diff --git a/bin/docs/generate_issues_list_doc.php b/bin/docs/generate_issues_list_doc.php
index 0b324af3504..e75266af371 100755
--- a/bin/docs/generate_issues_list_doc.php
+++ b/bin/docs/generate_issues_list_doc.php
@@ -3,7 +3,7 @@
 
 declare(strict_types=1);
 
-$docs_dir = dirname(__DIR__) . DIRECTORY_SEPARATOR . "docs"
+$docs_dir = dirname(__DIR__, 2) . DIRECTORY_SEPARATOR . "docs"
     . DIRECTORY_SEPARATOR . "running_psalm" . DIRECTORY_SEPARATOR;
 $issues_index = "{$docs_dir}issues.md";
 $issues_dir = "{$docs_dir}issues";
diff --git a/bin/docs/generate_levels_doc.php b/bin/docs/generate_levels_doc.php
index 10915c9a577..4e01d091c81 100644
--- a/bin/docs/generate_levels_doc.php
+++ b/bin/docs/generate_levels_doc.php
@@ -5,7 +5,7 @@
 use Psalm\Config\IssueHandler;
 use Psalm\Issue\CodeIssue;
 
-require_once(dirname(__DIR__) . '/vendor/autoload.php');
+require_once(dirname(__DIR__, 2) . '/vendor/autoload.php');
 
 $issue_types = IssueHandler::getAllIssueTypes();
 
@@ -60,7 +60,7 @@
     $result .= ' - [' . $issue_type . '](issues/' . $issue_type . '.md)' . "\n";
 }
 
-$f = dirname(__DIR__).'/docs/running_psalm/error_levels.md';
+$f = dirname(__DIR__, 2).'/docs/running_psalm/error_levels.md';
 $content = file_get_contents($f);
 
 $content = explode('<!-- begin list -->', $content)[0].$result;
diff --git a/bin/docs/max_used_shortcode.php b/bin/docs/max_used_shortcode.php
index 54df5f0899d..f1c5b3b949f 100755
--- a/bin/docs/max_used_shortcode.php
+++ b/bin/docs/max_used_shortcode.php
@@ -5,7 +5,7 @@
 
 use Psalm\Config\IssueHandler;
 
-require_once(dirname(__DIR__) . '/vendor/autoload.php');
+require_once(dirname(__DIR__, 2) . '/vendor/autoload.php');
 
 $issue_types = IssueHandler::getAllIssueTypes();
 
diff --git a/bin/stubs/gen_base_callmap.php b/bin/stubs/gen_base_callmap.php
index cac6c652dfc..af1bfe53389 100644
--- a/bin/stubs/gen_base_callmap.php
+++ b/bin/stubs/gen_base_callmap.php
@@ -116,6 +116,6 @@ function paramsToEntries(ReflectionFunctionAbstract $reflectionFunction, string
 $payload = '<?php // phpcs:ignoreFile
 
 return '.var_export($callmap, true).';';
-$f = __DIR__.'/../dictionaries/autogen/CallMap_'.PHP_MAJOR_VERSION.PHP_MINOR_VERSION.'.php';
+$f = __DIR__.'/../../dictionaries/autogen/CallMap_'.PHP_MAJOR_VERSION.PHP_MINOR_VERSION.'.php';
 
 file_put_contents($f, $payload);
diff --git a/bin/stubs/gen_callmap.php b/bin/stubs/gen_callmap.php
index e2396a136ea..ce949ffe368 100644
--- a/bin/stubs/gen_callmap.php
+++ b/bin/stubs/gen_callmap.php
@@ -22,7 +22,7 @@
 
 // Load+normalize autogenerated maps
 $baseMaps = [];
-foreach (glob(__DIR__."/../dictionaries/autogen/CallMap_*.php") as $file) {
+foreach (glob(__DIR__."/../../dictionaries/autogen/CallMap_*.php") as $file) {
     Assert::eq(preg_match('/_(\d+)\.php/', $file, $matches), 1);
     $version = $matches[1];
 
@@ -97,11 +97,11 @@
 
 // Load+normalize hand-written diff maps
 $customMaps = [
-    84 => require __DIR__."/../dictionaries/override/CallMap.php",
+    84 => require __DIR__."/../../dictionaries/override/CallMap.php",
 ];
 
 $customDiffs = [];
-foreach (glob(__DIR__."/../dictionaries/override/CallMap_*.php") as $file) {
+foreach (glob(__DIR__."/../../dictionaries/override/CallMap_*.php") as $file) {
     if (!preg_match('/_(\d+)_delta\.php/', $file, $matches)) {
         continue;
     }
@@ -202,11 +202,11 @@
 // Merge hand-written full maps into autogenerated full maps, write to files
 foreach ($customMaps as $version => $data) {
     $data = normalizeCallMap(array_replace($baseMaps[$version] ?? [], $data));
-    writeCallMap(__DIR__."/../dictionaries/CallMap_$version.php", $data);
+    writeCallMap(__DIR__."/../../dictionaries/CallMap_$version.php", $data);
 }
 
 // Overwrite custom diff maps
-writeCallMap(__DIR__."/../dictionaries/override/CallMap.php", $customMaps[$last]);
+writeCallMap(__DIR__."/../../dictionaries/override/CallMap.php", $customMaps[$last]);
 
 // Regenerate diff maps from custom maps
 foreach ($customMaps as $prevVersion => $prevData) {
@@ -233,7 +233,7 @@
         }
     }
 
-    writeCallMap(__DIR__."/../dictionaries/override/CallMap_{$nextVersion}_delta.php", normalizeCallMap($diff));
+    writeCallMap(__DIR__."/../../dictionaries/override/CallMap_{$nextVersion}_delta.php", normalizeCallMap($diff));
 
     $nextVersion = $prevVersion;
     $nextData = $prevData;
diff --git a/bin/stubs/gen_callmap.sh b/bin/stubs/gen_callmap.sh
index e1a0538cb08..c18994dc32a 100755
--- a/bin/stubs/gen_callmap.sh
+++ b/bin/stubs/gen_callmap.sh
@@ -10,8 +10,8 @@ done
 wait
 
 for f in $VERSIONS; do
-    docker run --rm -it -v $PWD:/app psalm_test_$f php /app/bin/gen_base_callmap.php
+    docker run --rm -it -v $PWD:/app psalm_test_$f php /app/bin/stubs/gen_base_callmap.php
 done
 
-php bin/gen_callmap.php
-php bin/gen_callmap.php
\ No newline at end of file
+php bin/stubs/gen_callmap.php
+php bin/stubs/gen_callmap.php
diff --git a/bin/stubs/update-property-map.php b/bin/stubs/update-property-map.php
index 5d7188458d7..115bc01f912 100755
--- a/bin/stubs/update-property-map.php
+++ b/bin/stubs/update-property-map.php
@@ -33,7 +33,7 @@
 
 $stubbedClasses = [];
 foreach (new RecursiveDirectoryIterator(
-    __DIR__ . '/../stubs',
+    __DIR__ . '/../../stubs',
     FilesystemIterator::CURRENT_AS_PATHNAME|FilesystemIterator::SKIP_DOTS,
 ) as $file) {
     if (is_dir($file)) {
@@ -47,7 +47,7 @@
 }
 unset($file, $contents, $stmts);
 
-$docDir = realpath(__DIR__ . '/../build/doc-en');
+$docDir = realpath(__DIR__ . '/../../build/doc-en');
 
 if (false === $docDir) {
     echo 'PHP doc not found!' . PHP_EOL;
diff --git a/config.xsd b/config.xsd
index c0a9fd37db2..3d9a2c13b04 100644
--- a/config.xsd
+++ b/config.xsd
@@ -219,6 +219,7 @@
             <xs:element name="AssignmentToVoid" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="CheckType" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="CircularReference" type="IssueHandlerType" minOccurs="0" />
+            <xs:element name="ClassMustBeFinal" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="ComplexFunction" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="ComplexMethod" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="ConfigIssue" type="IssueHandlerType" minOccurs="0" />
diff --git a/docs/running_psalm/error_levels.md b/docs/running_psalm/error_levels.md
index 490696d547f..1dd02d7562b 100644
--- a/docs/running_psalm/error_levels.md
+++ b/docs/running_psalm/error_levels.md
@@ -136,6 +136,7 @@ Level 5 and above allows a more non-verifiable code, and higher levels are even
 
 These issues are treated as errors at level 2 and below.
 
+ - [ClassMustBeFinal](issues/ClassMustBeFinal.md)
  - [DeprecatedClass](issues/DeprecatedClass.md)
  - [DeprecatedConstant](issues/DeprecatedConstant.md)
  - [DeprecatedFunction](issues/DeprecatedFunction.md)
diff --git a/docs/running_psalm/issues.md b/docs/running_psalm/issues.md
index d438b9a3d43..62614decd43 100644
--- a/docs/running_psalm/issues.md
+++ b/docs/running_psalm/issues.md
@@ -7,6 +7,7 @@
  - [AssignmentToVoid](issues/AssignmentToVoid.md)
  - [CheckType](issues/CheckType.md)
  - [CircularReference](issues/CircularReference.md)
+ - [ClassMustBeFinal](issues/ClassMustBeFinal.md)
  - [ComplexFunction](issues/ComplexFunction.md)
  - [ComplexMethod](issues/ComplexMethod.md)
  - [ConfigIssue](issues/ConfigIssue.md)
diff --git a/docs/running_psalm/issues/ClassMustBeFinal.md b/docs/running_psalm/issues/ClassMustBeFinal.md
new file mode 100644
index 00000000000..b477a37b38b
--- /dev/null
+++ b/docs/running_psalm/issues/ClassMustBeFinal.md
@@ -0,0 +1,48 @@
+# ClassMustBeFinal
+
+Emitted when a non-final, non-abstract class with no child classes is found.  
+
+```php
+<?php
+
+class A {}
+```
+
+## Why this is bad
+
+Non-final classes are bad for multiple reasons:
+
+- They allow overriding non-final methods and properties, which can lead to unexpected behavior and bugs if implementation details are changed during inheritance of classes not explicitly part of the public API (marked using the `@api` attribute).  
+- A corollary of the above is that non-final classes increase the amount of code that must be covered by any backwards-compatibility promise.  
+  - In final classes, only public functions/properties/constants must be covered by the backwards compatibility promise.  
+  - In non-final classes, all private, protected and public functions/properties/constants must be covered by the backwards compatibility promise (private methods too, because changes to their code may not be compatible with overridden protected/public methods).
+- They are not optimized by Opcache and PHP itself, and thus are more expensive to use at runtime.  
+- Psalm type inference is more complex and not as exact for non-`final` classes.  
+
+In general, the number of non-final classes in the codebase should be reduced as much as possible, both to speed up code execution and avoid unexpected bugs.  
+
+## How to fix
+
+Recommended, make the class `final`:    
+
+```php
+<?php
+
+final class A {}
+```
+
+The above can also be automated using `vendor/bin/psalm --alter --issues=ClassMustBeFinal`.  
+
+If inheritance should still be allowed, reduce the surface covered by the backwards compatibility promise by making the class abstract (containing **only** the logic that should be overridable), and move any non-overridable logic to a new `A` class:
+
+```php
+<?php
+
+abstract class A {}
+
+final class NewA extends A {}
+```
+
+**Note**: if non-`final` classes are needed for mocking in unit tests, simply use [dg/bypass-finals](https://packagist.org/packages/dg/bypass-finals) in your unit tests to allow mocking `final` classes.  
+
+An alternative, not recommended for the [above reasons](#why-this-is-bad), is to make the class part of the public API of your library with `@api`.  
\ No newline at end of file
diff --git a/docs/running_psalm/issues/UnusedClass.md b/docs/running_psalm/issues/UnusedClass.md
index abad5a50ff1..2250d545b0e 100644
--- a/docs/running_psalm/issues/UnusedClass.md
+++ b/docs/running_psalm/issues/UnusedClass.md
@@ -8,7 +8,7 @@ If this class is used and part of the public API, annotate it with `@psalm-api`.
 ```php
 <?php
 
-class A {}
-class B {}
+final class A {}
+final class B {}
 $a = new A();
 ```
diff --git a/psalm-baseline.xml b/psalm-baseline.xml
index e6840922eca..cea11c74fe8 100644
--- a/psalm-baseline.xml
+++ b/psalm-baseline.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<files psalm-version="6.x-dev@d5ee11cc5a050760e4ac0b0801f43c3780a66fda">
+<files psalm-version="dev-master@d577f78e60d7aff42e42af7825c0c978b094a558">
   <file src="examples/TemplateChecker.php">
     <PossiblyUndefinedIntArrayOffset>
       <code><![CDATA[$comment_block->tags['variablesfrom'][0]]]></code>
@@ -66,6 +66,7 @@
     </PossiblyUnusedMethod>
     <PropertyTypeCoercion>
       <code><![CDATA[$this]]></code>
+      <code><![CDATA[$this]]></code>
     </PropertyTypeCoercion>
     <RiskyTruthyFalsyComparison>
       <code><![CDATA[!$composer_json]]></code>
diff --git a/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php b/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php
index b9477098912..80b0862a07a 100644
--- a/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php
@@ -22,6 +22,7 @@
 use Psalm\Internal\Provider\ProjectCacheProvider;
 use Psalm\Internal\Provider\Providers;
 use Psalm\Internal\Provider\StatementsProvider;
+use Psalm\Issue\ClassMustBeFinal;
 use Psalm\Issue\CodeIssue;
 use Psalm\Issue\InvalidFalsableReturnType;
 use Psalm\Issue\InvalidNullableReturnType;
@@ -164,6 +165,7 @@ final class ProjectAnalyzer
      * @var array<int, class-string<CodeIssue>>
      */
     private const SUPPORTED_ISSUES_TO_FIX = [
+        ClassMustBeFinal::class,
         InvalidFalsableReturnType::class,
         InvalidNullableReturnType::class,
         InvalidReturnType::class,
diff --git a/src/Psalm/Internal/Codebase/ClassLikes.php b/src/Psalm/Internal/Codebase/ClassLikes.php
index 0f6318efc3f..ebe746214dd 100644
--- a/src/Psalm/Internal/Codebase/ClassLikes.php
+++ b/src/Psalm/Internal/Codebase/ClassLikes.php
@@ -24,6 +24,7 @@
 use Psalm\Internal\Provider\FileReferenceProvider;
 use Psalm\Internal\Provider\StatementsProvider;
 use Psalm\Internal\Type\TypeExpander;
+use Psalm\Issue\ClassMustBeFinal;
 use Psalm\Issue\PossiblyUnusedMethod;
 use Psalm\Issue\PossiblyUnusedParam;
 use Psalm\Issue\PossiblyUnusedProperty;
@@ -861,6 +862,34 @@ public function consolidateAnalyzedData(Methods $methods, ?Progress $progress, b
                     }
                     $this->checkMethodParamReferences($classlike_storage);
                 }
+                if (!$classlike_storage->public_api
+                    && !$classlike_storage->has_children
+                    && !$classlike_storage->abstract
+                    && !$classlike_storage->final
+                    && !$classlike_storage->is_enum
+                    && !$classlike_storage->is_interface
+                ) {
+                    IssueBuffer::maybeAdd(
+                        new ClassMustBeFinal(
+                            'Class ' . $classlike_storage->name
+                                . ' is never extended and is not part of the public API, and thus must be made final.',
+                            $classlike_storage->location,
+                            $classlike_storage->name,
+                        ),
+                        $classlike_storage->suppressed_issues,
+                        true,
+                    );
+                    
+                    if ($codebase->alter_code
+                        && $classlike_storage->stmt_location !== null
+                        && isset($project_analyzer->getIssuesToFix()['ClassMustBeFinal'])
+                    ) {
+                        $idx = $classlike_storage->stmt_location->getSelectionBounds()[0];
+                        FileManipulationBuffer::add($classlike_storage->stmt_location->file_path, [
+                            new FileManipulation($idx, $idx, 'final ', true),
+                        ]);
+                    }
+                }
 
                 $this->findPossibleMethodParamTypes($classlike_storage);
 
diff --git a/src/Psalm/Internal/Codebase/Populator.php b/src/Psalm/Internal/Codebase/Populator.php
index f00e45fa50e..7f9b74e550d 100644
--- a/src/Psalm/Internal/Codebase/Populator.php
+++ b/src/Psalm/Internal/Codebase/Populator.php
@@ -560,6 +560,8 @@ private function populateDataFromParentClass(
                 $storage->declaring_pseudo_method_ids[$method_name] = $pseudo_method_id;
             };
         }
+
+        $parent_storage->has_children = true;
     }
 
     private function populateInterfaceData(
diff --git a/src/Psalm/Internal/Provider/ParamsProvider/ArrayFilterParamsProvider.php b/src/Psalm/Internal/Provider/ParamsProvider/ArrayFilterParamsProvider.php
index 4404473fe47..a1f264bd11f 100644
--- a/src/Psalm/Internal/Provider/ParamsProvider/ArrayFilterParamsProvider.php
+++ b/src/Psalm/Internal/Provider/ParamsProvider/ArrayFilterParamsProvider.php
@@ -29,7 +29,7 @@
 /**
  * @internal
  */
-class ArrayFilterParamsProvider implements FunctionParamsProviderInterface
+final class ArrayFilterParamsProvider implements FunctionParamsProviderInterface
 {
     /**
      * @return array<lowercase-string>
diff --git a/src/Psalm/Internal/Provider/ParamsProvider/ArrayMultisortParamsProvider.php b/src/Psalm/Internal/Provider/ParamsProvider/ArrayMultisortParamsProvider.php
index a27b79566cd..a7018149e97 100644
--- a/src/Psalm/Internal/Provider/ParamsProvider/ArrayMultisortParamsProvider.php
+++ b/src/Psalm/Internal/Provider/ParamsProvider/ArrayMultisortParamsProvider.php
@@ -32,7 +32,7 @@
 /**
  * @internal
  */
-class ArrayMultisortParamsProvider implements FunctionParamsProviderInterface
+final class ArrayMultisortParamsProvider implements FunctionParamsProviderInterface
 {
     /**
      * @return array<lowercase-string>
diff --git a/src/Psalm/Internal/Provider/ParamsProvider/ArrayUArrayParamsProvider.php b/src/Psalm/Internal/Provider/ParamsProvider/ArrayUArrayParamsProvider.php
index a57ca3058b3..ccfe60aef32 100644
--- a/src/Psalm/Internal/Provider/ParamsProvider/ArrayUArrayParamsProvider.php
+++ b/src/Psalm/Internal/Provider/ParamsProvider/ArrayUArrayParamsProvider.php
@@ -19,7 +19,7 @@
 /**
  * @internal
  */
-class ArrayUArrayParamsProvider implements FunctionParamsProviderInterface
+final class ArrayUArrayParamsProvider implements FunctionParamsProviderInterface
 {
 
