diff --git a/.gitignore b/.gitignore
index 9a9b3fb..153aba6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,4 @@ composer.lock
 tests/test_app/database/data
 tests/test_app/vendor
 .php_cs.cache
+.phpunit.result.cache
diff --git a/composer.json b/composer.json
index b188d07..a2a9df6 100644
--- a/composer.json
+++ b/composer.json
@@ -9,7 +9,7 @@
     "require-dev": {
         "phpunit/phpunit": "^8.5",
         "cakephp/cakephp": "^4.0",
-        "cakephp/cakephp-codesniffer": "~4.0.0"
+        "cakephp/cakephp-codesniffer": "^4.0"
     },
     "license": "MIT",
     "authors": [
@@ -32,6 +32,6 @@
         "test": "phpunit",
         "cs-check": "phpcs --colors -p ./src ./tests/TestCase",
         "stan": "phpstan.phar analyse src/ tests/TestCase",
-        "stan-setup": "cp composer.json composer.backup && composer require --dev phpstan/phpstan:^0.12 && mv composer.backup composer.json"
+        "stan-setup": "cp composer.json composer.backup && composer require --dev phpstan/phpstan:@stable && mv composer.backup composer.json"
     }
 }
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index 549f072..8a4f429 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -3,11 +3,4 @@
   <config name="installed_paths" value="../../cakephp/cakephp-codesniffer" />
 
   <rule ref="CakePHP"/>
-  <rule ref="SlevomatCodingStandard.TypeHints.DeclareStrictTypes" >
-    <properties>
-      <property name="newlinesCountAfterDeclare" value="2" />
-      <property name="spacesCountAroundEqualsSign" value="0" />
-      <property name="newlinesCountBetweenOpenTagAndDeclare" value="2" />
-    </properties>
-  </rule> />
 </ruleset>
diff --git a/phpstan.neon b/phpstan.neon
index 9139975..eb7e589 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,4 +1,5 @@
 parameters:
-    level: 5
+    level: 6
+    checkMissingIterableValueType: false
     autoload_files:
         - tests/bootstrap.php
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index cdefb23..e59982a 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -3,7 +3,6 @@
     colors="true"
     processIsolation="false"
     stopOnFailure="false"
-    syntaxCheck="false"
     bootstrap="./tests/bootstrap.php"
     >
 
diff --git a/src/Database/Connection/MasterReplicaConnection.php b/src/Database/Connection/MasterReplicaConnection.php
index bd0a03a..dad580a 100644
--- a/src/Database/Connection/MasterReplicaConnection.php
+++ b/src/Database/Connection/MasterReplicaConnection.php
@@ -1,11 +1,9 @@
 <?php
-
 declare(strict_types=1);
 
 namespace Connehito\CakephpMasterReplica\Database\Connection;
 
 use Cake\Database\Connection;
-use Cake\Database\Driver;
 use Cake\Database\DriverInterface;
 
 /**
@@ -53,7 +51,7 @@ public function __construct($config)
      * @param string $role master or replica
      * @return $this
      */
-    public function switchRole(string $role): self
+    public function switchRole(string $role)
     {
         $this->role = $role;
         $driver = $this->getDriver();
diff --git a/tests/TestCase/Database/Connection/MasterReplicaConnectionTest.php b/tests/TestCase/Database/Connection/MasterReplicaConnectionTest.php
index 102a485..56e8d7b 100644
--- a/tests/TestCase/Database/Connection/MasterReplicaConnectionTest.php
+++ b/tests/TestCase/Database/Connection/MasterReplicaConnectionTest.php
@@ -1,5 +1,4 @@
 <?php
-
 declare(strict_types=1);
 
 namespace Connehito\CakephpMasterReplica\Test\TestCase\Database\Connection;
@@ -13,7 +12,7 @@
 use Connehito\CakephpMasterReplica\Database\Connection\MasterReplicaConnection;
 use ReflectionProperty;
 
-class MasterReplicaConnectionTest extends TestCase
+final class MasterReplicaConnectionTest extends TestCase
 {
     /**
      * @var MasterReplicaConnection
@@ -36,7 +35,7 @@ class MasterReplicaConnectionTest extends TestCase
     ];
 
     /**
-     * {@inheritdoc}
+     * @inheritDoc
      */
     public function setUp(): void
     {
@@ -47,10 +46,8 @@ public function setUp(): void
 
