.java
+++ b/src/main/java/eu/stamp_project/descartes/reporting/models/MethodClassification.java
@@ -1,21 +1,22 @@
 package eu.stamp_project.descartes.reporting.models;
 
 public enum MethodClassification {
-    TESTED("tested"),
-    PSEUDO_TESTED("pseudo-tested"),
-    PARTIALLY_TESTED("partially-tested"),
-    NOT_COVERED("not-covered");
+  TESTED("tested"),
+  PSEUDO_TESTED("pseudo-tested"),
+  PARTIALLY_TESTED("partially-tested"),
+  NOT_COVERED("not-covered");
 
-    MethodClassification(String name) {
-        this.name = name;
-    }
+  MethodClassification(String name) {
+    this.name = name;
+  }
 
-    private final String name;
+  private final String name;
 
-    public String toString() {
-        return name;
-    }
-
-    public String getName() { return name; } // Making it compatible with Velocity
+  public String toString() {
+    return name;
+  }
 
+  public String getName() {
+    return name;
+  } // Making it compatible with Velocity
 }
diff --git a/src/main/java/eu/stamp_project/descartes/reporting/models/MethodRecord.java b/src/main/java/eu/stamp_project/descartes/reporting/models/MethodRecord.java
index e3a39b5..bcfc2e1 100644
--- a/src/main/java/eu/stamp_project/descartes/reporting/models/MethodRecord.java
+++ b/src/main/java/eu/stamp_project/descartes/reporting/models/MethodRecord.java
@@ -1,6 +1,15 @@
 package eu.stamp_project.descartes.reporting.models;
 
+import static eu.stamp_project.descartes.reporting.models.MethodClassification.*;
+import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.toSet;
 
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 import org.objectweb.asm.signature.SignatureReader;
 import org.objectweb.asm.util.TraceSignatureVisitor;
 import org.pitest.coverage.TestInfo;
@@ -9,168 +18,180 @@
 import org.pitest.mutationtest.MutationResult;
 import org.pitest.mutationtest.engine.Location;
 
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.Set;
-import java.util.stream.Collectors;
-import java.util.stream.Stream;
-import static java.util.stream.Collectors.toList;
-
-import static eu.stamp_project.descartes.reporting.models.MethodClassification.*;
-import static java.util.stream.Collectors.toSet;
-
-public class MethodRecord {
-
-    private Location location;
-    private MethodClassification classification;
-    private final Set<MutationResult> mutationResults = new HashSet<>();
-    private String fileName;
-    private int lineNumber;
-
-    public MethodRecord(MutationResult mutation) {
-        initialize(mutation);
-    }
-
-    public MethodRecord(MutationResult... mutations) {
-        if(mutations == null || mutations.length == 0)
-            throw new IllegalArgumentException("At least one mutation result must be provided.");
-        initialize(mutations[0]);
-        for (MutationResult mutation : mutations) {
-            add(mutation);
-        }
-    }
-
-    public MethodRecord(Collection<MutationResult> mutations) {
-        this(toArray(mutations));
-    }
-
-    public MethodRecord(Stream<MutationResult> mutations) {
-        this(mutations.collect(toList()));
-    }
-
-
-    private MethodClassification statusToClassification(DetectionStatus status) {
-        if(status.isDetected())
-            return TESTED;
-        if(status == DetectionStatus.NO_COVERAGE)
-            return NOT_COVERED;
-        return PSEUDO_TESTED;
-    }
-
-    private static MutationResult[] toArray(Collection<MutationResult> mutationResults) {
-        MutationResult[] results = new MutationResult[mutationResults.size()];
-        mutationResults.toArray(results);
-        return results;
-    }
-
-    private void initialize(MutationResult mutation) {
-        mutationResults.add(mutation);
-        location = mutation.getDetails().getId().getLocation();
-        classification = statusToClassification(mutation.getStatus());
-        fileName = mutation.getDetails().getFilename();
-        lineNumber = mutation.getDetails().getLineNumber();
-    }
-
-    private void updateStatus(DetectionStatus status) {
-        if(status == DetectionStatus.NO_COVERAGE) {
-            if(classification != NOT_COVERED)
-                throw new IllegalArgumentException("Method " + location.getMethodName() + " has been marked as covered and can not accept a non-covered mutation.");
-            return;
-        }
-        if(classification == NOT_COVERED)
-            throw new IllegalArgumentException("Method " + location.getMethodName() + " has been marked as non-covered and can not accept a covered mutation");
-        if((status.isDetected() && classification == PSEUDO_TESTED)
-                || (!status.isDetected() && classification == TESTED))
-            classification = PARTIALLY_TESTED;
-    }
-
-    public void add(MutationResult mutation) {
-        if(!mutation.getDetails().getId().getLocation().equals(location))
-            throw new IllegalArgumentException("All related mutations should be placed in the same location");
-        mutationResults.add(mutation);
-        updateStatus(mutation.getStatus());
-    }
-
-    public MethodClassification getClassification() {
-        return classification;
-    }
-
-    public Collection<TestInfo> getTests() {
-        return mutationResults.stream()
-                .flatMap( (mutation) -> mutation.getDetails().getTestsInOrder().stream())
-                .collect(toSet());
-    }
-
-    public Collection<MutationResult> getMutations() {
-        return Collections.unmodifiableSet(mutationResults);
-    }
-
-    public Collection<MutationResult> getDetectedMutations() {
-        return mutationResults.stream().filter(mutation -> mutation.getStatus().isDetected()).collect(toList());
-    }
-
-    public Collection<MutationResult> getUndetectedMutations() {
-        return mutationResults.stream().filter(mutation -> !mutation.getStatus().isDetected()).collect(toList());
-    }
-
-    public Location getLocation() {
-        return location;
-    }
-
-    public String getName() {
-        return location.getMethodName();
-    }
-
-    public String getDesc() {
-        return location.getMethodDesc();
-    }
-
-    public String getClassName() {
-        return location.getClassName().getNameWithoutPackage().asInternalName();
-    }
-
-    public String getPackageName() {
-        return location.getClassName().getPackage().asInternalName();
-    }
-
-    public String getFileName() { return fileName; }
-
-    public int getLineNumber() { return lineNumber; }
-
-
-    public String getDeclaration() {
-
-        TraceSignatureVisitor visitor = new TraceSignatureVisitor(0);
-        new SignatureReader(getDesc()).accept(visitor);
-        return getName() + visitor.getDeclaration();
-    }
-
-    public String getReturnType() {
-        TraceSignatureVisitor visitor = new TraceSignatureVisitor(0);
-        new SignatureReader(getDesc()).accept(visitor);
-        return visitor.getReturnType();
-    }
-
-    public boolean hasIssues() {
-        return classification == PSEUDO_TESTED || classification == PARTIALLY_TESTED;
-    }
-
-    public boolean isVoid() {
-        return getDesc().endsWith(")V");
-    }
-
-    public static String methodKey(MutationResult mutation) {
-        String className = mutation.getDetails().getClassName().asJavaName();
-        String methodName = mutation.getDetails().getMethod();
-        String methodDescription = mutation.getDetails().getId().getLocation().getMethodDesc();
-
-        return className + "." + methodName + methodDescription;
-    }
-
-    public static Stream<MethodRecord> getRecords(ClassMutationResults results) {
-        return results.getMutations().stream()
-                .collect(Collectors.groupingBy(MethodRecord::methodKey))
-                .values().stream().map(MethodRecord::new);
-    }
+public final class MethodRecord {
+
+  private Location location;
+  private MethodClassification classification;
+  private final Set<MutationResult> mutationResults = new HashSet<>();
+  private String fileName;
+  private int lineNumber;
+
+  public MethodRecord(MutationResult mutation) {
+    initialize(mutation);
+  }
+
+  public MethodRecord(MutationResult... mutations) {
+    if (mutations == null || mutations.length == 0) {
+      throw new IllegalArgumentException("At least one mutation result must be provided.");
+    }
+    initialize(mutations[0]);
+    for (MutationResult mutation : mutations) {
+      add(mutation);
+    }
+  }
+
+  public MethodRecord(Collection<MutationResult> mutations) {
+    this(toArray(mutations));
+  }
+
+  public MethodRecord(Stream<MutationResult> mutations) {
+    this(mutations.collect(toList()));
+  }
+
+  private MethodClassification statusToClassification(DetectionStatus status) {
+    if (status.isDetected()) {
+      return TESTED;
+    }
+    if (status == DetectionStatus.NO_COVERAGE) {
+      return NOT_COVERED;
+    }
+    return PSEUDO_TESTED;
+  }
+
+  private static MutationResult[] toArray(Collection<MutationResult> mutationResults) {
+    MutationResult[] results = new MutationResult[mutationResults.size()];
+    mutationResults.toArray(results);
+    return results;
+  }
+
+  private void initialize(MutationResult mutation) {
+    mutationResults.add(mutation);
+    location = mutation.getDetails().getId().getLocation();
+    classification = statusToClassification(mutation.getStatus());
+    fileName = mutation.getDetails().getFilename();
+    lineNumber = mutation.getDetails().getLineNumber();
+  }
+
+  private void updateStatus(DetectionStatus status) {
+    // TODO: Add the state machine in the comments
+    // TODO: Complete test cases based on the state machine
+    if (status == DetectionStatus.NO_COVERAGE) {
+      if (classification != NOT_COVERED) {
+        throw new IllegalArgumentException(
+            "Method "
+                + location.getMethodName()
+                + " has been marked as covered and can not accept a non-covered mutation.");
+      }
+    } else if (classification == NOT_COVERED) {
+      throw new IllegalArgumentException(
+          "Method "
+              + location.getMethodName()
+              + " has been marked as non-covered and can not accept a covered mutation");
+    } else {
+      if ((status.isDetected() && classification == PSEUDO_TESTED)
+          || (!status.isDetected() && classification == TESTED)) {
+        classification = PARTIALLY_TESTED;
+      }
+    }
+  }
+
+  public void add(MutationResult mutation) {
+    if (!mutation.getDetails().getId().getLocation().equals(location)) {
+      throw new IllegalArgumentException(
+          "All related mutations should be placed in the same location");
+    }
+    mutationResults.add(mutation);
+    updateStatus(mutation.getStatus());
+  }
+
+  public MethodClassification getClassification() {
+    return classification;
+  }
+
+  public Collection<TestInfo> getTests() {
+    return mutationResults.stream()
+        .flatMap((mutation) -> mutation.getDetails().getTestsInOrder().stream())
+        .collect(toSet());
+  }
+
+  public Collection<MutationResult> getMutations() {
+    return Collections.unmodifiableSet(mutationResults);
+  }
+
+  public Collection<MutationResult> getDetectedMutations() {
+    return mutationResults.stream()
+        .filter(mutation -> mutation.getStatus().isDetected())
+        .collect(toList());
+  }
+
+  public Collection<MutationResult> getUndetectedMutations() {
+    return mutationResults.stream()
+        .filter(mutation -> !mutation.getStatus().isDetected())
+        .collect(toList());
+  }
+
+  public Location getLocation() {
+    return location;
+  }
+
+  public String getName() {
+    return location.getMethodName();
+  }
+
+  public String getDesc() {
+    return location.getMethodDesc();
+  }
+
+  public String getClassName() {
+    return location.getClassName().getNameWithoutPackage().asInternalName();
+  }
+
+  public String getPackageName() {
+    return location.getClassName().getPackage().asInternalName();
+  }
+
+  public String getFileName() {
+    return fileName;
+  }
+
+  public int getLineNumber() {
+    return lineNumber;
+  }
+
+  public String getDeclaration() {
+
+    TraceSignatureVisitor visitor = new TraceSignatureVisitor(0);
+    new SignatureReader(getDesc()).accept(visitor);
+    return getName() + visitor.getDeclaration();
+  }
+
+  public String getReturnType() {
+    TraceSignatureVisitor visitor = new TraceSignatureVisitor(0);
+    new SignatureReader(getDesc()).accept(visitor);
+    return visitor.getReturnType();
+  }
+
+  public boolean hasIssues() {
+    return classification == PSEUDO_TESTED || classification == PARTIALLY_TESTED;
+  }
+
+  public boolean isVoid() {
+    return getDesc().endsWith(")V");
+  }
+
+  public static String methodKey(MutationResult mutation) {
+    String className = mutation.getDetails().getClassName().asJavaName();
+    String methodName = mutation.getDetails().getMethod();
+    String methodDescription = mutation.getDetails().getId().getLocation().getMethodDesc();
+
+    return className + "." + methodName + methodDescription;
+  }
+
+  public static Stream<MethodRecord> getRecords(ClassMutationResults results) {
+    return results.getMutations().stream()
+        .collect(Collectors.groupingBy(MethodRecord::methodKey))
+        .values()
+        .stream()
+        .map(MethodRecord::new);
+  }
 }
diff --git a/src/main/java/eu/stamp_project/utils/Converter.java b/src/main/java/eu/stamp_project/utils/Converter.java
index 82c3525..8a14f1b 100644
--- a/src/main/java/eu/stamp_project/utils/Converter.java
+++ b/src/main/java/eu/stamp_project/utils/Converter.java
@@ -1,4 +1,3 @@
-
 package eu.stamp_project.utils;
 
 import java.lang.reflect.InvocationTargetException;
@@ -7,59 +6,69 @@
 
 public abstract class Converter {
 
-    /**
-     * Generic call to valueOf static method of a given numeric type. Ignores underscores in the process.
-     * @param type Numeric type to which the given string representation should be converted.
-     * @param number String representation of the number.
-     * @param <T> A type that extends {@link Number}.
-     * @return Returns an instance of the given type resulted from the conversion. If conversion did not succeed returns null.
-     */
-    public static <T extends Number> T valueOf(Class<T> type, String number) {
-        try {
-            return valueOf(type, type.getDeclaredMethod("valueOf", String.class), new Object[]{number});
-        }catch(NoSuchMethodException exc) {
-            throw new RuntimeException(exc);
-        }
+  /**
+   * Generic call to valueOf static method of a given numeric type. Ignores underscores in the
+   * process.
+   *
+   * @param type Numeric type to which the given string representation should be converted.
+   * @param number String representation of the number.
+   * @param <T> A type that extends {@link Number}.
+   * @return Returns an instance of the given type resulted from the conversion. If conversion did
+   *     not succeed returns null.
+   */
+  public static <T extends Number> T valueOf(Class<T> type, String number) {
+    try {
+      return valueOf(type, type.getDeclaredMethod("valueOf", String.class), number);
+    } catch (NoSuchMethodException exc) {
+      throw new IllegalArgumentException(
+          "Given type does not have a valueOf method receiving a String as only parameter",
+          exc);
     }
+  }
 
-    /**
-     * Generic call to valueOf method of given numeric type considering a radix. Ignores underscores in the process.
-     * @param type Numeric type to which the given string representation should be converted.
-     * @param number String representation of the number.
-     * @param radix Radix to use in the conversion.
-     * @param <T> A type that extends {@link Number}.
-     * @return Returns an instance of the given type resulted form the conversion. If conversion did not succeed returns null.
-     */
-    public static <T extends Number> T valueOf(Class<T> type, String number, int radix) {
-        try {
-            return valueOf(type, type.getDeclaredMethod("valueOf", String.class, int.class), new Object[]{number, radix});
-        }catch (NoSuchMethodException exc) {
-            throw new RuntimeException(exc);
-        }
-
+  /**
+   * Generic call to valueOf method of given numeric type considering a radix. Ignores underscores
+   * in the process.
+   *
+   * @param type Numeric type to which the given string representation should be converted.
+   * @param number String representation of the number.
+   * @param radix Radix to use in the conversion.
+   * @param <T> A type that extends {@link Number}.
+   * @return Returns an instance of the given type resulted form the conversion. If conversion did
+   *     not succeed returns null.
+   */
+  public static <T extends Number> T valueOf(Class<T> type, String number, int radix) {
+    try {
+      return valueOf(
+          type,
+          type.getDeclaredMethod("valueOf", String.class, int.class),
+          number, radix);
+    } catch (NoSuchMethodException exc) {
+      throw new IllegalArgumentException(
+          "Provided value type does not have a valueOf method receiving"
+              + "a String and integer as parameters",
+          exc);
     }
+  }
 
-    private static <T extends Number> T valueOf(Class<T> type, Method method, Object... args) {
-        T result;
-        try {
-            args[0] = args[0].toString().replace("_", "");
-            result = type.cast(method.invoke(null, args));
-        }
-        catch(InvocationTargetException exc) {
-            //Parsing error
-            result = null;
-        }
-        catch(Exception exc) {
-            //This should not happen
-            throw new RuntimeException(exc.getMessage(), exc);
-        }
-        return result;
-        /* /NOTE:
-        *  I have tried to encapsulate the code for obtaining the valueOf method
-        *  by getting the type of actual parameters in args.
-        *  But when you assign an int value to an Object then it becomes an Integer.
-        *  So getDeclaredMethod is not able to find the requested method.
-        * */
+  private static <T extends Number> T valueOf(Class<T> type, Method method, Object... args) {
+    T result;
+    try {
+      args[0] = args[0].toString().replace("_", "");
+      result = type.cast(method.invoke(null, args));
+    } catch (InvocationTargetException exc) {
+      // Parsing error
+      result = null;
+    } catch (Exception exc) {
+      // This should not happen
+      throw new IllegalStateException(exc.getMessage(), exc);
     }
-
+    return result;
+    /* /NOTE:
+     *  I have tried to encapsulate the code for obtaining the valueOf method
+     *  by getting the type of actual parameters in args.
+     *  But when you assign an int value to an Object then it becomes an Integer.
+     *  So getDeclaredMethod is not able to find the requested method.
+     * */
+  }
 }
diff --git a/src/main/java/eu/stamp_project/utils/TypeHelper.java b/src/main/java/eu/stamp_project/utils/TypeHelper.java
index 24a0b17..f488f1f 100644
--- a/src/main/java/eu/stamp_project/utils/TypeHelper.java
+++ b/src/main/java/eu/stamp_project/utils/TypeHelper.java
@@ -5,65 +5,65 @@
 import java.util.Set;
 
 /**
- * Utility class to handle the interaction between primitive types and their wrappers
- * Part of the code inspired by/taken from google guava (https://github/google/guava)
+ * Utility class to handle the interaction between primitive types and their wrappers Part of the
+ * code inspired by/taken from <a href="https://github/google/guava">Google Guava</a>.
  */
 public final class TypeHelper {
 
-    private TypeHelper() {}
-
-    private static final Map<Class<?>, Class<?>> PRIMITIVE_TO_WRAPPER_MAP;
-
-    private static final Map<Class<?>,Class<?>> WRAPPER_TO_PRIMITIVE_MAP;
-
-    static {
-        PRIMITIVE_TO_WRAPPER_MAP = new HashMap<>(16);
-        WRAPPER_TO_PRIMITIVE_MAP = new HashMap<>(16);
-
-        add(boolean.class, Boolean.class);
-        add(byte.class, Byte.class);
-        add(char.class, Character.class);
-        add(double.class, Double.class);
-        add(float.class, Float.class);
-        add(int.class, Integer.class);
-        add(long.class, Long.class);
-        add(short.class, Short.class);
-        add(void.class, Void.class);
-    }
-
-    private static void add(Class<?> primitive, Class<?> wrapper) {
-        PRIMITIVE_TO_WRAPPER_MAP.put(primitive, wrapper);
-        WRAPPER_TO_PRIMITIVE_MAP.put(wrapper, primitive);
-    }
-
-    public static Set<Class<?>> getPrimitiveTypes() { return PRIMITIVE_TO_WRAPPER_MAP.keySet(); }
-
-
-    public static Set<Class<?>> getWrapperTypes() { return WRAPPER_TO_PRIMITIVE_MAP.keySet(); }
-
-    public static boolean isPrimitiveType(Class<?> type) {
-        //Just for symmetry
-        return type.isPrimitive();
-    }
-
-    public static boolean isWrapperType(Class<?> type) {
-        return WRAPPER_TO_PRIMITIVE_MAP.containsKey(type);
-    }
-
-    public static boolean isConstantType(Class<?> type) {
-        return  (!type.equals(void.class) && !type.equals(Void.class)) && //Not void
-                ((type.isPrimitive() || isWrapperType(type)) || type.equals(String.class));
-    }
-
-    public static Class<?> wrap(Class<?> type) {
-        if(type.isPrimitive())
-            return PRIMITIVE_TO_WRAPPER_MAP.get(type);
-        return type;
-    }
-
-    public static Class<?> unwrap(Class<?> type) {
-        if(isWrapperType(type))
-            return WRAPPER_TO_PRIMITIVE_MAP.get(type);
-        return type;
-    }
+  private TypeHelper() {}
+
+  private static final Map<Class<?>, Class<?>> PRIMITIVE_TO_WRAPPER_MAP;
+
+  private static final Map<Class<?>, Class<?>> WRAPPER_TO_PRIMITIVE_MAP;
+
+  static {
+    PRIMITIVE_TO_WRAPPER_MAP = new HashMap<>(16);
+    WRAPPER_TO_PRIMITIVE_MAP = new HashMap<>(16);
+
+    add(boolean.class, Boolean.class);
+    add(byte.class, Byte.class);
+    add(char.class, Character.class);
+    add(double.class, Double.class);
+    add(float.class, Float.class);
+    add(int.class, Integer.class);
+    add(long.class, Long.class);
+    add(short.class, Short.class);
+    add(void.class, Void.class);
+  }
+
+  private static void add(Class<?> primitive, Class<?> wrapper) {
+    PRIMITIVE_TO_WRAPPER_MAP.put(primitive, wrapper);
+    WRAPPER_TO_PRIMITIVE_MAP.put(wrapper, primitive);
+  }
+
+  public static Set<Class<?>> getPrimitiveTypes() {
+    return PRIMITIVE_TO_WRAPPER_MAP.keySet();
+  }
+
+  public static Set<Class<?>> getWrapperTypes() {
+    return WRAPPER_TO_PRIMITIVE_MAP.keySet();
+  }
+
+  public static boolean isPrimitiveType(Class<?> type) {
+    // Just for symmetry
+    return type.isPrimitive();
+  }
+
+  public static boolean isWrapperType(Class<?> type) {
+    return WRAPPER_TO_PRIMITIVE_MAP.containsKey(type);
+  }
+
+  public static boolean isConstantType(Class<?> type) {
+    return (!type.equals(void.class) && !type.equals(Void.class))
+        && // Not void
+        ((type.isPrimitive() || isWrapperType(type)) || type.equals(String.class));
+  }
+
+  public static Class<?> wrap(Class<?> type) {
+    return (type.isPrimitive()) ? PRIMITIVE_TO_WRAPPER_MAP.get(type) : type;
+  }
+
+  public static Class<?> unwrap(Class<?> type) {
+    return isWrapperType(type) ? WRAPPER_TO_PRIMITIVE_MAP.get(type) : type;
+  }
 }
diff --git a/src/main/java/eu/stamp_project/utils/Utils.java b/src/main/java/eu/stamp_project/utils/Utils.java
index f250c5f..6e69023 100644
--- a/src/main/java/eu/stamp_project/utils/Utils.java
+++ b/src/main/java/eu/stamp_project/utils/Utils.java
@@ -2,9 +2,11 @@
 
 public class Utils {
 
-    public static boolean hasFlag(int value, int flag) {
-        return (value & flag) != 0;
-    }
+  public static boolean hasFlag(int value, int flag) {
+    return (value & flag) != 0;
+  }
 
