diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 571924a2..3e120cc7 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -14,11 +14,7 @@
 
     <filter>
         <whitelist>
-            <directory>.</directory>
-            <exclude>
-                <directory>tests</directory>
-                <directory>vendor</directory>
-            </exclude>
+            <directory>src</directory>
         </whitelist>
     </filter>
 </phpunit>
diff --git a/tests/AnnotationGenerator/ApiPlatformCoreAnnotationGeneratorTest.php b/tests/AnnotationGenerator/ApiPlatformCoreAnnotationGeneratorTest.php
index a2ea8f2d..1da55e81 100644
--- a/tests/AnnotationGenerator/ApiPlatformCoreAnnotationGeneratorTest.php
+++ b/tests/AnnotationGenerator/ApiPlatformCoreAnnotationGeneratorTest.php
@@ -59,23 +59,23 @@ protected function setUp(): void
         );
     }
 
-    public function testGenerateClassAnnotations()
+    public function testGenerateClassAnnotations(): void
     {
         $this->assertSame(['@ApiResource(iri="http://schema.org/Res")'], $this->generator->generateClassAnnotations('Res'));
     }
 
-    public function testGenerateClassAnnotationsWithOperations()
+    public function testGenerateClassAnnotationsWithOperations(): void
     {
         $this->assertSame(['@ApiResource(iri="http://schema.org/WithOperations", itemOperations={"get"={"route_name"="api_about_get"}}, collectionOperations={})'], $this->generator->generateClassAnnotations('WithOperations'));
     }
 
-    public function testGenerateFieldAnnotations()
+    public function testGenerateFieldAnnotations(): void
     {
         $this->assertSame(['@ApiProperty(iri="http://schema.org/prop")'], $this->generator->generateFieldAnnotations('Res', 'prop'));
         $this->assertSame([], $this->generator->generateFieldAnnotations('Res', 'customProp'));
     }
 
-    public function testGenerateUses()
+    public function testGenerateUses(): void
     {
         $this->assertSame(['ApiPlatform\Core\Annotation\ApiResource', 'ApiPlatform\Core\Annotation\ApiProperty'], $this->generator->generateUses('Res'));
         $this->assertSame([], $this->generator->generateUses('MyEnum'));
diff --git a/tests/AnnotationGenerator/DoctrineOrmAnnotationGeneratorTest.php b/tests/AnnotationGenerator/DoctrineOrmAnnotationGeneratorTest.php
index 216c3150..526436dc 100644
--- a/tests/AnnotationGenerator/DoctrineOrmAnnotationGeneratorTest.php
+++ b/tests/AnnotationGenerator/DoctrineOrmAnnotationGeneratorTest.php
@@ -28,7 +28,7 @@ class DoctrineOrmAnnotationGeneratorTest extends TestCase
      */
     private $generator;
 
-    public function setUp()
+    protected function setUp(): void
     {
         $graph = new \EasyRdf_Graph();
         $myEnum = new \EasyRdf_Resource('https://schema.org/MyEnum', $graph);
@@ -79,7 +79,7 @@ public function setUp()
         );
     }
 
-    public function testGenerateClassAnnotations()
+    public function testGenerateClassAnnotations(): void
     {
         $this->assertSame([], $this->generator->generateClassAnnotations('MyEnum'));
         $this->assertSame(['', '@ORM\MappedSuperclass'], $this->generator->generateClassAnnotations('Product'));
@@ -87,7 +87,7 @@ public function testGenerateClassAnnotations()
         $this->assertSame(['', '@ORM\Embeddable'], $this->generator->generateClassAnnotations('QuantitativeValue'));
     }
 
-    public function testGenerateFieldAnnotations()
+    public function testGenerateFieldAnnotations(): void
     {
         $this->assertSame(
             ['@ORM\Embedded(class="QuantitativeValue", columnPrefix=false)'],
diff --git a/tests/Command/DumpConfigurationTest.php b/tests/Command/DumpConfigurationTest.php
index 1a9b72e2..9000a884 100644
--- a/tests/Command/DumpConfigurationTest.php
+++ b/tests/Command/DumpConfigurationTest.php
@@ -22,7 +22,7 @@
  */
 class DumpConfigurationTest extends TestCase
 {
-    public function testDumpConfiguration()
+    public function testDumpConfiguration(): void
     {
         $commandTester = new CommandTester(new DumpConfigurationCommand());
         $this->assertEquals(0, $commandTester->execute([]));
diff --git a/tests/Command/ExtractCardinalitiesCommandTest.php b/tests/Command/ExtractCardinalitiesCommandTest.php
index fb3ba6a1..419604f2 100644
--- a/tests/Command/ExtractCardinalitiesCommandTest.php
+++ b/tests/Command/ExtractCardinalitiesCommandTest.php
@@ -22,7 +22,7 @@
  */
 class ExtractCardinalitiesCommandTest extends TestCase
 {
-    public function testExtractCardinalities()
+    public function testExtractCardinalities(): void
     {
         $commandTester = new CommandTester(new ExtractCardinalitiesCommand());
         $this->assertEquals(0, $commandTester->execute(
diff --git a/tests/Command/GenerateTypesCommandTest.php b/tests/Command/GenerateTypesCommandTest.php
index 2a9c7ea8..b8d2a626 100644
--- a/tests/Command/GenerateTypesCommandTest.php
+++ b/tests/Command/GenerateTypesCommandTest.php
@@ -36,7 +36,7 @@ protected function setUp(): void
     /**
      * @dataProvider getArguments
      */
-    public function testCommand($output, $config)
+    public function testCommand($output, $config): void
     {
         $this->fs->mkdir($output);
 