     /**
      * @test
-     *
-     * @return void
      */
-    public function constructToSetDrivers()
+    public function constructToSetDrivers(): void
     {
         $getDriverConfig = function (DriverInterface $driver) {
             $configProperty = new ReflectionProperty($driver, '_config');
@@ -98,10 +95,8 @@ public function constructToSetDrivers()
 
     /**
      * @test
-     *
-     * @return void
      */
-    public function constructToSetDefaultRole()
+    public function constructToSetDefaultRole(): void
     {
         $driversProperty = new ReflectionProperty($this->subject, 'drivers');
         $driversProperty->setAccessible(true);
@@ -120,10 +115,8 @@ public function constructToSetDefaultRole()
 
     /**
      * @test
-     *
-     * @return void
      */
-    public function switchRole()
+    public function switchRole(): void
     {
         $roleProperty = new ReflectionProperty($this->subject, 'role');
         $roleProperty->setAccessible(true);
@@ -159,9 +152,8 @@ public function switchRole()
      * @test
      *
      * @depends switchRole
-     * @return  void
      */
-    public function getDriver()
+    public function getDriver(): void
     {
         $driversProperty = new ReflectionProperty($this->subject, 'drivers');
         $driversProperty->setAccessible(true);
diff --git a/tests/TestCase/MasterReplicaConnectionIntegrationTest.php b/tests/TestCase/MasterReplicaConnectionIntegrationTest.php
index 6fe7592..42cba03 100644
--- a/tests/TestCase/MasterReplicaConnectionIntegrationTest.php
+++ b/tests/TestCase/MasterReplicaConnectionIntegrationTest.php
@@ -1,5 +1,4 @@
 <?php
-
 declare(strict_types=1);
 
 namespace Connehito\CakephpMasterReplica\Test\TestCase;
@@ -10,10 +9,10 @@
 use Connehito\CakephpMasterReplica\Database\Connection\MasterReplicaConnection;
 use PDOException;
 
-class MasterReplicaConnectionIntegrationTest extends TestCase
+final class MasterReplicaConnectionIntegrationTest extends TestCase
 {
     /**
-     * {@inheritDoc}}
+     * @inheritDoc
      */
     public function tearDown(): void
     {
@@ -26,10 +25,8 @@ public function tearDown(): void
 
     /**
      * @test
-     *
-     * @return void
      */
-    public function switchRoleThenChangingSession()
+    public function switchRoleThenChangingSession(): void
     {
         $subject = ConnectionManager::get('test');
         assert($subject instanceof MasterReplicaConnection);
@@ -48,10 +45,8 @@ public function switchRoleThenChangingSession()
 
     /**
      * @test
-     *
-     * @return void
      */
-    public function switchToReadOnlyUserThenNotWritable()
+    public function switchToReadOnlyUserThenNotWritable(): void
     {
         $table = $this->getTableLocator()->get('Users');
         $query = $table->query()
@@ -72,7 +67,7 @@ public function switchToReadOnlyUserThenNotWritable()
         // Secondary user is not writable, so PDO throws the exception.
         $connection->switchRole('secondary');
         $this->expectException(PDOException::class);
-        $this->expectExceptionMessageRegExp(
+        $this->expectExceptionMessageMatches(
             "/INSERT command denied to user '(.*?)'@'(.*?)' for table 'users'/"
         );
         $query->cleanCopy()->execute();
diff --git a/tests/test_app/composer.json b/tests/test_app/composer.json
index e520494..501dfbc 100644
--- a/tests/test_app/composer.json
+++ b/tests/test_app/composer.json
@@ -9,13 +9,13 @@
     }
     ],
     "require": {
-        "cakephp/cakephp": "^3.5",
+        "cakephp/cakephp": "^4.0",
         "connehito/cakephp-master-replica": "@dev"
     },
     "require-dev": {
-        "phpunit/phpunit": "^6.0",
-        "phpstan/phpstan": "^0.11.9",
-        "squizlabs/php_codesniffer": "^3.4"
+        "phpunit/phpunit": "^8.5",
+        "phpstan/phpstan": "@stable",
+        "squizlabs/php_codesniffer": "@stable"
     },
     "license": "MIT",
     "authors": [