-    public static boolean isConstructor(String name) {  return name.equals("<init>"); }
+  public static boolean isConstructor(String name) {
+    return name.equals("<init>");
+  }
 }
diff --git a/src/main/resources/META-INF/services/org.pitest.mutationtest.MutationResultListenerFactory b/src/main/resources/META-INF/services/org.pitest.mutationtest.MutationResultListenerFactory
index 7b9d310..276486e 100644
--- a/src/main/resources/META-INF/services/org.pitest.mutationtest.MutationResultListenerFactory
+++ b/src/main/resources/META-INF/services/org.pitest.mutationtest.MutationResultListenerFactory
@@ -1,3 +1,3 @@
-eu.stamp_project.descartes.reporting.JSONReportFactory
+eu.stamp_project.descartes.reporting.JsonReportFactory
 eu.stamp_project.descartes.reporting.MethodTestingFactory
 eu.stamp_project.descartes.reporting.IssuesReportFactory
diff --git a/src/test/java/eu/stamp_project/descartes/IntegrationTest.java b/src/test/java/eu/stamp_project/descartes/IntegrationTest.java
index 09fcbd9..337eb48 100644
--- a/src/test/java/eu/stamp_project/descartes/IntegrationTest.java
+++ b/src/test/java/eu/stamp_project/descartes/IntegrationTest.java
@@ -1,6 +1,17 @@
 package eu.stamp_project.descartes;
 
+import static eu.stamp_project.test.Utils.getClassTree;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.*;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import eu.stamp_project.test.input.*;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
 import org.junit.jupiter.api.Test;
 import org.pitest.bytecode.analysis.ClassTree;
 import org.pitest.classinfo.ClassByteArraySource;
@@ -18,99 +29,92 @@
 import org.pitest.mutationtest.engine.MutationEngine;
 import tests.Person;
 
-import java.io.IOException;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.List;
-import java.util.Set;
-import java.util.stream.Collectors;
-
-import static eu.stamp_project.test.Utils.getClassTree;
-import static org.hamcrest.MatcherAssert.assertThat;
-import static org.hamcrest.Matchers.*;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
 class IntegrationTest {
 
-    @Test
-    void testShouldNotFindMutationsInKotlinDataClass() throws IOException {
-        assertThat(findMutationsWithDefaultOptions(Person.class), empty());
-    }
-
-    @Test
-    void testShouldNotFinAnyStopMethod() throws IOException {
-        assertThat(findMutationsWithDefaultOptions(StopMethods.class), empty());
-    }
-
-    @Test
-    void shouldNotFindNativeMethods() throws IOException  {
-        assertThat(findMutations(NativeMethodClass.class, noFeatures()), empty());
-    }
-
-    @Test
-    void shouldNotFindAnyMutationPointInInterface() throws IOException {
-        assertThat(findMutationsWithDefaultOptions(Interface.class), empty());
-    }
-
-    @Test
-    void shouldSkipMethodsWithPattern() throws IOException {
-        Collection<MutationDetails> mutations = findMutations(Calculator.class, excludeMethods("get*"));
-        Set<String> methods = methodsFrom(mutations);
-        assertTrue(methods.stream().noneMatch(name -> name.startsWith("get")), "No mutated method should start by 'get'.");
-    }
-
-    @Test
-    void shouldNotFindAbstractMethods() throws IOException {
-        Collection<MutationDetails> mutations = findMutations(AbstractClass.class, noFeatures());
-        Set<String> methods = methodsFrom(mutations);
-        assertThat(methods, both(contains("nonAbstractMethod")).and(not(contains("abstractMethod"))));
-    }
-
-    private static Set<String> methodsFrom(Collection<MutationDetails> mutations) {
-        return mutations.stream().map(MutationDetails::getMethod).collect(Collectors.toSet());
-    }
-
-    private static Collection<MutationDetails> findMutationsWithDefaultOptions(Class<?> target) throws IOException {
-        return findMutations(target, defaultOptions());
-    }
-
-    private static Collection<MutationDetails> findMutations(Class<?> target, ReportOptions options) throws IOException {
-        SettingsFactory factory = new SettingsFactory(options, PluginServices.makeForContextLoader());
-        EngineArguments arguments = new EngineArguments(options.getMutators(), options.getExcludedMethods());
-        MutationEngineFactory engineFactory = factory.createEngine();
-        MutationEngine engine = engineFactory.createEngine(arguments);
-        ClassByteArraySource source = ClassloaderByteArraySource.fromContext();
-        CompoundInterceptorFactory interceptorFactory = factory.getInterceptor();
-        // Interceptors with no coverage information and no test prioritization
-        MutationInterceptor interceptor = interceptorFactory.createInterceptor(options, null, source, null);
-        Mutater mutater = engine.createMutator(source);
-        ClassName className = ClassName.fromClass(target);
-        List<MutationDetails> mutations = mutater.findMutations(className);
-        ClassTree classTree = getClassTree(target);
-        interceptor.begin(classTree);
-        return interceptor.intercept(mutations, mutater);
-    }
-
-    private static ReportOptions defaultOptions() {
-        ReportOptions options = new ReportOptions();
-        options.setMutationEngine("descartes");
-        return options;
-    }
-
-    private static ReportOptions useFeatures(String... features) {
-        ReportOptions options = defaultOptions();
-        options.setFeatures(Arrays.asList(features));
-        return options;
-    }
-
-    private static ReportOptions noFeatures() {
-        return useFeatures("-DO_NOT_MUTATE()", "-AVOID_NULL", "-STOP_METHODS()");
-    }
-
-    private static ReportOptions excludeMethods(String... methods) {
-        ReportOptions options = defaultOptions();
-        options.setExcludedMethods(Arrays.asList(methods));
-        return options;
-    }
-
+  @Test
+  void testShouldNotFindMutationsInKotlinDataClass() throws IOException {
+    assertThat(findMutationsWithDefaultOptions(Person.class), empty());
+  }
+
+  @Test
+  void testShouldNotFinAnyStopMethod() throws IOException {
+    assertThat(findMutationsWithDefaultOptions(StopMethods.class), empty());
+  }
+
+  @Test
+  void shouldNotFindNativeMethods() throws IOException {
+    assertThat(findMutations(NativeMethodClass.class, noFeatures()), empty());
+  }
+
+  @Test
+  void shouldNotFindAnyMutationPointInInterface() throws IOException {
+    assertThat(findMutationsWithDefaultOptions(Interface.class), empty());
+  }
+
+  @Test
+  void shouldSkipMethodsWithPattern() throws IOException {
+    Collection<MutationDetails> mutations = findMutations(Calculator.class, excludeMethods("get*"));
+    Set<String> methods = methodsFrom(mutations);
+    assertTrue(
+        methods.stream().noneMatch(name -> name.startsWith("get")),
+        "No mutated method should start by 'get'.");
+  }
+
+  @Test
+  void shouldNotFindAbstractMethods() throws IOException {
+    Collection<MutationDetails> mutations = findMutations(AbstractClass.class, noFeatures());
+    Set<String> methods = methodsFrom(mutations);
+    assertThat(methods, both(contains("nonAbstractMethod")).and(not(contains("abstractMethod"))));
+  }
+
+  private static Set<String> methodsFrom(Collection<MutationDetails> mutations) {
+    return mutations.stream().map(MutationDetails::getMethod).collect(Collectors.toSet());
+  }
+
+  private static Collection<MutationDetails> findMutationsWithDefaultOptions(Class<?> target)
+      throws IOException {
+    return findMutations(target, defaultOptions());
+  }
+
+  private static Collection<MutationDetails> findMutations(Class<?> target, ReportOptions options)
+      throws IOException {
+    SettingsFactory factory = new SettingsFactory(options, PluginServices.makeForContextLoader());
+    EngineArguments arguments =
+        new EngineArguments(options.getMutators(), options.getExcludedMethods());
+    MutationEngineFactory engineFactory = factory.createEngine();
+    MutationEngine engine = engineFactory.createEngine(arguments);
+    ClassByteArraySource source = ClassloaderByteArraySource.fromContext();
+    CompoundInterceptorFactory interceptorFactory = factory.getInterceptor();
+    // Interceptors with no coverage information and no test prioritization
+    MutationInterceptor interceptor =
+        interceptorFactory.createInterceptor(options, null, source, null);
+    Mutater mutater = engine.createMutator(source);
+    ClassName className = ClassName.fromClass(target);
+    List<MutationDetails> mutations = mutater.findMutations(className);
+    ClassTree classTree = getClassTree(target);
+    interceptor.begin(classTree);
+    return interceptor.intercept(mutations, mutater);
+  }
+
+  private static ReportOptions defaultOptions() {
+    ReportOptions options = new ReportOptions();
+    options.setMutationEngine("descartes");
+    return options;
+  }
+
+  private static ReportOptions useFeatures(String... features) {
+    ReportOptions options = defaultOptions();
+    options.setFeatures(Arrays.asList(features));
+    return options;
+  }
+
+  private static ReportOptions noFeatures() {
+    return useFeatures("-DO_NOT_MUTATE()", "-AVOID_NULL", "-STOP_METHODS()");
+  }
+
+  private static ReportOptions excludeMethods(String... methods) {
+    ReportOptions options = defaultOptions();
+    options.setExcludedMethods(Arrays.asList(methods));
+    return options;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilterTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilterTest.java
index 5e020ad..dc9d8bd 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilterTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/AvoidNullInNotNullFilterTest.java
@@ -1,46 +1,43 @@
-
 package eu.stamp_project.descartes.interceptors;
 
-import org.junit.jupiter.api.Test;
-import org.pitest.mutationtest.engine.MutationDetails;
-import tests.Person;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.IOException;
 import java.lang.reflect.Method;
-
-import static eu.stamp_project.test.Utils.getClassTree;
-import static eu.stamp_project.test.Utils.toMutationIdentifier;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import org.junit.jupiter.api.Test;
+import tests.Person;
 
 public class AvoidNullInNotNullFilterTest extends MutationFilterTest<AvoidNullInNotNullFilter> {
 
-    //NOTE: Not using parameterized tests to make explicit the intention of each test case.
-
-    @Override
-    public AvoidNullInNotNullFilter getFilter() { return new AvoidNullInNotNullFilter(); }
-
-    private Method method(String name, Class<?>... params) throws NoSuchMethodException {
-        return tests.PersonKt.class.getDeclaredMethod(name, params);
-    }
-
-    @Test
-    public void testNullOperatorNonNullResult() throws IOException, NoSuchMethodException {
-        assertFalse(allows(method("getNonNullString"), "null"));
-    }
-
-    @Test
-    public void testNullOperatorPotentialNullResult() throws NoSuchMethodException, IOException {
-        assertTrue(allows(method("getPossiblyNullString", Person.class), "null"));
-    }
-
-    @Test
-    public void testNonNullOperatorNonNullResult() throws NoSuchMethodException, IOException {
-        assertTrue(allows(method("getNonNullString"), "\"A\""));
-    }
-
-    @Test
-    public void testNonNullOperatorPotentiallyNulResult() throws NoSuchMethodException, IOException {
-        assertTrue(allows(method("getPossiblyNullString", Person.class), "\"A\""));
-    }
-}
\ No newline at end of file
+  // NOTE: Not using parameterized tests to make explicit the intention of each test case.
+
+  @Override
+  public AvoidNullInNotNullFilter getFilter() {
+    return new AvoidNullInNotNullFilter();
+  }
+
+  private Method method(String name, Class<?>... params) throws NoSuchMethodException {
+    return tests.PersonKt.class.getDeclaredMethod(name, params);
+  }
+
+  @Test
+  public void testNullOperatorNonNullResult() throws IOException, NoSuchMethodException {
+    assertFalse(allows(method("getNonNullString"), "null"));
+  }
+
+  @Test
+  public void testNullOperatorPotentialNullResult() throws NoSuchMethodException, IOException {
+    assertTrue(allows(method("getPossiblyNullString", Person.class), "null"));
+  }
+
+  @Test
+  public void testNonNullOperatorNonNullResult() throws NoSuchMethodException, IOException {
+    assertTrue(allows(method("getNonNullString"), "\"A\""));
+  }
+
+  @Test
+  public void testNonNullOperatorPotentiallyNulResult() throws NoSuchMethodException, IOException {
+    assertTrue(allows(method("getPossiblyNullString", Person.class), "\"A\""));
+  }
+}
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/MutationFilterTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/MutationFilterTest.java
index 0d96226..010ef96 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/MutationFilterTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/MutationFilterTest.java
@@ -1,24 +1,23 @@
 package eu.stamp_project.descartes.interceptors;
 
-import org.pitest.mutationtest.engine.MutationDetails;
+import static eu.stamp_project.test.Utils.getClassTree;
+import static eu.stamp_project.test.Utils.toMutationIdentifier;
 
 import java.io.IOException;
 import java.lang.reflect.Method;
-
-import static eu.stamp_project.test.Utils.getClassTree;
-import static eu.stamp_project.test.Utils.toMutationIdentifier;
+import org.pitest.mutationtest.engine.MutationDetails;
 
 public abstract class MutationFilterTest<T extends MutationFilter> {
 
-    public abstract T getFilter();
+  public abstract T getFilter();
 
-    protected MutationDetails getMutationDetails(Method method, String operator) {
-        return new MutationDetails(toMutationIdentifier(method, operator), "", "", 0, 0);
-    }
+  protected MutationDetails getMutationDetails(Method method, String operator) {
+    return new MutationDetails(toMutationIdentifier(method, operator), "", "", 0, 0);
+  }
 
-    protected boolean allows(Method method, String mutator) throws IOException {
-        MutationFilter filter = getFilter();
-        filter.begin(getClassTree(method.getDeclaringClass()));
-        return filter.allows(getMutationDetails(method, mutator));
-    }
+  protected boolean allows(Method method, String mutator) throws IOException {
+    MutationFilter filter = getFilter();
+    filter.begin(getClassTree(method.getDeclaringClass()));
+    return filter.allows(getMutationDetails(method, mutator));
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilterTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilterTest.java
index e97dfaf..0bbf711 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilterTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/SkipDoNotMutateFilterTest.java
@@ -1,56 +1,59 @@
 package eu.stamp_project.descartes.interceptors;
 
+import static org.junit.jupiter.api.Assertions.*;
+
 import eu.stamp_project.test.input.SkipFalseMutationOnAllButOne;
 import eu.stamp_project.test.input.SkipMutationOnMethod;
 import eu.stamp_project.test.input.SkipMutationTarget;
-import org.junit.jupiter.api.Test;
-
 import java.io.IOException;
 import java.lang.reflect.Method;
-
-import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.Test;
 
 class SkipDoNotMutateFilterTest extends MutationFilterTest {
 
-    @Override
-    public MutationFilter getFilter() { return new SkipDoNotMutateFilter(); }
-
-    @Test
-    public void testSkipMethodInAnnotatedClass () throws NoSuchMethodException, IOException {
-        Method method = SkipMutationTarget.class.getDeclaredMethod("methodToSkip");
-        assertFalse(allows(method, "void"));
-    }
-
-    @Test
-    public void testSkipAnnotatedMethodInNonAnnotatedClass() throws NoSuchMethodException, IOException {
-        Method method = SkipMutationOnMethod.class.getDeclaredMethod("methodToSkip");
-        assertFalse(allows(method, "void"));
-    }
-
-    @Test
-    public void testSkipSpecificMutationFromClassAnnotation() throws NoSuchMethodException, IOException {
-        Method method = SkipFalseMutationOnAllButOne.class.getDeclaredMethod("returnFalse");
-        assertFalse(allows(method, "false"));
-    }
-
-    @Test
-    public void testAllowSpecificMutationFromClassAnnotation() throws NoSuchMethodException, IOException {
-        Method method = SkipFalseMutationOnAllButOne.class.getDeclaredMethod("returnFalse");
-        assertTrue(allows(method, "true"));
-    }
-
-    @Test
-    public void testSkipSpecificMutationFromMethodAnnotation() throws NoSuchMethodException, IOException {
-        Method method = SkipFalseMutationOnAllButOne.class.getDeclaredMethod("returnTrue");
-        assertFalse(allows(method, "true"));
-    }
-
-    @Test
-    public void testAllowSpecificMutationAsPerMethodAnnotation() throws NoSuchMethodException, IOException {
-        Method method = SkipFalseMutationOnAllButOne.class.getDeclaredMethod("returnTrue");
-        assertTrue(allows(method, "false"));
-    }
-
-
-
-}
\ No newline at end of file
+  @Override
+  public MutationFilter getFilter() {
+    return new SkipDoNotMutateFilter();
+  }
+
+  @Test
+  public void testSkipMethodInAnnotatedClass() throws NoSuchMethodException, IOException {
+    Method method = SkipMutationTarget.class.getDeclaredMethod("methodToSkip");
+    assertFalse(allows(method, "void"));
+  }
+
+  @Test
+  public void testSkipAnnotatedMethodInNonAnnotatedClass()
+      throws NoSuchMethodException, IOException {
+    Method method = SkipMutationOnMethod.class.getDeclaredMethod("methodToSkip");
+    assertFalse(allows(method, "void"));
+  }
+
+  @Test
+  public void testSkipSpecificMutationFromClassAnnotation()
+      throws NoSuchMethodException, IOException {
+    Method method = SkipFalseMutationOnAllButOne.class.getDeclaredMethod("returnFalse");
+    assertFalse(allows(method, "false"));
+  }
+
+  @Test
+  public void testAllowSpecificMutationFromClassAnnotation()
+      throws NoSuchMethodException, IOException {
+    Method method = SkipFalseMutationOnAllButOne.class.getDeclaredMethod("returnFalse");
+    assertTrue(allows(method, "true"));
+  }
+
+  @Test
+  public void testSkipSpecificMutationFromMethodAnnotation()
+      throws NoSuchMethodException, IOException {
+    Method method = SkipFalseMutationOnAllButOne.class.getDeclaredMethod("returnTrue");
+    assertFalse(allows(method, "true"));
+  }
+
+  @Test
+  public void testAllowSpecificMutationAsPerMethodAnnotation()
+      throws NoSuchMethodException, IOException {
+    Method method = SkipFalseMutationOnAllButOne.class.getDeclaredMethod("returnTrue");
+    assertTrue(allows(method, "false"));
+  }
+}
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilterTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilterTest.java
index d9f699d..056b1a2 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilterTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/SkipShortMethodsFilterTest.java
@@ -1,31 +1,29 @@
 package eu.stamp_project.descartes.interceptors;
 
-import eu.stamp_project.test.input.Calculator;
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import eu.stamp_project.test.input.Calculator;
 import java.io.IOException;
 import java.lang.reflect.Method;
-
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import org.junit.jupiter.api.Test;
 
 class SkipShortMethodsFilterTest extends MutationFilterTest<SkipShortMethodsFilter> {
 
-    @Override
-    public SkipShortMethodsFilter getFilter() {
-        return new SkipShortMethodsFilter(3);
-    }
-
-    @Test
-    public void testAllowsLargeEnoughMethod() throws NoSuchMethodException, IOException {
-        Method method = Calculator.class.getDeclaredMethod("getSomething");
-        assertTrue(allows(method, "1.2f"));
-    }
-
-    @Test
-    public void testInterceptShortMethod() throws IOException, NoSuchMethodException {
-        Method method = Calculator.class.getDeclaredMethod("getCeiling");
-        assertFalse(allows(method, "1"));
-    }
-
-}
\ No newline at end of file
+  @Override
+  public SkipShortMethodsFilter getFilter() {
+    return new SkipShortMethodsFilter(3);
+  }
+
+  @Test
+  public void testAllowsLargeEnoughMethod() throws NoSuchMethodException, IOException {
+    Method method = Calculator.class.getDeclaredMethod("getSomething");
+    assertTrue(allows(method, "1.2f"));
+  }
+
+  @Test
+  public void testInterceptShortMethod() throws IOException, NoSuchMethodException {
+    Method method = Calculator.class.getDeclaredMethod("getCeiling");
+    assertFalse(allows(method, "1"));
+  }
+}
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/DelegateMethodMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/DelegateMethodMatcherTest.java
index 4f023f4..7305ee3 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/DelegateMethodMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/DelegateMethodMatcherTest.java
@@ -1,41 +1,40 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-
 public class DelegateMethodMatcherTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        return fromClass(StopMethods.class)
-                .method("delegateSelfStaticVoid", int.class)
-                .method("delegateSelfVoid", int.class)
-                .method("delegateSelfValue", String.class, int.class, int.class)
-                .method("delegateParameterValue", String.class, int.class, int.class)
-                .method("delegateFieldValue", int.class, int.class)
-                .method("delegateToExternalClass", String.class)
-                .method("delegateToStatic", String.class)
-                .method("delegateToStatic")
-                .toStream();
-    }
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return fromClass(StopMethods.class)
+        .method("delegateSelfStaticVoid", int.class)
+        .method("delegateSelfVoid", int.class)
+        .method("delegateSelfValue", String.class, int.class, int.class)
+        .method("delegateParameterValue", String.class, int.class, int.class)
+        .method("delegateFieldValue", int.class, int.class)
+        .method("delegateToExternalClass", String.class)
+        .method("delegateToStatic", String.class)
+        .method("delegateToStatic")
+        .toStream();
+  }
 
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("getMultipleCalculators", int.class)
-                .method("isOdd")
-                .method("getCeiling")
-                .method("getSquare")
-                .toStream();
-    }
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("getMultipleCalculators", int.class)
+        .method("isOdd")
+        .method("getCeiling")
+        .method("getSquare")
+        .toStream();
+  }
 