     /**
diff --git a/src/Psalm/Internal/Provider/ReturnTypeProvider/FilterInputReturnTypeProvider.php b/src/Psalm/Internal/Provider/ReturnTypeProvider/FilterInputReturnTypeProvider.php
index 511f269f9b8..f4d0857e6dc 100644
--- a/src/Psalm/Internal/Provider/ReturnTypeProvider/FilterInputReturnTypeProvider.php
+++ b/src/Psalm/Internal/Provider/ReturnTypeProvider/FilterInputReturnTypeProvider.php
@@ -34,7 +34,7 @@
 /**
  * @internal
  */
-class FilterInputReturnTypeProvider implements FunctionReturnTypeProviderInterface
+final class FilterInputReturnTypeProvider implements FunctionReturnTypeProviderInterface
 {
     /**
      * @return array<lowercase-string>
diff --git a/src/Psalm/Issue/ClassMustBeFinal.php b/src/Psalm/Issue/ClassMustBeFinal.php
new file mode 100644
index 00000000000..99209e11e30
--- /dev/null
+++ b/src/Psalm/Issue/ClassMustBeFinal.php
@@ -0,0 +1,11 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psalm\Issue;
+
+final class ClassMustBeFinal extends ClassIssue
+{
+    public const ERROR_LEVEL = 2;
+    public const SHORTCODE = 361;
+}
diff --git a/src/Psalm/Issue/LiteralKeyUnshapedArray.php b/src/Psalm/Issue/LiteralKeyUnshapedArray.php
index 16d6b680dae..812967bad85 100644
--- a/src/Psalm/Issue/LiteralKeyUnshapedArray.php
+++ b/src/Psalm/Issue/LiteralKeyUnshapedArray.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Issue;
 
-class LiteralKeyUnshapedArray extends CodeIssue
+final class LiteralKeyUnshapedArray extends CodeIssue
 {
     public const ERROR_LEVEL = -2;
     public const SHORTCODE = 360;
diff --git a/src/Psalm/Issue/UnusedIssueHandlerSuppression.php b/src/Psalm/Issue/UnusedIssueHandlerSuppression.php
index 43699843d26..bd5633fca19 100644
--- a/src/Psalm/Issue/UnusedIssueHandlerSuppression.php
+++ b/src/Psalm/Issue/UnusedIssueHandlerSuppression.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Issue;
 
-class UnusedIssueHandlerSuppression extends CodeIssue
+final class UnusedIssueHandlerSuppression extends CodeIssue
 {
     public const ERROR_LEVEL = -1;
     public const SHORTCODE = 326;
diff --git a/src/Psalm/Storage/ClassLikeStorage.php b/src/Psalm/Storage/ClassLikeStorage.php
index 04c5fc94e86..9dccdb5feb1 100644
--- a/src/Psalm/Storage/ClassLikeStorage.php
+++ b/src/Psalm/Storage/ClassLikeStorage.php
@@ -180,6 +180,8 @@ final class ClassLikeStorage implements HasAttributesInterface
      */
     public array $pseudo_static_methods = [];
 
+    public bool $has_children = false;
+
     /**
      * Maps pseudo method names to the original declaring method identifier
      * The key is the method name in lowercase, and the value is the original `MethodIdentifier` instance
diff --git a/tests/AlgebraTest.php b/tests/AlgebraTest.php
index 24d96e9e202..8ba5f869f72 100644
--- a/tests/AlgebraTest.php
+++ b/tests/AlgebraTest.php
@@ -25,7 +25,7 @@
 
 use function spl_object_id;
 
-class AlgebraTest extends TestCase
+final class AlgebraTest extends TestCase
 {
     public function testNegateFormula(): void
     {
diff --git a/tests/AnnotationTest.php b/tests/AnnotationTest.php
index 88931effcf2..99ab8e7820b 100644
--- a/tests/AnnotationTest.php
+++ b/tests/AnnotationTest.php
@@ -12,7 +12,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class AnnotationTest extends TestCase
+final class AnnotationTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ArgTest.php b/tests/ArgTest.php
index ce75f65c15c..abbf76e4c7f 100644
--- a/tests/ArgTest.php
+++ b/tests/ArgTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ArgTest extends TestCase
+final class ArgTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ArrayAccessTest.php b/tests/ArrayAccessTest.php
index dfd75a0d664..d2626f34f9f 100644
--- a/tests/ArrayAccessTest.php
+++ b/tests/ArrayAccessTest.php
@@ -12,7 +12,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ArrayAccessTest extends TestCase
+final class ArrayAccessTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ArrayAssignmentTest.php b/tests/ArrayAssignmentTest.php
index 8ae84b946c8..b6d4419d63f 100644
--- a/tests/ArrayAssignmentTest.php
+++ b/tests/ArrayAssignmentTest.php
@@ -9,7 +9,7 @@
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 use Psalm\Type;
 
-class ArrayAssignmentTest extends TestCase
+final class ArrayAssignmentTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ArrayFunctionCallTest.php b/tests/ArrayFunctionCallTest.php
index 6c229714fe3..d1db275ced6 100644
--- a/tests/ArrayFunctionCallTest.php
+++ b/tests/ArrayFunctionCallTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ArrayFunctionCallTest extends TestCase
+final class ArrayFunctionCallTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ArrayKeysTest.php b/tests/ArrayKeysTest.php
index 0f508733090..c382da5017f 100644
--- a/tests/ArrayKeysTest.php
+++ b/tests/ArrayKeysTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ArrayKeysTest extends TestCase
+final class ArrayKeysTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/AssertAnnotationTest.php b/tests/AssertAnnotationTest.php
index 6de01339abb..425fe971d2c 100644
--- a/tests/AssertAnnotationTest.php
+++ b/tests/AssertAnnotationTest.php
@@ -12,7 +12,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class AssertAnnotationTest extends TestCase
+final class AssertAnnotationTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/AssignmentTest.php b/tests/AssignmentTest.php
index 21062421040..7d4a9141601 100644
--- a/tests/AssignmentTest.php
+++ b/tests/AssignmentTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class AssignmentTest extends TestCase
+final class AssignmentTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/AsyncTestCase.php b/tests/AsyncTestCase.php
index 09c0eb81037..670bafb8d00 100644
--- a/tests/AsyncTestCase.php
+++ b/tests/AsyncTestCase.php
@@ -30,7 +30,7 @@
 use const ARRAY_FILTER_USE_KEY;
 use const DIRECTORY_SEPARATOR;
 
-class AsyncTestCase extends BaseAsyncTestCase
+abstract class AsyncTestCase extends BaseAsyncTestCase
 {
     protected static string $src_dir_path;
     protected ProjectAnalyzer $project_analyzer;
diff --git a/tests/AttributeTest.php b/tests/AttributeTest.php
index 072779059b0..59fa5ebdcf5 100644
--- a/tests/AttributeTest.php
+++ b/tests/AttributeTest.php
@@ -10,7 +10,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class AttributeTest extends TestCase
+final class AttributeTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/BadFormatTest.php b/tests/BadFormatTest.php
index 88c59f242fc..9d9637eaf15 100644
--- a/tests/BadFormatTest.php
+++ b/tests/BadFormatTest.php
@@ -7,7 +7,7 @@
 use Psalm\Context;
 use Psalm\Exception\CodeException;
 
-class BadFormatTest extends TestCase
+final class BadFormatTest extends TestCase
 {
     public function testMissingSemicolon(): void
     {
diff --git a/tests/BinaryOperationTest.php b/tests/BinaryOperationTest.php
index 13a995e4f8e..29cb3aec43f 100644
--- a/tests/BinaryOperationTest.php
+++ b/tests/BinaryOperationTest.php
@@ -12,7 +12,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class BinaryOperationTest extends TestCase
+final class BinaryOperationTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ByIssueLevelAndTypeReportTest.php b/tests/ByIssueLevelAndTypeReportTest.php
index 930d0dad65e..2d2e2a4bb86 100644
--- a/tests/ByIssueLevelAndTypeReportTest.php
+++ b/tests/ByIssueLevelAndTypeReportTest.php
@@ -9,7 +9,7 @@
 use Psalm\Report\ByIssueLevelAndTypeReport;
 use Psalm\Report\ReportOptions;
 
-class ByIssueLevelAndTypeReportTest extends TestCase
+final class ByIssueLevelAndTypeReportTest extends TestCase
 {
     public function testItGeneratesReport(): void
     {
diff --git a/tests/Cache/CacheTest.php b/tests/Cache/CacheTest.php
index f4a178a8ad7..cf5aeda3872 100644
--- a/tests/Cache/CacheTest.php
+++ b/tests/Cache/CacheTest.php
@@ -24,7 +24,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class CacheTest extends TestCase
+final class CacheTest extends TestCase
 {
     public function setUp(): void
     {
@@ -128,7 +128,7 @@ public static function provideCacheInteractions(): iterable
                     'files' => [
                         'src/A.php' => <<<'PHP'
                             <?php
-                            class A {
+                            final class A {
                                 public function do(B $b): void
                                 {
                                     $b->do();
@@ -137,7 +137,7 @@ public function do(B $b): void
                             PHP,
                         'src/B.php' => <<<'PHP'
                             <?php
-                            class B {
+                            final class B {
                                 public function do(): void
                                 {
                                     echo 'B';
@@ -165,7 +165,7 @@ public function do(): void
                     'files' => [
                         'src/A.php' => <<<'PHP'
                             <?php
-                            class A {
+                            final class A {
                                 public function foo(B $b): int
                                 {
                                     return $b->value;
@@ -174,7 +174,7 @@ public function foo(B $b): int
                             PHP,
                         'src/B.php' => <<<'PHP'
                             <?php
-                            class B {
+                            final class B {
                                 public ?int $value = 0;
                             }
                             PHP,
@@ -190,7 +190,7 @@ class B {
                     'files' => [
                         'src/B.php' => <<<'PHP'
                             <?php
-                            class B {
+                            final class B {
                                 public int $value = 0;
                             }
                             PHP,
@@ -210,7 +210,7 @@ class B {
                             /**
                              * @template T
                              */
-                            class A {
+                            final class A {
                                 /**
                                  * @param T $baz
                                  */
@@ -222,7 +222,7 @@ public function foo($baz): void
                         'src/B.php' => <<<'PHP'
                             <?php
 
-                            class B {
+                            final class B {
                                 public function foo(): void
                                 {
                                     (new A)->foo(1);
@@ -240,7 +240,7 @@ public function foo(): void
                             /**
                              * @template K
                              */
-                            class A {
+                            final class A {
                                 /**
                                  * @param T $baz
                                  */
@@ -268,7 +268,7 @@ public function foo($baz): void
                     'files' => [
                         'src/A.php' => <<<'PHP'
                             <?php
-                            class A {
+                            final class A {
                                 public function __construct(private string $foo)
                                 {
                                 }
@@ -285,7 +285,7 @@ public function bar(): string
                     'files' => [
                         'src/A.php' => <<<'PHP'
                             <?php
-                            class A
+                            final class A
                             {
                                 public function __construct()
                                 {
diff --git a/tests/CallableTest.php b/tests/CallableTest.php
index 93222a14afd..5e04b36d6da 100644
--- a/tests/CallableTest.php
+++ b/tests/CallableTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class CallableTest extends TestCase
+final class CallableTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/CastTest.php b/tests/CastTest.php
index 2aeb87b686d..33440ceea57 100644
--- a/tests/CastTest.php
+++ b/tests/CastTest.php
@@ -6,7 +6,7 @@
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class CastTest extends TestCase
+final class CastTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/CheckTypeTest.php b/tests/CheckTypeTest.php
index c8256a21243..2219abf7f0a 100644
--- a/tests/CheckTypeTest.php
+++ b/tests/CheckTypeTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class CheckTypeTest extends TestCase
+final class CheckTypeTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ClassLikeDocblockParserTest.php b/tests/ClassLikeDocblockParserTest.php
index 887a0ce2fb6..2d0a5ea8e57 100644
--- a/tests/ClassLikeDocblockParserTest.php
+++ b/tests/ClassLikeDocblockParserTest.php
@@ -11,7 +11,7 @@
 
 use function array_values;
 
-class ClassLikeDocblockParserTest extends TestCase
+final class ClassLikeDocblockParserTest extends TestCase
 {
     public function testDocblockDescription(): void
     {
diff --git a/tests/ClassLikeStringTest.php b/tests/ClassLikeStringTest.php
index dda82b65e51..24d3aeb84cf 100644
--- a/tests/ClassLikeStringTest.php
+++ b/tests/ClassLikeStringTest.php
@@ -10,7 +10,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ClassLikeStringTest extends TestCase
+final class ClassLikeStringTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ClassLoadOrderTest.php b/tests/ClassLoadOrderTest.php
index 31c4742e023..3529ce5e049 100644
--- a/tests/ClassLoadOrderTest.php
+++ b/tests/ClassLoadOrderTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ClassLoadOrderTest extends TestCase
+final class ClassLoadOrderTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ClassScopeTest.php b/tests/ClassScopeTest.php
index 67de84622dd..8da43a18e89 100644
--- a/tests/ClassScopeTest.php
+++ b/tests/ClassScopeTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ClassScopeTest extends TestCase
+final class ClassScopeTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ClassTest.php b/tests/ClassTest.php
index 526c3d2471c..137afb1fc6e 100644
--- a/tests/ClassTest.php
+++ b/tests/ClassTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ClassTest extends TestCase
+final class ClassTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/CloneTest.php b/tests/CloneTest.php
index 4595d0049bd..4b30ede7b81 100644
--- a/tests/CloneTest.php
+++ b/tests/CloneTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class CloneTest extends TestCase
+final class CloneTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ClosureTest.php b/tests/ClosureTest.php
index ed2892d17e8..4b0ef70a69d 100644
--- a/tests/ClosureTest.php
+++ b/tests/ClosureTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ClosureTest extends TestCase
+final class ClosureTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/CodebaseTest.php b/tests/CodebaseTest.php
index e7d1259f329..4506a6e76d1 100644
--- a/tests/CodebaseTest.php
+++ b/tests/CodebaseTest.php
@@ -28,7 +28,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class CodebaseTest extends TestCase
+final class CodebaseTest extends TestCase
 {
     private Codebase $codebase;
 
diff --git a/tests/CommentAnalyzerTest.php b/tests/CommentAnalyzerTest.php
index c663d27f5af..4bb5b36f360 100644
--- a/tests/CommentAnalyzerTest.php
+++ b/tests/CommentAnalyzerTest.php
@@ -11,7 +11,7 @@
 use Psalm\Internal\RuntimeCaches;
 use Psalm\Internal\Scanner\FileScanner;
 
-class CommentAnalyzerTest extends BaseTestCase
+final class CommentAnalyzerTest extends BaseTestCase
 {
     public function setUp(): void
     {
diff --git a/tests/ComposerLockTest.php b/tests/ComposerLockTest.php
index 8f34d28f3b6..7c59b04472e 100644
--- a/tests/ComposerLockTest.php
+++ b/tests/ComposerLockTest.php
@@ -12,7 +12,7 @@
 use const JSON_THROW_ON_ERROR;
 
 /** @group PluginManager */
-class ComposerLockTest extends TestCase
+final class ComposerLockTest extends TestCase
 {
     /**
      * @test
diff --git a/tests/Config/ConfigFileTest.php b/tests/Config/ConfigFileTest.php
index f6102f09ac6..4f41c56c3da 100644
--- a/tests/Config/ConfigFileTest.php
+++ b/tests/Config/ConfigFileTest.php
@@ -22,7 +22,7 @@
 use const PHP_EOL;
 
 /** @group PluginManager */
-class ConfigFileTest extends TestCase
+final class ConfigFileTest extends TestCase
 {
     private string $file_path;
 
diff --git a/tests/Config/ConfigTest.php b/tests/Config/ConfigTest.php
index 913f4fca5fb..bb9316e3431 100644
--- a/tests/Config/ConfigTest.php
+++ b/tests/Config/ConfigTest.php
@@ -47,7 +47,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ConfigTest extends TestCase
+final class ConfigTest extends TestCase
 {
     protected static TestConfig $config;
 
diff --git a/tests/Config/CreatorTest.php b/tests/Config/CreatorTest.php
index 2928e417c88..cbcd845d297 100644
--- a/tests/Config/CreatorTest.php
+++ b/tests/Config/CreatorTest.php
@@ -11,7 +11,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class CreatorTest extends TestCase
+final class CreatorTest extends TestCase
 {
     public static function setUpBeforeClass(): void
     {
diff --git a/tests/Config/Plugin/AfterAnalysisPlugin.php b/tests/Config/Plugin/AfterAnalysisPlugin.php
index fed6ef87bb1..bd716226cec 100644
--- a/tests/Config/Plugin/AfterAnalysisPlugin.php
+++ b/tests/Config/Plugin/AfterAnalysisPlugin.php
@@ -10,7 +10,7 @@
 use SimpleXMLElement;
 
 /** @psalm-suppress UnusedClass */
-class AfterAnalysisPlugin implements PluginEntryPointInterface
+final class AfterAnalysisPlugin implements PluginEntryPointInterface
 {
     public function __invoke(RegistrationInterface $registration, ?SimpleXMLElement $config = null): void
     {
diff --git a/tests/Config/Plugin/FilePlugin.php b/tests/Config/Plugin/FilePlugin.php
index 4fbfb51e1bd..96c697f650e 100644
--- a/tests/Config/Plugin/FilePlugin.php
+++ b/tests/Config/Plugin/FilePlugin.php
@@ -10,7 +10,7 @@
 use SimpleXMLElement;
 
