diff --git a/.github/workflows/integrate.yaml b/.github/workflows/integrate.yaml
index dcc5b536..a77f1b04 100644
--- a/.github/workflows/integrate.yaml
+++ b/.github/workflows/integrate.yaml
@@ -23,6 +23,7 @@ jobs:
           - "7.4"
           - "8.0"
           - "8.1"
+          - "8.2"
         dependencies:
           - "highest"
     steps:
@@ -60,6 +61,7 @@ jobs:
           - "7.4"
           - "8.0"
           - "8.1"
+          - "8.2"
         dependencies:
           - "highest"
     steps:
@@ -95,6 +97,7 @@ jobs:
           - "7.4"
           - "8.0"
           - "8.1"
+          - "8.2"
         dependencies:
           - "highest"
     steps:
@@ -132,6 +135,7 @@ jobs:
           - "7.4"
           - "8.0"
           - "8.1"
+          - "8.2"
         dependencies:
           - "highest"
     steps:
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 4d0d1d29..6c4ce424 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -1,6 +1,9 @@
 # Changelog
 All notable changes to this project will be documented in this file.
 
+## 0.10.15
+* Add `shouldNotBeReadonly` assertion.
+
 ## 0.10.14
 * Add `shouldInclude()` and `shouldNotInclude` assertions.
 * Detect catch blocks in dependency assertions.
diff --git a/src/Rule/Assertion/Declaration/ShouldNotBeReadonly/IsReadonlyRule.php b/src/Rule/Assertion/Declaration/ShouldNotBeReadonly/IsReadonlyRule.php
new file mode 100644
index 00000000..a20fd796
--- /dev/null
+++ b/src/Rule/Assertion/Declaration/ShouldNotBeReadonly/IsReadonlyRule.php
@@ -0,0 +1,15 @@
+<?php declare(strict_types=1);
+
+namespace PHPat\Rule\Assertion\Declaration\ShouldNotBeReadonly;
+
+use PHPat\Rule\Extractor\Declaration\ReadonlyExtractor;
+use PHPStan\Node\InClassNode;
+use PHPStan\Rules\Rule;
+
+/**
+ * @implements Rule<InClassNode>
+ */
+final class IsReadonlyRule extends ShouldNotBeReadonly implements Rule
+{
+    use ReadonlyExtractor;
+}
diff --git a/src/Rule/Assertion/Declaration/ShouldNotBeReadonly/ShouldNotBeReadonly.php b/src/Rule/Assertion/Declaration/ShouldNotBeReadonly/ShouldNotBeReadonly.php
new file mode 100644
index 00000000..5507d177
--- /dev/null
+++ b/src/Rule/Assertion/Declaration/ShouldNotBeReadonly/ShouldNotBeReadonly.php
@@ -0,0 +1,49 @@
+<?php declare(strict_types=1);
+
+namespace PHPat\Rule\Assertion\Declaration\ShouldNotBeReadonly;
+
+use PHPat\Configuration;
+use PHPat\Rule\Assertion\Declaration\DeclarationAssertion;
+use PHPat\Rule\Assertion\Declaration\ValidationTrait;
+use PHPat\Statement\Builder\StatementBuilderFactory;
+use PHPStan\Reflection\ClassReflection;
+use PHPStan\Reflection\ReflectionProvider;
+use PHPStan\Rules\RuleError;
+use PHPStan\Type\FileTypeMapper;
+
+abstract class ShouldNotBeReadonly extends DeclarationAssertion
+{
+    use ValidationTrait;
+
+    public function __construct(
+        StatementBuilderFactory $statementBuilderFactory,
+        Configuration $configuration,
+        ReflectionProvider $reflectionProvider,
+        FileTypeMapper $fileTypeMapper
+    ) {
+        parent::__construct(
+            __CLASS__,
+            $statementBuilderFactory,
+            $configuration,
+            $reflectionProvider,
+            $fileTypeMapper
+        );
+    }
+
+    /**
+     * @param  array<string>    $tips
+     * @return array<RuleError>
+     */
+    protected function applyValidation(string $ruleName, ClassReflection $subject, bool $meetsDeclaration, array $tips, array $params = []): array
+    {
+        return $this->applyShouldNot($ruleName, $subject, $meetsDeclaration, $tips, $params);
+    }
+
+    protected function getMessage(string $ruleName, string $subject, array $params = []): string
+    {
+        return $this->prepareMessage(
+            $ruleName,
+            sprintf('%s should not be readonly', $subject)
+        );
+    }
+}