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.isDelegate();
-    }
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.IS_DELEGATE;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/DeprecatedClassTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/DeprecatedClassTest.java
index cd30d96..4cdb873 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/DeprecatedClassTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/DeprecatedClassTest.java
@@ -1,35 +1,32 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+import static eu.stamp_project.test.MethodStreamBuilder.select;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.DeprecatedClass;
 import eu.stamp_project.test.input.StopMethods;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-import static eu.stamp_project.test.MethodStreamBuilder.select;
-
 public class DeprecatedClassTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        return select(
-                fromClass(DeprecatedClass.class)
-                        .method("methodInsideDeprecatedClass")
-                        .method("deprecatedInDeprecatedClass"),
-                fromClass(StopMethods.class)
-                        .method("isDeprecated"));
-    }
-
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return Stream.of(Calculator.class.getDeclaredMethod("getCeiling"));
-    }
-
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.isDeprecated();
-    }
-
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return select(
+        fromClass(DeprecatedClass.class)
+            .method("methodInsideDeprecatedClass")
+            .method("deprecatedInDeprecatedClass"),
+        fromClass(StopMethods.class).method("isDeprecated"));
+  }
+
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return Stream.of(Calculator.class.getDeclaredMethod("getCeiling"));
+  }
+
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.IS_DEPRECATED;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EmptyArrayMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EmptyArrayMatcherTest.java
index 9449914..e404951 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EmptyArrayMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EmptyArrayMatcherTest.java
@@ -1,38 +1,36 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-
 public class EmptyArrayMatcherTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept () throws NoSuchMethodException {
-        return fromClass(StopMethods.class)
-                .method("emptyIntArray")
-                .method("emptyInt2Array")
-                .method("emptyMatrix")
-                .method("emptyStringArray")
-                .method("emptyStringMatrix")
-                .toStream();
-    }
-
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("getSomeCalculators", int.class)
-                .method("getSomeMore", int.class)
-                .method("getRange", int.class)
-                .toStream();
-    }
-
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.returnsAnEmptyArray();
-    }
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return fromClass(StopMethods.class)
+        .method("emptyIntArray")
+        .method("emptyInt2Array")
+        .method("emptyMatrix")
+        .method("emptyStringArray")
+        .method("emptyStringMatrix")
+        .toStream();
+  }
+
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("getSomeCalculators", int.class)
+        .method("getSomeMore", int.class)
+        .method("getRange", int.class)
+        .toStream();
+  }
+
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.RETURNS_EMPTY_ARRAY;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EmptyVoidMethodMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EmptyVoidMethodMatcherTest.java
index ec59679..51de747 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EmptyVoidMethodMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EmptyVoidMethodMatcherTest.java
@@ -2,24 +2,23 @@
 
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
 class EmptyVoidMethodMatcherTest extends MethodMatcherTest {
 
-    @Override
-    public Stream<Method> toIntercept() throws NoSuchMethodException {
-        return Stream.of(StopMethods.class.getDeclaredMethod("emptyVoidMethod"));
-    }
+  @Override
+  public Stream<Method> toIntercept() throws NoSuchMethodException {
+    return Stream.of(StopMethods.class.getDeclaredMethod("emptyVoidMethod"));
+  }
 
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return Stream.of(Calculator.class.getDeclaredMethod("clear"));
-    }
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return Stream.of(Calculator.class.getDeclaredMethod("clear"));
+  }
 
-    @Override
-    public StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.isEmptyVoid();
-    }
+  @Override
+  public MethodMatcher getMatcher() {
+    return StopMethodMatchers.IS_EMPTY_VOID;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EnumMethodMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EnumMethodMatcherTest.java
index 4139c31..b558389 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EnumMethodMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/EnumMethodMatcherTest.java
@@ -1,33 +1,29 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+import static eu.stamp_project.test.MethodStreamBuilder.select;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.Numbers;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-import static eu.stamp_project.test.MethodStreamBuilder.select;
-
-public class EnumMethodMatcherTest extends MethodMatcherTest{
+public class EnumMethodMatcherTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        return fromClass(Numbers.class).allDeclaredMethods()
-                .except("extraMethod")
-                .toStream();
-    }
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return fromClass(Numbers.class).allDeclaredMethods().except("extraMethod").toStream();
+  }
 
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return select(
-                fromClass(Numbers.class).method("extraMethod"),
-                fromClass(Calculator.class).method("getRange", int.class)
-        );
-    }
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return select(
+        fromClass(Numbers.class).method("extraMethod"),
+        fromClass(Calculator.class).method("getRange", int.class));
+  }
 
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.isEnumGenerated();
-    }
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.IS_ENUM_GENERATED;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/HashcodeMethodMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/HashcodeMethodMatcherTest.java
index 3567c83..73cc639 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/HashcodeMethodMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/HashcodeMethodMatcherTest.java
@@ -1,32 +1,29 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-
 class HashcodeMethodMatcherTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        return fromClass(StopMethods.class).method("hashCode")
-                .toStream();
-    }
-
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("getCeiling") // Same signature
-                .method("hashCode", int.class) // Same name
-                .toStream();
-    }
-
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.isHashCode();
-    }
-
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return fromClass(StopMethods.class).method("hashCode").toStream();
+  }
+
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("getCeiling") // Same signature
+        .method("hashCode", int.class) // Same name
+        .toStream();
+  }
+
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.IS_HASH_CODE;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/IsKotlinGeneratedSetterMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/IsKotlinGeneratedSetterMatcherTest.java
index 17513a1..906b3f2 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/IsKotlinGeneratedSetterMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/IsKotlinGeneratedSetterMatcherTest.java
@@ -5,20 +5,20 @@
 
 public class IsKotlinGeneratedSetterMatcherTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        // Generated setter with null checks
-        return Stream.of(tests.Person.class.getDeclaredMethod("setName", String.class));
-    }
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    // Generated setter with null checks
+    return Stream.of(tests.Person.class.getDeclaredMethod("setName", String.class));
+  }
 
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        // This is also generated by the Kotlin compiler but it is a regular setter
-        return Stream.of(tests.Person.class.getDeclaredMethod("setAge", int.class));
-    }
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    // This is also generated by the Kotlin compiler, but it is a regular setter
+    return Stream.of(tests.Person.class.getDeclaredMethod("setAge", int.class));
+  }
 
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.isKotlinGeneratedSetter();
-    }
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.IS_KOTLIN_GENERATED_SETTER;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/MethodMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/MethodMatcherTest.java
index ac2d8d6..0110376 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/MethodMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/MethodMatcherTest.java
@@ -1,5 +1,13 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.Utils.getClassTree;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+import java.lang.reflect.Method;
+import java.util.Optional;
+import java.util.stream.Stream;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.DynamicTest;
 import org.junit.jupiter.api.TestFactory;
@@ -8,57 +16,56 @@
 import org.pitest.mutationtest.engine.Location;
 import org.pitest.reloc.asm.Type;
 
-import java.io.IOException;
-import java.lang.reflect.Method;
-import java.util.Optional;
-import java.util.stream.Stream;
-
-import static eu.stamp_project.test.Utils.getClassTree;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
 abstract class MethodMatcherTest {
 
-    abstract Stream<Method> toIntercept() throws NoSuchMethodException;
-
-    abstract Stream<Method> toAllow() throws NoSuchMethodException;
+  abstract Stream<Method> toIntercept() throws NoSuchMethodException;
 
-    abstract StopMethodMatcher getMatcher();
+  abstract Stream<Method> toAllow() throws NoSuchMethodException;
 
-    @TestFactory
-    @DisplayName("Matcher should intercept")
-    Stream<DynamicTest> testShouldInterceptMethods() throws NoSuchMethodException {
-        return toIntercept().map(
-                method -> DynamicTest.dynamicTest(
-                        method.toGenericString(),
-                        () -> assertTrue(matches(method), "Matcher should intercept method " + method.toGenericString())
-                )
-        );
-    }
+  abstract MethodMatcher getMatcher();
 
-    @TestFactory
-    @DisplayName("Matcher should not intercept")
-    Stream<DynamicTest> testShouldNotInterceptMethods() throws NoSuchMethodException {
-        return toAllow().map(
-                method -> DynamicTest.dynamicTest(
-                        method.toGenericString(),
-                        () -> assertFalse(matches(method), "Matcher should not intercept method " + method.toGenericString())
-                )
-        );
+  @TestFactory
+  @DisplayName("Matcher should intercept")
+  Stream<DynamicTest> testShouldInterceptMethods() throws NoSuchMethodException {
+    return toIntercept()
+        .map(
+            method ->
+                DynamicTest.dynamicTest(
+                    method.toGenericString(),
+                    () ->
+                        assertTrue(
+                            matches(method),
+                            "Matcher should intercept method " + method.toGenericString())));
+  }
 
-    }
+  @TestFactory
+  @DisplayName("Matcher should not intercept")
+  Stream<DynamicTest> testShouldNotInterceptMethods() throws NoSuchMethodException {
+    return toAllow()
+        .map(
+            method ->
+                DynamicTest.dynamicTest(
+                    method.toGenericString(),
+                    () ->
+                        assertFalse(
+                            matches(method),
+                            "Matcher should not intercept method " + method.toGenericString())));
+  }
 
-    private boolean matches(Method method) throws IOException {
-        Class<?> owner = method.getDeclaringClass();
-        ClassTree classTree = getClassTree(owner);
-        MethodTree methodTree = getMethodTree(classTree, method);
-        return getMatcher().matches(classTree, methodTree);
-    }
+  private boolean matches(Method method) throws IOException {
+    Class<?> owner = method.getDeclaringClass();
+    ClassTree classTree = getClassTree(owner);
+    MethodTree methodTree = getMethodTree(classTree, method);
+    return getMatcher().matches(classTree, methodTree);
+  }
 
-    private MethodTree getMethodTree(ClassTree owner, Method target) {
-        Location methodLocation = Location.location(owner.name(), target.getName(), Type.getMethodDescriptor(target));
-        Optional<MethodTree> potentialMethodTree = owner.method(methodLocation);
-        assertTrue(potentialMethodTree.isPresent(), "Method " + target.toGenericString() + " not found, test can not continue");
-        return potentialMethodTree.get();
-    }
+  private MethodTree getMethodTree(ClassTree owner, Method target) {
+    Location methodLocation =
+        Location.location(owner.name(), target.getName(), Type.getMethodDescriptor(target));
+    Optional<MethodTree> potentialMethodTree = owner.method(methodLocation);
+    assertTrue(
+        potentialMethodTree.isPresent(),
+        "Method " + target.toGenericString() + " not found, test can not continue");
+    return potentialMethodTree.get();
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnConstantMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnConstantMatcherTest.java
index 06de99e..5ec8f61 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnConstantMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnConstantMatcherTest.java
@@ -1,44 +1,42 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-import org.pitest.bytecode.analysis.MethodTree;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-
 class ReturnConstantMatcherTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        return fromClass(StopMethods.class)
-                .method("returnTrue")
-                .method("returnByte")
-                .method("returnShort")
-                .method("returnNegativeInt")
-                .method("returnPositiveInt")
-                .method("returnOne")
-                .method("returnPositiveLong")
-                .method("returnNegativeLong")
-                .method("returnPositiveFloat")
-                .method("returnNegativeFloat")
-                .method("returnPositiveDouble")
-                .method("returnNegativeDouble")
-                .method("returnChar")
-                .method("returnString")
-                .method("returnNull") //?
-                .toStream();
-    }
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return fromClass(StopMethods.class)
+        .method("returnTrue")
+        .method("returnByte")
+        .method("returnShort")
+        .method("returnNegativeInt")
+        .method("returnPositiveInt")
+        .method("returnOne")
+        .method("returnPositiveLong")
+        .method("returnNegativeLong")
+        .method("returnPositiveFloat")
+        .method("returnNegativeFloat")
+        .method("returnPositiveDouble")
+        .method("returnNegativeDouble")
+        .method("returnChar")
+        .method("returnString")
+        .method("returnNull") // ?
+        .toStream();
+  }
 
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return Stream.of(Calculator.class.getDeclaredMethod("conditionalReturn", boolean.class));
-    }
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return Stream.of(Calculator.class.getDeclaredMethod("conditionalReturn", boolean.class));
+  }
 
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.returnsAConstant();
-    }
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.RETURNS_CONSTANT;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsNullMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsNullMatcherTest.java
index 04e100d..d1a5d42 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsNullMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsNullMatcherTest.java
@@ -1,31 +1,29 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-import org.pitest.bytecode.analysis.MethodTree;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-
 class ReturnsNullMatcherTest extends MethodMatcherTest {
 
-    @Override
-    public Stream<Method> toIntercept() throws NoSuchMethodException {
-        return Stream.of(StopMethods.class.getDeclaredMethod("returnNull"));
-    }
+  @Override
+  public Stream<Method> toIntercept() throws NoSuchMethodException {
+    return Stream.of(StopMethods.class.getDeclaredMethod("returnNull"));
+  }
 
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("getClone")
-                .method("getConditionalClone", boolean.class)
-                .toStream();
-    }
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("getClone")
+        .method("getConditionalClone", boolean.class)
+        .toStream();
+  }
 
-    @Override
-    public StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.returnsNull();
-    }
+  @Override
+  public MethodMatcher getMatcher() {
+    return StopMethodMatchers.RETURNS_NULL;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsParameterMethodMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsParameterMethodMatcherTest.java
index beed9b4..e186fa0 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsParameterMethodMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsParameterMethodMatcherTest.java
@@ -1,33 +1,32 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-
 class ReturnsParameterMethodMatcherTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        return fromClass(StopMethods.class)
-                .method("onlyReturnsAPrimitiveParameter", int.class, int.class, int.class)
-                .method("onlyReturnsAReferenceParameter", int.class, int.class, String.class)
-                .toStream();
-    }
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return fromClass(StopMethods.class)
+        .method("onlyReturnsAPrimitiveParameter", int.class, int.class, int.class)
+        .method("onlyReturnsAReferenceParameter", int.class, int.class, String.class)
+        .toStream();
+  }
 
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("getSomeCalculators", int.class)
-                .method("add", double.class)
-                .toStream();
-    }
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("getSomeCalculators", int.class)
+        .method("add", double.class)
+        .toStream();
+  }
 
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.returnsAParameter();
-    }
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.RETURNS_PARAMETER;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsThisMethodMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsThisMethodMatcherTest.java
index 28d9595..86c78f1 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsThisMethodMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ReturnsThisMethodMatcherTest.java
@@ -2,26 +2,23 @@
 
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-
 class ReturnsThisMethodMatcherTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        return Stream.of(StopMethods.class.getDeclaredMethod("onlyReturnsThis"));
-    }
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return Stream.of(StopMethods.class.getDeclaredMethod("onlyReturnsThis"));
+  }
 
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return Stream.of(Calculator.class.getDeclaredMethod("getConditionalClone", boolean.class));
-    }
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return Stream.of(Calculator.class.getDeclaredMethod("getConditionalClone", boolean.class));
+  }
 
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.returnsThis();
-    }
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.RETURNS_THIS;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/SimpleGetterMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/SimpleGetterMatcherTest.java
index d518a73..5303203 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/SimpleGetterMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/SimpleGetterMatcherTest.java
@@ -1,41 +1,40 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-
 class SimpleGetterMatcherTest extends MethodMatcherTest {
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        return fromClass(StopMethods.class)
-                .method("getAByte")
-                .method("getAChar")
-                .method("getADouble")
-                .method("getAFloat")
-                .method("getAnInt")
-                .method("getALong")
-                .method("getAShort")
-                .method("getAString")
-                .method("getAnObject")
-                .method("getStaticField")
-                .toStream();
-    }
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return fromClass(StopMethods.class)
+        .method("getAByte")
+        .method("getAChar")
+        .method("getADouble")
+        .method("getAFloat")
+        .method("getAnInt")
+        .method("getALong")
+        .method("getAShort")
+        .method("getAString")
+        .method("getAnObject")
+        .method("getStaticField")
+        .toStream();
+  }
 
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("getClone")
-                .method("getScreen")
-                .method("getOptionalCalculator")
-                .toStream();
-    }
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("getClone")
+        .method("getScreen")
+        .method("getOptionalCalculator")
+        .toStream();
+  }
 
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.isSimpleGetter();
-    }
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.IS_SIMPLE_GETTER;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/SimpleSetterMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/SimpleSetterMatcherTest.java
index 7874a04..f07a411 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/SimpleSetterMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/SimpleSetterMatcherTest.java
@@ -1,41 +1,39 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-import org.pitest.bytecode.analysis.MethodTree;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-
-class SimpleSetterMatcherTest extends MethodMatcherTest{
+class SimpleSetterMatcherTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        return fromClass(StopMethods.class)
-                .method("setABoolean", boolean.class)
-                .method("setAByte", byte.class)
-                .method("setAChar", char.class)
-                .method("setADouble", double.class)
-                .method("setAFloat", float.class)
-                .method("setALong", long.class)
-                .method("setAnInt", int.class)
-                .method("setAShort", short.class)
-                .method("setAString", String.class)
-                .method("setAnObject", Object.class)
-                .method("setStaticField", int.class)
-                .method("setFluent", int.class)
-                .toStream();
-    }
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return fromClass(StopMethods.class)
+        .method("setABoolean", boolean.class)
+        .method("setAByte", byte.class)
+        .method("setAChar", char.class)
+        .method("setADouble", double.class)
+        .method("setAFloat", float.class)
+        .method("setALong", long.class)
+        .method("setAnInt", int.class)
+        .method("setAShort", short.class)
+        .method("setAString", String.class)
+        .method("setAnObject", Object.class)
+        .method("setStaticField", int.class)
+        .method("setFluent", int.class)
+        .toStream();
+  }
 
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return Stream.of(Calculator.class.getDeclaredMethod("setDoubleRegistry", double.class));
-    }
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return Stream.of(Calculator.class.getDeclaredMethod("setDoubleRegistry", double.class));
+  }
 
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.isSimpleSetter();
-    }
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.IS_SIMPLE_SETTER;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ToStringMethodMatcherTest.java b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ToStringMethodMatcherTest.java
index 80d8696..896ff97 100644
--- a/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ToStringMethodMatcherTest.java
+++ b/src/test/java/eu/stamp_project/descartes/interceptors/stopmethods/ToStringMethodMatcherTest.java
@@ -1,31 +1,29 @@
 package eu.stamp_project.descartes.interceptors.stopmethods;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.StopMethods;
-
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-
 class ToStringMethodMatcherTest extends MethodMatcherTest {
 
-    @Override
-    Stream<Method> toIntercept() throws NoSuchMethodException {
-        return Stream.of(StopMethods.class.getDeclaredMethod("toString"));
-    }
-
-    @Override
-    Stream<Method> toAllow() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("getScreen") // Same signature
-                .method("toString", String.class) // Same name
-                .toStream();
-    }
-
-    @Override
-    StopMethodMatcher getMatcher() {
-        return StopMethodMatchers.isToString();
-    }
-
+  @Override
+  Stream<Method> toIntercept() throws NoSuchMethodException {
+    return Stream.of(StopMethods.class.getDeclaredMethod("toString"));
+  }
+
+  @Override
+  Stream<Method> toAllow() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("getScreen") // Same signature
+        .method("toString", String.class) // Same name
+        .toStream();
+  }
+
+  @Override
+  MethodMatcher getMatcher() {
+    return StopMethodMatchers.IS_TO_STRING;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/operators/ArgumentPropagationOperatorTest.java b/src/test/java/eu/stamp_project/descartes/operators/ArgumentPropagationOperatorTest.java
index d4583b4..ebd1c15 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/ArgumentPropagationOperatorTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/ArgumentPropagationOperatorTest.java
@@ -1,54 +1,57 @@
 package eu.stamp_project.descartes.operators;
 
-import eu.stamp_project.test.input.Calculator;
-import org.junit.jupiter.api.DynamicTest;
-import org.junit.jupiter.api.TestFactory;
-
-import java.lang.reflect.Method;
-import java.util.stream.Stream;
-
 import static eu.stamp_project.test.Assertions.assertDifferent;
 import static eu.stamp_project.test.Assertions.assertResultEquals;
 import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
 import static eu.stamp_project.test.TestValues.defaultFor;
 
-class ArgumentPropagationOperatorTest extends ParameterlessOperatorTest<ArgumentPropagationOperator> {
-
-    @Override
-    ArgumentPropagationOperator buildOperator() {
-        return new ArgumentPropagationOperator();
-    }
-
-    @Override
-    Stream<Method> methodsToMutate() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("add", double.class)
-                .method("toString", String.class)
-                .method("hashCode", int.class)
-                .toStream();
-    }
-
-    @Override
-    Stream<Method> methodsToAvoid() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .allDeclaredMethods()
-                .except("add", double.class)
-                .except("toString", String.class)
-                .except("hashCode", int.class)
-                .toStream();
-    }
+import eu.stamp_project.test.input.Calculator;
+import java.lang.reflect.Method;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.DynamicTest;
+import org.junit.jupiter.api.TestFactory;
 
-    @TestFactory
-    Stream<DynamicTest> testMutation() throws NoSuchMethodException {
-        return methodsToMutate().map(method -> DynamicTest.dynamicTest(
-                method.toGenericString(),
-                () -> {
-                    Object defaultValue = defaultFor(method.getReturnType());
-                    Object value = invoke(method);
-                    assertDifferent (defaultValue, value);
-                    Class<?> mutant = mutate(method);
-                    Object mutatedResult = invoke(mutant, method);
-                    assertResultEquals(defaultValue, mutatedResult);
-                }));
-    }
-}
\ No newline at end of file
+class ArgumentPropagationOperatorTest
+    extends ParameterlessOperatorTest<ArgumentPropagationOperator> {
+
+  @Override
+  ArgumentPropagationOperator buildOperator() {
+    return new ArgumentPropagationOperator();
+  }
+
+  @Override
+  Stream<Method> methodsToMutate() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("add", double.class)
+        .method("toString", String.class)
+        .method("hashCode", int.class)
+        .toStream();
+  }
+
+  @Override
+  Stream<Method> methodsToAvoid() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .allDeclaredMethods()
+        .except("add", double.class)
+        .except("toString", String.class)
+        .except("hashCode", int.class)
+        .toStream();
+  }
+
+  @TestFactory
+  Stream<DynamicTest> testMutation() throws NoSuchMethodException {
+    return methodsToMutate()
+        .map(
+            method ->
+                DynamicTest.dynamicTest(
+                    method.toGenericString(),
+                    () -> {
+                      Object defaultValue = defaultFor(method.getReturnType());
+                      Object value = invoke(method);
+                      assertDifferent(defaultValue, value);
+                      Class<?> mutant = mutate(method);
+                      Object mutatedResult = invoke(mutant, method);
+                      assertResultEquals(defaultValue, mutatedResult);
+                    }));
+  }
+}
diff --git a/src/test/java/eu/stamp_project/descartes/operators/ConstantMutationOperatorTest.java b/src/test/java/eu/stamp_project/descartes/operators/ConstantMutationOperatorTest.java
index 440d681..26cce3a 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/ConstantMutationOperatorTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/ConstantMutationOperatorTest.java
@@ -1,90 +1,93 @@
 package eu.stamp_project.descartes.operators;
 
+import static eu.stamp_project.test.Assertions.assertDifferent;
+import static eu.stamp_project.test.Assertions.assertResultEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
 import eu.stamp_project.test.input.Calculator;
-import org.junit.jupiter.api.Test;
-import org.junit.jupiter.params.ParameterizedTest;
-import org.junit.jupiter.params.provider.Arguments;
-import org.junit.jupiter.params.provider.MethodSource;
-
-import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.Optional;
 import java.util.stream.Stream;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
 
-import static eu.stamp_project.test.Assertions.assertDifferent;
-import static eu.stamp_project.test.Assertions.assertResultEquals;
-import static org.junit.jupiter.api.Assertions.*;
-
-
-class ConstantMutationOperatorTest  extends MutationOperatorTest {
-
-    // In this test class we use MutationOperator.fromID to instantiate the operator, as the mutation requires a valid ID.
+class ConstantMutationOperatorTest extends MutationOperatorTest {
 
-    private static Stream<Arguments> methodsToMutate() throws NoSuchMethodException {
-        return Stream.of(
-          Arguments.of(Calculator.class.getDeclaredMethod("getByte"), "(byte)3"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getShort"), "(short)3"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getCeiling"), "3"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getWrapper"), "3"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getSquare"), "3L"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getRandomOperatorSymbol"), "'A'"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getSomething"), "3.3f"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getScreen"), "\"Literal\""),
-                Arguments.of(Calculator.class.getDeclaredMethod("isOdd"), "false"),
-                Arguments.of(Calculator.class.getDeclaredMethod("add", double.class), "3.3")
-        );
-    }
+  // In this test class we use MutationOperator.fromID to instantiate the operator, as the mutation
+  // requires a valid ID.
 