 /** @psalm-suppress UnusedClass */
-class FilePlugin implements PluginEntryPointInterface
+final class FilePlugin implements PluginEntryPointInterface
 {
     public function __invoke(RegistrationInterface $registration, ?SimpleXMLElement $config = null): void
     {
diff --git a/tests/Config/Plugin/FileTypeSelfRegisteringPlugin.php b/tests/Config/Plugin/FileTypeSelfRegisteringPlugin.php
index e9df9433663..1facf467616 100644
--- a/tests/Config/Plugin/FileTypeSelfRegisteringPlugin.php
+++ b/tests/Config/Plugin/FileTypeSelfRegisteringPlugin.php
@@ -9,7 +9,7 @@
 use SimpleXMLElement;
 use stdClass;
 
-class FileTypeSelfRegisteringPlugin implements PluginFileExtensionsInterface
+final class FileTypeSelfRegisteringPlugin implements PluginFileExtensionsInterface
 {
     public const FLAG_SCANNER_TWICE = 1;
     public const FLAG_ANALYZER_TWICE = 2;
diff --git a/tests/Config/Plugin/FunctionPlugin.php b/tests/Config/Plugin/FunctionPlugin.php
index 53746b73ebb..4eba18da7e0 100644
--- a/tests/Config/Plugin/FunctionPlugin.php
+++ b/tests/Config/Plugin/FunctionPlugin.php
@@ -10,7 +10,7 @@
 use SimpleXMLElement;
 
 /** @psalm-suppress UnusedClass */
-class FunctionPlugin implements PluginEntryPointInterface
+final class FunctionPlugin implements PluginEntryPointInterface
 {
     public function __invoke(RegistrationInterface $registration, ?SimpleXMLElement $config = null): void
     {
diff --git a/tests/Config/Plugin/Hook/AfterAnalysis.php b/tests/Config/Plugin/Hook/AfterAnalysis.php
index 5d9be05bb5e..16d1242d65d 100644
--- a/tests/Config/Plugin/Hook/AfterAnalysis.php
+++ b/tests/Config/Plugin/Hook/AfterAnalysis.php
@@ -7,7 +7,7 @@
 use Psalm\Plugin\EventHandler\AfterAnalysisInterface;
 use Psalm\Plugin\EventHandler\Event\AfterAnalysisEvent;
 
-class AfterAnalysis implements AfterAnalysisInterface
+final class AfterAnalysis implements AfterAnalysisInterface
 {
     /**
      * Called after analysis is complete
diff --git a/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php b/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php
index cb3284754f8..7c5b5f34942 100644
--- a/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php
+++ b/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php
@@ -19,7 +19,7 @@
 use function array_map;
 use function count;
 
-class CustomArrayMapFunctionStorageProvider implements DynamicFunctionStorageProviderInterface
+final class CustomArrayMapFunctionStorageProvider implements DynamicFunctionStorageProviderInterface
 {
     public static function getFunctionIds(): array
     {
diff --git a/tests/Config/Plugin/Hook/FileProvider.php b/tests/Config/Plugin/Hook/FileProvider.php
index b6835a42541..2b97d952ba5 100644
--- a/tests/Config/Plugin/Hook/FileProvider.php
+++ b/tests/Config/Plugin/Hook/FileProvider.php
@@ -9,7 +9,7 @@
 use Psalm\Plugin\EventHandler\Event\AfterFileAnalysisEvent;
 use Psalm\Plugin\EventHandler\Event\BeforeFileAnalysisEvent;
 
-class FileProvider implements
+final class FileProvider implements
     AfterFileAnalysisInterface,
     BeforeFileAnalysisInterface
 {
diff --git a/tests/Config/Plugin/Hook/FooMethodProvider.php b/tests/Config/Plugin/Hook/FooMethodProvider.php
index c8ee5ef3dd3..1e71525c693 100644
--- a/tests/Config/Plugin/Hook/FooMethodProvider.php
+++ b/tests/Config/Plugin/Hook/FooMethodProvider.php
@@ -15,7 +15,7 @@
 use Psalm\Type\Atomic\TNamedObject;
 use Psalm\Type\Union;
 
-class FooMethodProvider implements
+final class FooMethodProvider implements
     MethodExistenceProviderInterface,
     MethodParamsProviderInterface,
     MethodReturnTypeProviderInterface
diff --git a/tests/Config/Plugin/Hook/FooPropertyProvider.php b/tests/Config/Plugin/Hook/FooPropertyProvider.php
index cef5a56dd61..4834741c862 100644
--- a/tests/Config/Plugin/Hook/FooPropertyProvider.php
+++ b/tests/Config/Plugin/Hook/FooPropertyProvider.php
@@ -13,7 +13,7 @@
 use Psalm\Type;
 use Psalm\Type\Union;
 
-class FooPropertyProvider implements
+final class FooPropertyProvider implements
     PropertyExistenceProviderInterface,
     PropertyVisibilityProviderInterface,
     PropertyTypeProviderInterface
diff --git a/tests/Config/Plugin/Hook/MagicFunctionProvider.php b/tests/Config/Plugin/Hook/MagicFunctionProvider.php
index 8dd5e926eb7..9664251273f 100644
--- a/tests/Config/Plugin/Hook/MagicFunctionProvider.php
+++ b/tests/Config/Plugin/Hook/MagicFunctionProvider.php
@@ -14,7 +14,7 @@
 use Psalm\Type;
 use Psalm\Type\Union;
 
-class MagicFunctionProvider implements
+final class MagicFunctionProvider implements
     FunctionExistenceProviderInterface,
     FunctionParamsProviderInterface,
     FunctionReturnTypeProviderInterface
diff --git a/tests/Config/Plugin/MethodPlugin.php b/tests/Config/Plugin/MethodPlugin.php
index a8fbefc361b..073c39031d6 100644
--- a/tests/Config/Plugin/MethodPlugin.php
+++ b/tests/Config/Plugin/MethodPlugin.php
@@ -10,7 +10,7 @@
 use SimpleXMLElement;
 
 /** @psalm-suppress UnusedClass */
-class MethodPlugin implements PluginEntryPointInterface
+final class MethodPlugin implements PluginEntryPointInterface
 {
     public function __invoke(RegistrationInterface $registration, ?SimpleXMLElement $config = null): void
     {
diff --git a/tests/Config/Plugin/PropertyPlugin.php b/tests/Config/Plugin/PropertyPlugin.php
index 1870a7ed4eb..c7052336b64 100644
--- a/tests/Config/Plugin/PropertyPlugin.php
+++ b/tests/Config/Plugin/PropertyPlugin.php
@@ -10,7 +10,7 @@
 use SimpleXMLElement;
 
 /** @psalm-suppress UnusedClass */
-class PropertyPlugin implements PluginEntryPointInterface
+final class PropertyPlugin implements PluginEntryPointInterface
 {
     public function __invoke(RegistrationInterface $registration, ?SimpleXMLElement $config = null): void
     {
diff --git a/tests/Config/Plugin/StoragePlugin.php b/tests/Config/Plugin/StoragePlugin.php
index 482d95781f8..a7460aeba1a 100644
--- a/tests/Config/Plugin/StoragePlugin.php
+++ b/tests/Config/Plugin/StoragePlugin.php
@@ -10,7 +10,7 @@
 use SimpleXMLElement;
 
 /** @psalm-suppress UnusedClass */
-class StoragePlugin implements PluginEntryPointInterface
+final class StoragePlugin implements PluginEntryPointInterface
 {
     public function __invoke(RegistrationInterface $registration, ?SimpleXMLElement $config = null): void
     {
diff --git a/tests/Config/PluginListTest.php b/tests/Config/PluginListTest.php
index 7083f0891a2..b977268ab2b 100644
--- a/tests/Config/PluginListTest.php
+++ b/tests/Config/PluginListTest.php
@@ -16,7 +16,7 @@
 use Psalm\Tests\TestCase;
 
 /** @group PluginManager */
-class PluginListTest extends TestCase
+final class PluginListTest extends TestCase
 {
     use MockeryPHPUnitIntegration;
 
diff --git a/tests/Config/PluginTest.php b/tests/Config/PluginTest.php
index 0ba40e9d83e..84835d7f0c4 100644
--- a/tests/Config/PluginTest.php
+++ b/tests/Config/PluginTest.php
@@ -40,7 +40,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class PluginTest extends TestCase
+final class PluginTest extends TestCase
 {
     protected static TestConfig $config;
 
diff --git a/tests/ConstValuesTest.php b/tests/ConstValuesTest.php
index 564867fdabf..ad7b7026309 100644
--- a/tests/ConstValuesTest.php
+++ b/tests/ConstValuesTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ConstValuesTest extends TestCase
+final class ConstValuesTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ConstantTest.php b/tests/ConstantTest.php
index 5227ce80cb2..b622c0cbef0 100644
--- a/tests/ConstantTest.php
+++ b/tests/ConstantTest.php
@@ -12,7 +12,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ConstantTest extends TestCase
+final class ConstantTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/CoreStubsTest.php b/tests/CoreStubsTest.php
index f45d40c9b5c..f71e364f83a 100644
--- a/tests/CoreStubsTest.php
+++ b/tests/CoreStubsTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class CoreStubsTest extends TestCase
+final class CoreStubsTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/DateTimeTest.php b/tests/DateTimeTest.php
index 7a6d955d470..a73502454ab 100644
--- a/tests/DateTimeTest.php
+++ b/tests/DateTimeTest.php
@@ -10,7 +10,7 @@
 
 use const PHP_VERSION_ID;
 
-class DateTimeTest extends TestCase
+final class DateTimeTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/DeprecatedAnnotationTest.php b/tests/DeprecatedAnnotationTest.php
index 20ed5566e2c..115f8c1a9bd 100644
--- a/tests/DeprecatedAnnotationTest.php
+++ b/tests/DeprecatedAnnotationTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class DeprecatedAnnotationTest extends TestCase
+final class DeprecatedAnnotationTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/DocCommentTest.php b/tests/DocCommentTest.php
index 03e64caf908..2a364fc733f 100644
--- a/tests/DocCommentTest.php
+++ b/tests/DocCommentTest.php
@@ -10,7 +10,7 @@
 use Psalm\Internal\RuntimeCaches;
 use Psalm\Internal\Scanner\ParsedDocblock;
 
-class DocCommentTest extends BaseTestCase
+final class DocCommentTest extends BaseTestCase
 {
     public function setUp(): void
     {
diff --git a/tests/DocblockInheritanceTest.php b/tests/DocblockInheritanceTest.php
index f007c19e36d..3505bfbe1b9 100644
--- a/tests/DocblockInheritanceTest.php
+++ b/tests/DocblockInheritanceTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class DocblockInheritanceTest extends TestCase
+final class DocblockInheritanceTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/DocumentationTest.php b/tests/DocumentationTest.php
index 91d132913d5..7511d873b1b 100644
--- a/tests/DocumentationTest.php
+++ b/tests/DocumentationTest.php
@@ -54,7 +54,7 @@
 use const FILE_SKIP_EMPTY_LINES;
 use const LIBXML_NONET;
 
-class DocumentationTest extends TestCase
+final class DocumentationTest extends TestCase
 {
     /**
      * a list of all files containing annotation documentation
@@ -307,6 +307,11 @@ public function providerInvalidCodeParse(): array
                     $ignored_issues = ['UnusedVariable'];
                     break;
 
+
+                case 'ClassMustBeFinal':
+                    $ignored_issues = ['UnusedClass'];
+                    break;
+
                 case 'AmbiguousConstantInheritance':
                 case 'DeprecatedConstant':
                 case 'DuplicateEnumCase':
@@ -331,7 +336,8 @@ public function providerInvalidCodeParse(): array
                 $blocks[0],
                 $issue_name,
                 $ignored_issues,
-                strpos($issue_name, 'Unused') !== false
+                $issue_name === 'ClassMustBeFinal'
+                    || strpos($issue_name, 'Unused') !== false
                     || strpos($issue_name, 'Unevaluated') !== false
                     || strpos($issue_name, 'Unnecessary') !== false,
                 $php_version,
diff --git a/tests/EndToEnd/DestructiveAutoloaderTest.php b/tests/EndToEnd/DestructiveAutoloaderTest.php
index 74a8a59e6de..5876162ab84 100644
--- a/tests/EndToEnd/DestructiveAutoloaderTest.php
+++ b/tests/EndToEnd/DestructiveAutoloaderTest.php
@@ -10,7 +10,7 @@
 
 use const PHP_VERSION;
 
-class DestructiveAutoloaderTest extends TestCase
+final class DestructiveAutoloaderTest extends TestCase
 {
     use PsalmRunnerTrait;
 
diff --git a/tests/EndToEnd/PsalmEndToEndTest.php b/tests/EndToEnd/PsalmEndToEndTest.php
index c92bb736f05..07a621a0710 100644
--- a/tests/EndToEnd/PsalmEndToEndTest.php
+++ b/tests/EndToEnd/PsalmEndToEndTest.php
@@ -36,7 +36,7 @@
  *
  * This is primarily intended to test the code in `psalm`, `src/psalm.php` and related files.
  */
-class PsalmEndToEndTest extends TestCase
+final class PsalmEndToEndTest extends TestCase
 {
     use PsalmRunnerTrait;
 
diff --git a/tests/EndToEnd/SuicidalAutoloaderTest.php b/tests/EndToEnd/SuicidalAutoloaderTest.php
index 722520fe0cd..1ef23dc6350 100644
--- a/tests/EndToEnd/SuicidalAutoloaderTest.php
+++ b/tests/EndToEnd/SuicidalAutoloaderTest.php
@@ -10,7 +10,7 @@
 
 use const PHP_VERSION;
 
-class SuicidalAutoloaderTest extends TestCase
+final class SuicidalAutoloaderTest extends TestCase
 {
     use PsalmRunnerTrait;
 
diff --git a/tests/EnumTest.php b/tests/EnumTest.php
index 6ac7a511d25..8a8bf09051a 100644
--- a/tests/EnumTest.php
+++ b/tests/EnumTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class EnumTest extends TestCase
+final class EnumTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/ErrorBaselineTest.php b/tests/ErrorBaselineTest.php
index a6970af30e8..f4196fe251b 100644
--- a/tests/ErrorBaselineTest.php
+++ b/tests/ErrorBaselineTest.php
@@ -19,7 +19,7 @@
 
 use const LIBXML_NOBLANKS;
 
-class ErrorBaselineTest extends TestCase
+final class ErrorBaselineTest extends TestCase
 {
     use MockeryPHPUnitIntegration;
 
diff --git a/tests/ExpressionTest.php b/tests/ExpressionTest.php
index 5c63430829f..d18fdbe4395 100644
--- a/tests/ExpressionTest.php
+++ b/tests/ExpressionTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ExpressionTest extends TestCase
+final class ExpressionTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/ExtLibxmlStubTest.php b/tests/ExtLibxmlStubTest.php
index 6522db48c46..fa4142daf43 100644
--- a/tests/ExtLibxmlStubTest.php
+++ b/tests/ExtLibxmlStubTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ExtLibxmlStubTest extends TestCase
+final class ExtLibxmlStubTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/ExtendsFinalClassTest.php b/tests/ExtendsFinalClassTest.php
index 229d7c51ac2..ead50327ed3 100644
--- a/tests/ExtendsFinalClassTest.php
+++ b/tests/ExtendsFinalClassTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ExtendsFinalClassTest extends TestCase
+final class ExtendsFinalClassTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ExtensionRequirementTest.php b/tests/ExtensionRequirementTest.php
index 154a514c271..b0a4c962c53 100644
--- a/tests/ExtensionRequirementTest.php
+++ b/tests/ExtensionRequirementTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ExtensionRequirementTest extends TestCase
+final class ExtensionRequirementTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/FFITest.php b/tests/FFITest.php
index d3198681425..946f08a3220 100644
--- a/tests/FFITest.php
+++ b/tests/FFITest.php
@@ -11,7 +11,7 @@
  *
  * https://www.php.net/manual/en/book.ffi.php
  */
-class FFITest extends TestCase
+final class FFITest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/FileDiffTest.php b/tests/FileDiffTest.php
index 2e206537b7b..bea2d1239fa 100644
--- a/tests/FileDiffTest.php
+++ b/tests/FileDiffTest.php
@@ -16,7 +16,7 @@
 use function strpos;
 use function var_export;
 
-class FileDiffTest extends TestCase
+final class FileDiffTest extends TestCase
 {
     /**
      * @dataProvider getChanges
diff --git a/tests/FileManipulation/ClassConstantMoveTest.php b/tests/FileManipulation/ClassConstantMoveTest.php
index 3e22aa14a0b..68fe5e8cadb 100644
--- a/tests/FileManipulation/ClassConstantMoveTest.php
+++ b/tests/FileManipulation/ClassConstantMoveTest.php
@@ -15,7 +15,7 @@
 
 use function strpos;
 
-class ClassConstantMoveTest extends TestCase
+final class ClassConstantMoveTest extends TestCase
 {
     protected ProjectAnalyzer $project_analyzer;
 
diff --git a/tests/FileManipulation/ClassMoveTest.php b/tests/FileManipulation/ClassMoveTest.php
index c2f5c8ee7a5..b694bc12ba3 100644
--- a/tests/FileManipulation/ClassMoveTest.php
+++ b/tests/FileManipulation/ClassMoveTest.php
@@ -15,7 +15,7 @@
 
 use function strpos;
 
-class ClassMoveTest extends TestCase
+final class ClassMoveTest extends TestCase
 {
     protected ProjectAnalyzer $project_analyzer;
 
diff --git a/tests/FileManipulation/ImmutableAnnotationAdditionTest.php b/tests/FileManipulation/ImmutableAnnotationAdditionTest.php
index 0e3083911c4..dd2e391e94d 100644
--- a/tests/FileManipulation/ImmutableAnnotationAdditionTest.php
+++ b/tests/FileManipulation/ImmutableAnnotationAdditionTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class ImmutableAnnotationAdditionTest extends FileManipulationTestCase
+final class ImmutableAnnotationAdditionTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/MethodMoveTest.php b/tests/FileManipulation/MethodMoveTest.php
index 51c9b18dc6b..93cf7546e75 100644
--- a/tests/FileManipulation/MethodMoveTest.php
+++ b/tests/FileManipulation/MethodMoveTest.php
@@ -15,7 +15,7 @@
 
 use function strpos;
 
-class MethodMoveTest extends TestCase
+final class MethodMoveTest extends TestCase
 {
     protected ProjectAnalyzer $project_analyzer;
 
diff --git a/tests/FileManipulation/MissingPropertyTypeTest.php b/tests/FileManipulation/MissingPropertyTypeTest.php
index 2bd15250b48..64546209d60 100644
--- a/tests/FileManipulation/MissingPropertyTypeTest.php
+++ b/tests/FileManipulation/MissingPropertyTypeTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class MissingPropertyTypeTest extends FileManipulationTestCase
+final class MissingPropertyTypeTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/MissingReturnTypeTest.php b/tests/FileManipulation/MissingReturnTypeTest.php
index 848398b2d01..c5af1e83050 100644
--- a/tests/FileManipulation/MissingReturnTypeTest.php
+++ b/tests/FileManipulation/MissingReturnTypeTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class MissingReturnTypeTest extends FileManipulationTestCase
+final class MissingReturnTypeTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/NamespaceMoveTest.php b/tests/FileManipulation/NamespaceMoveTest.php
index 537d20b836c..83db9764f15 100644
--- a/tests/FileManipulation/NamespaceMoveTest.php
+++ b/tests/FileManipulation/NamespaceMoveTest.php
@@ -15,7 +15,7 @@
 
 use function strpos;
 
-class NamespaceMoveTest extends TestCase
+final class NamespaceMoveTest extends TestCase
 {
     protected ProjectAnalyzer $project_analyzer;
 
diff --git a/tests/FileManipulation/ParamNameMismatchTest.php b/tests/FileManipulation/ParamNameMismatchTest.php
index 186885a4309..0263dd77942 100644
--- a/tests/FileManipulation/ParamNameMismatchTest.php
+++ b/tests/FileManipulation/ParamNameMismatchTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class ParamNameMismatchTest extends FileManipulationTestCase
+final class ParamNameMismatchTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/ParamTypeManipulationTest.php b/tests/FileManipulation/ParamTypeManipulationTest.php
index 172a383d608..11404ef15a0 100644
--- a/tests/FileManipulation/ParamTypeManipulationTest.php
+++ b/tests/FileManipulation/ParamTypeManipulationTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class ParamTypeManipulationTest extends FileManipulationTestCase
+final class ParamTypeManipulationTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/PropertyMoveTest.php b/tests/FileManipulation/PropertyMoveTest.php
index 5b0afa6dd6d..8127cf62523 100644
--- a/tests/FileManipulation/PropertyMoveTest.php
+++ b/tests/FileManipulation/PropertyMoveTest.php
@@ -15,7 +15,7 @@
 
 use function strpos;
 
-class PropertyMoveTest extends TestCase
+final class PropertyMoveTest extends TestCase
 {
     protected ProjectAnalyzer $project_analyzer;
 
diff --git a/tests/FileManipulation/PureAnnotationAdditionTest.php b/tests/FileManipulation/PureAnnotationAdditionTest.php
index 2b44581a82e..cb71c785347 100644
--- a/tests/FileManipulation/PureAnnotationAdditionTest.php
+++ b/tests/FileManipulation/PureAnnotationAdditionTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class PureAnnotationAdditionTest extends FileManipulationTestCase
+final class PureAnnotationAdditionTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/RedundantCastManipulationTest.php b/tests/FileManipulation/RedundantCastManipulationTest.php
index 71342cb4ad9..96f7b88688b 100644
--- a/tests/FileManipulation/RedundantCastManipulationTest.php
+++ b/tests/FileManipulation/RedundantCastManipulationTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class RedundantCastManipulationTest extends FileManipulationTestCase
+final class RedundantCastManipulationTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/ReturnTypeManipulationTest.php b/tests/FileManipulation/ReturnTypeManipulationTest.php
index be9333c556d..36777f80e25 100644
--- a/tests/FileManipulation/ReturnTypeManipulationTest.php
+++ b/tests/FileManipulation/ReturnTypeManipulationTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class ReturnTypeManipulationTest extends FileManipulationTestCase
+final class ReturnTypeManipulationTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/ThrowsBlockAdditionTest.php b/tests/FileManipulation/ThrowsBlockAdditionTest.php
index 8111eef2b36..f2b70b021f1 100644
--- a/tests/FileManipulation/ThrowsBlockAdditionTest.php
+++ b/tests/FileManipulation/ThrowsBlockAdditionTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class ThrowsBlockAdditionTest extends FileManipulationTestCase
+final class ThrowsBlockAdditionTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/UndefinedVariableManipulationTest.php b/tests/FileManipulation/UndefinedVariableManipulationTest.php
index 945e4463073..5c7ad8536da 100644
--- a/tests/FileManipulation/UndefinedVariableManipulationTest.php
+++ b/tests/FileManipulation/UndefinedVariableManipulationTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class UndefinedVariableManipulationTest extends FileManipulationTestCase
+final class UndefinedVariableManipulationTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/UnnecessaryVarAnnotationManipulationTest.php b/tests/FileManipulation/UnnecessaryVarAnnotationManipulationTest.php
index 95ca370bbac..8d9bf1fc56e 100644
--- a/tests/FileManipulation/UnnecessaryVarAnnotationManipulationTest.php
+++ b/tests/FileManipulation/UnnecessaryVarAnnotationManipulationTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class UnnecessaryVarAnnotationManipulationTest extends FileManipulationTestCase
+final class UnnecessaryVarAnnotationManipulationTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/UnusedCodeManipulationTest.php b/tests/FileManipulation/UnusedCodeManipulationTest.php
index 8dd8aaf892e..daec4204834 100644
--- a/tests/FileManipulation/UnusedCodeManipulationTest.php
+++ b/tests/FileManipulation/UnusedCodeManipulationTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class UnusedCodeManipulationTest extends FileManipulationTestCase
+final class UnusedCodeManipulationTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileManipulation/UnusedVariableManipulationTest.php b/tests/FileManipulation/UnusedVariableManipulationTest.php
index dc1c65662ad..9c08e5b74f0 100644
--- a/tests/FileManipulation/UnusedVariableManipulationTest.php
+++ b/tests/FileManipulation/UnusedVariableManipulationTest.php
@@ -4,7 +4,7 @@
 
 namespace Psalm\Tests\FileManipulation;
 
-class UnusedVariableManipulationTest extends FileManipulationTestCase
+final class UnusedVariableManipulationTest extends FileManipulationTestCase
 {
     public function providerValidCodeParse(): array
     {
diff --git a/tests/FileReferenceTest.php b/tests/FileReferenceTest.php
index 770e96a2ec9..3f36c9efc69 100644
--- a/tests/FileReferenceTest.php
+++ b/tests/FileReferenceTest.php
@@ -15,7 +15,7 @@
 use function count;
 use function strpos;
 
-class FileReferenceTest extends TestCase
+final class FileReferenceTest extends TestCase
 {
     protected ProjectAnalyzer $project_analyzer;
 
diff --git a/tests/FileUpdates/AnalyzedMethodTest.php b/tests/FileUpdates/AnalyzedMethodTest.php
index 598efeb6189..0f619c27cce 100644
--- a/tests/FileUpdates/AnalyzedMethodTest.php
+++ b/tests/FileUpdates/AnalyzedMethodTest.php
@@ -20,7 +20,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class AnalyzedMethodTest extends TestCase
+final class AnalyzedMethodTest extends TestCase
 {
     public function setUp(): void
     {
diff --git a/tests/FileUpdates/CachedStorageTest.php b/tests/FileUpdates/CachedStorageTest.php
index a41a33b86bb..cfdfc6bd113 100644
--- a/tests/FileUpdates/CachedStorageTest.php
+++ b/tests/FileUpdates/CachedStorageTest.php
@@ -21,7 +21,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class CachedStorageTest extends TestCase
+final class CachedStorageTest extends TestCase
 {
     public function setUp(): void
     {
diff --git a/tests/FileUpdates/ErrorAfterUpdateTest.php b/tests/FileUpdates/ErrorAfterUpdateTest.php
index 162c71c1f8e..cce87dc5a85 100644
--- a/tests/FileUpdates/ErrorAfterUpdateTest.php
+++ b/tests/FileUpdates/ErrorAfterUpdateTest.php
@@ -22,7 +22,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ErrorAfterUpdateTest extends TestCase
+final class ErrorAfterUpdateTest extends TestCase
 {
     public function setUp(): void
     {
@@ -119,11 +119,11 @@ public function foo() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B extends A { }',
+                            final class B extends A { }',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'C.php' => '<?php
                             namespace Foo;
 
-                            class C {
+                            final class C {
                                 public function bar() : void {
                                     (new B)->foo();
                                 }
@@ -139,11 +139,11 @@ class A { }',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B extends A { }',
+                            final class B extends A { }',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'C.php' => '<?php
                             namespace Foo;
 
-                            class C {
+                            final class C {
                                 public function bar() : void {
                                     (new B)->foo();
                                 }
@@ -160,14 +160,14 @@ public function bar() : void {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo = "bar";
                             }',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {
+                            final class B {
                                 public function foo() : string {
                                     return (new A)->foo;
                                 }
@@ -179,14 +179,14 @@ public function foo() : string {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var int */
                                 public $foo = 5;
                             }',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {
+                            final class B {
                                 public function foo() : string {
                                     return (new A)->foo;
                                 }
@@ -203,13 +203,13 @@ public function foo() : string {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public const FOO = "bar";
                             }',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {
+                            final class B {
                                 public function foo() : string {
                                     return A::FOO;
                                 }
@@ -221,13 +221,13 @@ public function foo() : string {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public const FOO = 5;
                             }',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {
+                            final class B {
                                 public function foo() : string {
                                     return A::FOO;
                                 }
@@ -244,7 +244,7 @@ public function foo() : string {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function getB() : B {
                                     return new B;
                                 }
@@ -252,7 +252,7 @@ public function getB() : B {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {
+                            final class B {
                                 public function getString() : string {
                                     return "foo";
                                 }
@@ -260,7 +260,7 @@ public function getString() : string {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'C.php' => '<?php
                             namespace Foo;
 
-                            class C {
+                            final class C {
                                 public function existingMethod() : string {
                                     return (new A)->getB()->getString();
                                 }
@@ -272,7 +272,7 @@ public function existingMethod() : string {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function getB() : B {
                                     return new B;
                                 }
@@ -280,7 +280,7 @@ public function getB() : B {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {
+                            final class B {
                                 public function getString() : string {
                                     return "foo";
                                 }
@@ -288,7 +288,7 @@ public function getString() : string {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'C.php' => '<?php
                             namespace Foo;
 
-                            class C {
+                            final class C {
                                 public function existingMethod() : string {
                                     return (new A)->getB()->getString();
                                 }
@@ -304,7 +304,7 @@ public function newMethod() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function getB() : B {
                                     return new B;
                                 }
@@ -312,7 +312,7 @@ public function getB() : B {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {
+                            final class B {
                                 public function getString() : ?string {
                                     return "foo";
                                 }
@@ -320,7 +320,7 @@ public function getString() : ?string {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'C.php' => '<?php
                             namespace Foo;
 
-                            class C {
+                            final class C {
                                 public function existingMethod() : string {
                                     return (new A)->getB()->getString();
                                 }
@@ -337,7 +337,7 @@ public function existingMethod() : string {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo = "bar";
                             }
@@ -348,7 +348,7 @@ class A {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo;
                             }
@@ -364,7 +364,7 @@ class A {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo = "bar";
 
@@ -377,7 +377,7 @@ public function __construct() {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo;
 
@@ -395,7 +395,7 @@ public function __construct() {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 use T;
 
                                 /** @var string */
@@ -414,7 +414,7 @@ public function __construct() {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 use T;
 
                                 /** @var string */
@@ -438,7 +438,7 @@ public function __construct() {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 use T;
                             }
 
@@ -457,7 +457,7 @@ public function __construct() {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 use T;
 
                                 /** @var string */
@@ -484,7 +484,7 @@ public function __construct() {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo;
 
@@ -503,7 +503,7 @@ private function setFoo() : void {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo;
 
@@ -533,7 +533,7 @@ abstract class A {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B extends A {}
+                            final class B extends A {}
 
                             echo (new B)->foo;',
                     ],
@@ -548,7 +548,7 @@ abstract class A {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B extends A {}
+                            final class B extends A {}
 
                             echo (new B)->foo;',
                     ],
@@ -568,13 +568,13 @@ abstract class A {
                                 public function __construct() {}
                             }
 
-                            class C extends A {}
+                            final class C extends A {}
 
                             new C();',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B extends A {
+                            final class B extends A {
                                 public function __construct() {}
                             }
 
@@ -593,7 +593,7 @@ public function __construct() {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B extends A {
+                            final class B extends A {
                                 public function __construct() {}
                             }
 
@@ -608,7 +608,7 @@ public function __construct() {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {}
+                            final class A {}
 
                             new A();',
                     ],
@@ -628,7 +628,7 @@ class A {}',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function foo() : void {}
                             }
 
@@ -638,7 +638,7 @@ public function foo() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function foo() : void {}
                                 public function foo() : void {}
                             }',
@@ -652,7 +652,7 @@ public function foo() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {}
+                            final class A {}
 
                             $a = new A();
                             print_r($a);',
@@ -661,7 +661,7 @@ class A {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {}',
+                            final class A {}',
                     ],
                 ],
                 'error_message' => 'UnusedClass',
@@ -672,7 +672,7 @@ class A {}',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function foo() : void {}
                             }
 
@@ -682,7 +682,7 @@ public function foo() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function foo() : void {}
                             }
 
@@ -698,7 +698,7 @@ public function foo() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public static function foo() : void {}
                                 public static function bar() : void {}
                             }',
@@ -710,7 +710,7 @@ public static function bar() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public static function foo() : void {}
                                 public static function bar() : void {}
                             }',
@@ -730,7 +730,7 @@ class A {
                                 public function foo(string $s) : void {}
                             }
 
-                            class B extends A {
+                            final class B extends A {
                                 public function foo(string $s) : void {
                                     echo $s;
                                 }
@@ -746,7 +746,7 @@ class A {
                                 public function foo(string $s) : void {}
                             }
 
-                            class B extends A {
+                            final class B extends A {
                             }
 
                             (new B)->foo("hello");',
@@ -760,11 +760,11 @@ class B extends A {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function foo() : void {}
                             }
 
-                            class B {
+                            final class B {
                                 public function bar() : void {
                                     (new A)->foo();
                                 }
@@ -776,11 +776,11 @@ public function bar() : void {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function foo() : void {}
                             }
 
-                            class B {
+                            final class B {
                                 public function bar() : void {
                                     new A();
                                 }
@@ -797,7 +797,7 @@ public function bar() : void {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo = "hello";
                             }
@@ -808,7 +808,7 @@ class A {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo = "hello";
                             }
@@ -824,12 +824,12 @@ class A {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo = "hello";
                             }
 
-                            class B {
+                            final class B {
                                 public function bar() : void {
                                     echo (new A)->foo;
                                 }
@@ -841,12 +841,12 @@ public function bar() : void {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 /** @var string */
                                 public $foo = "hello";
                             }
 
-                            class B {
+                            final class B {
                                 public function bar() : void {
                                     new A();
                                 }
@@ -873,7 +873,7 @@ abstract protected function setFoo() : void;
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'AChild.php' => '<?php
                             namespace Foo;
 
-                            class AChild extends A {
+                            final class AChild extends A {
                                 /** @var string */
                                 public $foo;
 
@@ -900,7 +900,7 @@ abstract protected function setFoo() : void;
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'AChild.php' => '<?php
                             namespace Foo;
 
-                            class AChild extends A {
+                            final class AChild extends A {
                                 /** @var string */
                                 public $foo;
 
@@ -928,7 +928,7 @@ public function foo(string $s) : void {
                                 }
                             }
 
-                            class AChild extends A {
+                            final class AChild extends A {
                                 public function foo(string $s) : void {
                                     echo $s;
                                 }
@@ -944,7 +944,7 @@ public function foo(string $s = "") : void {
                                 }
                             }
 
-                            class AChild extends A {
+                            final class AChild extends A {
                                 public function foo(string $s) : void {
                                     echo $s;
                                 }
diff --git a/tests/FileUpdates/ErrorFixTest.php b/tests/FileUpdates/ErrorFixTest.php
index c6e9ffc0132..0772fce7d5f 100644
--- a/tests/FileUpdates/ErrorFixTest.php
+++ b/tests/FileUpdates/ErrorFixTest.php
@@ -21,7 +21,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ErrorFixTest extends TestCase
+final class ErrorFixTest extends TestCase
 {
     public function setUp(): void
     {
diff --git a/tests/FileUpdates/TemporaryUpdateTest.php b/tests/FileUpdates/TemporaryUpdateTest.php
index f5a5cb6e33a..b0529064222 100644
--- a/tests/FileUpdates/TemporaryUpdateTest.php
+++ b/tests/FileUpdates/TemporaryUpdateTest.php
@@ -25,7 +25,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class TemporaryUpdateTest extends TestCase
+final class TemporaryUpdateTest extends TestCase
 {
     protected Codebase $codebase;
 
@@ -1714,11 +1714,11 @@ public function foo() : void {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {}',
+                            final class A {}',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {}',
+                            final class B {}',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'user.php' => '<?php
                             namespace Foo;
 
@@ -1728,18 +1728,18 @@ class B {}',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {}',
+                            final class A {}',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {}',
+                            final class B {}',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'user.php' => '<?php
                             namespace Foo;
 
                             new B();',
                     ],
                 ],
-                'error_positions' => [[84], [84]],
+                'error_positions' => [[90], [90]],
                 'ignored_issues' => [],
                 'test_save' => false,
                 'check_unused_code' => true,
@@ -1750,7 +1750,7 @@ class B {}',
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function foo() : void {}
 
                                 public function bar() : void {}
@@ -1764,7 +1764,7 @@ public function bar() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class A {
+                            final class A {
                                 public function foo() : void {
                                 }
 