-    @ParameterizedTest(name = "{1} for {0}")
-    @MethodSource("methodsToMutate")
-    void testCanMutate(Method method, String identifier) {
-        ConstantMutationOperator operator = (ConstantMutationOperator)MutationOperator.fromID(identifier);
-        assertTrue(operator.canMutate(new MethodInfo(method)));
-    }
+  private static Stream<Arguments> methodsToMutate() throws NoSuchMethodException {
+    return Stream.of(
+        Arguments.of(Calculator.class.getDeclaredMethod("getByte"), "(byte)3"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getShort"), "(short)3"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getCeiling"), "3"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getWrapper"), "3"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getSquare"), "3L"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getRandomOperatorSymbol"), "'A'"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getSomething"), "3.3f"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getScreen"), "\"Literal\""),
+        Arguments.of(Calculator.class.getDeclaredMethod("isOdd"), "false"),
+        Arguments.of(Calculator.class.getDeclaredMethod("add", double.class), "3.3"));
+  }
 
-    @ParameterizedTest(name = "{1} for {0}")
-    @MethodSource("methodsToMutate")
-    void testMutantReturnsRightValue(Method method, String identifier) throws IOException, InvocationTargetException, NoSuchMethodException, InstantiationException, IllegalAccessException {
-        ConstantMutationOperator operator = (ConstantMutationOperator)MutationOperator.fromID(identifier);
-        Class<?> mutant = mutate(method, operator);
-        Object originalResult = invoke(method);
-        assertDifferent(operator.getConstant(), originalResult);
-        Object resultFromMutant = invoke(mutant, method);
-        assertResultEquals(operator.getConstant(), resultFromMutant);
-    }
+  @ParameterizedTest(name = "{1} for {0}")
+  @MethodSource("methodsToMutate")
+  void testCanMutate(Method method, String identifier) {
+    ConstantMutationOperator operator =
+        (ConstantMutationOperator) MutationOperator.fromIdentifier(identifier);
+    assertTrue(operator.canMutate(new MethodInfo(method)));
+  }
 
-    private static Stream<Arguments> invalidMutations() throws NoSuchMethodException {
-        return Stream.of(
-                Arguments.of(Calculator.class.getDeclaredMethod("getByte"), "3"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getShort"), "(byte)3"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getCeiling"), "(short)3"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getSquare"), "true"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getWrapper"), "3.3"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getRandomOperatorSymbol"), "\"A\""),
-                Arguments.of(Calculator.class.getDeclaredMethod("getSomething"), "3.3"),
-                Arguments.of(Calculator.class.getDeclaredMethod("getScreen"), "'A'"),
-                Arguments.of(Calculator.class.getDeclaredMethod("isOdd"), "1"),
-                Arguments.of(Calculator.class.getDeclaredMethod("add", double.class), "3")
-        );
-    }
+  @ParameterizedTest(name = "{1} for {0}")
+  @MethodSource("methodsToMutate")
+  void testMutantReturnsRightValue(Method method, String identifier)
+      throws InvocationTargetException, NoSuchMethodException, InstantiationException,
+          IllegalAccessException {
+    ConstantMutationOperator operator =
+        (ConstantMutationOperator) MutationOperator.fromIdentifier(identifier);
+    Class<?> mutant = mutate(method, operator);
+    Object originalResult = invoke(method);
+    assertDifferent(operator.getConstant(), originalResult);
+    Object resultFromMutant = invoke(mutant, method);
+    assertResultEquals(operator.getConstant(), resultFromMutant);
+  }
 
-    @ParameterizedTest(name = "Can not use {1} to mutate {0}")
-    @MethodSource("invalidMutations")
-    void testCanNotMutate(Method method, String identifier) {
-        ConstantMutationOperator operator = (ConstantMutationOperator)MutationOperator.fromID(identifier);
-        assertFalse(operator.canMutate(new MethodInfo(method)));
-    }
+  private static Stream<Arguments> invalidMutations() throws NoSuchMethodException {
+    return Stream.of(
+        Arguments.of(Calculator.class.getDeclaredMethod("getByte"), "3"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getShort"), "(byte)3"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getCeiling"), "(short)3"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getSquare"), "true"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getWrapper"), "3.3"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getRandomOperatorSymbol"), "\"A\""),
+        Arguments.of(Calculator.class.getDeclaredMethod("getSomething"), "3.3"),
+        Arguments.of(Calculator.class.getDeclaredMethod("getScreen"), "'A'"),
+        Arguments.of(Calculator.class.getDeclaredMethod("isOdd"), "1"),
+        Arguments.of(Calculator.class.getDeclaredMethod("add", double.class), "3"));
+  }
 
-    @Test
-    void testInvalidConstant() {
-        assertThrows(IllegalArgumentException.class, () -> new ConstantMutationOperator("", Optional.of(2)));
-    }
+  @ParameterizedTest(name = "Can not use {1} to mutate {0}")
+  @MethodSource("invalidMutations")
+  void testCanNotMutate(Method method, String identifier) {
+    ConstantMutationOperator operator =
+        (ConstantMutationOperator) MutationOperator.fromIdentifier(identifier);
+    assertFalse(operator.canMutate(new MethodInfo(method)));
+  }
 
-    @Test
-    void testNull() {
-        assertThrows(NullPointerException.class, () -> new ConstantMutationOperator("null", null));
-    }
+  @Test
+  void testInvalidConstant() {
+    assertThrows(
+        IllegalArgumentException.class, () -> new ConstantMutationOperator("", Optional.of(2)));
+  }
 
+  @Test
+  void testNull() {
+    assertThrows(NullPointerException.class, () -> new ConstantMutationOperator("null", null));
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/operators/EmptyArrayMutationOperatorTest.java b/src/test/java/eu/stamp_project/descartes/operators/EmptyArrayMutationOperatorTest.java
index a644326..6ba270c 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/EmptyArrayMutationOperatorTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/EmptyArrayMutationOperatorTest.java
@@ -1,67 +1,64 @@
 package eu.stamp_project.descartes.operators;
 
-import eu.stamp_project.test.input.Calculator;
-import org.junit.jupiter.api.DynamicTest;
-import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.TestFactory;
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+import static org.junit.jupiter.api.Assertions.*;
 
+import eu.stamp_project.test.input.Calculator;
 import java.lang.reflect.Array;
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
-
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.DynamicTest;
+import org.junit.jupiter.api.TestFactory;
 
 class EmptyArrayMutationOperatorTest extends ParameterlessOperatorTest<EmptyArrayMutationOperator> {
 
-    @Override
-    EmptyArrayMutationOperator buildOperator() {
-        return new EmptyArrayMutationOperator();
-    }
-
-    @Override
-    Stream<Method> methodsToMutate() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("getSomeCalculators", int.class)
-                .method("getSomeMore", int.class)
-                .method("getRange", int.class)
-                .toStream();
-    }
+  @Override
+  EmptyArrayMutationOperator buildOperator() {
+    return new EmptyArrayMutationOperator();
+  }
 
-    @Override
-    Stream<Method> methodsToAvoid() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("clear")
-                .method("getByte")
-                .method("getShort")
-                .method("getCeiling")
-                .method("getSquare")
-                .method("getRandomOperatorSymbol")
-                .method("add", double.class)
-                .method("getSomething")
-                .method("isOdd")
-                .method("getScreen")
-                .method("getClone")
-                .method("getMultipleCalculators", int.class)
-                .method("getOptionalCalculator")
-                .toStream();
-    }
+  @Override
+  Stream<Method> methodsToMutate() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("getSomeCalculators", int.class)
+        .method("getSomeMore", int.class)
+        .method("getRange", int.class)
+        .toStream();
+  }
 
-    @TestFactory
-    Stream<DynamicTest> testGeneratesEmptyArray() throws NoSuchMethodException {
-        return methodsToMutate().map(
-                method -> DynamicTest.dynamicTest(
-                        method.toGenericString(),
-                        () -> {
-                            Object originalResult = invoke(method);
-                            assertNotEquals(0, Array.getLength(originalResult));
+  @Override
+  Stream<Method> methodsToAvoid() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("clear")
+        .method("getByte")
+        .method("getShort")
+        .method("getCeiling")
+        .method("getSquare")
+        .method("getRandomOperatorSymbol")
+        .method("add", double.class)
+        .method("getSomething")
+        .method("isOdd")
+        .method("getScreen")
+        .method("getClone")
+        .method("getMultipleCalculators", int.class)
+        .method("getOptionalCalculator")
+        .toStream();
+  }
 
-                            Class<?> mutant = mutate(method, buildOperator());
-                            Object mutatedResult = invoke(mutant, method);
-                            assertEquals(0, Array.getLength(mutatedResult));
-                        }
-                )
-        );
-    }
+  @TestFactory
+  Stream<DynamicTest> testGeneratesEmptyArray() throws NoSuchMethodException {
+    return methodsToMutate()
+        .map(
+            method ->
+                DynamicTest.dynamicTest(
+                    method.toGenericString(),
+                    () -> {
+                      Object originalResult = invoke(method);
+                      assertNotEquals(0, Array.getLength(originalResult));
 
+                      Class<?> mutant = mutate(method, buildOperator());
+                      Object mutatedResult = invoke(mutant, method);
+                      assertEquals(0, Array.getLength(mutatedResult));
+                    }));
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/operators/MutationOperatorTest.java b/src/test/java/eu/stamp_project/descartes/operators/MutationOperatorTest.java
index 9660617..84210ab 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/MutationOperatorTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/MutationOperatorTest.java
@@ -1,54 +1,61 @@
 package eu.stamp_project.descartes.operators;
 
-import eu.stamp_project.descartes.DescartesMutater;
-import org.pitest.classpath.ClassloaderByteArraySource;
-import org.pitest.mutationtest.engine.Mutant;
+import static eu.stamp_project.test.TestValues.defaultsFor;
+import static eu.stamp_project.test.Utils.toMutationIdentifier;
 
+import eu.stamp_project.descartes.DescartesMutater;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.List;
-
-import static eu.stamp_project.test.TestValues.defaultsFor;
-import static eu.stamp_project.test.Utils.toMutationIdentifier;
+import org.pitest.classpath.ClassloaderByteArraySource;
+import org.pitest.mutationtest.engine.Mutant;
 
 abstract class MutationOperatorTest {
 
-    Class<?> mutate(Method method, MutationOperator operator) {
-        DescartesMutater mutater = new DescartesMutater(
-                ClassloaderByteArraySource.fromContext(),
-                m -> false,
-                List.of(operator));
-        Mutant mutant = mutater.getMutation(toMutationIdentifier(method, operator.getIdentifier()));
-        return load(method.getDeclaringClass().getName(), mutant.getBytes());
-    }
-
-    private Class<?> load(String name, byte[] bytes) {
-        return new ClassLoader() {
-            Class<?> load() {
-                return defineClass(name, bytes, 0, bytes.length);
-            }
-        }.load();
-    }
-
-    Object newInstance(Class<?> type) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException { return type.getConstructor().newInstance(); }
-
-    Object invoke(Method method) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
-        return invokeOn(newInstance(method.getDeclaringClass()), method);
-    }
-
-    Object invokeOn(Object receiver, Method method) throws InvocationTargetException, IllegalAccessException, NoSuchMethodException {
-        method = receiver.getClass().equals(method.getDeclaringClass())?
-                method
-                :
-                getCorrespondingMethod(receiver.getClass(), method);
-        return method.invoke(receiver, defaultsFor(method.getParameterTypes()));
-    }
-
-    Method getCorrespondingMethod(Class<?> type, Method query) throws NoSuchMethodException {
-        return type.getDeclaredMethod(query.getName(), query.getParameterTypes());
-    }
-
-    Object invoke(Class<?> type, Method method) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
-        return invokeOn(newInstance(type), method);
-    }
+  Class<?> mutate(Method method, MutationOperator operator) {
+    DescartesMutater mutater =
+        new DescartesMutater(
+            ClassloaderByteArraySource.fromContext(), m -> false, List.of(operator));
+    Mutant mutant = mutater.getMutation(toMutationIdentifier(method, operator.getIdentifier()));
+    return load(method.getDeclaringClass().getName(), mutant.getBytes());
+  }
+
+  private Class<?> load(String name, byte[] bytes) {
+    return new ClassLoader() {
+      Class<?> load() {
+        return defineClass(name, bytes, 0, bytes.length);
+      }
+    }.load();
+  }
+
+  Object newInstance(Class<?> type)
+      throws NoSuchMethodException, IllegalAccessException, InvocationTargetException,
+          InstantiationException {
+    return type.getConstructor().newInstance();
+  }
+
+  Object invoke(Method method)
+      throws NoSuchMethodException, IllegalAccessException, InvocationTargetException,
+          InstantiationException {
+    return invokeOn(newInstance(method.getDeclaringClass()), method);
+  }
+
+  Object invokeOn(Object receiver, Method method)
+      throws InvocationTargetException, IllegalAccessException, NoSuchMethodException {
+    final Method targetMethod =
+        receiver.getClass().equals(method.getDeclaringClass())
+            ? method
+            : getCorrespondingMethod(receiver.getClass(), method);
+    return targetMethod.invoke(receiver, defaultsFor(method.getParameterTypes()));
+  }
+
+  Method getCorrespondingMethod(Class<?> type, Method query) throws NoSuchMethodException {
+    return type.getDeclaredMethod(query.getName(), query.getParameterTypes());
+  }
+
+  Object invoke(Class<?> type, Method method)
+      throws NoSuchMethodException, IllegalAccessException, InvocationTargetException,
+          InstantiationException {
+    return invokeOn(newInstance(type), method);
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/operators/NewInstanceMutationOperatorTest.java b/src/test/java/eu/stamp_project/descartes/operators/NewInstanceMutationOperatorTest.java
index ebd3e86..20a86a6 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/NewInstanceMutationOperatorTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/NewInstanceMutationOperatorTest.java
@@ -1,52 +1,53 @@
 package eu.stamp_project.descartes.operators;
 
-import eu.stamp_project.test.input.Calculator;
-import org.junit.jupiter.api.Test;
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.empty;
+import static org.hamcrest.Matchers.not;
 
+import eu.stamp_project.test.input.Calculator;
 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.List;
 import java.util.stream.Stream;
+import org.junit.jupiter.api.Test;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-import static org.hamcrest.MatcherAssert.assertThat;
-import static org.hamcrest.Matchers.empty;
-import static org.hamcrest.Matchers.not;
-
-class NewInstanceMutationOperatorTest extends ParameterlessOperatorTest<NewInstanceMutationOperator> {
-
-    @Override
-    NewInstanceMutationOperator buildOperator() {
-        return new NewInstanceMutationOperator();
-    }
-
-    @Override
-    Stream<Method> methodsToMutate() throws NoSuchMethodException {
-        return fromClass(Calculator.class).method("getMultipleCalculators", int.class).toStream();
-    }
-
-
-    @Override
-    Stream<Method> methodsToAvoid() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("getScreen") // Returning String
-                .method("getClone") // Returning class from other packages
-                .method("getOptionalCalculator") // Returning class with no public default constructor
-                .toStream();
-    }
-
-    @Test
-    void testReturnEmptyList() throws NoSuchMethodException, IllegalAccessException, InstantiationException, InvocationTargetException, IOException {
-        Method method = Calculator.class.getDeclaredMethod("getMultipleCalculators", int.class);
-
-        List<?> result = (List<?>)invoke(method);
-        assertThat("Original result should not be an empty list. Fix the test input.", result, not(empty()));
-
-        Class<?> mutant = mutate(method);
-        List<?> resultFromMutant = (List<?>)invoke(mutant, method);
-
-        assertThat("Result should be an empty list", resultFromMutant, empty());
-    }
-
+class NewInstanceMutationOperatorTest
+    extends ParameterlessOperatorTest<NewInstanceMutationOperator> {
+
+  @Override
+  NewInstanceMutationOperator buildOperator() {
+    return new NewInstanceMutationOperator();
+  }
+
+  @Override
+  Stream<Method> methodsToMutate() throws NoSuchMethodException {
+    return fromClass(Calculator.class).method("getMultipleCalculators", int.class).toStream();
+  }
+
+  @Override
+  Stream<Method> methodsToAvoid() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("getScreen") // Returning String
+        .method("getClone") // Returning class from other packages
+        .method("getOptionalCalculator") // Returning class with no public default constructor
+        .toStream();
+  }
+
+  @Test
+  void testReturnEmptyList()
+      throws NoSuchMethodException, IllegalAccessException, InstantiationException,
+          InvocationTargetException, IOException {
+    Method method = Calculator.class.getDeclaredMethod("getMultipleCalculators", int.class);
+
+    List<?> result = (List<?>) invoke(method);
+    assertThat(
+        "Original result should not be an empty list. Fix the test input.", result, not(empty()));
+
+    Class<?> mutant = mutate(method);
+    List<?> resultFromMutant = (List<?>) invoke(mutant, method);
+
+    assertThat("Result should be an empty list", resultFromMutant, empty());
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/operators/NullMutationOperatorTest.java b/src/test/java/eu/stamp_project/descartes/operators/NullMutationOperatorTest.java
index 9906b7a..935f057 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/NullMutationOperatorTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/NullMutationOperatorTest.java
@@ -1,61 +1,63 @@
 package eu.stamp_project.descartes.operators;
 
-import eu.stamp_project.test.input.Calculator;
-import org.junit.jupiter.api.DynamicTest;
-import org.junit.jupiter.api.TestFactory;
-
-import java.lang.reflect.Method;
-import java.util.stream.Stream;
-
 import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 
-class NullMutationOperatorTest extends ParameterlessOperatorTest<NullMutationOperator> {
-
-    @Override
-    NullMutationOperator buildOperator() {
-        return new NullMutationOperator();
-    }
-
-    @Override
-    Stream<Method> methodsToMutate() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("getClone")
-                .method("getSomeCalculators", int.class)
-                .method("getSomeMore", int.class)
-                .method("getMultipleCalculators", int.class)
-                .method("getRange", int.class)
-                .method("getOptionalCalculator")
-                .method("getScreen")
-                .toStream();
-    }
-
-    @Override
-    Stream<Method> methodsToAvoid() throws NoSuchMethodException {
-        return fromClass(Calculator.class)
-                .method("clear")
-                .method("getCeiling")
-                .method("getByte")
-                .method("getShort")
-                .method("getCeiling")
-                .method("getSquare")
-                .method("getRandomOperatorSymbol")
-                .method("add", double.class)
-                .method("getSomething")
-                .method("isOdd")
-                .toStream();
-    }
+import eu.stamp_project.test.input.Calculator;
+import java.lang.reflect.Method;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.DynamicTest;
+import org.junit.jupiter.api.TestFactory;
 
-    @TestFactory
-    Stream<DynamicTest> testMutationReturnsNull() throws NoSuchMethodException {
-        return methodsToMutate().map( method -> DynamicTest.dynamicTest(
-                method.toGenericString(),
-                () -> {
-                    assertNotNull(invoke(method), "Original method invocation must not be null, so it is possible to observe the effects of the operator");
-                    assertNull(invoke(mutate(method), method), "Mutated method must return null");
-                }
-        ));
-    }
+class NullMutationOperatorTest extends ParameterlessOperatorTest<NullMutationOperator> {
 
-}
\ No newline at end of file
+  @Override
+  NullMutationOperator buildOperator() {
+    return new NullMutationOperator();
+  }
+
+  @Override
+  Stream<Method> methodsToMutate() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("getClone")
+        .method("getSomeCalculators", int.class)
+        .method("getSomeMore", int.class)
+        .method("getMultipleCalculators", int.class)
+        .method("getRange", int.class)
+        .method("getOptionalCalculator")
+        .method("getScreen")
+        .toStream();
+  }
+
+  @Override
+  Stream<Method> methodsToAvoid() throws NoSuchMethodException {
+    return fromClass(Calculator.class)
+        .method("clear")
+        .method("getCeiling")
+        .method("getByte")
+        .method("getShort")
+        .method("getCeiling")
+        .method("getSquare")
+        .method("getRandomOperatorSymbol")
+        .method("add", double.class)
+        .method("getSomething")
+        .method("isOdd")
+        .toStream();
+  }
+
+  @TestFactory
+  Stream<DynamicTest> testMutationReturnsNull() throws NoSuchMethodException {
+    return methodsToMutate()
+        .map(
+            method ->
+                DynamicTest.dynamicTest(
+                    method.toGenericString(),
+                    () -> {
+                      assertNotNull(
+                          invoke(method),
+                          "Original method invocation must not be null, so it is possible to observe the effects of the operator");
+                      assertNull(invoke(mutate(method), method), "Mutated method must return null");
+                    }));
+  }
+}
diff --git a/src/test/java/eu/stamp_project/descartes/operators/OptionalMutationOperatorTest.java b/src/test/java/eu/stamp_project/descartes/operators/OptionalMutationOperatorTest.java
index f0b8a0a..0043d37 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/OptionalMutationOperatorTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/OptionalMutationOperatorTest.java
@@ -1,58 +1,61 @@
 package eu.stamp_project.descartes.operators;
 