@@ -1776,7 +1776,7 @@ public function bar() : void {}
                             (new A())->foo();',
                     ],
                 ],
-                'error_positions' => [[201], [234]],
+                'error_positions' => [[207], [240]],
                 'ignored_issues' => [],
                 'test_save' => false,
                 'check_unused_code' => true,
@@ -1787,7 +1787,7 @@ public function bar() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class Z {
+                            final class Z {
                                 const ONE = "1";
                                 const TWO = "2";
 
@@ -1796,7 +1796,7 @@ public static function foo() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {
+                            final class B {
                                 public function doFoo() : void {
                                     echo Z::ONE;
                                     Z::foo();
@@ -1812,7 +1812,7 @@ public function doFoo() : void {
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'A.php' => '<?php
                             namespace Foo;
 
-                            class Z {
+                            final class Z {
                                 const ONE = "1";
                                 const TWO = "2";
                                 const THREE = "3";
@@ -1822,7 +1822,7 @@ public static function foo() : void {}
                         (string) getcwd() . DIRECTORY_SEPARATOR . 'src' . DIRECTORY_SEPARATOR . 'B.php' => '<?php
                             namespace Foo;
 
-                            class B {
+                            final class B {
                                 public function doFoo() : void {
                                     echo Z::ONE;
                                     Z::foo();
diff --git a/tests/ForbiddenCodeTest.php b/tests/ForbiddenCodeTest.php
index 2c1153915fa..b92607d5821 100644
--- a/tests/ForbiddenCodeTest.php
+++ b/tests/ForbiddenCodeTest.php
@@ -16,7 +16,7 @@
 use function dirname;
 use function getcwd;
 
-class ForbiddenCodeTest extends TestCase
+final class ForbiddenCodeTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/FunctionCallTest.php b/tests/FunctionCallTest.php
index b551896681e..c6867bc53bd 100644
--- a/tests/FunctionCallTest.php
+++ b/tests/FunctionCallTest.php
@@ -11,7 +11,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class FunctionCallTest extends TestCase
+final class FunctionCallTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/FunctionLikeDocblockParserTest.php b/tests/FunctionLikeDocblockParserTest.php
index 07e38c91518..095e52701da 100644
--- a/tests/FunctionLikeDocblockParserTest.php
+++ b/tests/FunctionLikeDocblockParserTest.php
@@ -17,7 +17,7 @@
 use Psalm\Internal\RuntimeCaches;
 use Psalm\Tests\Internal\Provider\FakeParserCacheProvider;
 
-class FunctionLikeDocblockParserTest extends BaseTestCase
+final class FunctionLikeDocblockParserTest extends BaseTestCase
 {
     public string $test_cased_function_id = 'hello_world';
 
diff --git a/tests/GeneratorTest.php b/tests/GeneratorTest.php
index 61b50b27935..91d2a20965a 100644
--- a/tests/GeneratorTest.php
+++ b/tests/GeneratorTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class GeneratorTest extends TestCase
+final class GeneratorTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/IfThisIsTest.php b/tests/IfThisIsTest.php
index 1b8aeea2d91..8e0001d1469 100644
--- a/tests/IfThisIsTest.php
+++ b/tests/IfThisIsTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class IfThisIsTest extends TestCase
+final class IfThisIsTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/ImmutableAnnotationTest.php b/tests/ImmutableAnnotationTest.php
index 5755578194f..5ab24f14b75 100644
--- a/tests/ImmutableAnnotationTest.php
+++ b/tests/ImmutableAnnotationTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ImmutableAnnotationTest extends TestCase
+final class ImmutableAnnotationTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ImplementationRequirementTest.php b/tests/ImplementationRequirementTest.php
index a5ab348292e..ef11725e7f1 100644
--- a/tests/ImplementationRequirementTest.php
+++ b/tests/ImplementationRequirementTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ImplementationRequirementTest extends TestCase
+final class ImplementationRequirementTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/IncludeTest.php b/tests/IncludeTest.php
index 6aa37c925dd..7875f6ea6ad 100644
--- a/tests/IncludeTest.php
+++ b/tests/IncludeTest.php
@@ -14,7 +14,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class IncludeTest extends TestCase
+final class IncludeTest extends TestCase
 {
     /**
      * @dataProvider providerTestValidIncludes
diff --git a/tests/IntRangeTest.php b/tests/IntRangeTest.php
index 9a1d5cd05ff..6094cd8f3ff 100644
--- a/tests/IntRangeTest.php
+++ b/tests/IntRangeTest.php
@@ -10,7 +10,7 @@
 use Psalm\Type\Atomic\TIntRange;
 use Psalm\Type\Atomic\TLiteralInt;
 
-class IntRangeTest extends TestCase
+final class IntRangeTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/InterfaceTest.php b/tests/InterfaceTest.php
index f9792e6e22c..143ab92206b 100644
--- a/tests/InterfaceTest.php
+++ b/tests/InterfaceTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class InterfaceTest extends TestCase
+final class InterfaceTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Internal/CallMapTest.php b/tests/Internal/CallMapTest.php
index f49c60732c3..fef0a322a79 100644
--- a/tests/Internal/CallMapTest.php
+++ b/tests/Internal/CallMapTest.php
@@ -15,7 +15,7 @@
  * @psalm-type TCallMap=array<string, array<int|string, string>>
  * @psalm-type TCallMaps=array<int, array<string, array<int|string, string>>>
  */
-class CallMapTest extends TestCase
+final class CallMapTest extends TestCase
 {
     protected const DICTIONARY_PATH = 'dictionaries';
 
diff --git a/tests/Internal/CliUtilsTest.php b/tests/Internal/CliUtilsTest.php
index 1f67fa50832..3e8a66d12dd 100644
--- a/tests/Internal/CliUtilsTest.php
+++ b/tests/Internal/CliUtilsTest.php
@@ -11,7 +11,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class CliUtilsTest extends TestCase
+final class CliUtilsTest extends TestCase
 {
     /**
      * @var list<string>
diff --git a/tests/Internal/Codebase/InternalCallMapHandlerTest.php b/tests/Internal/Codebase/InternalCallMapHandlerTest.php
index 459ca64226f..bb380f903f3 100644
--- a/tests/Internal/Codebase/InternalCallMapHandlerTest.php
+++ b/tests/Internal/Codebase/InternalCallMapHandlerTest.php
@@ -50,7 +50,7 @@
 use const PHP_VERSION_ID;
 
 /** @group callmap */
-class InternalCallMapHandlerTest extends TestCase
+final class InternalCallMapHandlerTest extends TestCase
 {
     /**
      * Regex patterns for callmap entries that should be skipped.
diff --git a/tests/Internal/Provider/ClassLikeStorageInstanceCacheProvider.php b/tests/Internal/Provider/ClassLikeStorageInstanceCacheProvider.php
index 657ac4a2d93..6420c13c98a 100644
--- a/tests/Internal/Provider/ClassLikeStorageInstanceCacheProvider.php
+++ b/tests/Internal/Provider/ClassLikeStorageInstanceCacheProvider.php
@@ -10,7 +10,7 @@
 
 use function strtolower;
 
-class ClassLikeStorageInstanceCacheProvider extends ClassLikeStorageCacheProvider
+final class ClassLikeStorageInstanceCacheProvider extends ClassLikeStorageCacheProvider
 {
     /** @var array<lowercase-string, ClassLikeStorage> */
     private array $cache = [];
diff --git a/tests/Internal/Provider/FakeFileReferenceCacheProvider.php b/tests/Internal/Provider/FakeFileReferenceCacheProvider.php
index caa5e92ad73..f3ea07b5977 100644
--- a/tests/Internal/Provider/FakeFileReferenceCacheProvider.php
+++ b/tests/Internal/Provider/FakeFileReferenceCacheProvider.php
@@ -11,7 +11,7 @@
  * Used to determine which files reference other files, necessary for using the --diff
  * option from the command line.
  */
-class FakeFileReferenceCacheProvider extends FileReferenceCacheProvider
+final class FakeFileReferenceCacheProvider extends FileReferenceCacheProvider
 {
     private ?array $cached_file_references = null;
 
diff --git a/tests/Internal/Provider/FakeParserCacheProvider.php b/tests/Internal/Provider/FakeParserCacheProvider.php
index db5f8c6e835..fe76a4bee9d 100644
--- a/tests/Internal/Provider/FakeParserCacheProvider.php
+++ b/tests/Internal/Provider/FakeParserCacheProvider.php
@@ -6,7 +6,7 @@
 
 use Psalm\Internal\Provider\ParserCacheProvider;
 
-class FakeParserCacheProvider extends ParserCacheProvider
+final class FakeParserCacheProvider extends ParserCacheProvider
 {
     public function __construct()
     {
diff --git a/tests/Internal/Provider/FileStorageInstanceCacheProvider.php b/tests/Internal/Provider/FileStorageInstanceCacheProvider.php
index d32bc4e63f2..2d9dde04d92 100644
--- a/tests/Internal/Provider/FileStorageInstanceCacheProvider.php
+++ b/tests/Internal/Provider/FileStorageInstanceCacheProvider.php
@@ -9,7 +9,7 @@
 
 use function strtolower;
 
-class FileStorageInstanceCacheProvider extends FileStorageCacheProvider
+final class FileStorageInstanceCacheProvider extends FileStorageCacheProvider
 {
     /** @var array<lowercase-string, FileStorage> */
     private array $cache = [];
diff --git a/tests/Internal/Provider/ParserInstanceCacheProvider.php b/tests/Internal/Provider/ParserInstanceCacheProvider.php
index c227fec9935..ba2a4769a6e 100644
--- a/tests/Internal/Provider/ParserInstanceCacheProvider.php
+++ b/tests/Internal/Provider/ParserInstanceCacheProvider.php
@@ -9,7 +9,7 @@
 
 use function microtime;
 
-class ParserInstanceCacheProvider extends ParserCacheProvider
+final class ParserInstanceCacheProvider extends ParserCacheProvider
 {
     /**
      * @var array<string, string>
diff --git a/tests/Internal/Provider/ProjectCacheProvider.php b/tests/Internal/Provider/ProjectCacheProvider.php
index a8ad1219b4f..e3a0529af72 100644
--- a/tests/Internal/Provider/ProjectCacheProvider.php
+++ b/tests/Internal/Provider/ProjectCacheProvider.php
@@ -6,7 +6,7 @@
 
 use Psalm\Internal\Provider\ProjectCacheProvider as PsalmProjectCacheProvider;
 
-class ProjectCacheProvider extends PsalmProjectCacheProvider
+final class ProjectCacheProvider extends PsalmProjectCacheProvider
 {
     private int $last_run = 0;
 
diff --git a/tests/Internal/Scanner/FileScannerTest.php b/tests/Internal/Scanner/FileScannerTest.php
index 588738fa041..40af1ab936d 100644
--- a/tests/Internal/Scanner/FileScannerTest.php
+++ b/tests/Internal/Scanner/FileScannerTest.php
@@ -15,7 +15,7 @@
 use Psalm\Tests\TestCase;
 use Psalm\Tests\TestConfig;
 
-class FileScannerTest extends TestCase
+final class FileScannerTest extends TestCase
 {
     /**
      * @dataProvider providerScan
diff --git a/tests/InternalAnnotationTest.php b/tests/InternalAnnotationTest.php
index c54ea686e48..4f48a15bae9 100644
--- a/tests/InternalAnnotationTest.php
+++ b/tests/InternalAnnotationTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class InternalAnnotationTest extends TestCase
+final class InternalAnnotationTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/IssueBufferTest.php b/tests/IssueBufferTest.php
index 375e701274c..69273f2e2e8 100644
--- a/tests/IssueBufferTest.php
+++ b/tests/IssueBufferTest.php
@@ -17,7 +17,7 @@
 use function ob_get_clean;
 use function ob_start;
 
-class IssueBufferTest extends TestCase
+final class IssueBufferTest extends TestCase
 {
 
     public function testFinishDoesNotCorruptInternalState(): void
diff --git a/tests/IssueSuppressionTest.php b/tests/IssueSuppressionTest.php
index 3b703bb4260..9fd22b64c5e 100644
--- a/tests/IssueSuppressionTest.php
+++ b/tests/IssueSuppressionTest.php
@@ -15,7 +15,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class IssueSuppressionTest extends TestCase
+final class IssueSuppressionTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
@@ -217,7 +217,7 @@ public function testPossiblyUnusedPropertySuppressedOnClass(): void
             $file_path,
             '<?php
                 /** @psalm-suppress PossiblyUnusedProperty */
-                class Foo {
+                final class Foo {
                     public string $bar = "baz";
                 }
 
@@ -238,7 +238,7 @@ public function testPossiblyUnusedPropertySuppressedOnProperty(): void
         $this->addFile(
             $file_path,
             '<?php
-                class Foo {
+                final class Foo {
                     /** @psalm-suppress PossiblyUnusedProperty */
                     public string $bar = "baz";
                 }
diff --git a/tests/JsonOutputTest.php b/tests/JsonOutputTest.php
index 2e4c2c1a934..ec19b50fe2e 100644
--- a/tests/JsonOutputTest.php
+++ b/tests/JsonOutputTest.php
@@ -16,7 +16,7 @@
 
 use function substr;
 
-class JsonOutputTest extends TestCase
+final class JsonOutputTest extends TestCase
 {
     public function setUp(): void
     {
diff --git a/tests/KeyOfArrayTest.php b/tests/KeyOfArrayTest.php
index 8ae17ab91c1..8ef67eb7ce9 100644
--- a/tests/KeyOfArrayTest.php
+++ b/tests/KeyOfArrayTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class KeyOfArrayTest extends TestCase
+final class KeyOfArrayTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/LanguageServer/CompletionTest.php b/tests/LanguageServer/CompletionTest.php
index 4880432398e..4f8d8f26aa8 100644
--- a/tests/LanguageServer/CompletionTest.php
+++ b/tests/LanguageServer/CompletionTest.php
@@ -19,7 +19,7 @@
 
 use function count;
 
-class CompletionTest extends TestCase
+final class CompletionTest extends TestCase
 {
     protected Codebase $codebase;
 
diff --git a/tests/LanguageServer/DiagnosticTest.php b/tests/LanguageServer/DiagnosticTest.php
index e7c774461c9..0232d0cedba 100644
--- a/tests/LanguageServer/DiagnosticTest.php
+++ b/tests/LanguageServer/DiagnosticTest.php
@@ -27,7 +27,7 @@
 use function getcwd;
 use function rand;
 
-class DiagnosticTest extends AsyncTestCase
+final class DiagnosticTest extends AsyncTestCase
 {
     protected Codebase $codebase;
     private int $increment = 0;
diff --git a/tests/LanguageServer/FileMapTest.php b/tests/LanguageServer/FileMapTest.php
index 43609251290..2d2574c1e0e 100644
--- a/tests/LanguageServer/FileMapTest.php
+++ b/tests/LanguageServer/FileMapTest.php
@@ -17,7 +17,7 @@
 
 use function count;
 
-class FileMapTest extends TestCase
+final class FileMapTest extends TestCase
 {
     protected Codebase $codebase;
 
diff --git a/tests/LanguageServer/MockProtocolStream.php b/tests/LanguageServer/MockProtocolStream.php
index f3db6aebd95..8a0c7670e2a 100644
--- a/tests/LanguageServer/MockProtocolStream.php
+++ b/tests/LanguageServer/MockProtocolStream.php
@@ -14,7 +14,7 @@
 /**
  * A fake duplex protocol stream
  */
-class MockProtocolStream implements ProtocolReader, ProtocolWriter, EmitterInterface
+final class MockProtocolStream implements ProtocolReader, ProtocolWriter, EmitterInterface
 {
     use EmitterTrait;
     /**
diff --git a/tests/LanguageServer/SymbolLookupTest.php b/tests/LanguageServer/SymbolLookupTest.php
index 6701846f404..f7b7e785940 100644
--- a/tests/LanguageServer/SymbolLookupTest.php
+++ b/tests/LanguageServer/SymbolLookupTest.php
@@ -19,7 +19,7 @@
 use Psalm\Tests\TestCase;
 use Psalm\Tests\TestConfig;
 
-class SymbolLookupTest extends TestCase
+final class SymbolLookupTest extends TestCase
 {
     protected Codebase $codebase;
 
diff --git a/tests/ListTest.php b/tests/ListTest.php
index c36c4bac7df..a9f0732f92b 100644
--- a/tests/ListTest.php
+++ b/tests/ListTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ListTest extends TestCase
+final class ListTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Loop/DoTest.php b/tests/Loop/DoTest.php
index a6d4552fd38..95d1df29998 100644
--- a/tests/Loop/DoTest.php
+++ b/tests/Loop/DoTest.php
@@ -10,7 +10,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class DoTest extends TestCase
+final class DoTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Loop/ForTest.php b/tests/Loop/ForTest.php
index 037893b1ef4..6411be863ae 100644
--- a/tests/Loop/ForTest.php
+++ b/tests/Loop/ForTest.php
@@ -10,7 +10,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ForTest extends TestCase
+final class ForTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Loop/ForeachTest.php b/tests/Loop/ForeachTest.php
index 2b186949c9f..f7ce3c2c35a 100644
--- a/tests/Loop/ForeachTest.php
+++ b/tests/Loop/ForeachTest.php
@@ -10,7 +10,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ForeachTest extends TestCase
+final class ForeachTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Loop/WhileTest.php b/tests/Loop/WhileTest.php
index ab7c3967eb3..40b0c9b60d5 100644
--- a/tests/Loop/WhileTest.php
+++ b/tests/Loop/WhileTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class WhileTest extends TestCase
+final class WhileTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/MagicMethodAnnotationTest.php b/tests/MagicMethodAnnotationTest.php
index ec70655a161..41b0d4331a2 100644
--- a/tests/MagicMethodAnnotationTest.php
+++ b/tests/MagicMethodAnnotationTest.php
@@ -13,7 +13,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class MagicMethodAnnotationTest extends TestCase
+final class MagicMethodAnnotationTest extends TestCase
 {
     use InvalidCodeAnalysisWithIssuesTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/MagicPropertyTest.php b/tests/MagicPropertyTest.php
index 7962cf89f50..a69932adca0 100644
--- a/tests/MagicPropertyTest.php
+++ b/tests/MagicPropertyTest.php
@@ -13,7 +13,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class MagicPropertyTest extends TestCase
+final class MagicPropertyTest extends TestCase
 {
     use InvalidCodeAnalysisWithIssuesTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/MatchTest.php b/tests/MatchTest.php
index 43c1e0c1492..ce0d13ab092 100644
--- a/tests/MatchTest.php
+++ b/tests/MatchTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class MatchTest extends TestCase
+final class MatchTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/MethodCallTest.php b/tests/MethodCallTest.php
index 3754d455a0b..c74d4ad0222 100644
--- a/tests/MethodCallTest.php
+++ b/tests/MethodCallTest.php
@@ -11,7 +11,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class MethodCallTest extends TestCase
+final class MethodCallTest extends TestCase
 {
     use InvalidCodeAnalysisWithIssuesTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/MethodMutationTest.php b/tests/MethodMutationTest.php
index 9213906834a..695f86ad58c 100644
--- a/tests/MethodMutationTest.php
+++ b/tests/MethodMutationTest.php
@@ -8,7 +8,7 @@
 use Psalm\Internal\Analyzer\FileAnalyzer;
 use Psalm\Internal\MethodIdentifier;
 