-import eu.stamp_project.test.input.Calculator;
-import org.junit.jupiter.api.Test;
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import eu.stamp_project.test.input.Calculator;
 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.Optional;
 import java.util.stream.Stream;
-
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-import static org.hamcrest.MatcherAssert.assertThat;
-import static org.hamcrest.Matchers.equalTo;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import org.junit.jupiter.api.Test;
 
 class OptionalMutationOperatorTest extends ParameterlessOperatorTest<OptionalMutationOperator> {
 
-    @Override
-    OptionalMutationOperator buildOperator() {
-        return new OptionalMutationOperator();
-    }
-
-    private Method getMethod() throws NoSuchMethodException {
-        return Calculator.class.getDeclaredMethod("getOptionalCalculator");
-    }
-
-    @Override
-    Stream<Method> methodsToMutate() throws NoSuchMethodException {
-        return Stream.of(getMethod());
-    }
-
-    @Override
-    Stream<Method> methodsToAvoid() throws NoSuchMethodException {
-        return fromClass(Calculator.class).except("getOptionalCalculator").toStream();
-    }
-
-    @Test
-    void testReturnsEmptyOptional() throws InvocationTargetException, NoSuchMethodException, InstantiationException, IllegalAccessException, IOException {
-        checkOriginalValueIsNotEmpty();
-        checkMutatedMethodReturnsEmptyOptional();
-    }
-
-    private void checkOriginalValueIsNotEmpty() {
-        Calculator calc = new Calculator();
-        Optional<Calculator> originalValue = calc.getOptionalCalculator();
-        assertTrue(originalValue.isPresent(), "Method getOptionalCalculator in Calculator class must not return an empty Optional");
-    }
-
-    private void checkMutatedMethodReturnsEmptyOptional() throws NoSuchMethodException, IOException, IllegalAccessException, InstantiationException, InvocationTargetException {
-        Method method = getMethod();
-        Class<?> mutant = mutate(method);
-        Object result = invoke(mutant, method);
-        assertThat("Mutated method must return the empty Optional", result, equalTo(Optional.empty()));
-    }
-
+  @Override
+  OptionalMutationOperator buildOperator() {
+    return new OptionalMutationOperator();
+  }
+
+  private Method getMethod() throws NoSuchMethodException {
+    return Calculator.class.getDeclaredMethod("getOptionalCalculator");
+  }
+
+  @Override
+  Stream<Method> methodsToMutate() throws NoSuchMethodException {
+    return Stream.of(getMethod());
+  }
+
+  @Override
+  Stream<Method> methodsToAvoid() throws NoSuchMethodException {
+    return fromClass(Calculator.class).except("getOptionalCalculator").toStream();
+  }
+
+  @Test
+  void testReturnsEmptyOptional()
+      throws InvocationTargetException, NoSuchMethodException, InstantiationException,
+          IllegalAccessException, IOException {
+    checkOriginalValueIsNotEmpty();
+    checkMutatedMethodReturnsEmptyOptional();
+  }
+
+  private void checkOriginalValueIsNotEmpty() {
+    Calculator calc = new Calculator();
+    Optional<Calculator> originalValue = calc.getOptionalCalculator();
+    assertTrue(
+        originalValue.isPresent(),
+        "Method getOptionalCalculator in Calculator class must not return an empty Optional");
+  }
+
+  private void checkMutatedMethodReturnsEmptyOptional()
+      throws NoSuchMethodException, IOException, IllegalAccessException, InstantiationException,
+          InvocationTargetException {
+    Method method = getMethod();
+    Class<?> mutant = mutate(method);
+    Object result = invoke(mutant, method);
+    assertThat("Mutated method must return the empty Optional", result, equalTo(Optional.empty()));
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/operators/ParameterlessOperatorTest.java b/src/test/java/eu/stamp_project/descartes/operators/ParameterlessOperatorTest.java
index ce34704..0d44786 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/ParameterlessOperatorTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/ParameterlessOperatorTest.java
@@ -1,60 +1,59 @@
 package eu.stamp_project.descartes.operators;
 
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.*;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
+import java.io.IOException;
+import java.lang.reflect.Method;
+import java.util.stream.Stream;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.DynamicTest;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestFactory;
 
-import java.io.IOException;
-import java.lang.reflect.Method;
-import java.util.stream.Stream;
-
-import static org.hamcrest.Matchers.*;
-import static org.hamcrest.MatcherAssert.assertThat;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
 abstract class ParameterlessOperatorTest<T extends MutationOperator> extends MutationOperatorTest {
 
-    abstract T buildOperator();
-
-    @Test
-    void testBuildFromIdentifier() {
-        T operator = buildOperator();
-        MutationOperator operatorFromID = MutationOperator.fromID(operator.getIdentifier());
-        assertThat(operatorFromID, instanceOf(operator.getClass()));
-        assertThat(operatorFromID.getIdentifier(), equalTo(operator.getIdentifier()));
-        assertThat(operatorFromID.getDescription(), equalTo(operatorFromID.getDescription()));
-    }
-
-    abstract Stream<Method> methodsToMutate() throws NoSuchMethodException;
-
-    @TestFactory
-    @DisplayName("Should mutate")
-    Stream<DynamicTest> testShouldMutateMethods() throws NoSuchMethodException {
-        return methodsToMutate().map(
-                method -> DynamicTest.dynamicTest(
-                        method.toGenericString(),
-                        () -> assertTrue(buildOperator().canMutate(new MethodInfo(method)))
-                )
-        );
-    }
-
-    abstract Stream<Method> methodsToAvoid() throws NoSuchMethodException;
-
-    @TestFactory
-    @DisplayName("Should not mutate")
-    Stream<DynamicTest> testShouldAvoidMethods() throws NoSuchMethodException {
-        return methodsToAvoid().map(
-                method -> DynamicTest.dynamicTest(
-                        "Should avoid method " + method.toGenericString(),
-                        () -> assertFalse(buildOperator().canMutate(new MethodInfo(method))))
-        );
-    }
-
-    Class<?> mutate(Method method) throws IOException {
-        return mutate(method, buildOperator());
-    }
+  abstract T buildOperator();
+
+  @Test
+  void testBuildFromIdentifier() {
+    T operator = buildOperator();
+    MutationOperator operatorFromID = MutationOperator.fromIdentifier(operator.getIdentifier());
+    assertThat(operatorFromID, instanceOf(operator.getClass()));
+    assertThat(operatorFromID.getIdentifier(), equalTo(operator.getIdentifier()));
+    assertThat(operatorFromID.getDescription(), equalTo(operatorFromID.getDescription()));
+  }
+
+  abstract Stream<Method> methodsToMutate() throws NoSuchMethodException;
+
+  @TestFactory
+  @DisplayName("Should mutate")
+  Stream<DynamicTest> testShouldMutateMethods() throws NoSuchMethodException {
+    return methodsToMutate()
+        .map(
+            method ->
+                DynamicTest.dynamicTest(
+                    method.toGenericString(),
+                    () -> assertTrue(buildOperator().canMutate(new MethodInfo(method)))));
+  }
+
+  abstract Stream<Method> methodsToAvoid() throws NoSuchMethodException;
+
+  @TestFactory
+  @DisplayName("Should not mutate")
+  Stream<DynamicTest> testShouldAvoidMethods() throws NoSuchMethodException {
+    return methodsToAvoid()
+        .map(
+            method ->
+                DynamicTest.dynamicTest(
+                    "Should avoid method " + method.toGenericString(),
+                    () -> assertFalse(buildOperator().canMutate(new MethodInfo(method)))));
+  }
+
+  Class<?> mutate(Method method) throws IOException {
+    return mutate(method, buildOperator());
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/operators/ThisMutationOperatorTest.java b/src/test/java/eu/stamp_project/descartes/operators/ThisMutationOperatorTest.java
index 2776972..3fbbd3e 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/ThisMutationOperatorTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/ThisMutationOperatorTest.java
@@ -1,62 +1,65 @@
 package eu.stamp_project.descartes.operators;
 
-import eu.stamp_project.descartes.annotations.Operator;
-import eu.stamp_project.test.input.Fluent;
-import org.junit.jupiter.api.DynamicTest;
-import org.junit.jupiter.api.TestFactory;
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+import static org.junit.jupiter.api.Assertions.*;
 
+import eu.stamp_project.test.input.Fluent;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
+import org.junit.jupiter.api.DynamicTest;
+import org.junit.jupiter.api.TestFactory;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-import static org.junit.jupiter.api.Assertions.*;
+class ThisMutationOperatorTest extends ParameterlessOperatorTest<ThisMutationOperator> {
 
+  @Override
+  ThisMutationOperator buildOperator() {
+    return new ThisMutationOperator();
+  }
 
-class ThisMutationOperatorTest extends ParameterlessOperatorTest<ThisMutationOperator> {
+  @Override
+  Stream<Method> methodsToMutate() throws NoSuchMethodException {
+    return fromClass(Fluent.class).method("addOne").method("addTwo").method("addThree").toStream();
+  }
+
+  @Override
+  Stream<Method> methodsToAvoid() throws NoSuchMethodException {
+    return fromClass(Fluent.class)
+        .method("createNew")
+        .method("getValueAsString")
+        .method("createAndGetValue")
+        .method("abstractMethod")
+        .method("voidMethod")
+        .toStream();
+  }
+
+  @TestFactory
+  Stream<DynamicTest> testMutation() throws NoSuchMethodException {
+    return methodsToMutate()
+        .map(
+            method ->
+                DynamicTest.dynamicTest(
+                    method.toGenericString(),
+                    () -> {
+                      assertTrue(
+                          checkFluentAnEffect(Fluent.class, method),
+                          "Original fluent input method does not have an effect on the receiver. Check the test input");
+                      Class<?> mutant = mutate(method);
+                      assertFalse(
+                          checkFluentAnEffect(mutant, method),
+                          "Mutated method must not have an effect on the receiver");
+                    }));
+  }
 
-    @Override
-    ThisMutationOperator buildOperator() {
-        return new ThisMutationOperator();
-    }
-
-    @Override
-    Stream<Method> methodsToMutate() throws NoSuchMethodException {
-        return fromClass(Fluent.class)
-                .method("addOne")
-                .method("addTwo")
-                .method("addThree")
-                .toStream();
-    }
-
-    @Override
-    Stream<Method> methodsToAvoid() throws NoSuchMethodException {
-        return fromClass(Fluent.class)
-                .method("createNew")
-                .method("getValueAsString")
-                .method("createAndGetValue")
-                .method("abstractMethod")
-                .method("voidMethod")
-                .toStream();
-    }
-
-    @TestFactory
-    Stream<DynamicTest> testMutation() throws NoSuchMethodException {
-        return methodsToMutate().map(method ->
-            DynamicTest.dynamicTest(method.toGenericString(), () -> {
-                assertTrue(checkFluentAnEffect(Fluent.class, method), "Original fluent input method does not have an effect on the receiver. Check the test input");
-                Class<?> mutant = mutate(method);
-                assertFalse(checkFluentAnEffect(mutant, method), "Mutated method must not have an effect on the receiver");
-            })
-        );
-    }
-
-    private boolean checkFluentAnEffect(Class<?> owner, Method method) throws InvocationTargetException, NoSuchMethodException, InstantiationException, IllegalAccessException, NoSuchFieldException {
-        Object receiver = newInstance(owner);
-        int initialValue = owner.getDeclaredField("value").getInt(receiver);
-        Object result = invokeOn(receiver, method);
-        int finalValue = owner.getDeclaredField("value").getInt(receiver);
-        assertEquals(receiver, result,  "Fluent invocation should return the same instance as the receiver");
-        return initialValue != finalValue;
-    }
-}
\ No newline at end of file
+  private boolean checkFluentAnEffect(Class<?> owner, Method method)
+      throws InvocationTargetException, NoSuchMethodException, InstantiationException,
+          IllegalAccessException, NoSuchFieldException {
+    Object receiver = newInstance(owner);
+    int initialValue = owner.getDeclaredField("value").getInt(receiver);
+    Object result = invokeOn(receiver, method);
+    int finalValue = owner.getDeclaredField("value").getInt(receiver);
+    assertEquals(
+        receiver, result, "Fluent invocation should return the same instance as the receiver");
+    return initialValue != finalValue;
+  }
+}
diff --git a/src/test/java/eu/stamp_project/descartes/operators/VoidMutationOperatorTest.java b/src/test/java/eu/stamp_project/descartes/operators/VoidMutationOperatorTest.java
index e56adf5..d411a1a 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/VoidMutationOperatorTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/VoidMutationOperatorTest.java
@@ -1,57 +1,63 @@
 package eu.stamp_project.descartes.operators;
 
+import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.not;
+
 import eu.stamp_project.test.input.Calculator;
 import eu.stamp_project.test.input.SideEffect;
-import org.junit.jupiter.api.Test;
-
 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.stream.Stream;
+import org.junit.jupiter.api.Test;
 
-import static eu.stamp_project.test.MethodStreamBuilder.fromClass;
-import static org.hamcrest.MatcherAssert.assertThat;
-import static org.hamcrest.Matchers.is;
-import static org.hamcrest.Matchers.not;
-
-class VoidMutationOperatorTest extends ParameterlessOperatorTest<VoidMutationOperator>{
-
-    @Override
-    VoidMutationOperator buildOperator() {
-        return new VoidMutationOperator();
-    }
-
-    @Override
-    Stream<Method> methodsToMutate() throws NoSuchMethodException {
-        return fromClass(SideEffect.class).method("increment").toStream();
-    }
-
-    @Override
-    Stream<Method> methodsToAvoid() throws NoSuchMethodException { return fromClass(Calculator.class).method("getCeiling").toStream(); }
-
-    @Test
-    void testRemoveSideEffects() throws NoSuchMethodException, IOException, IllegalAccessException, InvocationTargetException, InstantiationException, NoSuchFieldException {
-        // Save guard against errors in the input class\
-        checkThereIsASideEffect();
-        // Actual verification
-        checkSideEffectWasRemoved();
-    }
-
-    private void checkThereIsASideEffect() {
-        SideEffect instance = new SideEffect();
-        int initialValue = instance.count;
-        instance.increment();
-        assertThat("No detected side effect from method increment in class SideEffect. Value of field count remains the same after method invocation",
-                instance.count, is(not(initialValue)));
-    }
-
-    private void checkSideEffectWasRemoved() throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException, NoSuchFieldException, IOException {
-        Class<?> mutant = mutate(SideEffect.class.getDeclaredMethod("increment"));
-        Object instance = newInstance(mutant);
-        int initialValue = mutant.getDeclaredField("count").getInt(instance);
-        mutant.getDeclaredMethod("increment").invoke(instance);
-        int result = mutant.getDeclaredField("count").getInt(instance);
-        assertThat("Side effect was not removed after mutation.", result, is(initialValue));
-    }
-
+class VoidMutationOperatorTest extends ParameterlessOperatorTest<VoidMutationOperator> {
+
+  @Override
+  VoidMutationOperator buildOperator() {
+    return new VoidMutationOperator();
+  }
+
+  @Override
+  Stream<Method> methodsToMutate() throws NoSuchMethodException {
+    return fromClass(SideEffect.class).method("increment").toStream();
+  }
+
+  @Override
+  Stream<Method> methodsToAvoid() throws NoSuchMethodException {
+    return fromClass(Calculator.class).method("getCeiling").toStream();
+  }
+
+  @Test
+  void testRemoveSideEffects()
+      throws NoSuchMethodException, IOException, IllegalAccessException, InvocationTargetException,
+          InstantiationException, NoSuchFieldException {
+    // Save guard against errors in the input class\
+    checkThereIsASideEffect();
+    // Actual verification
+    checkSideEffectWasRemoved();
+  }
+
+  private void checkThereIsASideEffect() {
+    SideEffect instance = new SideEffect();
+    int initialValue = instance.count;
+    instance.increment();
+    assertThat(
+        "No detected side effect from method increment in class SideEffect. Value of field count remains the same after method invocation",
+        instance.count,
+        is(not(initialValue)));
+  }
+
+  private void checkSideEffectWasRemoved()
+      throws NoSuchMethodException, IllegalAccessException, InvocationTargetException,
+          InstantiationException, NoSuchFieldException, IOException {
+    Class<?> mutant = mutate(SideEffect.class.getDeclaredMethod("increment"));
+    Object instance = newInstance(mutant);
+    int initialValue = mutant.getDeclaredField("count").getInt(instance);
+    mutant.getDeclaredMethod("increment").invoke(instance);
+    int result = mutant.getDeclaredField("count").getInt(instance);
+    assertThat("Side effect was not removed after mutation.", result, is(initialValue));
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/operators/VoidWrapperTest.java b/src/test/java/eu/stamp_project/descartes/operators/VoidWrapperTest.java
index f1609d9..f190950 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/VoidWrapperTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/VoidWrapperTest.java
@@ -1,67 +1,74 @@
 package eu.stamp_project.descartes.operators;
 
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import eu.stamp_project.descartes.codemanipulation.MethodInfo;
 import eu.stamp_project.test.input.SideEffect;
-import org.junit.jupiter.api.Test;
-
 import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
-
-import static org.hamcrest.MatcherAssert.assertThat;
-import static org.hamcrest.Matchers.is;
-import static org.junit.jupiter.api.Assertions.assertNotEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import org.junit.jupiter.api.Test;
 
 class VoidWrapperTest extends MutationOperatorTest {
 
-    /*
-    This test class is pretty much similar to VoidMutationOperatorTest.
-    However, the Void wrapper type is handled by the NullMutationOperator.
-    This is a strange case.
-    Conceptually, the Void type might be better handled by the VoidMutationOperator.
-    However, doing this, will create code duplication and extra verifications
-    in the code of both operators, Null.. and Void...
-    Therefore, to keep it simple, we leave it like that for the moment.
-    This test class exists just to highlight this fact and in case we decide
-    to move the code to VoidMutationOperator.
-     */
-
-    private MutationOperator getOperator() { return new NullMutationOperator(); }
+  /*
+  This test class is pretty much similar to VoidMutationOperatorTest.
+  However, the Void wrapper type is handled by the NullMutationOperator.
+  This is a strange case.
+  Conceptually, the Void type might be better handled by the VoidMutationOperator.
+  However, doing this, will create code duplication and extra verifications
+  in the code of both operators, Null.. and Void...
+  Therefore, to keep it simple, we leave it like that for the moment.
+  This test class exists just to highlight this fact and in case we decide
+  to move the code to VoidMutationOperator.
+   */
 
-    private Method getMethod() throws NoSuchMethodException {
-        return SideEffect.class.getDeclaredMethod("nextOdd");
-    }
+  private MutationOperator getOperator() {
+    return new NullMutationOperator();
+  }
 
-    @Test
-    void testCanMutateVoidWrapper() throws NoSuchMethodException {
-        Method method = getMethod();
-        MutationOperator operator = getOperator();
-        assertTrue(operator.canMutate(new MethodInfo(method)));
-    }
+  private Method getMethod() throws NoSuchMethodException {
+    return SideEffect.class.getDeclaredMethod("nextOdd");
+  }
 
-    @Test
-    void testSideEffectsRemovedInMutation() throws NoSuchMethodException, IOException, InstantiationException, IllegalAccessException, InvocationTargetException, NoSuchFieldException {
-        checkOriginalSideEffect();
-        checkSideEffectsRemoved();
-    }
+  @Test
+  void testCanMutateVoidWrapper() throws NoSuchMethodException {
+    Method method = getMethod();
+    MutationOperator operator = getOperator();
+    assertTrue(operator.canMutate(new MethodInfo(method)));
+  }
 
-    private void checkOriginalSideEffect() {
-        SideEffect obj = new SideEffect();
-        int initialValue = obj.count;
-        obj.nextOdd();
-        assertNotEquals(initialValue, obj.count, "Method nextOdd in SideEffect test class has no effect on the count field");
-    }
+  @Test
+  void testSideEffectsRemovedInMutation()
+      throws NoSuchMethodException, IOException, InstantiationException, IllegalAccessException,
+          InvocationTargetException, NoSuchFieldException {
+    checkOriginalSideEffect();
+    checkSideEffectsRemoved();
+  }
 
-    private void checkSideEffectsRemoved() throws NoSuchMethodException, IOException, IllegalAccessException, InstantiationException, InvocationTargetException, NoSuchFieldException {
-        Method method = getMethod();
-        Class<?> mutant = mutate(method, getOperator());
-        Object instance = newInstance(mutant);
-        Object initialValue = mutant.getDeclaredField("count").get(instance);
-        Method mutatedMethod = mutant.getDeclaredMethod(method.getName(), method.getParameterTypes());
-        mutatedMethod.invoke(instance);
-        Object result = mutant.getDeclaredField("count").get(instance);
-        assertThat("Field count should have changed after mutation", result, is(initialValue));
-    }
+  private void checkOriginalSideEffect() {
+    SideEffect obj = new SideEffect();
+    int initialValue = obj.count;
+    obj.nextOdd();
+    assertNotEquals(
+        initialValue,
+        obj.count,
+        "Method nextOdd in SideEffect test class has no effect on the count field");
+  }
 
+  private void checkSideEffectsRemoved()
+      throws NoSuchMethodException, IOException, IllegalAccessException, InstantiationException,
+          InvocationTargetException, NoSuchFieldException {
+    Method method = getMethod();
+    Class<?> mutant = mutate(method, getOperator());
+    Object instance = newInstance(mutant);
+    Object initialValue = mutant.getDeclaredField("count").get(instance);
+    Method mutatedMethod = mutant.getDeclaredMethod(method.getName(), method.getParameterTypes());
+    mutatedMethod.invoke(instance);
+    Object result = mutant.getDeclaredField("count").get(instance);
+    assertThat("Field count should have changed after mutation", result, is(initialValue));
+  }
 }
diff --git a/src/test/java/eu/stamp_project/descartes/operators/parsing/LiteralParserTest.java b/src/test/java/eu/stamp_project/descartes/operators/parsing/LiteralParserTest.java
index 4c771fd..52c83f5 100644
--- a/src/test/java/eu/stamp_project/descartes/operators/parsing/LiteralParserTest.java
+++ b/src/test/java/eu/stamp_project/descartes/operators/parsing/LiteralParserTest.java
@@ -1,114 +1,107 @@
 package eu.stamp_project.descartes.operators.parsing;
 
-import org.junit.jupiter.api.DisplayName;
-import org.junit.jupiter.params.ParameterizedTest;
-import org.junit.jupiter.params.provider.Arguments;
-import org.junit.jupiter.params.provider.MethodSource;
-
-import java.util.stream.Stream;
-
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import java.util.stream.Stream;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
 
 class LiteralParserTest {
 
-    @DisplayName("Should parse valid literal specifications")
-    @ParameterizedTest(name = "Input: {0}")
-    @MethodSource
-    public void testParseLiteral(String input, Object expected) {
-        LiteralParser parser = new LiteralParser();
-        LiteralParser.Result result = parser.parse(input);
-        assertFalse( result.hasError(), "Parsing should succeed. Got error: " + result.getError());
-        assertThat(result.getValue(), equalTo(expected));
-    }
-
-    private static Stream<Arguments> testParseLiteral() {
-        return Stream.of(
-                Arguments.of("1", 1),
-                Arguments.of("-1", -1),
-                Arguments.of("1.2f", 1.2f),
-                Arguments.of("1.0", 1.0),
-                Arguments.of("(short)-1", (short) -1),
-                Arguments.of("(short)3", (short)3),
-                Arguments.of("(byte)1", (byte) 1),
-                Arguments.of("(byte)-2", (byte) -2),
-                Arguments.of("123L", 123L),
-                Arguments.of("true", true),
-                Arguments.of("'\\n'", '\n'),
-                Arguments.of("\"\"", ""),
-                Arguments.of("\"A\"", "A"),
-                Arguments.of("0b1101", 0b1101),
-                Arguments.of("0b1_0_0", 0b1_0_0),
-                Arguments.of("0B1", 0B1),
-                Arguments.of("0XFF", 0XFF),
-                Arguments.of("0xA_a", 0xA_a),
-                Arguments.of("0111", 0111),
-                Arguments.of("07_1_1", 07_1_1),
-                Arguments.of("-2L", -2L),
-                Arguments.of("-4.5", -4.5),
-                Arguments.of("12_345_678_910L", 12_345_678_910L),
-                Arguments.of("0133767016076l", 0133767016076l),
-                Arguments.of("0x2DFDC1C3El", 0x2DFDC1C3El),
-                Arguments.of("\"\\123\"","\123"),
-                Arguments.of("\"\\uFFAA\"", "\uFFAA"),
-                Arguments.of("'a'",'a'),
-                Arguments.of("'\\r'",'\r'),
-                Arguments.of("'\\n'",'\n'),
-                Arguments.of("'\\t'",'\t'),
-                Arguments.of("'\\b'",'\b'),
-                Arguments.of("'\\f'",'\f'),
-                Arguments.of("'\\''",'\''),
-                Arguments.of("'\\\\'",'\\'),
-                Arguments.of("'\\7'",'\7'),
-                Arguments.of("'\\67'",'\67'),
-                Arguments.of("'\\354'",'\354'),
-                Arguments.of("'\\u1234'",'\u1234')
-        );
-    }
-
-
+  @DisplayName("Should parse valid literal specifications")
+  @ParameterizedTest(name = "Input: {0}")
+  @MethodSource
+  public void testParseLiteral(String input, Object expected) {
+    LiteralParser parser = new LiteralParser();
+    LiteralParser.Result result = parser.parse(input);
+    assertFalse(result.hasError(), "Parsing should succeed. Got error: " + result.getError());
+    assertThat(result.getValue(), equalTo(expected));
+  }
 
-    @DisplayName("Should not parse invalid literal specifications")
-    @ParameterizedTest(name = "Input: {0}")
-    @MethodSource
-    public void testShouldNotParseWrongInput(String input) {
-        LiteralParser parser = new LiteralParser();
-        LiteralParser.Result result = parser.parse(input);
+  private static Stream<Arguments> testParseLiteral() {
+    return Stream.of(
+        Arguments.of("1", 1),
+        Arguments.of("-1", -1),
+        Arguments.of("1.2f", 1.2f),
+        Arguments.of("1.0", 1.0),
+        Arguments.of("(short)-1", (short) -1),
+        Arguments.of("(short)3", (short) 3),
+        Arguments.of("(byte)1", (byte) 1),
+        Arguments.of("(byte)-2", (byte) -2),
+        Arguments.of("123L", 123L),
+        Arguments.of("true", true),
+        Arguments.of("'\\n'", '\n'),
+        Arguments.of("\"\"", ""),
+        Arguments.of("\"A\"", "A"),
+        Arguments.of("0b1101", 0b1101),
+        Arguments.of("0b1_0_0", 0b1_0_0),
+        Arguments.of("0B1", 0B1),
+        Arguments.of("0XFF", 0XFF),
+        Arguments.of("0xA_a", 0xA_a),
+        Arguments.of("0111", 0111),
+        Arguments.of("07_1_1", 07_1_1),
+        Arguments.of("-2L", -2L),
+        Arguments.of("-4.5", -4.5),
+        Arguments.of("12_345_678_910L", 12_345_678_910L),
+        Arguments.of("0133767016076l", 0133767016076l),
+        Arguments.of("0x2DFDC1C3El", 0x2DFDC1C3El),
+        Arguments.of("\"\\123\"", "\123"),
+        Arguments.of("\"\\uFFAA\"", "\uFFAA"),
+        Arguments.of("'a'", 'a'),
+        Arguments.of("'\\r'", '\r'),
+        Arguments.of("'\\n'", '\n'),
+        Arguments.of("'\\t'", '\t'),
+        Arguments.of("'\\b'", '\b'),
+        Arguments.of("'\\f'", '\f'),
+        Arguments.of("'\\''", '\''),
+        Arguments.of("'\\\\'", '\\'),
+        Arguments.of("'\\7'", '\7'),
+        Arguments.of("'\\67'", '\67'),
+        Arguments.of("'\\354'", '\354'),
+        Arguments.of("'\\u1234'", '\u1234'));
+  }
 
-        assertTrue(result.hasError(), "Accepted wrong input.");
-    }
+  @DisplayName("Should not parse invalid literal specifications")
+  @ParameterizedTest(name = "Input: {0}")
+  @MethodSource
+  public void testShouldNotParseWrongInput(String input) {
+    LiteralParser parser = new LiteralParser();
+    LiteralParser.Result result = parser.parse(input);
 
-    private static Stream<String> testShouldNotParseWrongInput() {
-        return Stream.of(
-                "1 2",
-                "-",
-                "",
-                "(",
-                "(short)true",
-                "@",
-                "vod",
-                "nothing",
-                "nil",
-                "3A",
-                "B3",
-                ")1",
-                "-'S'",
-                "\"a",
-                "a\"",
-                "(1)2",
-                "(type)8",
-                "(short 3",
-                "(byte 3",
-                "(byte) 'A'",
-                "(short) 'B'",
-                "''",
-                "'a",
-                "'tu'",
-                "'\\500'"
-        );
-    }
+    assertTrue(result.hasError(), "Accepted wrong input.");
+  }
 
-}
\ No newline at end of file
+  private static Stream<String> testShouldNotParseWrongInput() {
+    return Stream.of(
+        "1 2",
+        "-",
+        "",
+        "(",
+        "(short)true",
+        "@",
+        "vod",
+        "nothing",
+        "nil",
+        "3A",
+        "B3",
+        ")1",
+        "-'S'",
+        "\"a",
+        "a\"",
+        "(1)2",
+        "(type)8",
+        "(short 3",
+        "(byte 3",
+        "(byte) 'A'",
+        "(short) 'B'",
+        "''",
+        "'a",
+        "'tu'",
+        "'\\500'");
+  }
+}
diff --git a/src/test/java/eu/stamp_project/descartes/reporting/JSONWriterTest.java b/src/test/java/eu/stamp_project/descartes/reporting/JSONWriterTest.java
index e0adc36..faf3f76 100644
--- a/src/test/java/eu/stamp_project/descartes/reporting/JSONWriterTest.java
+++ b/src/test/java/eu/stamp_project/descartes/reporting/JSONWriterTest.java
@@ -1,110 +1,106 @@
 package eu.stamp_project.descartes.reporting;
 
-
-import org.junit.jupiter.params.ParameterizedTest;
-import org.junit.jupiter.params.provider.Arguments;
-import org.junit.jupiter.params.provider.MethodSource;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.is;
 
 import java.io.IOException;
 import java.io.StringWriter;
 import java.util.stream.Stream;
-
-import static org.hamcrest.MatcherAssert.assertThat;
-import static org.hamcrest.Matchers.equalTo;
-import static org.hamcrest.Matchers.is;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
 
 public class JSONWriterTest {
 
-    public static Stream<Arguments> testData() {
-        return Stream.of(
-                Arguments.of(
-                        "[1,true,\"somestring\",\" escaped \\n \\\" \"]",
-                        (Generation) ((JSONWriter json) -> {
-                            json.beginList();
-                            json.write(1);
-                            json.write(true);
-                            json.write("somestring");
-                            json.write(" escaped \n \" ");
-                            json.endList();
-                        })
-                ),
-                Arguments.of(
-                        "{\"i\":1,\"b\":true,\"s\":\"string\"}",
-                        (Generation) ((JSONWriter json) -> {
-                            json.beginObject();
-                            json.writeAttribute("i", 1);
-                            json.writeAttribute("b", true);
-                            json.writeAttribute("s", "string");
-                            json.endObject();
-                        })
-                ),
-                Arguments.of(
-                        "{\"value\":2,\"left\":{\"value\":1},\"right\":{\"value\":4,\"left\":{\"value\":3},\"right\":{\"value\":5}}}",
-                        (Generation) ((JSONWriter json) -> {
-                            json.beginObject();
-                            json.writeAttribute("value", 2);
-
-                            json.beginObjectAttribute("left");
-                            json.writeAttribute("value", 1);
-                            json.endObject();
+  public static Stream<Arguments> testData() {
+    return Stream.of(
+        Arguments.of(
+            "[1,true,\"somestring\",\" escaped \\n \\\" \"]",
+            (Generation)
+                ((JsonWriter json) -> {
+                  json.beginList();
+                  json.write(1);
+                  json.write(true);
+                  json.write("somestring");
+                  json.write(" escaped \n \" ");
+                  json.endList();
+                })),
+        Arguments.of(
+            "{\"i\":1,\"b\":true,\"s\":\"string\"}",
+            (Generation)
+                ((JsonWriter json) -> {
+                  json.beginObject();
+                  json.writeAttribute("i", 1);
+                  json.writeAttribute("b", true);
+                  json.writeAttribute("s", "string");
+                  json.endObject();
+                })),
+        Arguments.of(
+            "{\"value\":2,\"left\":{\"value\":1},\"right\":{\"value\":4,\"left\":{\"value\":3},\"right\":{\"value\":5}}}",
+            (Generation)
+                ((JsonWriter json) -> {
+                  json.beginObject();
+                  json.writeAttribute("value", 2);
 
-                            json.beginObjectAttribute("right");
-                            json.writeAttribute("value", 4);
+                  json.beginObjectAttribute("left");
+                  json.writeAttribute("value", 1);
+                  json.endObject();
 
-                            json.beginObjectAttribute("left");
-                            json.writeAttribute("value", 3);
-                            json.endObject();
+                  json.beginObjectAttribute("right");
+                  json.writeAttribute("value", 4);
 
-                            json.beginObjectAttribute("right");
-                            json.writeAttribute("value", 5);
-                            json.endObject();
-                            json.endObject();
+                  json.beginObjectAttribute("left");
+                  json.writeAttribute("value", 3);
+                  json.endObject();
 
-                            json.endObject();
-                        })
-                ),
-                Arguments.of(
-                        "[[1,0,0],[0,1,0],[0,0,1]]",
-                        (Generation) ((JSONWriter json) -> {
-                            int[][] matrix = {{1, 0, 0}, {0, 1, 0}, {0, 0, 1}};
-                            json.beginList();
-                            for (int i = 0; i < matrix.length; i++) {
-                                json.beginList();
-                                for (int j = 0; j < matrix[i].length; j++) {
-                                    json.write(matrix[i][j]);
-                                }
-                                json.endList();
-                            }
-                            json.endList();
-                        })
-                ),
-                Arguments.of(
-                        "[{\"value\":1},{\"value\":2},{\"value\":3}]",
-                        (Generation) ((JSONWriter json) -> {
-                            json.beginList();
-                            for (int i = 0; i < 3; i++) {
-                                json.beginObject();
-                                json.writeAttribute("value", i + 1);
-                                json.endObject();
-                            }
-                            json.endList();
-                        })
-                )
-        );
-    }
+                  json.beginObjectAttribute("right");
+                  json.writeAttribute("value", 5);
+                  json.endObject();
+                  json.endObject();
 
-    @ParameterizedTest(name = "{0}")
-    @MethodSource("testData")
-    public void testWritesCorrectDocument(String content, Generation action) throws IOException {
-        StringWriter writer = new StringWriter();
-        JSONWriter json = new JSONWriter(writer);
-        action.generate(json);
-        String result = writer.getBuffer().toString();
-        assertThat(content, is(equalTo(result)));
-    }
+                  json.endObject();
+                })),
+        Arguments.of(
+            "[[1,0,0],[0,1,0],[0,0,1]]",
+            (Generation)
+                ((JsonWriter json) -> {
+                  int[][] matrix = {{1, 0, 0}, {0, 1, 0}, {0, 0, 1}};
+                  json.beginList();
+                  for (int i = 0; i < matrix.length; i++) {
+                    json.beginList();
+                    for (int j = 0; j < matrix[i].length; j++) {
+                      json.write(matrix[i][j]);
+                    }
+                    json.endList();
+                  }
+                  json.endList();
+                })),
+        Arguments.of(
+            "[{\"value\":1},{\"value\":2},{\"value\":3}]",
+            (Generation)
+                ((JsonWriter json) -> {
+                  json.beginList();
+                  for (int i = 0; i < 3; i++) {
+                    json.beginObject();
+                    json.writeAttribute("value", i + 1);
+                    json.endObject();
+                  }
+                  json.endList();
+                })));
+  }
 
-    interface Generation {
-        void generate(JSONWriter json) throws IOException;
-    }
+  @ParameterizedTest(name = "{0}")
+  @MethodSource("testData")
+  public void testWritesCorrectDocument(String content, Generation action) throws IOException {
+    StringWriter writer = new StringWriter();
+    JsonWriter json = new JsonWriter(writer);
+    action.generate(json);
+    String result = writer.getBuffer().toString();
+    assertThat(content, is(equalTo(result)));
+  }
 
-}
\ No newline at end of file
+  interface Generation {
+    void generate(JsonWriter json) throws IOException;
+  }
+}
diff --git a/src/test/java/eu/stamp_project/descartes/reporting/models/MethodRecordTest.java b/src/test/java/eu/stamp_project/descartes/reporting/models/MethodRecordTest.java
index 63f96ad..ad78a85 100644
--- a/src/test/java/eu/stamp_project/descartes/reporting/models/MethodRecordTest.java
+++ b/src/test/java/eu/stamp_project/descartes/reporting/models/MethodRecordTest.java
@@ -1,7 +1,12 @@
 package eu.stamp_project.descartes.reporting.models;
 
 import static eu.stamp_project.descartes.reporting.models.MethodClassification.*;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.pitest.mutationtest.DetectionStatus.*;
 
+import java.util.Arrays;
+import java.util.stream.Stream;
 import org.junit.jupiter.api.DynamicTest;
 import org.junit.jupiter.api.TestFactory;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -9,123 +14,100 @@
 import org.junit.jupiter.params.provider.MethodSource;
 import org.pitest.classinfo.ClassName;
 import org.pitest.mutationtest.DetectionStatus;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertThrows;
-import static org.pitest.mutationtest.DetectionStatus.*;
-
 import org.pitest.mutationtest.MutationResult;
 import org.pitest.mutationtest.MutationStatusTestPair;
 import org.pitest.mutationtest.engine.Location;
 import org.pitest.mutationtest.engine.MutationDetails;
 import org.pitest.mutationtest.engine.MutationIdentifier;
 
-import java.util.Arrays;
-import java.util.stream.Stream;
-
-
 public class MethodRecordTest {
 
-
-    //TODO: Logic coverage
-    private static Stream<Arguments> methodRecords() {
-        return Stream.of(
-                Arguments.of(TESTED,           record(KILLED,      KILLED,      KILLED)),
-                Arguments.of(PSEUDO_TESTED,    record(SURVIVED,    SURVIVED,    SURVIVED)),
-                Arguments.of(PARTIALLY_TESTED, record(KILLED,      SURVIVED,    KILLED)),
-                Arguments.of(PARTIALLY_TESTED, record(KILLED,      SURVIVED,    SURVIVED)),
-                Arguments.of(PARTIALLY_TESTED, record(SURVIVED,    KILLED,      KILLED)),
-                Arguments.of(PARTIALLY_TESTED, record(SURVIVED,    KILLED,      SURVIVED)),
-                Arguments.of(PARTIALLY_TESTED, record(KILLED,      KILLED,      SURVIVED)),
-                Arguments.of(PARTIALLY_TESTED, record(SURVIVED,    SURVIVED,    KILLED)),
-                Arguments.of(NOT_COVERED,      record(NO_COVERAGE, NO_COVERAGE, NO_COVERAGE))
-        );
-    }
-
-    @ParameterizedTest
-    @MethodSource("methodRecords")
-    public void shouldHaveTheRightClassification(MethodClassification expectedClassification, MethodRecord record) {
-        assertEquals(expectedClassification, record.getClassification());
-    }
-
-    @TestFactory
-
-    public Stream<DynamicTest> shouldNotYieldValidRecords() {
-
-        return invalidStatusCombinations().map(
-                combination ->
-                        DynamicTest.dynamicTest(Arrays.toString(combination),
-                                () -> assertThrows(
-                                        IllegalArgumentException.class,
-                                        () -> record(combination)
-                                )
-                        )
-        );
-    }
-
-    private static Stream<DetectionStatus[]> invalidStatusCombinations() {
-        return Stream.of(
-                new DetectionStatus[]{KILLED, KILLED, NO_COVERAGE},
-                new DetectionStatus[]{KILLED, NO_COVERAGE, KILLED},
-                new DetectionStatus[]{KILLED, NO_COVERAGE, NO_COVERAGE},
-                new DetectionStatus[]{KILLED, NO_COVERAGE, SURVIVED},
-                new DetectionStatus[]{KILLED, SURVIVED, NO_COVERAGE},
-                new DetectionStatus[]{SURVIVED, KILLED, NO_COVERAGE},
-                new DetectionStatus[]{SURVIVED, NO_COVERAGE, KILLED},
-                new DetectionStatus[]{SURVIVED, NO_COVERAGE, NO_COVERAGE},
-                new DetectionStatus[]{SURVIVED, NO_COVERAGE, SURVIVED},
-                new DetectionStatus[]{SURVIVED, SURVIVED, NO_COVERAGE},
-                new DetectionStatus[]{NO_COVERAGE, KILLED, KILLED},
-                new DetectionStatus[]{NO_COVERAGE, KILLED, NO_COVERAGE},
-                new DetectionStatus[]{NO_COVERAGE, KILLED, SURVIVED},
-                new DetectionStatus[]{NO_COVERAGE, NO_COVERAGE, KILLED},
-                new DetectionStatus[]{NO_COVERAGE, NO_COVERAGE, SURVIVED},
-                new DetectionStatus[]{NO_COVERAGE, SURVIVED, KILLED},
-                new DetectionStatus[]{NO_COVERAGE, SURVIVED, NO_COVERAGE},
-                new DetectionStatus[]{NO_COVERAGE, SURVIVED, SURVIVED});
-    }
-
-
-    // Stubs
-    public static MutationResult mutation(DetectionStatus status, String mutant) {
-        return new MutationResult(
-                new MutationDetails(
-                        new MutationIdentifier(
-                                new Location(
-                                        ClassName.fromString("AClass"),
-                                        "aMethod",
-                                        "()I"),
-                                1,
-                                mutant),
-                        "path/to/file",
-                        "Mutation description",
-                        1,
-                        0),
-                new MutationStatusTestPair(1, status, null));
-    }
-
-    public static MutationResult detected(String mutant) {
-        return mutation(DetectionStatus.KILLED, mutant);
-    }
-
-    public static MutationResult survived(String mutant) {
-        return mutation(DetectionStatus.SURVIVED, mutant);
-    }
-
-    public static MutationResult notCovered(String mutant) {
-        return mutation(DetectionStatus.NO_COVERAGE, mutant);
-    }
-
-    public static MethodRecord record(DetectionStatus... statuses) {
-        MutationResult[] results = new MutationResult[statuses.length];
-        for(int i = 0; i < statuses.length; i++)
-            results[i] = mutation(statuses[i], Integer.toString(i));
-        return record(results);
-    }
-
-    public static MethodRecord  record(MutationResult... results) {
-        return new MethodRecord(results);
-    }
-
-
-}
\ No newline at end of file
+  private static Stream<Arguments> methodRecords() {
+    return Stream.of(
+        Arguments.of(TESTED, record(KILLED, KILLED, KILLED)),
+        Arguments.of(PSEUDO_TESTED, record(SURVIVED, SURVIVED, SURVIVED)),
+        Arguments.of(PARTIALLY_TESTED, record(KILLED, SURVIVED, KILLED)),
+        Arguments.of(PARTIALLY_TESTED, record(KILLED, SURVIVED, SURVIVED)),
+        Arguments.of(PARTIALLY_TESTED, record(SURVIVED, KILLED, KILLED)),
+        Arguments.of(PARTIALLY_TESTED, record(SURVIVED, KILLED, SURVIVED)),
+        Arguments.of(PARTIALLY_TESTED, record(KILLED, KILLED, SURVIVED)),
+        Arguments.of(PARTIALLY_TESTED, record(SURVIVED, SURVIVED, KILLED)),
+        Arguments.of(NOT_COVERED, record(NO_COVERAGE, NO_COVERAGE, NO_COVERAGE)));
+  }
+
+  @ParameterizedTest
+  @MethodSource("methodRecords")
+  public void shouldHaveTheRightClassification(
+      MethodClassification expectedClassification, MethodRecord record) {
+    assertEquals(expectedClassification, record.getClassification());
+  }
+
+  @TestFactory
+  public Stream<DynamicTest> shouldNotYieldValidRecords() {
+
+    return invalidStatusCombinations()
+        .map(
+            combination ->
+                DynamicTest.dynamicTest(
+                    Arrays.toString(combination),
+                    () -> assertThrows(IllegalArgumentException.class, () -> record(combination))));
+  }
+
+  private static Stream<DetectionStatus[]> invalidStatusCombinations() {
+    return Stream.of(
+        new DetectionStatus[] {KILLED, KILLED, NO_COVERAGE},
+        new DetectionStatus[] {KILLED, NO_COVERAGE, KILLED},
+        new DetectionStatus[] {KILLED, NO_COVERAGE, NO_COVERAGE},
+        new DetectionStatus[] {KILLED, NO_COVERAGE, SURVIVED},
+        new DetectionStatus[] {KILLED, SURVIVED, NO_COVERAGE},
+        new DetectionStatus[] {SURVIVED, KILLED, NO_COVERAGE},
+        new DetectionStatus[] {SURVIVED, NO_COVERAGE, KILLED},
+        new DetectionStatus[] {SURVIVED, NO_COVERAGE, NO_COVERAGE},
+        new DetectionStatus[] {SURVIVED, NO_COVERAGE, SURVIVED},
+        new DetectionStatus[] {SURVIVED, SURVIVED, NO_COVERAGE},
+        new DetectionStatus[] {NO_COVERAGE, KILLED, KILLED},
+        new DetectionStatus[] {NO_COVERAGE, KILLED, NO_COVERAGE},
+        new DetectionStatus[] {NO_COVERAGE, KILLED, SURVIVED},
+        new DetectionStatus[] {NO_COVERAGE, NO_COVERAGE, KILLED},
+        new DetectionStatus[] {NO_COVERAGE, NO_COVERAGE, SURVIVED},
+        new DetectionStatus[] {NO_COVERAGE, SURVIVED, KILLED},
+        new DetectionStatus[] {NO_COVERAGE, SURVIVED, NO_COVERAGE},
+        new DetectionStatus[] {NO_COVERAGE, SURVIVED, SURVIVED});
+  }
+
+  // Stubs
+  public static MutationResult mutation(DetectionStatus status, String mutant) {
+    return new MutationResult(
+        new MutationDetails(
+            new MutationIdentifier(
+                new Location(ClassName.fromString("AClass"), "aMethod", "()I"), 1, mutant),
+            "path/to/file",
+            "Mutation description",
+            1,
+            0),
+        new MutationStatusTestPair(1, status, null));
+  }
+
+  public static MutationResult detected(String mutant) {
+    return mutation(DetectionStatus.KILLED, mutant);
+  }
+
+  public static MutationResult survived(String mutant) {
+    return mutation(DetectionStatus.SURVIVED, mutant);
+  }
+
+  public static MutationResult notCovered(String mutant) {
+    return mutation(DetectionStatus.NO_COVERAGE, mutant);
+  }
+
+  public static MethodRecord record(DetectionStatus... statuses) {
+    MutationResult[] results = new MutationResult[statuses.length];
+    for (int i = 0; i < statuses.length; i++)
+      results[i] = mutation(statuses[i], Integer.toString(i));
+    return record(results);
+  }
+
+  public static MethodRecord record(MutationResult... results) {
+    return new MethodRecord(results);
+  }
+}
diff --git a/src/test/java/eu/stamp_project/test/Assertions.java b/src/test/java/eu/stamp_project/test/Assertions.java
index 9c8eaa8..d38b679 100644
--- a/src/test/java/eu/stamp_project/test/Assertions.java
+++ b/src/test/java/eu/stamp_project/test/Assertions.java
@@ -2,40 +2,36 @@
 
 import static org.junit.jupiter.api.Assertions.*;
 