-class MethodMutationTest extends TestCase
+final class MethodMutationTest extends TestCase
 {
     public function testControllerMutation(): void
     {
diff --git a/tests/MethodSignatureTest.php b/tests/MethodSignatureTest.php
index 3b29c356311..23aea048a37 100644
--- a/tests/MethodSignatureTest.php
+++ b/tests/MethodSignatureTest.php
@@ -12,7 +12,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class MethodSignatureTest extends TestCase
+final class MethodSignatureTest extends TestCase
 {
     use InvalidCodeAnalysisWithIssuesTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/MissingClassConstTypeTest.php b/tests/MissingClassConstTypeTest.php
index adabb5ab269..bbab2b942f7 100644
--- a/tests/MissingClassConstTypeTest.php
+++ b/tests/MissingClassConstTypeTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class MissingClassConstTypeTest extends TestCase
+final class MissingClassConstTypeTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/MixinAnnotationTest.php b/tests/MixinAnnotationTest.php
index 3c2c9fb19e9..2ab95933587 100644
--- a/tests/MixinAnnotationTest.php
+++ b/tests/MixinAnnotationTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisWithIssuesTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class MixinAnnotationTest extends TestCase
+final class MixinAnnotationTest extends TestCase
 {
     use InvalidCodeAnalysisWithIssuesTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/NamespaceTest.php b/tests/NamespaceTest.php
index 3e1736214f1..733e1c52772 100644
--- a/tests/NamespaceTest.php
+++ b/tests/NamespaceTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class NamespaceTest extends TestCase
+final class NamespaceTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/NativeIntersectionsTest.php b/tests/NativeIntersectionsTest.php
index 94f65bfee2c..4bfc7f70822 100644
--- a/tests/NativeIntersectionsTest.php
+++ b/tests/NativeIntersectionsTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class NativeIntersectionsTest extends TestCase
+final class NativeIntersectionsTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/NativeUnionsTest.php b/tests/NativeUnionsTest.php
index 0b7cc18ecf6..6d9c1be080d 100644
--- a/tests/NativeUnionsTest.php
+++ b/tests/NativeUnionsTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class NativeUnionsTest extends TestCase
+final class NativeUnionsTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/OverrideTest.php b/tests/OverrideTest.php
index 6dd2d878cc8..b55e3a5e273 100644
--- a/tests/OverrideTest.php
+++ b/tests/OverrideTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class OverrideTest extends TestCase
+final class OverrideTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/Php40Test.php b/tests/Php40Test.php
index d9e274de643..a4496022663 100644
--- a/tests/Php40Test.php
+++ b/tests/Php40Test.php
@@ -6,7 +6,7 @@
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class Php40Test extends TestCase
+final class Php40Test extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/Php55Test.php b/tests/Php55Test.php
index f2f9445dac5..2f2d17fd3fe 100644
--- a/tests/Php55Test.php
+++ b/tests/Php55Test.php
@@ -6,7 +6,7 @@
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class Php55Test extends TestCase
+final class Php55Test extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/Php56Test.php b/tests/Php56Test.php
index 3f34b0c041d..6c54fbda7de 100644
--- a/tests/Php56Test.php
+++ b/tests/Php56Test.php
@@ -6,7 +6,7 @@
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class Php56Test extends TestCase
+final class Php56Test extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/Php70Test.php b/tests/Php70Test.php
index 4775ce77943..2e2bbfd73c9 100644
--- a/tests/Php70Test.php
+++ b/tests/Php70Test.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class Php70Test extends TestCase
+final class Php70Test extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Php71Test.php b/tests/Php71Test.php
index 048debd219a..8622c97cda1 100644
--- a/tests/Php71Test.php
+++ b/tests/Php71Test.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class Php71Test extends TestCase
+final class Php71Test extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Progress/EchoProgress.php b/tests/Progress/EchoProgress.php
index 11c77be937e..3da15e0d798 100644
--- a/tests/Progress/EchoProgress.php
+++ b/tests/Progress/EchoProgress.php
@@ -6,7 +6,7 @@
 
 use Psalm\Progress\DefaultProgress;
 
-class EchoProgress extends DefaultProgress
+final class EchoProgress extends DefaultProgress
 {
     public function write(string $message): void
     {
diff --git a/tests/ProjectCheckerTest.php b/tests/ProjectCheckerTest.php
index a959ab58e59..1d397161606 100644
--- a/tests/ProjectCheckerTest.php
+++ b/tests/ProjectCheckerTest.php
@@ -35,7 +35,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ProjectCheckerTest extends TestCase
+final class ProjectCheckerTest extends TestCase
 {
     protected static TestConfig $config;
 
@@ -242,7 +242,7 @@ public function testCheckAfterFileChange(): void
 
 namespace Vimeo\Test\DummyProject;
 
-class Bat
+final class Bat
 {
     public function __construct()
     {
diff --git a/tests/PropertiesOfTest.php b/tests/PropertiesOfTest.php
index 99a14e678d6..a4e7d3a85be 100644
--- a/tests/PropertiesOfTest.php
+++ b/tests/PropertiesOfTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class PropertiesOfTest extends TestCase
+final class PropertiesOfTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/PropertyTypeInvarianceTest.php b/tests/PropertyTypeInvarianceTest.php
index 07fe43387e6..28686a12015 100644
--- a/tests/PropertyTypeInvarianceTest.php
+++ b/tests/PropertyTypeInvarianceTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class PropertyTypeInvarianceTest extends TestCase
+final class PropertyTypeInvarianceTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/PropertyTypeTest.php b/tests/PropertyTypeTest.php
index e6eccffdef0..6a29a5fe4b1 100644
--- a/tests/PropertyTypeTest.php
+++ b/tests/PropertyTypeTest.php
@@ -13,7 +13,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class PropertyTypeTest extends TestCase
+final class PropertyTypeTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/PsalmPluginTest.php b/tests/PsalmPluginTest.php
index 5b97dc23136..da3eedb4196 100644
--- a/tests/PsalmPluginTest.php
+++ b/tests/PsalmPluginTest.php
@@ -21,7 +21,7 @@
 use function preg_quote;
 
 /** @group PluginManager */
-class PsalmPluginTest extends TestCase
+final class PsalmPluginTest extends TestCase
 {
     use MockeryPHPUnitIntegration;
 
diff --git a/tests/PureAnnotationTest.php b/tests/PureAnnotationTest.php
index bf575406a98..678cf8200f9 100644
--- a/tests/PureAnnotationTest.php
+++ b/tests/PureAnnotationTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class PureAnnotationTest extends TestCase
+final class PureAnnotationTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/PureCallableTest.php b/tests/PureCallableTest.php
index 6360ee55412..29a8fcefb5b 100644
--- a/tests/PureCallableTest.php
+++ b/tests/PureCallableTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class PureCallableTest extends TestCase
+final class PureCallableTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/ReadonlyPropertyTest.php b/tests/ReadonlyPropertyTest.php
index cd80e5c7cf3..38d3d18b62c 100644
--- a/tests/ReadonlyPropertyTest.php
+++ b/tests/ReadonlyPropertyTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ReadonlyPropertyTest extends TestCase
+final class ReadonlyPropertyTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ReferenceConstraintTest.php b/tests/ReferenceConstraintTest.php
index 1b17810813d..9050e3cc390 100644
--- a/tests/ReferenceConstraintTest.php
+++ b/tests/ReferenceConstraintTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ReferenceConstraintTest extends TestCase
+final class ReferenceConstraintTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ReferenceTest.php b/tests/ReferenceTest.php
index 20819d3aca6..172f00c4a29 100644
--- a/tests/ReferenceTest.php
+++ b/tests/ReferenceTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ReferenceTest extends TestCase
+final class ReferenceTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ReflectionTest.php b/tests/ReflectionTest.php
index fb6e54cb387..d37e3dc5795 100644
--- a/tests/ReflectionTest.php
+++ b/tests/ReflectionTest.php
@@ -6,7 +6,7 @@
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ReflectionTest extends TestCase
+final class ReflectionTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/ReportOutputTest.php b/tests/ReportOutputTest.php
index 5c4292f573e..830591fa8a1 100644
--- a/tests/ReportOutputTest.php
+++ b/tests/ReportOutputTest.php
@@ -29,7 +29,7 @@
 
 use const JSON_THROW_ON_ERROR;
 
-class ReportOutputTest extends TestCase
+final class ReportOutputTest extends TestCase
 {
     public function setUp(): void
     {
diff --git a/tests/ReturnTypeProvider/ArrayColumnTest.php b/tests/ReturnTypeProvider/ArrayColumnTest.php
index 143557369d5..34f28814261 100644
--- a/tests/ReturnTypeProvider/ArrayColumnTest.php
+++ b/tests/ReturnTypeProvider/ArrayColumnTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ArrayColumnTest extends TestCase
+final class ArrayColumnTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ReturnTypeProvider/ArraySliceTest.php b/tests/ReturnTypeProvider/ArraySliceTest.php
index f2d839b9fcb..03a0ab408df 100644
--- a/tests/ReturnTypeProvider/ArraySliceTest.php
+++ b/tests/ReturnTypeProvider/ArraySliceTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\TestCase;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ArraySliceTest extends TestCase
+final class ArraySliceTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/ReturnTypeProvider/BasenameTest.php b/tests/ReturnTypeProvider/BasenameTest.php
index 6e61ffea06a..d372ea6c4aa 100644
--- a/tests/ReturnTypeProvider/BasenameTest.php
+++ b/tests/ReturnTypeProvider/BasenameTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class BasenameTest extends TestCase
+final class BasenameTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/ReturnTypeProvider/DirnameTest.php b/tests/ReturnTypeProvider/DirnameTest.php
index 029f91d0a8c..8a6757530d7 100644
--- a/tests/ReturnTypeProvider/DirnameTest.php
+++ b/tests/ReturnTypeProvider/DirnameTest.php
@@ -11,7 +11,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class DirnameTest extends TestCase
+final class DirnameTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/ReturnTypeProvider/ExceptionCodeTest.php b/tests/ReturnTypeProvider/ExceptionCodeTest.php
index b78cc4aa58b..259632b2cab 100644
--- a/tests/ReturnTypeProvider/ExceptionCodeTest.php
+++ b/tests/ReturnTypeProvider/ExceptionCodeTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\TestCase;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ExceptionCodeTest extends TestCase
+final class ExceptionCodeTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/ReturnTypeProvider/GetObjectVarsTest.php b/tests/ReturnTypeProvider/GetObjectVarsTest.php
index 814b9decb91..1a2b831f0dc 100644
--- a/tests/ReturnTypeProvider/GetObjectVarsTest.php
+++ b/tests/ReturnTypeProvider/GetObjectVarsTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\TestCase;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class GetObjectVarsTest extends TestCase
+final class GetObjectVarsTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/ReturnTypeProvider/InArrayTest.php b/tests/ReturnTypeProvider/InArrayTest.php
index e56855d3e61..f6e58ffeb5a 100644
--- a/tests/ReturnTypeProvider/InArrayTest.php
+++ b/tests/ReturnTypeProvider/InArrayTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\TestCase;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class InArrayTest extends TestCase
+final class InArrayTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/ReturnTypeProvider/MinMaxReturnTypeProviderTest.php b/tests/ReturnTypeProvider/MinMaxReturnTypeProviderTest.php
index fed70c3e7f0..67ec9514404 100644
--- a/tests/ReturnTypeProvider/MinMaxReturnTypeProviderTest.php
+++ b/tests/ReturnTypeProvider/MinMaxReturnTypeProviderTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\TestCase;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class MinMaxReturnTypeProviderTest extends TestCase
+final class MinMaxReturnTypeProviderTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/ReturnTypeProvider/PowReturnTypeProviderTest.php b/tests/ReturnTypeProvider/PowReturnTypeProviderTest.php
index 76c84500201..46835f4870a 100644
--- a/tests/ReturnTypeProvider/PowReturnTypeProviderTest.php
+++ b/tests/ReturnTypeProvider/PowReturnTypeProviderTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\TestCase;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class PowReturnTypeProviderTest extends TestCase
+final class PowReturnTypeProviderTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/ReturnTypeProvider/SprintfTest.php b/tests/ReturnTypeProvider/SprintfTest.php
index b5674c49026..1d6de543855 100644
--- a/tests/ReturnTypeProvider/SprintfTest.php
+++ b/tests/ReturnTypeProvider/SprintfTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class SprintfTest extends TestCase
+final class SprintfTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/ReturnTypeTest.php b/tests/ReturnTypeTest.php
index 2273bb98c7f..22aa7171d93 100644
--- a/tests/ReturnTypeTest.php
+++ b/tests/ReturnTypeTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ReturnTypeTest extends TestCase
+final class ReturnTypeTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/StubTest.php b/tests/StubTest.php
index fff4b559eff..be5789a5709 100644
--- a/tests/StubTest.php
+++ b/tests/StubTest.php
@@ -32,7 +32,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class StubTest extends TestCase
+final class StubTest extends TestCase
 {
     protected static TestConfig $config;
 
@@ -1292,7 +1292,7 @@ public static function vendorFunction(VendorClass $v) : void {
         $this->addFile(
             $file_path,
             '<?php
-                class MyClass extends \SomeVendor\VendorClass {
+                final class MyClass extends \SomeVendor\VendorClass {
                     public function foo() : void {}
                 }
 
diff --git a/tests/SuperGlobalsTest.php b/tests/SuperGlobalsTest.php
index 42e6212d628..6d3afe80561 100644
--- a/tests/SuperGlobalsTest.php
+++ b/tests/SuperGlobalsTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class SuperGlobalsTest extends TestCase
+final class SuperGlobalsTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/SwitchTypeTest.php b/tests/SwitchTypeTest.php
index a4252c89b9f..b8aed882cc2 100644
--- a/tests/SwitchTypeTest.php
+++ b/tests/SwitchTypeTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class SwitchTypeTest extends TestCase
+final class SwitchTypeTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TaintTest.php b/tests/TaintTest.php
index 3399d08c886..f29294f177d 100644
--- a/tests/TaintTest.php
+++ b/tests/TaintTest.php
@@ -16,7 +16,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class TaintTest extends TestCase
+final class TaintTest extends TestCase
 {
     /**
      * @dataProvider providerValidCodeParse
diff --git a/tests/Template/ClassStringMapTest.php b/tests/Template/ClassStringMapTest.php
index 78ed8b7f354..1134767fe83 100644
--- a/tests/Template/ClassStringMapTest.php
+++ b/tests/Template/ClassStringMapTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ClassStringMapTest extends TestCase
+final class ClassStringMapTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/Template/ClassTemplateCovarianceTest.php b/tests/Template/ClassTemplateCovarianceTest.php
index f82c3bc4159..18fb9b036ca 100644
--- a/tests/Template/ClassTemplateCovarianceTest.php
+++ b/tests/Template/ClassTemplateCovarianceTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ClassTemplateCovarianceTest extends TestCase
+final class ClassTemplateCovarianceTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Template/ClassTemplateExtendsTest.php b/tests/Template/ClassTemplateExtendsTest.php
index 99ec92a6c22..640f4f8aceb 100644
--- a/tests/Template/ClassTemplateExtendsTest.php
+++ b/tests/Template/ClassTemplateExtendsTest.php
@@ -10,7 +10,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ClassTemplateExtendsTest extends TestCase
+final class ClassTemplateExtendsTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Template/ClassTemplateTest.php b/tests/Template/ClassTemplateTest.php
index 65836bc51ce..06b9b341041 100644
--- a/tests/Template/ClassTemplateTest.php
+++ b/tests/Template/ClassTemplateTest.php
@@ -10,7 +10,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ClassTemplateTest extends TestCase
+final class ClassTemplateTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Template/ConditionalReturnTypeTest.php b/tests/Template/ConditionalReturnTypeTest.php
index 67e8225455a..c8a3e999e3f 100644
--- a/tests/Template/ConditionalReturnTypeTest.php
+++ b/tests/Template/ConditionalReturnTypeTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\TestCase;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ConditionalReturnTypeTest extends TestCase
+final class ConditionalReturnTypeTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/Template/FunctionClassStringTemplateTest.php b/tests/Template/FunctionClassStringTemplateTest.php
index 2b8cc2515bf..1382d35e1e8 100644
--- a/tests/Template/FunctionClassStringTemplateTest.php
+++ b/tests/Template/FunctionClassStringTemplateTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class FunctionClassStringTemplateTest extends TestCase
+final class FunctionClassStringTemplateTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Template/FunctionTemplateAssertTest.php b/tests/Template/FunctionTemplateAssertTest.php
index df609f0d028..459bf73b608 100644
--- a/tests/Template/FunctionTemplateAssertTest.php
+++ b/tests/Template/FunctionTemplateAssertTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class FunctionTemplateAssertTest extends TestCase
+final class FunctionTemplateAssertTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Template/FunctionTemplateTest.php b/tests/Template/FunctionTemplateTest.php
index fec1ec19569..9b08c724dba 100644
--- a/tests/Template/FunctionTemplateTest.php
+++ b/tests/Template/FunctionTemplateTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class FunctionTemplateTest extends TestCase
+final class FunctionTemplateTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Template/KeyOfTemplateTest.php b/tests/Template/KeyOfTemplateTest.php
index 291bfbd5ad9..573179b741b 100644
--- a/tests/Template/KeyOfTemplateTest.php
+++ b/tests/Template/KeyOfTemplateTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class KeyOfTemplateTest extends TestCase
+final class KeyOfTemplateTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Template/NestedTemplateTest.php b/tests/Template/NestedTemplateTest.php
index fd33578bc1d..fb025412a84 100644
--- a/tests/Template/NestedTemplateTest.php
+++ b/tests/Template/NestedTemplateTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class NestedTemplateTest extends TestCase
+final class NestedTemplateTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Template/PropertiesOfTemplateTest.php b/tests/Template/PropertiesOfTemplateTest.php
index aba8efd9db6..75100818f0a 100644
--- a/tests/Template/PropertiesOfTemplateTest.php
+++ b/tests/Template/PropertiesOfTemplateTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class PropertiesOfTemplateTest extends TestCase
+final class PropertiesOfTemplateTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/Template/TraitTemplateTest.php b/tests/Template/TraitTemplateTest.php
index 7074c24ea10..13d45fe4a1d 100644
--- a/tests/Template/TraitTemplateTest.php
+++ b/tests/Template/TraitTemplateTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class TraitTemplateTest extends TestCase
+final class TraitTemplateTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/Template/ValueOfTemplateTest.php b/tests/Template/ValueOfTemplateTest.php
index 011181e7beb..b8d16f7a0d5 100644
--- a/tests/Template/ValueOfTemplateTest.php
+++ b/tests/Template/ValueOfTemplateTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ValueOfTemplateTest extends TestCase
+final class ValueOfTemplateTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TestConfig.php b/tests/TestConfig.php
index 5c827ab7619..b46867ec452 100644
--- a/tests/TestConfig.php
+++ b/tests/TestConfig.php
@@ -11,7 +11,7 @@
 
 use function getcwd;
 