-public class Assertions {
+public final class Assertions {
 
-    private Assertions() {}
+  private Assertions() {}
 
-    private static final double delta = 0.00001;
+  private static final double DELTA = 0.00001;
 
-    public static void assertDifferent(Object unexpected, Object actual) {
-        if(unexpected == null) {
-            assertNotNull(actual, "Method should not return null");
-            return;
-        }
-        String message = "Original method returned the same value as the mutant should return.";
-        if(actual.getClass() == Double.class) {
-            assertNotEquals((double)unexpected, (double)actual, delta, message);
-        }
-        else if(actual.getClass() == Float.class) {
-            assertNotEquals((float)unexpected, (float)actual, (float)delta, message);
-        }
-        assertNotEquals(unexpected, actual, message);
+  public static void assertDifferent(Object unexpected, Object actual) {
+    if (unexpected == null) {
+      assertNotNull(actual, "Method should not return null");
+      return;
     }
-
-    public static void assertResultEquals(Object expected, Object actual) {
-        if(expected == null) {
-            assertNull(actual, "Method expected to return null");
-            return;
-        }
-        if(actual.getClass() == Double.class) {
-            assertEquals((double)expected, (double)actual, delta);
-        }
-        else if(actual.getClass() == Float.class) {
-            assertEquals((float)expected, (float)actual, (float)delta);
-        }
-        assertEquals(expected, actual);
+    String message = "Original method returned the same value as the mutant should return.";
+    if (actual.getClass() == Double.class) {
+      assertNotEquals((double) unexpected, (double) actual, DELTA, message);
+    } else if (actual.getClass() == Float.class) {
+      assertNotEquals((float) unexpected, (float) actual, (float) DELTA, message);
     }
+    assertNotEquals(unexpected, actual, message);
+  }
 
-
+  public static void assertResultEquals(Object expected, Object actual) {
+    if (expected == null) {
+      assertNull(actual, "Method expected to return null");
+      return;
+    }
+    if (actual.getClass() == Double.class) {
+      assertEquals((double) expected, (double) actual, DELTA);
+    } else if (actual.getClass() == Float.class) {
+      assertEquals((float) expected, (float) actual, (float) DELTA);
+    }
+    assertEquals(expected, actual);
+  }
 }
diff --git a/src/test/java/eu/stamp_project/test/MethodStreamBuilder.java b/src/test/java/eu/stamp_project/test/MethodStreamBuilder.java
index 014c591..ceac5bb 100644
--- a/src/test/java/eu/stamp_project/test/MethodStreamBuilder.java
+++ b/src/test/java/eu/stamp_project/test/MethodStreamBuilder.java
@@ -4,48 +4,55 @@
 import java.util.*;
 import java.util.stream.Stream;
 
-public class MethodStreamBuilder {
-
-    private final Class<?> methodOwner;
-    private final ArrayList<Method> methodsToReturn;
-    private final Set<Method> exceptions = new HashSet<>();
-
-    private MethodStreamBuilder(Class<?> methodOwner) {
-        Objects.requireNonNull(methodOwner, "Class for method selection can not be null.");
-        this.methodOwner = methodOwner;
-        methodsToReturn = new ArrayList<>();
+public final class MethodStreamBuilder {
+
+  private final Class<?> methodOwner;
+  private final ArrayList<Method> methodsToReturn;
+  private final Set<Method> exceptions = new HashSet<>();
+
+  private MethodStreamBuilder(Class<?> methodOwner) {
+    Objects.requireNonNull(methodOwner, "Class for method selection can not be null.");
+    this.methodOwner = methodOwner;
+    methodsToReturn = new ArrayList<>();
+  }
+
+  public MethodStreamBuilder method(String name, Class<?>... parameterTypes)
+      throws NoSuchMethodException {
+    methodsToReturn.add(methodOwner.getMethod(name, parameterTypes));
+    return this;
+  }
+
+  public MethodStreamBuilder allDeclaredMethods() {
+    methodsToReturn.addAll(List.of(methodOwner.getDeclaredMethods()));
+    return this;
+  }
+
+  public MethodStreamBuilder except(String name, Class<?>... parameterTypes)
+      throws NoSuchMethodException {
+    exceptions.add(methodOwner.getMethod(name, parameterTypes));
+    return this;
+  }
+
+  public Stream<Method> toStream() {
+    return methodsToReturn.stream().filter(method -> !exceptions.contains(method));
+  }
+
+  public static MethodStreamBuilder fromClass(Class<?> methodOwner) {
+    return new MethodStreamBuilder(methodOwner);
+  }
+
+  public static Stream<Method> select(MethodStreamBuilder... selections) {
+    Objects.requireNonNull(selections, "Method selection can not be null.");
+    if (selections.length == 0) {
+      return Stream.empty();
     }
-
-    public MethodStreamBuilder method(String name, Class<?>... parameterTypes) throws NoSuchMethodException {
-        methodsToReturn.add(methodOwner.getMethod(name, parameterTypes));
-        return this;
+    if (selections.length == 1) {
+      return selections[0].toStream();
     }
-
-    public MethodStreamBuilder allDeclaredMethods() {
-        methodsToReturn.addAll(List.of(methodOwner.getDeclaredMethods()));
-        return this;
+    Stream<Method> result = selections[0].toStream();
+    for (int i = 1; i < selections.length; i++) {
+      result = Stream.concat(result, selections[i].toStream());
     }
-
-    public MethodStreamBuilder except(String name, Class<?>... parameterTypes) throws NoSuchMethodException {
-        exceptions.add(methodOwner.getMethod(name, parameterTypes));
-        return this;
-    }
-
-    public Stream<Method> toStream() { return methodsToReturn.stream().filter(method -> ! exceptions.contains(method)); }
-
-    public static MethodStreamBuilder fromClass(Class<?> methodOwner) { return new MethodStreamBuilder(methodOwner); }
-
-    public static Stream<Method> select(MethodStreamBuilder... selections) {
-        Objects.requireNonNull(selections, "Method selection can not be null.");
-        if(selections.length == 0)
-            return Stream.empty();
-        if(selections.length == 1)
-            return selections[0].toStream();
-        Stream<Method> result = selections[0].toStream();
-        for(int i = 1; i < selections.length; i++) {
-            result = Stream.concat(result, selections[i].toStream());
-        }
-        return result;
-    }
-
+    return result;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/test/TestValues.java b/src/test/java/eu/stamp_project/test/TestValues.java
index f9caa08..26c4498 100644
--- a/src/test/java/eu/stamp_project/test/TestValues.java
+++ b/src/test/java/eu/stamp_project/test/TestValues.java
@@ -1,45 +1,53 @@
 package eu.stamp_project.test;
 
 import eu.stamp_project.utils.TypeHelper;
-
 import java.util.Arrays;
 
 public class TestValues {
 
-    private static boolean DEFAULT_BOOL;
-    private static char DEFAULT_CHAR;
-    private static byte DEFAULT_BYTE;
-    private static short DEFAULT_SHORT;
-    private static int DEFAULT_INT = 10;
-    private static long DEFAULT_LONG;
-    private static float DEFAULT_FLOAT;
-    private static double DEFAULT_DOUBLE;
-    private static String DEFAULT_STRING = "default";
+  private static final boolean DEFAULT_BOOL = false;
+  private static final char DEFAULT_CHAR = '\0';
+  private static final byte DEFAULT_BYTE = 0;
+  private static final short DEFAULT_SHORT = 0;
+  private static final int DEFAULT_INT = 10;
+  private static final long DEFAULT_LONG = 0L;
+  private static final float DEFAULT_FLOAT = 0.0f;
+  private static final double DEFAULT_DOUBLE = 0.0;
+  private static final String DEFAULT_STRING = "default";
 
-    public static Object defaultFor(Class<?> type) {
-        Class<?> target = TypeHelper.wrap(type);
-        if (target == Boolean.class)
-            return DEFAULT_BOOL;
-        if (target == Character.class)
-            return DEFAULT_CHAR;
-        if (target == Byte.class)
-            return DEFAULT_BYTE;
-        if(target == Short.class)
-            return DEFAULT_SHORT;
-        if (target == Integer.class)
-            return DEFAULT_INT;
-        if (target == Long.class)
-            return DEFAULT_LONG;
-        if (target == Float.class)
-            return DEFAULT_FLOAT;
-        if (target == Double.class)
-            return DEFAULT_DOUBLE;
-        if(target == String.class)
-            return DEFAULT_STRING;
-        return null;
+  public static Object defaultFor(Class<?> type) {
+    Class<?> target = TypeHelper.wrap(type);
+    if (target == Boolean.class) {
+      return DEFAULT_BOOL;
     }
-
-    public static Object[] defaultsFor(Class<?>[] types) {
-        return Arrays.stream(types).map(TestValues::defaultFor).toArray(Object[]::new);
+    if (target == Character.class) {
+      return DEFAULT_CHAR;
+    }
+    if (target == Byte.class) {
+      return DEFAULT_BYTE;
+    }
+    if (target == Short.class) {
+      return DEFAULT_SHORT;
+    }
+    if (target == Integer.class) {
+      return DEFAULT_INT;
     }
+    if (target == Long.class) {
+      return DEFAULT_LONG;
+    }
+    if (target == Float.class) {
+      return DEFAULT_FLOAT;
+    }
+    if (target == Double.class) {
+      return DEFAULT_DOUBLE;
+    }
+    if (target == String.class) {
+      return DEFAULT_STRING;
+    }
+    return null;
+  }
+
+  public static Object[] defaultsFor(Class<?>[] types) {
+    return Arrays.stream(types).map(TestValues::defaultFor).toArray(Object[]::new);
+  }
 }
diff --git a/src/test/java/eu/stamp_project/test/Utils.java b/src/test/java/eu/stamp_project/test/Utils.java
index c6aec1a..25cdbe9 100644
--- a/src/test/java/eu/stamp_project/test/Utils.java
+++ b/src/test/java/eu/stamp_project/test/Utils.java
@@ -1,5 +1,7 @@
 package eu.stamp_project.test;
 
+import java.io.IOException;
+import java.lang.reflect.Method;
 import org.objectweb.asm.ClassReader;
 import org.objectweb.asm.tree.ClassNode;
 import org.pitest.bytecode.analysis.ClassTree;
@@ -8,25 +10,21 @@
 import org.pitest.mutationtest.engine.MutationIdentifier;
 import org.pitest.reloc.asm.Type;
 
-import java.io.IOException;
-import java.lang.reflect.Method;
-
-public class Utils {
-
-    private Utils() {}
+public final class Utils {
 
+  private Utils() {}
 
-    public static MutationIdentifier toMutationIdentifier(Method method, String operator) {
-        ClassName className = ClassName.fromClass(method.getDeclaringClass());
-        Location location = new Location(className, method.getName(), Type.getMethodDescriptor(method));
-        return new MutationIdentifier(location, 0, operator);
-    }
+  public static MutationIdentifier toMutationIdentifier(Method method, String operator) {
+    ClassName className = ClassName.fromClass(method.getDeclaringClass());
+    Location location = new Location(className, method.getName(), Type.getMethodDescriptor(method));
+    return new MutationIdentifier(location, 0, operator);
+  }
 
-    public static ClassTree getClassTree(Class<?> target) throws IOException {
-        ClassReader reader = new org.objectweb.asm.ClassReader(target.getName());
-        ClassNode classNode = new ClassNode();
-        ClassTree classTree = new ClassTree(classNode);
-        reader.accept(classNode, 0);
-        return classTree;
-    }
+  public static ClassTree getClassTree(Class<?> target) throws IOException {
+    ClassReader reader = new org.objectweb.asm.ClassReader(target.getName());
+    ClassNode classNode = new ClassNode();
+    ClassTree classTree = new ClassTree(classNode);
+    reader.accept(classNode, 0);
+    return classTree;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/test/input/AbstractClass.java b/src/test/java/eu/stamp_project/test/input/AbstractClass.java
index f7365fb..f069fb0 100644
--- a/src/test/java/eu/stamp_project/test/input/AbstractClass.java
+++ b/src/test/java/eu/stamp_project/test/input/AbstractClass.java
@@ -1,13 +1,11 @@
 package eu.stamp_project.test.input;
 
-/**
- * Meaningless abstract class for testing purposes
- */
+/** Meaningless abstract class for testing purposes */
 public abstract class AbstractClass {
 
-    public abstract void abstractMethod();
+  public abstract void abstractMethod();
 
-    public int nonAbstractMethod(int parameter) {
-        return 2 * parameter;
-    }
+  public int nonAbstractMethod(int parameter) {
+    return 2 * parameter;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/test/input/Calculator.java b/src/test/java/eu/stamp_project/test/input/Calculator.java
index ca58cbd..2624b66 100644
--- a/src/test/java/eu/stamp_project/test/input/Calculator.java
+++ b/src/test/java/eu/stamp_project/test/input/Calculator.java
@@ -1,148 +1,143 @@
 package eu.stamp_project.test.input;
 
-import org.pitest.mutationtest.build.InterceptorParameters;
-
 import java.util.Arrays;
 import java.util.List;
 import java.util.Optional;
 
-/**
- * Meaningless target class for mutation
- */
-public class Calculator {
+/** Meaningless target class for mutation */
+public final class Calculator {
 
+  private double registry;
+  private char lastOperatorSymbol;
 
-    private double registry;
-    private char lastOperatorSymbol;
+  public Calculator() {
+    clear();
+  }
 
-    public Calculator() {clear();}
+  // void method
 
-    //void method
+  public void clear() {
+    registry = 2;
+    lastOperatorSymbol = '\0';
+  }
 
-    public void clear() {
-        registry = 2;
-        lastOperatorSymbol = '\0';
-    }
+  // Integral types
 
+  public byte getByte() {
+    return (byte) Math.min(Math.abs(registry), 127);
+  }
 
+  public short getShort() {
+    return (short) Math.min(getCeiling(), 32000);
+  }
 
-    //Integral types
+  public int getCeiling() {
+    return (int) Math.ceil(registry + 18000);
+  }
 
-    public byte getByte() {
-        return (byte)Math.min(Math.abs(registry), 127);
-    }
+  public Integer getWrapper() {
+    return Integer.valueOf(2 + 3);
+  }
 
-    public short getShort() {
-        return (short) Math.min(getCeiling(), 32000);
-    }
+  public long getSquare() {
+    int value = getCeiling();
+    return value * value;
+  }
 
-    public int getCeiling() {
-        return (int)Math.ceil(registry + 18000);
-    }
+  public int conditionalReturn(boolean cond) {
+    return cond ? 1 : 2;
+  }
 
-    public Integer getWrapper() {
-        return Integer.valueOf(2 + 3);
-    }
+  public char getRandomOperatorSymbol() {
+    // Non sense code to avoid creating a getter
+    char[] symbols = {'+', '-', '*', '/'};
+    return symbols[getCeiling() % symbols.length];
+  }
 
-    public long getSquare() {
-        int value = getCeiling();
-        return value * value;
-    }
+  // Floating point types
 
-    public int conditionalReturn(boolean cond) {
-        return cond?1:2;
-    }
+  public double add(double input) {
+    registry += input;
+    lastOperatorSymbol = '+';
+    return registry;
+  }
 
+  public float getSomething() {
+    float value = getCeiling();
+    float root = (float) Math.sqrt(2);
+    return value * value * root;
+  }
 
-    public char getRandomOperatorSymbol() {
-        //Non sense code to avoid creating a getter
-        char[] symbols = {'+', '-', '*', '/'};
-        return symbols[getCeiling()%symbols.length];
-    }
+  // Boolean
 
-    //Floating point types
+  public boolean isOdd() {
+    return getCeiling() % 2 == 0;
+  }
 
-    public double add(double input) {
-        registry += input;
-        lastOperatorSymbol = '+';
-        return registry;
-    }
+  // String
 
-    public float getSomething() {
-        float value = getCeiling();
-        float root = (float)Math.sqrt(2);
-        return value * value * root;
-    }
+  public String getScreen() {
+    return Double.toString(registry);
+  }
 
-    //Boolean
+  // Other reference type
 
-    public boolean isOdd() {
-        return getCeiling() % 2 == 0;
-    }
+  public Calculator getClone() {
+    Calculator result = new Calculator();
+    result.registry = registry;
+    return result;
+  }
 
-    //String
-
-    public String getScreen() {
-        return Double.toString(registry);
+  public Calculator getConditionalClone(boolean cond) {
+    if (cond) {
+      return this;
     }
+    return null;
+  }
 
-    // Other reference type
-
-    public Calculator getClone() {
-        Calculator result = new Calculator();
-        result.registry = registry;
-        return result;
+  public Calculator[] getSomeCalculators(int number) {
+    Calculator[] result = new Calculator[number];
+    for (int i = 0; i < number; i++) {
+      result[i] = getClone();
     }
+    return result;
+  }
 
-    public Calculator getConditionalClone(boolean cond) {
-       if(cond){
-           return this;
-       }
-       return null;
+  public Calculator[][] getSomeMore(int number) {
+    Calculator[][] result = new Calculator[number][number];
+    for (int i = 0; i < number; i++) {
+      for (int j = 0; j < number; j++) {
+        result[i][j] = getClone();
+      }
     }
+    return result;
+  }
 
-    public Calculator[] getSomeCalculators(int number) {
-        Calculator[] result = new Calculator[number];
-        for(int i=0; i< number; i++) {
-            result[i] = getClone();
-        }
-        return result;
-    }
-
-    public Calculator[][] getSomeMore(int number) {
-        Calculator [][] result = new Calculator[number][number];
-        for (int i = 0; i < number; i++) {
-            for (int j = 0; j < number; j++) {
-                result[i][j] = getClone();
-            }
-        }
-        return result;
-    }
-
-    public List<Calculator> getMultipleCalculators(int size) {
-        return Arrays.asList(getSomeCalculators(size));
-    }
-
-    public int[] getRange(int top) {
-        int[] result = new int[top];
-        for(int i=0; i< top; i++) {
-            result[i] = i;
-        }
-        return result;
-    }
-
-    public Optional<Calculator> getOptionalCalculator() {
-        return Optional.of(this);
-    }
-
-    public void setDoubleRegistry(double value) {
-        this.registry = 2*value;
-    }
-
-    public int hashCode(int seed) {
-        return seed * seed + 2;
-    }
-
-    public String toString(String base) { return base + toString(); }
-
-}
\ No newline at end of file
+  public List<Calculator> getMultipleCalculators(int size) {
+    return Arrays.asList(getSomeCalculators(size));
+  }
+
+  public int[] getRange(int top) {
+    int[] result = new int[top];
+    for (int i = 0; i < top; i++) {
+      result[i] = i;
+    }
+    return result;
+  }
+
+  public Optional<Calculator> getOptionalCalculator() {
+    return Optional.of(this);
+  }
+
+  public void setDoubleRegistry(double value) {
+    this.registry = 2 * value;
+  }
+
+  public int hashCode(int seed) {
+    return seed * seed + 2;
+  }
+
+  public String toString(String base) {
+    return base + toString();
+  }
+}
diff --git a/src/test/java/eu/stamp_project/test/input/DeprecatedClass.java b/src/test/java/eu/stamp_project/test/input/DeprecatedClass.java
index 7c8fd53..c9d9112 100644
--- a/src/test/java/eu/stamp_project/test/input/DeprecatedClass.java
+++ b/src/test/java/eu/stamp_project/test/input/DeprecatedClass.java
@@ -3,9 +3,8 @@
 @Deprecated
 public class DeprecatedClass {
 
-    public void methodInsideDeprecatedClass() {}
-
-    @Deprecated
-    public void deprecatedInDeprecatedClass() {}
+  public void methodInsideDeprecatedClass() {}
 
+  @Deprecated
+  public void deprecatedInDeprecatedClass() {}
 }
diff --git a/src/test/java/eu/stamp_project/test/input/Fluent.java b/src/test/java/eu/stamp_project/test/input/Fluent.java
index 8a66d0a..dc9b7da 100644
--- a/src/test/java/eu/stamp_project/test/input/Fluent.java
+++ b/src/test/java/eu/stamp_project/test/input/Fluent.java
@@ -2,39 +2,38 @@
 
 public class Fluent extends AbstractClass implements Interface {
 
-    public int value = 1;
+  public int value = 1;
 
-    public Fluent addOne() {
-        value += 1;
-        return this;
-    }
+  public Fluent addOne() {
+    value += 1;
+    return this;
+  }
 
-    public AbstractClass addTwo() {
-        value += 2;
-        return this;
-    }
+  public AbstractClass addTwo() {
+    value += 2;
+    return this;
+  }
 
-    public Interface addThree() {
-        value += 2;
-        return this;
-    }
+  public Interface addThree() {
+    value += 2;
+    return this;
+  }
 
-    public static Fluent createNew() {
-        return new Fluent().addOne();
-    }
+  public static Fluent createNew() {
+    return new Fluent().addOne();
+  }
 
+  public String getValueAsString() {
+    return Integer.toString(value);
+  }
 
-    public String getValueAsString() {
-        return Integer.toString(value);
-    }
+  public static String createAndGetValue() {
+    return new Fluent().addOne().getValueAsString();
+  }
 
-    public static String createAndGetValue() {
-        return new Fluent().addOne().getValueAsString();
-    }
+  @Override
+  public void abstractMethod() {}
 
-    @Override
-    public void abstractMethod() { }
-
-    @Override
-    public void voidMethod() { }
+  @Override
+  public void voidMethod() {}
 }
diff --git a/src/test/java/eu/stamp_project/test/input/Index.java b/src/test/java/eu/stamp_project/test/input/Index.java
index c9f4ac2..bcb23a8 100644
--- a/src/test/java/eu/stamp_project/test/input/Index.java
+++ b/src/test/java/eu/stamp_project/test/input/Index.java
@@ -1,16 +1,18 @@
 package eu.stamp_project.test.input;
 
 public enum Index {
-    ONE, TWO, THREE;
+  ONE,
+  TWO,
+  THREE;
 
-    public Index next() {
-        switch (this) {
-            case ONE:
-                return TWO;
-            case TWO:
-                return THREE;
-            default:
-                return ONE;
-        }
+  public Index next() {
+    switch (this) {
+      case ONE:
+        return TWO;
+      case TWO:
+        return THREE;
+      default:
+        return ONE;
     }
+  }
 }
diff --git a/src/test/java/eu/stamp_project/test/input/Interface.java b/src/test/java/eu/stamp_project/test/input/Interface.java
index cb3da01..336bd72 100644
--- a/src/test/java/eu/stamp_project/test/input/Interface.java
+++ b/src/test/java/eu/stamp_project/test/input/Interface.java
@@ -1,6 +1,5 @@
 package eu.stamp_project.test.input;
 
-
 public interface Interface {
-    void voidMethod();
+  void voidMethod();
 }
diff --git a/src/test/java/eu/stamp_project/test/input/NativeMethodClass.java b/src/test/java/eu/stamp_project/test/input/NativeMethodClass.java
index 4a3f5cc..af975b8 100644
--- a/src/test/java/eu/stamp_project/test/input/NativeMethodClass.java
+++ b/src/test/java/eu/stamp_project/test/input/NativeMethodClass.java
@@ -1,5 +1,5 @@
 package eu.stamp_project.test.input;
 
 public class NativeMethodClass {
-    public static native void sayHello();
+  public static native void sayHello();
 }
diff --git a/src/test/java/eu/stamp_project/test/input/Numbers.java b/src/test/java/eu/stamp_project/test/input/Numbers.java
index 3a5b293..95fac3c 100644
--- a/src/test/java/eu/stamp_project/test/input/Numbers.java
+++ b/src/test/java/eu/stamp_project/test/input/Numbers.java
@@ -1,9 +1,11 @@
 package eu.stamp_project.test.input;
 
 public enum Numbers {
-    ONE, TWO, THREE;
+  ONE,
+  TWO,
+  THREE;
 
-    public void extraMethod() {
-        System.out.println("Extra method to enum class");
-    }
-}
\ No newline at end of file
+  public void extraMethod() {
+    System.out.println("Extra method to enum class");
+  }
+}
diff --git a/src/test/java/eu/stamp_project/test/input/Parameterless.java b/src/test/java/eu/stamp_project/test/input/Parameterless.java
index e10cfa5..933e1a5 100644
--- a/src/test/java/eu/stamp_project/test/input/Parameterless.java
+++ b/src/test/java/eu/stamp_project/test/input/Parameterless.java
@@ -2,89 +2,112 @@
 
 import java.util.Optional;
 
-
-
 public class Parameterless {
 
-
-    public Object getAnObject() {
-        return new Exception("Dummy exception");
-    }
-
-    public int sumInt() {
-        int result = 0;
-        for (int i = 0; i < 10; i++, result+=i);
-        return result;
+  public Object getAnObject() {
+    return new Exception("Dummy exception");
+  }
+
+  public int sumInt() {
+    int result = 0;
+    for (int i = 0; i < 10; i++, result += i)
+      ;
+    return result;
+  }
+
+  public int[] getVector() {
+    int[] result = {1, 0, 0};
+    for (int i = 0; i < result.length; i++) {
+      result[i] += i;
     }
-
-    public int[] getVector() {
-        int[] result = {1, 0, 0};
-        for(int i = 0; i < result.length; i++) {
-            result[i] += i;
-        }
-        return result;
-    }
-
-    public int[][] eye() {
-
-        int[][] result = {{0, 0, 0}, {0, 0, 0}, {0, 0, 0}};
-        for(int i =0; i < result.length; i++)
-            result[i][i] = 1;
-        return result;
-    }
-
-    public Exception[] getExceptions() {
-        return new Exception[]{
-                new Exception("one"),
-                new Exception("two"),
-                new Exception("three"),
-        };
-    }
-
-    public long sumLong() {
-        long result = 0;
-        for (int i = 0; i < 10; i++, result+=i);
-        return result;
-    }
-
-    public double getDouble() {
-        return Math.abs(Math.E);
-    }
-
-    public float getFloat() {
-        float x = .5f;
-        for (int i = 0; i < 10; i++, x += 2);
-        return x;
-    }
-
-    public short workShort() {
-        return (short) (System.currentTimeMillis() % 2);
-    }
-
-    public byte getAByte() { return (byte)(128 << 2); }
-
-    public boolean isOdd() { return "odd".length() % 2 == 1; }
-
-    public char first() { return "first".charAt(0); }
-
-    //Wrappers
-    public Long longWrapper() { return Long.valueOf("1"); }
-
-    public Integer integerWrapper() { return Integer.getInteger("123"); }
-
-    public Short shortWrapper() { return Short.valueOf("1"); }
-
-    public Byte byteWrapper() { return Byte.valueOf("1"); }
-
-    public Double doubleWrapper() { return Double.valueOf("1.0"); }
-
-    public Float floatWrapper() { return Float.valueOf("1f"); }
-
-    public Boolean booleanWrapper() { return Boolean.getBoolean("false"); }
-
-    public Character charWrapper() { return Character.toLowerCase('C'); }
-
-    public String getAString() { return Integer.toString(123);  }
-
-    public Optional<Integer> getOptionalInt() { return Optional.of(3); }
+    return result;
+  }
+
+  public int[][] eye() {
+
+    int[][] result = {{0, 0, 0}, {0, 0, 0}, {0, 0, 0}};
+    for (int i = 0; i < result.length; i++) result[i][i] = 1;
+    return result;
+  }
+
+  public Exception[] getExceptions() {
+    return new Exception[] {
+      new Exception("one"), new Exception("two"), new Exception("three"),
+    };
+  }
+
+  public long sumLong() {
+    long result = 0;
+    for (int i = 0; i < 10; i++, result += i)
+      ;
+    return result;
+  }
+
+  public double getDouble() {
+    return Math.abs(Math.E);
+  }
+
+  public float getFloat() {
+    float x = .5f;
+    for (int i = 0; i < 10; i++, x += 2)
+      ;
+    return x;
+  }
+
+  public short workShort() {
+    return (short) (System.currentTimeMillis() % 2);
+  }
+
+  public byte getAByte() {
+    return (byte) (128 << 2);
+  }
+
+  public boolean isOdd() {
+    return "odd".length() % 2 == 1;
+  }
+
+  public char first() {
+    return "first".charAt(0);
+  }
+
+  // Wrappers
+  public Long longWrapper() {
+    return Long.valueOf("1");
+  }
+
+  public Integer integerWrapper() {
+    return Integer.getInteger("123");
+  }
+
+  public Short shortWrapper() {
+    return Short.valueOf("1");
+  }
+
+  public Byte byteWrapper() {
+    return Byte.valueOf("1");
+  }
+
+  public Double doubleWrapper() {
+    return Double.valueOf("1.0");
+  }
+
+  public Float floatWrapper() {
+    return Float.valueOf("1f");
+  }
+
+  public Boolean booleanWrapper() {
+    return Boolean.getBoolean("false");
+  }
+
+  public Character charWrapper() {
+    return Character.toLowerCase('C');
+  }
+
+  public String getAString() {
+    return Integer.toString(123);
+  }
+
+  public Optional<Integer> getOptionalInt() {
+    return Optional.of(3);
+  }
 }
diff --git a/src/test/java/eu/stamp_project/test/input/SideEffect.java b/src/test/java/eu/stamp_project/test/input/SideEffect.java
index d834421..12d12ff 100644
--- a/src/test/java/eu/stamp_project/test/input/SideEffect.java
+++ b/src/test/java/eu/stamp_project/test/input/SideEffect.java
@@ -2,13 +2,14 @@
 
 public class SideEffect {
 
-    public int count = 0;
+  public int count = 0;
 
-    public void increment() { count++; }
-
-    public Void nextOdd() {
-        count += 1 + count % 2;
-        return null;
-    }
+  public void increment() {
+    count++;
+  }
 
+  public Void nextOdd() {
+    count += 1 + count % 2;
+    return null;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/test/input/SkipFalseMutationOnAllButOne.java b/src/test/java/eu/stamp_project/test/input/SkipFalseMutationOnAllButOne.java
index e0ef54e..533faef 100644
--- a/src/test/java/eu/stamp_project/test/input/SkipFalseMutationOnAllButOne.java
+++ b/src/test/java/eu/stamp_project/test/input/SkipFalseMutationOnAllButOne.java
@@ -5,9 +5,12 @@
 @DoNotMutate(operators = "false")
 public class SkipFalseMutationOnAllButOne {
 
-    public boolean returnFalse() { return false; }
-
-    @DoNotMutate(operators = "true")
-    public boolean returnTrue() { return true; }
+  public boolean returnFalse() {
+    return false;
+  }
 
+  @DoNotMutate(operators = "true")
+  public boolean returnTrue() {
+    return true;
+  }
 }
diff --git a/src/test/java/eu/stamp_project/test/input/SkipMutationOnMethod.java b/src/test/java/eu/stamp_project/test/input/SkipMutationOnMethod.java
index 19fb051..cce21ee 100644
--- a/src/test/java/eu/stamp_project/test/input/SkipMutationOnMethod.java
+++ b/src/test/java/eu/stamp_project/test/input/SkipMutationOnMethod.java
@@ -3,8 +3,8 @@
 import eu.stamp_project.descartes.annotations.DoNotMutate;
 
 public class SkipMutationOnMethod {
-    @DoNotMutate
-    public void methodToSkip() {
-        throw new IllegalArgumentException();
-    }
-}
\ No newline at end of file
+  @DoNotMutate
+  public void methodToSkip() {
+    throw new IllegalArgumentException();
+  }
+}
diff --git a/src/test/java/eu/stamp_project/test/input/SkipMutationTarget.java b/src/test/java/eu/stamp_project/test/input/SkipMutationTarget.java
index 01ee9c4..b61232c 100644
--- a/src/test/java/eu/stamp_project/test/input/SkipMutationTarget.java
+++ b/src/test/java/eu/stamp_project/test/input/SkipMutationTarget.java
@@ -5,11 +5,7 @@
 @DoNotMutate
 public class SkipMutationTarget {
 
-    public void methodToSkip() {
-        throw new IllegalArgumentException();
-    }
-
+  public void methodToSkip() {
+    throw new IllegalArgumentException();
+  }
 }
-
-
-
diff --git a/src/test/java/eu/stamp_project/test/input/StopMethods.java b/src/test/java/eu/stamp_project/test/input/StopMethods.java
index dbbbc10..3b47098 100644
--- a/src/test/java/eu/stamp_project/test/input/StopMethods.java
+++ b/src/test/java/eu/stamp_project/test/input/StopMethods.java
@@ -1,208 +1,259 @@
 package eu.stamp_project.test.input;
 
-
 /*
- This class contains examples of methods that should be detected by mutation filters
- */
+This class contains examples of methods that should be detected by mutation filters
+*/
 
 public class StopMethods {
 
-    static {
-        System.out.println("Static initializer");
-    }
-
-    public void emptyVoidMethod() {}
-
-    public boolean returnTrue () { return true; }
-
-    public byte returnByte() { return (byte)11; }
-
-    public short returnShort() { return (short)12; }
-
-    public int returnNegativeInt() { return -11; }
-
-    public int returnPositiveInt() { return  11; }
-
-    public int returnOne() { return 1; }
-
-    public long returnPositiveLong() { return 1234567890L; }
-
-    public long returnNegativeLong() { return -1234567890L; }
-
-    public float returnPositiveFloat() { return 3.14f; }
-
-    public float returnNegativeFloat() { return -3.14f; }
-
-    public double returnPositiveDouble() { return 6.28; }
-
-    public double returnNegativeDouble() { return -6.28; }
-
-    public char returnChar() { return 'A'; }
-
-    public String returnString() {  return "A"; }
-
-    public Object returnNull() { return null; }
-
-
-    public int[] emptyIntArray() {
-        return new int[0];
-
-    }
-
-    //The actually produces the same bytecode for this method as the code produced for the previous version
-    public int[] emptyInt2Array() {
-        return new int[]{};
-    }
-
-    public int[][] emptyMatrix() { return new int[0][]; }
-
-    public String[] emptyStringArray() { return new String[0]; }
-
-    public String[][] emptyStringMatrix() { return new String[0][]; }
-
-
-    boolean aBoolean;
-    byte aByte;
-    short aShort;
-    int anInt;
-    long aLong;
-    float aFloat;
-    double aDouble;
-    char aChar;
-    String aString;
-    Object anObject;
-
-    public void setABoolean(boolean aBoolean) {
-        this.aBoolean = aBoolean;
-    }
-
-    public void setAByte(byte aByte) {
-        this.aByte = aByte;
-    }
-
-    public void setAChar(char aChar) {
-        this.aChar = aChar;
-    }
-
-    public void setADouble(double aDouble) {
-        this.aDouble = aDouble;
-    }
-
-    public void setAFloat(float aFloat) {
-        this.aFloat = aFloat;
-    }
-
-    public void setALong(long aLong) {
-        this.aLong = aLong;
-    }
-
-    public void setAnInt(int anInt) {
-        this.anInt = anInt;
-    }
-
-    public void setAShort(short aShort) {
-        this.aShort = aShort;
-    }
-
-    public void setAString(String aString) {
-        this.aString = aString;
-    }
-
-    public void setAnObject(Object anObject) {
-        this.anObject = anObject;
-    }
-
-    public byte getAByte() {
-        return aByte;
-    }
-
-    public char getAChar() {
-        return aChar;
-    }
-
-    public double getADouble() {
-        return aDouble;
-    }
-
-    public float getAFloat() {
-        return aFloat;
-    }
-
-    public int getAnInt() {
-        return anInt;
-    }
-
-    public long getALong() {
-        return aLong;
-    }
-
-    public short getAShort() {
-        return aShort;
-    }
-
-    public String getAString() {
-        return aString;
-    }
-
-    public Object getAnObject() {
-        return anObject;
-    }
-
-    public StopMethods setFluent(int value) {
-        this.anInt = value;
-        return this;
-    }
-
-    public StopMethods onlyReturnsThis() { return this; }
-
-    public int onlyReturnsAPrimitiveParameter(int a, int b, int c) { return b;  }
-
-    public String onlyReturnsAReferenceParameter(int a, int b, String c) { return c; }
-
-    @Deprecated
-    public boolean isDeprecated() { return  Boolean.valueOf("tr " + "ue"); }
+  static {
+    System.out.println("Static initializer");
+  }
+
+  public void emptyVoidMethod() {}
+
+  public boolean returnTrue() {
+    return true;
+  }
+
+  public byte returnByte() {
+    return (byte) 11;
+  }
+
+  public short returnShort() {
+    return (short) 12;
+  }
+
+  public int returnNegativeInt() {
+    return -11;
+  }
+
+  public int returnPositiveInt() {
+    return 11;
+  }
+
+  public int returnOne() {
+    return 1;
+  }
+
+  public long returnPositiveLong() {
+    return 1234567890L;
+  }
+
+  public long returnNegativeLong() {
+    return -1234567890L;
+  }
+
+  public float returnPositiveFloat() {
+    return 3.14f;
+  }
+
+  public float returnNegativeFloat() {
+    return -3.14f;
+  }
+
+  public double returnPositiveDouble() {
+    return 6.28;
+  }
+
+  public double returnNegativeDouble() {
+    return -6.28;
+  }
+
+  public char returnChar() {
+    return 'A';
+  }
+
+  public String returnString() {
+    return "A";
+  }
+
+  public Object returnNull() {
+    return null;
+  }
+
+  public int[] emptyIntArray() {
+    return new int[0];
+  }
+
+  // The actually produces the same bytecode for this method as the code produced for the previous
+  // version
+  public int[] emptyInt2Array() {
+    return new int[] {};
+  }
+
+  public int[][] emptyMatrix() {
+    return new int[0][];
+  }
+
+  public String[] emptyStringArray() {
+    return new String[0];
+  }
+
+  public String[][] emptyStringMatrix() {
+    return new String[0][];
+  }
+
+  boolean aBoolean;
+  byte aByte;
+  short aShort;
+  int anInt;
+  long aLong;
+  float aFloat;
+  double aDouble;
+  char aChar;
+  String aString;
+  Object anObject;
+
+  public void setABoolean(boolean aBoolean) {
+    this.aBoolean = aBoolean;
+  }
+
+  public void setAByte(byte aByte) {
+    this.aByte = aByte;
+  }
+
+  public void setAChar(char aChar) {
+    this.aChar = aChar;
+  }
+
+  public void setADouble(double aDouble) {
+    this.aDouble = aDouble;
+  }
+
+  public void setAFloat(float aFloat) {
+    this.aFloat = aFloat;
+  }
+
+  public void setALong(long aLong) {
+    this.aLong = aLong;
+  }
+
+  public void setAnInt(int anInt) {
+    this.anInt = anInt;
+  }
+
+  public void setAShort(short aShort) {
+    this.aShort = aShort;
+  }
+
+  public void setAString(String aString) {
+    this.aString = aString;
+  }
+
+  public void setAnObject(Object anObject) {
+    this.anObject = anObject;
+  }
+
+  public byte getAByte() {
+    return aByte;
+  }
+
+  public char getAChar() {
+    return aChar;
+  }
+
+  public double getADouble() {
+    return aDouble;
+  }
+
+  public float getAFloat() {
+    return aFloat;
+  }
+
+  public int getAnInt() {
+    return anInt;
+  }
+
+  public long getALong() {
+    return aLong;
+  }
+
+  public short getAShort() {
+    return aShort;
+  }
+
+  public String getAString() {
+    return aString;
+  }
+
+  public Object getAnObject() {
+    return anObject;
+  }
+
+  public StopMethods setFluent(int value) {
+    this.anInt = value;
+    return this;
+  }
+
+  public StopMethods onlyReturnsThis() {
+    return this;
+  }
+
+  public int onlyReturnsAPrimitiveParameter(int a, int b, int c) {
+    return b;
+  }
+
+  public String onlyReturnsAReferenceParameter(int a, int b, String c) {
+    return c;
+  }
+
+  @Deprecated
+  public boolean isDeprecated() {
+    return Boolean.valueOf("tr " + "ue");
+  }
 
-    static int staticField;
+  static int staticField;
 
-    public int getStaticField() { return staticField; }
+  public int getStaticField() {
+    return staticField;
+  }
 
-    public void setStaticField(int value) { staticField = value; }
+  public void setStaticField(int value) {
+    staticField = value;
+  }
 
-    @Override
-    public int hashCode() { return "1234".length() << 2; }
+  @Override
+  public int hashCode() {
+    return "1234".length() << 2;
+  }
 
-    @Override
-    public String toString() { return this.getClass().getName(); }
+  @Override
+  public String toString() {
+    return this.getClass().getName();
+  }
 
-    public void delegateSelfStaticVoid(int value) {
-        this.setStaticField(value);
-    }
+  public void delegateSelfStaticVoid(int value) {
+    this.setStaticField(value);
+  }
 
-    public void delegateSelfVoid(int value) {
-        this.setAnInt(value);
-    }
+  public void delegateSelfVoid(int value) {
+    this.setAnInt(value);
+  }
 
-    public String delegateSelfValue(String that, int start, int end) {
-        return this.delegateParameterValue(that, start, end);
-    }
+  public String delegateSelfValue(String that, int start, int end) {
+    return this.delegateParameterValue(that, start, end);
+  }
 
-    public String delegateParameterValue(String that, int start, int end) {
-        return that.substring(start, end);
-    }
+  public String delegateParameterValue(String that, int start, int end) {
+    return that.substring(start, end);
+  }
 
-    public String delegateFieldValue(int start, int end) {
-        return aString.substring(start, end);
-    }
+  public String delegateFieldValue(int start, int end) {
+    return aString.substring(start, end);
+  }
 
-    public static void delegateToExternalClass(String message) {
-        System.out.println(message);
-    }
+  public static void delegateToExternalClass(String message) {
+    System.out.println(message);
+  }
 
-    public static void emptyStatic() {}
+  public static void emptyStatic() {}
 
-    public void delegateToStatic (String message) {
-        delegateToExternalClass(message);
-    }
+  public void delegateToStatic(String message) {
+    delegateToExternalClass(message);
+  }
 
-    public void delegateToStatic() { emptyStatic(); }
+  public void delegateToStatic() {
+    emptyStatic();
+  }
 }