-class TestConfig extends Config
+final class TestConfig extends Config
 {
     private static ?ProjectFileFilter $cached_project_files = null;
 
diff --git a/tests/TestEnvironmentTest.php b/tests/TestEnvironmentTest.php
index 7b6a1b587b1..bb9b9e4e209 100644
--- a/tests/TestEnvironmentTest.php
+++ b/tests/TestEnvironmentTest.php
@@ -8,7 +8,7 @@
 
 use function ini_get;
 
-class TestEnvironmentTest extends PHPUnitTestCase
+final class TestEnvironmentTest extends PHPUnitTestCase
 {
     public function testIniSettings(): void
     {
diff --git a/tests/ThisOutTest.php b/tests/ThisOutTest.php
index 737b927a913..27fd9298365 100644
--- a/tests/ThisOutTest.php
+++ b/tests/ThisOutTest.php
@@ -6,7 +6,7 @@
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ThisOutTest extends TestCase
+final class ThisOutTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/ThrowsAnnotationTest.php b/tests/ThrowsAnnotationTest.php
index 8930054129f..e2c3c9c9e03 100644
--- a/tests/ThrowsAnnotationTest.php
+++ b/tests/ThrowsAnnotationTest.php
@@ -8,7 +8,7 @@
 use Psalm\Context;
 use Psalm\Exception\CodeException;
 
-class ThrowsAnnotationTest extends TestCase
+final class ThrowsAnnotationTest extends TestCase
 {
     public function testUndefinedClassAsThrows(): void
     {
diff --git a/tests/ThrowsInGlobalScopeTest.php b/tests/ThrowsInGlobalScopeTest.php
index b22f8e7a8dc..d6244ae0a89 100644
--- a/tests/ThrowsInGlobalScopeTest.php
+++ b/tests/ThrowsInGlobalScopeTest.php
@@ -8,7 +8,7 @@
 use Psalm\Context;
 use Psalm\Exception\CodeException;
 
-class ThrowsInGlobalScopeTest extends TestCase
+final class ThrowsInGlobalScopeTest extends TestCase
 {
     public function testUncaughtDocumentedThrowCall(): void
     {
diff --git a/tests/ToStringTest.php b/tests/ToStringTest.php
index a3dff64f766..f527f7cca62 100644
--- a/tests/ToStringTest.php
+++ b/tests/ToStringTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ToStringTest extends TestCase
+final class ToStringTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TraceTest.php b/tests/TraceTest.php
index 564fd7475a1..6d8161dd783 100644
--- a/tests/TraceTest.php
+++ b/tests/TraceTest.php
@@ -6,7 +6,7 @@
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 
-class TraceTest extends TestCase
+final class TraceTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
 
diff --git a/tests/TraitTest.php b/tests/TraitTest.php
index 4daae48a3e8..b20cbb893bf 100644
--- a/tests/TraitTest.php
+++ b/tests/TraitTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class TraitTest extends TestCase
+final class TraitTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TryCatchTest.php b/tests/TryCatchTest.php
index 87a714e2359..8f14ce7904e 100644
--- a/tests/TryCatchTest.php
+++ b/tests/TryCatchTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class TryCatchTest extends TestCase
+final class TryCatchTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/TypeAnnotationTest.php b/tests/TypeAnnotationTest.php
index d61b060c547..a2a36becb2f 100644
--- a/tests/TypeAnnotationTest.php
+++ b/tests/TypeAnnotationTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class TypeAnnotationTest extends TestCase
+final class TypeAnnotationTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TypeCombinationTest.php b/tests/TypeCombinationTest.php
index e429a58c8ab..8e3b2c97b2c 100644
--- a/tests/TypeCombinationTest.php
+++ b/tests/TypeCombinationTest.php
@@ -11,7 +11,7 @@
 
 use function array_reverse;
 
-class TypeCombinationTest extends TestCase
+final class TypeCombinationTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/TypeComparatorTest.php b/tests/TypeComparatorTest.php
index 3c62dd45613..541e06beaf7 100644
--- a/tests/TypeComparatorTest.php
+++ b/tests/TypeComparatorTest.php
@@ -19,7 +19,7 @@
 use function array_keys;
 use function array_map;
 
-class TypeComparatorTest extends TestCase
+final class TypeComparatorTest extends TestCase
 {
     public function setUp(): void
     {
diff --git a/tests/TypeParseTest.php b/tests/TypeParseTest.php
index 5b694a638db..f09352a56d8 100644
--- a/tests/TypeParseTest.php
+++ b/tests/TypeParseTest.php
@@ -26,7 +26,7 @@
 use function print_r;
 use function stripos;
 
-class TypeParseTest extends TestCase
+final class TypeParseTest extends TestCase
 {
     public function setUp(): void
     {
diff --git a/tests/TypeReconciliation/ArrayKeyExistsTest.php b/tests/TypeReconciliation/ArrayKeyExistsTest.php
index 25d8b8edad0..49d104c66d2 100644
--- a/tests/TypeReconciliation/ArrayKeyExistsTest.php
+++ b/tests/TypeReconciliation/ArrayKeyExistsTest.php
@@ -10,7 +10,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ArrayKeyExistsTest extends TestCase
+final class ArrayKeyExistsTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/TypeReconciliation/AssignmentInConditionalTest.php b/tests/TypeReconciliation/AssignmentInConditionalTest.php
index ebf621d1abe..084ef8b2faf 100644
--- a/tests/TypeReconciliation/AssignmentInConditionalTest.php
+++ b/tests/TypeReconciliation/AssignmentInConditionalTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class AssignmentInConditionalTest extends TestCase
+final class AssignmentInConditionalTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TypeReconciliation/ConditionalTest.php b/tests/TypeReconciliation/ConditionalTest.php
index bafc9696723..4b47cef7f58 100644
--- a/tests/TypeReconciliation/ConditionalTest.php
+++ b/tests/TypeReconciliation/ConditionalTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ConditionalTest extends TestCase
+final class ConditionalTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TypeReconciliation/EmptyTest.php b/tests/TypeReconciliation/EmptyTest.php
index 8804692efab..1aa98b6b848 100644
--- a/tests/TypeReconciliation/EmptyTest.php
+++ b/tests/TypeReconciliation/EmptyTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class EmptyTest extends TestCase
+final class EmptyTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TypeReconciliation/InArrayTest.php b/tests/TypeReconciliation/InArrayTest.php
index ff584d63a98..cceef1bcc61 100644
--- a/tests/TypeReconciliation/InArrayTest.php
+++ b/tests/TypeReconciliation/InArrayTest.php
@@ -10,7 +10,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class InArrayTest extends TestCase
+final class InArrayTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/TypeReconciliation/IssetTest.php b/tests/TypeReconciliation/IssetTest.php
index a5ac9393271..e7804fe95ed 100644
--- a/tests/TypeReconciliation/IssetTest.php
+++ b/tests/TypeReconciliation/IssetTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class IssetTest extends TestCase
+final class IssetTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/TypeReconciliation/ReconcilerTest.php b/tests/TypeReconciliation/ReconcilerTest.php
index 18f47e4913a..bfdfc97931f 100644
--- a/tests/TypeReconciliation/ReconcilerTest.php
+++ b/tests/TypeReconciliation/ReconcilerTest.php
@@ -39,7 +39,7 @@
 use Psalm\Type\Atomic\TTrue;
 use Psalm\Type\Union;
 
-class ReconcilerTest extends TestCase
+final class ReconcilerTest extends TestCase
 {
     protected FileAnalyzer $file_analyzer;
 
diff --git a/tests/TypeReconciliation/RedundantConditionTest.php b/tests/TypeReconciliation/RedundantConditionTest.php
index 19abb93e479..56b8d17da21 100644
--- a/tests/TypeReconciliation/RedundantConditionTest.php
+++ b/tests/TypeReconciliation/RedundantConditionTest.php
@@ -10,7 +10,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class RedundantConditionTest extends TestCase
+final class RedundantConditionTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/TypeReconciliation/ScopeTest.php b/tests/TypeReconciliation/ScopeTest.php
index b94ac5a9033..b64155af720 100644
--- a/tests/TypeReconciliation/ScopeTest.php
+++ b/tests/TypeReconciliation/ScopeTest.php
@@ -10,7 +10,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class ScopeTest extends TestCase
+final class ScopeTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TypeReconciliation/TypeAlgebraTest.php b/tests/TypeReconciliation/TypeAlgebraTest.php
index b15526afd41..416114f4428 100644
--- a/tests/TypeReconciliation/TypeAlgebraTest.php
+++ b/tests/TypeReconciliation/TypeAlgebraTest.php
@@ -8,7 +8,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class TypeAlgebraTest extends TestCase
+final class TypeAlgebraTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TypeReconciliation/TypeTest.php b/tests/TypeReconciliation/TypeTest.php
index 475e4a0faa4..837edd48e9a 100644
--- a/tests/TypeReconciliation/TypeTest.php
+++ b/tests/TypeReconciliation/TypeTest.php
@@ -10,7 +10,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class TypeTest extends TestCase
+final class TypeTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/TypeReconciliation/ValueTest.php b/tests/TypeReconciliation/ValueTest.php
index ab93e7de6a2..7c0d978893d 100644
--- a/tests/TypeReconciliation/ValueTest.php
+++ b/tests/TypeReconciliation/ValueTest.php
@@ -14,7 +14,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ValueTest extends TestCase
+final class ValueTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/UnresolvableIncludeTest.php b/tests/UnresolvableIncludeTest.php
index dec1ae9b7e1..c50f9c102a1 100644
--- a/tests/UnresolvableIncludeTest.php
+++ b/tests/UnresolvableIncludeTest.php
@@ -7,7 +7,7 @@
 use Psalm\Context;
 use Psalm\Exception\CodeException;
 
-class UnresolvableIncludeTest extends TestCase
+final class UnresolvableIncludeTest extends TestCase
 {
     /**
      * @dataProvider providerUnresolvableInclude
diff --git a/tests/UnsupportedPropertyReferenceUsage.php b/tests/UnsupportedPropertyReferenceUsage.php
index d3ccdbcddaf..0ebd5eb6a8e 100644
--- a/tests/UnsupportedPropertyReferenceUsage.php
+++ b/tests/UnsupportedPropertyReferenceUsage.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class UnsupportedPropertyReferenceUsage extends TestCase
+final class UnsupportedPropertyReferenceUsage extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/UnusedCodeTest.php b/tests/UnusedCodeTest.php
index 382202ad39f..250b76d1c0c 100644
--- a/tests/UnusedCodeTest.php
+++ b/tests/UnusedCodeTest.php
@@ -20,7 +20,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class UnusedCodeTest extends TestCase
+final class UnusedCodeTest extends TestCase
 {
     protected ProjectAnalyzer $project_analyzer;
 
@@ -120,7 +120,7 @@ public function testSeesClassesUsedAfterUnevaluatedCodeIssue(): void
                     $f->bar();
                 }
 
-                class Foo {
+                final class Foo {
                     function bar(): void{
                         echo "foo";
                     }
@@ -152,7 +152,7 @@ public function testSeesUnusedClassReferencedByUnevaluatedCode(): void
                     echo "bar";
                 }
 
-                class Foo {
+                final class Foo {
                     function bar(): void{
                         echo "foo";
                     }
@@ -174,9 +174,27 @@ function bar(): void{
     public function providerValidCodeParse(): array
     {
         return [
+            'nonFinalClassWithChildren' => [
+                'code' => '<?php
+                    class a {}
+                    /** @api */
+                    final class b extends a {}',
+            ],
+            'apiNonFinalClass' => [
+                'code' => '<?php
+                    /** @api */
+                    class a {}',
+            ],
+            'abstractClass' => [
+                'code' => '<?php
+                    abstract class a {}
+                    trait c {}
+                    final class b extends a {}
+                    new b;',
+            ],
             'magicCall' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         /** @var string */
                         private $value = "default";
 
@@ -219,7 +237,7 @@ public function foo(): void {
                         }
                     }
 
-                    class B extends A {
+                    final class B extends A {
                         use T;
                     }
 
@@ -232,7 +250,7 @@ interface I {
                         public function foo(): void;
                     }
 
-                    class A implements I {
+                    final class A implements I {
                         public function foo(): void {}
                     }
 
@@ -240,7 +258,7 @@ public function foo(): void {}
             ],
             'constructorIsUsed' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public function __construct() {
                             $this->foo();
                         }
@@ -254,11 +272,11 @@ private function foo() : void {}
                     interface I {
                         public function foo() : void;
                     }
-                    class B implements I {
+                    final class B implements I {
                         public function foo() : void {}
                     }
 
-                    class A
+                    final class A
                     {
                         /**
                          * @var I
@@ -312,7 +330,7 @@ function foo(int $unusedArg) : void {}
             ],
             'possiblyUnusedParamWithUnderscore' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public static function foo(int $_ = null) : void {}
                     }
 
@@ -320,7 +338,7 @@ public static function foo(int $_ = null) : void {}
             ],
             'possiblyUnusedParamWithUnusedPrefix' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public static function foo(int $unusedArg = null) : void {}
                     }
 
@@ -328,7 +346,7 @@ public static function foo(int $unusedArg = null) : void {}
             ],
             'usedClass' => [
                 'code' => '<?php
-                    class A { }
+                    final class A { }
                     new A();',
             ],
             'usedTraitMethodWithImplicitCall' => [
@@ -339,7 +357,7 @@ public function foo() : void {}
                     trait T {
                         public function foo() : void {}
                     }
-                    class B extends A {
+                    final class B extends A {
                         use T;
                     }
                     function takesA(A $a) : void {
@@ -354,11 +372,11 @@ protected function getC() : C {
                             return new C;
                         }
                     }
-                    class C {
+                    final class C {
                         public function foo() : void {}
                     }
 
-                    class B extends A {
+                    final class B extends A {
                         public function bar() : void {
                             $c = $this->getC();
 
@@ -374,7 +392,7 @@ public function bar() : void {
             ],
             'suppressPrivateUnusedMethod' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         /**
                          * @psalm-suppress UnusedMethod
                          * @return void
@@ -394,7 +412,7 @@ public function doIt(): void {
                         abstract protected function inner(): void;
                     }
 
-                    class MyFooBar extends Foobar {
+                    final class MyFooBar extends Foobar {
                         protected function inner(): void {
                             // Do nothing
                         }
@@ -405,7 +423,7 @@ protected function inner(): void {
             ],
             'methodUsedAsCallable' => [
                 'code' => '<?php
-                    class C {
+                    final class C {
                         public static function foo() : void {}
                     }
 
@@ -424,7 +442,7 @@ class A {
                         public function bar() : void {}
                     }
 
-                    class B extends A {
+                    final class B extends A {
                         /** @var string */
                         public $foo = "goodbye";
 
@@ -452,7 +470,7 @@ public function getFoo(): void {
                     }
                 }
 
-                class D extends C {
+                final class D extends C {
                     protected int $foo = 2;
                 }
 
@@ -461,7 +479,7 @@ class D extends C {
             ],
             'usedClassAfterExtensionLoaded' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public function __construct() {}
                     }
 
@@ -500,8 +518,8 @@ function process(b $handler): a {
             ],
             'usedParamInIf' => [
                 'code' => '<?php
-                    class O {}
-                    class C {
+                    final class O {}
+                    final class C {
                         private bool $a = false;
                         public array $_types = [];
 
@@ -526,7 +544,7 @@ public function addType(?string $type, array $ids = array()): void
             ],
             'usedMethodAfterClassExists' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public static function bar() : void {}
                     }
 
@@ -536,7 +554,7 @@ public static function bar() : void {}
             ],
             'usedParamInLoopBeforeBreak' => [
                 'code' => '<?php
-                    class Foo {}
+                    final class Foo {}
 
                     function takesFoo(Foo $foo1, Foo $foo2): Foo {
                         while (rand(0, 1)) {
@@ -554,7 +572,7 @@ function takesFoo(Foo $foo1, Foo $foo2): Foo {
             ],
             'usedParamInLoopBeforeContinue' => [
                 'code' => '<?php
-                    class Foo {}
+                    final class Foo {}
 
                     function takesFoo(Foo $foo1, Foo $foo2): Foo {
                         while (rand(0, 1)) {
@@ -572,9 +590,9 @@ function takesFoo(Foo $foo1, Foo $foo2): Foo {
             ],
             'usedParamInLoopBeforeWithChangeContinue' => [
                 'code' => '<?php
-                    class Foo {}
+                    final class Foo {}
 
-                    class Bar {
+                    final class Bar {
                         public static function build(Foo $foo) : ?self {
                             echo get_class($foo);
                             return new self();
@@ -601,7 +619,7 @@ function takesFoo(Foo $foo): Foo {
             ],
             'suppressUnusedMethod' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         /**
                          * @psalm-suppress UnusedMethod
                          */
@@ -630,7 +648,7 @@ function foo(string $s, object $o) : void {
             ],
             'usedFunctioninMethodCallName' => [
                 'code' => '<?php
-                    class Foo {
+                    final class Foo {
                         /**
                          * @psalm-suppress MixedArgument
                          */
@@ -648,7 +666,7 @@ public function bar(string $request): void {
                     /**
                      * @psalm-external-mutation-free
                      */
-                    class A {
+                    final class A {
                         private string $foo;
 
                         public function __construct(string $foo) {
@@ -678,7 +696,7 @@ function inc(array $arr) : array {
             'pureFunctionUsesMethodBeforeReturning' => [
                 'code' => '<?php
                     /** @psalm-external-mutation-free */
-                    class Counter {
+                    final class Counter {
                         private int $count = 0;
 
                         public function __construct(int $count) {
@@ -761,7 +779,7 @@ function getArg(string $method) : void {
             ],
             'ignoreJsonSerialize' => [
                 'code' => '<?php
-                    class Foo implements JsonSerializable {
+                    final class Foo implements JsonSerializable {
                         public function jsonSerialize() : array {
                             return [];
                         }
@@ -771,7 +789,7 @@ public function jsonSerialize() : array {
             ],
             'ignoreSerializerSerialize' => [
                 'code' => '<?php
-                    class Foo implements Serializable {
+                    final class Foo implements Serializable {
                         public function serialize() : string {
                             return "";
                         }
@@ -783,7 +801,7 @@ public function unserialize($data) : void {}
             ],
             'ignoreSerializeAndUnserialize' => [
                 'code' => '<?php
-                    class Foo
+                    final class Foo
                     {
                         public function __sleep(): array
                         {
@@ -814,7 +832,7 @@ function test(Foo|int $foo, mixed $bar, iterable $baz): bool {
             'useIteratorMethodsWhenCallingForeach' => [
                 'code' => '<?php
                     /** @psalm-suppress UnimplementedInterfaceMethod, MissingTemplateParam */
-                    class IterableResult implements \Iterator {
+                    final class IterableResult implements \Iterator {
                         public function current() {
                             return null;
                         }
@@ -850,13 +868,13 @@ function createFoo($type): FooBase {
                         return new $type();
                     }
 
-                    class Foo extends FooBase {}
+                    final class Foo extends FooBase {}
 
                     createFoo(Foo::class)->baz();',
             ],
             'usedMethodReferencedByString' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         static function b(): void {}
                     }
                     $methodRef = "A::b";
@@ -864,7 +882,7 @@ static function b(): void {}
             ],
             'usedMethodReferencedByStringWithLeadingBackslash' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         static function b(): void {}
                     }
                     $methodRef = "\A::b";
@@ -880,7 +898,7 @@ static function b(): void {}
             ],
             'callMethodThatUpdatesStaticVar' => [
                 'code' => '<?php
-                    class References {
+                    final class References {
                         /**
                          * @var array<string, string>
                          */
@@ -898,7 +916,7 @@ public function bar(array $map) : void {
             ],
             'promotedPropertyIsUsed' => [
                 'code' => '<?php
-                    class Test {
+                    final class Test {
                         public function __construct(public int $id, public string $name) {}
                     }
 
@@ -1057,7 +1075,7 @@ public function create(bool $returnNull): ?Test {
             ],
             'publicPropertyReadInFile' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public string $a;
 
                         public function __construct() {
@@ -1070,11 +1088,11 @@ public function __construct() {
             ],
             'publicPropertyReadInMethod' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public string $a = "hello";
                     }
 
-                    class B {
+                    final class B {
                         public function foo(A $a): void {
                             if ($a->a === "goodbye") {}
                         }
@@ -1084,7 +1102,7 @@ public function foo(A $a): void {
             ],
             'privatePropertyReadInMethod' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         private string $a;
 
                         public function __construct() {
@@ -1100,7 +1118,7 @@ public function emitA(): void {
             ],
             'fluentMethodsAllowed' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public function foo(): static {
                             return $this;
                         }
@@ -1119,7 +1137,7 @@ interface IWorker {
                         public function work(): bool;
                     }
 
-                    class Worker implements IWorker{
+                    final class Worker implements IWorker{
                         public function work(): bool {
                             return true;
                         }
@@ -1137,19 +1155,19 @@ interface IWorker {
                         public function work(): int;
                     }
 
-                    class AbstractWorker implements IWorker {
+                    abstract class AbstractWorker implements IWorker {
                         public function work(): int {
                             return 0;
                         }
                     }
 
-                    class Worker extends AbstractWorker {
+                    final class Worker extends AbstractWorker {
                         public function work(): int {
                             return 1;
                         }
                     }
 
-                    class AnotherWorker extends AbstractWorker {}
+                    final class AnotherWorker extends AbstractWorker {}
 
                     function f(IWorker $worker): void {
                         echo $worker->work();
@@ -1160,7 +1178,7 @@ function f(IWorker $worker): void {
             ],
             'methodReturnValueUsedInThrow' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public function foo() : Exception {
                             return new Exception;
                         }
@@ -1170,7 +1188,7 @@ public function foo() : Exception {
             ],
             'staticMethodReturnValueUsedInThrow' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public static function foo() : Exception {
                             return new Exception;
                         }
@@ -1221,7 +1239,7 @@ function unrelated():void{
             'NotUnusedWhenAssert' => [
                 'code' => '<?php
 
-                    class A {
+                    final class A {
                         public function getVal(?string $val): string {
                             $this->assert($val);
 
@@ -1272,7 +1290,7 @@ public function validate(): void
             ],
             'usedPropertyAsAssignmentKey' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public string $foo = "bar";
                         public array $bar = [];
                     }
@@ -1285,7 +1303,7 @@ class A {
                 'code' => <<<'PHP'
                     <?php
                     /** @psalm-api */
-                    class A {}
+                    final class A {}
                     PHP,
             ],
             'psalm-api with unused public and protected property' => [
@@ -1311,7 +1329,7 @@ protected function c(): void {}
             'psalm-api on unused public method' => [
                 'code' => <<<'PHP'
                     <?php
-                    class A {
+                    final class A {
                         /** @psalm-api */
                         public function b(): void {}
                     }
@@ -1322,13 +1340,13 @@ public function b(): void {}
                 'code' => <<<'PHP'
                     <?php
                     /** @api */
-                    class A {}
+                    final class A {}
                     PHP,
             ],
             'api on unused public method' => [
                 'code' => <<<'PHP'
                     <?php
-                    class A {
+                    final class A {
                         /** @api */
                         public function b(): void {}
                     }
@@ -1375,12 +1393,12 @@ public function providerInvalidCodeParse(): array
         return [
             'unusedClass' => [
                 'code' => '<?php
-                    class A { }',
+                    final class A { }',
                 'error_message' => 'UnusedClass',
             ],
             'publicUnusedMethod' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         /** @return void */
                         public function foo() {}
                     }
@@ -1408,7 +1426,7 @@ function foo(int $i) {}
             ],
             'possiblyUnusedProperty' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         /** @var string */
                         public $foo = "hello";
                     }
@@ -1419,7 +1437,7 @@ class A {
             ],
             'possiblyUnusedPropertyWrittenNeverRead' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         /** @var string */
                         public $foo = "hello";
                     }
@@ -1431,7 +1449,7 @@ class A {
             ],
             'possiblyUnusedPropertyWithArrayWrittenNeverRead' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         /** @var list<string> */
                         public array $foo = [];
                     }
@@ -1443,7 +1461,7 @@ class A {
             ],
             'unusedProperty' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         /** @var string */
                         private $foo = "hello";
                     }
@@ -1454,7 +1472,7 @@ class A {
             ],
             'privateUnusedMethod' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         /** @return void */
                         private function foo() {}
                     }
@@ -1480,7 +1498,7 @@ public function foo() : void {}
 
                         public function bar() : void {}
                     }
-                    class B extends A {
+                    final class B extends A {
                         use T;
                     }
                     function takesA(A $a) : void {
@@ -1491,7 +1509,7 @@ function takesA(A $a) : void {
             ],
             'unusedRecursivelyUsedMethod' => [
                 'code' => '<?php
-                    class C {
+                    final class C {
                         public function foo() : void {
                             if (rand(0, 1)) {
                                 $this->foo();
@@ -1506,7 +1524,7 @@ public function bar() : void {}
             ],
             'unusedRecursivelyUsedStaticMethod' => [
                 'code' => '<?php
-                    class C {
+                    final class C {
                         public static function foo() : void {
                             if (rand(0, 1)) {
                                 self::foo();
@@ -1549,7 +1567,7 @@ class A {
                         public $foo = "hello";
                     }
 
-                    class B extends A {
+                    final class B extends A {
                         /** @var string */
                         public $foo = "goodbye";
                     }
@@ -1559,7 +1577,7 @@ class B extends A {
             ],
             'propertyUsedOnlyInConstructor' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         /** @var int */
                         private $used;
 
@@ -1588,7 +1606,7 @@ public function handle(): void
                     /**
                      * @psalm-external-mutation-free
                      */
-                    class A {
+                    final class A {
                         private string $foo;
 
                         public function __construct(string $foo) {
@@ -1610,7 +1628,7 @@ function foo() : void {
                     /**
                      * @psalm-external-mutation-free
                      */
-                    class A {
+                    final class A {
                         private string $foo;
 
                         public function __construct(string $foo) {
@@ -1636,7 +1654,7 @@ function foo() : void {
             ],
             'annotatedMutationFreeUnused' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         private string $s;
 
                         public function __construct(string $s) {
@@ -1664,7 +1682,7 @@ function foo(DateTimeImmutable $dt) : void {
                 'code' => '<?php
                     class A {}
 
-                    class AChild extends A {
+                    final class AChild extends A {
                         public function __construct() {
                             self::foo();
                         }
@@ -1752,7 +1770,7 @@ function baz(): string
             ],
             'propertyWrittenButNotRead' => [
                 'code' => '<?php
-                    class A {
+                    final class A {
                         public string $a = "hello";
                         public string $b = "world";
 
@@ -1783,7 +1801,7 @@ interface IWorker {
                         public function work(): bool;
                     }
 
-                    class Worker implements IWorker{
+                    final class Worker implements IWorker{
                         public function work(): bool {
                             return true;
                         }
@@ -1802,7 +1820,7 @@ interface IWorker {
                         public function work(): void;
                     }
 
-                    class Worker implements IWorker {
+                    final class Worker implements IWorker {
                         public function work(): void {}
                     }
 
@@ -1839,7 +1857,7 @@ function f(): void {
             ],
             'methodNeverUnevaluatedCode' => [
                 'code' => '<?php
-                    class A{
+                    final class A{
                         /** @return never */
                         function neverReturns() {
                             die();
@@ -1888,7 +1906,7 @@ public static function f()
                 'code' => <<<'PHP'
                     <?php
                     /** @psalm-api */
-                    class A {
+                    final class A {
                         private int $b = 0;
                     }
                     PHP,
@@ -1908,7 +1926,7 @@ final class A {
                 'code' => <<<'PHP'
                     <?php
                     /** @psalm-api */
-                    class A {
+                    final class A {
                         private function b(): void {}
                     }
                     PHP,
@@ -1954,6 +1972,12 @@ function f(): void {}
                     PHP,
                 'error_message' => 'UnusedDocblockParam',
             ],
+            'nonFinalClass' => [
+                'code' => '<?php
+                    class a {}
+                    new a;',
+                'error_message' => 'ClassMustBeFinal',
+            ],
         ];
     }
 }
diff --git a/tests/UnusedVariableTest.php b/tests/UnusedVariableTest.php
index 03dba56ae84..34a4c261f88 100644
--- a/tests/UnusedVariableTest.php
+++ b/tests/UnusedVariableTest.php
@@ -9,7 +9,7 @@
 
 use const DIRECTORY_SEPARATOR;
 
-class UnusedVariableTest extends TestCase
+final class UnusedVariableTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
     use InvalidCodeAnalysisTestTrait;
diff --git a/tests/ValueOfTest.php b/tests/ValueOfTest.php
index ee9c13b2540..072edec3203 100644
--- a/tests/ValueOfTest.php
+++ b/tests/ValueOfTest.php
@@ -7,7 +7,7 @@
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
 
-class ValueOfTest extends TestCase
+final class ValueOfTest extends TestCase
 {
     use InvalidCodeAnalysisTestTrait;
     use ValidCodeAnalysisTestTrait;
diff --git a/tests/VariadicTest.php b/tests/VariadicTest.php
index f8d67d7626c..5f7fb8480a0 100644
--- a/tests/VariadicTest.php
+++ b/tests/VariadicTest.php
@@ -17,7 +17,7 @@
 use function dirname;
 use function getcwd;
 
-class VariadicTest extends TestCase
+final class VariadicTest extends TestCase
 {
     use ValidCodeAnalysisTestTrait;
 
diff --git a/tests/autoload.php b/tests/autoload.php
index 449bca68efa..92ea18a9aff 100644
--- a/tests/autoload.php
+++ b/tests/autoload.php
@@ -7,3 +7,4 @@
 require __DIR__ . '/../vendor/autoload.php';
 
 BypassFinals::enable();
+BypassFinals::denyPaths(['*tests/fixtures/DummyProject*']);
diff --git a/tests/fixtures/DummyProject/Bar.php b/tests/fixtures/DummyProject/Bar.php
index 16245ebd252..7b114fab336 100644
--- a/tests/fixtures/DummyProject/Bar.php
+++ b/tests/fixtures/DummyProject/Bar.php
@@ -1,7 +1,7 @@
 <?php
 namespace Vimeo\Test\DummyProject;
 
-class Bar
+final class Bar
 {
     use SomeTrait;
 
diff --git a/tests/fixtures/DummyProject/Bat.php b/tests/fixtures/DummyProject/Bat.php
index d88e03c9d37..da83e3478dd 100644
--- a/tests/fixtures/DummyProject/Bat.php
+++ b/tests/fixtures/DummyProject/Bat.php
@@ -1,7 +1,7 @@
 <?php
 namespace Vimeo\Test\DummyProject;
 
-class Bat
+final class Bat
 {
     public function __construct()
     {
diff --git a/tests/fixtures/ModularConfig/Bar.php b/tests/fixtures/ModularConfig/Bar.php
index 16245ebd252..7b114fab336 100644
--- a/tests/fixtures/ModularConfig/Bar.php
+++ b/tests/fixtures/ModularConfig/Bar.php
@@ -1,7 +1,7 @@
 <?php
 namespace Vimeo\Test\DummyProject;
 
-class Bar
+final class Bar
 {
     use SomeTrait;
 
diff --git a/tests/fixtures/ModularConfig/Bat.php b/tests/fixtures/ModularConfig/Bat.php
index d88e03c9d37..da83e3478dd 100644
--- a/tests/fixtures/ModularConfig/Bat.php
+++ b/tests/fixtures/ModularConfig/Bat.php
@@ -1,7 +1,7 @@
 <?php
 namespace Vimeo\Test\DummyProject;
 
-class Bat
+final class Bat
 {
     public function __construct()
     {
diff --git a/tests/fixtures/config_discovery/files_in_lib/lib/Bat.php b/tests/fixtures/config_discovery/files_in_lib/lib/Bat.php
index 5376d1eda64..8184f69600c 100644
--- a/tests/fixtures/config_discovery/files_in_lib/lib/Bat.php
+++ b/tests/fixtures/config_discovery/files_in_lib/lib/Bat.php
@@ -1,6 +1,6 @@
 <?php
 namespace Foo\Bar;
 
-class Bat
+final class Bat
 {
 }
diff --git a/tests/fixtures/config_discovery/files_in_lib/lib/Baz.php b/tests/fixtures/config_discovery/files_in_lib/lib/Baz.php
index 3cd06c60027..476082f70e0 100644
--- a/tests/fixtures/config_discovery/files_in_lib/lib/Baz.php
+++ b/tests/fixtures/config_discovery/files_in_lib/lib/Baz.php
@@ -1,6 +1,6 @@
 <?php
 namespace Foo\Bar;
 
-class Baz
+final class Baz
 {
 }
diff --git a/tests/fixtures/performance/a.test b/tests/fixtures/performance/a.test
index fcb14f8bb41..44b7fbebf9f 100644
--- a/tests/fixtures/performance/a.test
+++ b/tests/fixtures/performance/a.test
@@ -28,7 +28,7 @@ namespace PHPMailer\PHPMailer;
  * @author  Andy Prevost (codeworxtech) <codeworxtech@users.sourceforge.net>
  * @author  Brent R. Matzelle (original founder)
  */
-class PHPMailer
+final class PHPMailer
 {
     const CHARSET_ISO88591 = 'iso-8859-1';
     const CHARSET_UTF8 = 'utf-8';
diff --git a/tests/fixtures/performance/b.test b/tests/fixtures/performance/b.test
index c750465932f..b47ed93ebd3 100644
--- a/tests/fixtures/performance/b.test
+++ b/tests/fixtures/performance/b.test
@@ -28,7 +28,7 @@ namespace PHPMailer\PHPMailer;
  * @author  Andy Prevost (codeworxtech) <codeworxtech@users.sourceforge.net>
  * @author  Brent R. Matzelle (original founder)
  */
-class PHPMailer
+final class PHPMailer
 {
     const CHARSET_ISO88591 = 'iso-8859-1';
     const CHARSET_UTF8 = 'utf-8';