@@ -44,7 +44,7 @@ public function testCommand($output, $config)
         $this->assertEquals(0, $commandTester->execute(['output' => $output, 'config' => $config]));
     }
 
-    public function getArguments()
+    public function getArguments(): array
     {
         return [
             [__DIR__.'/../../build/blog/', __DIR__.'/../config/blog.yaml'],
@@ -55,7 +55,7 @@ public function getArguments()
         ];
     }
 
-    public function testDoctrineCollection()
+    public function testDoctrineCollection(): void
     {
         $outputDir = __DIR__.'/../../build/address-book';
         $config = __DIR__.'/../config/address-book.yaml';
@@ -78,7 +78,7 @@ public function getFriends(): Collection
         , $person);
     }
 
-    public function testFluentMutators()
+    public function testFluentMutators(): void
     {
         $outputDir = __DIR__.'/../../build/fluent-mutators';
         $config = __DIR__.'/../config/fluent-mutators.yaml';
@@ -115,7 +115,7 @@ public function removeFriend(Person $friend): self
             , $person);
     }
 
-    public function testDoNotGenerateAccessorMethods()
+    public function testDoNotGenerateAccessorMethods(): void
     {
         $outputDir = __DIR__.'/../../build/public-properties';
         $config = __DIR__.'/../config/public-properties.yaml';
@@ -132,7 +132,7 @@ public function testDoNotGenerateAccessorMethods()
         $this->assertNotContains('function remove', $person);
     }
 
-    public function testImplicitAndExplicitPropertyInheritance()
+    public function testImplicitAndExplicitPropertyInheritance(): void
     {
         $outputDir = __DIR__.'/../../build/inherited-properties';
         $config = __DIR__.'/../config/inherited-properties.yaml';
@@ -164,7 +164,7 @@ public function testImplicitAndExplicitPropertyInheritance()
         $this->assertNotContains('function setName(', $webPage);
     }
 
-    public function testReadableWritable()
+    public function testReadableWritable(): void
     {
         $outputDir = __DIR__.'/../../build/readable-writable';
         $config = __DIR__.'/../config/readable-writable.yaml';
@@ -184,7 +184,7 @@ public function testReadableWritable()
         $this->assertNotContains('function removeFriend(', $person);
     }
 
-    public function testGeneratedId()
+    public function testGeneratedId(): void
     {
         $outputDir = __DIR__.'/../../build/generated-id';
         $config = __DIR__.'/../config/generated-id.yaml';
@@ -219,7 +219,7 @@ public function getId(): ?int
         $this->assertNotContains('function setId(', $person);
     }
 
-    public function testNonGeneratedId()
+    public function testNonGeneratedId(): void
     {
         $outputDir = __DIR__.'/../../build/non-generated-id';
         $config = __DIR__.'/../config/non-generated-id.yaml';
@@ -253,7 +253,7 @@ public function getId(): string
         $this->assertContains('public function setId(string $id): void', $person);
     }
 
-    public function testGeneratedUuid()
+    public function testGeneratedUuid(): void
     {
         $outputDir = __DIR__.'/../../build/generated-uuid';
         $config = __DIR__.'/../config/generated-uuid.yaml';
@@ -289,7 +289,7 @@ public function getId(): ?string
         $this->assertNotContains('function setId(', $person);
     }
 
-    public function testNonGeneratedUuid()
+    public function testNonGeneratedUuid(): void
     {
         $outputDir = __DIR__.'/../../build/non-generated-uuid';
         $config = __DIR__.'/../config/non-generated-uuid.yaml';
@@ -324,7 +324,7 @@ public function getId(): string
         $this->assertContains('public function setId(string $id): void', $person);
     }
 
-    public function testDoNotGenerateId()
+    public function testDoNotGenerateId(): void
     {
         $outputDir = __DIR__.'/../../build/no-id';
         $config = __DIR__.'/../config/no-id.yaml';
@@ -341,7 +341,7 @@ public function testDoNotGenerateId()
         $this->assertNotContains('function setId', $person);
     }
 
-    public function testNamespacesPrefix()
+    public function testNamespacesPrefix(): void
     {
         $outputDir = __DIR__.'/../../build/namespaces-prefix';
         $config = __DIR__.'/../config/namespaces-prefix.yaml';
@@ -356,7 +356,7 @@ public function testNamespacesPrefix()
         $this->assertContains('namespace App\Entity;', $person);
     }
 
-    public function testNamespacesPrefixAutodetect()
+    public function testNamespacesPrefixAutodetect(): void
     {
         $outputDir = __DIR__.'/../../build/namespaces-prefix-autodetect/';
 
@@ -378,7 +378,7 @@ public function testNamespacesPrefixAutodetect()
         }
     }
 
-    public function testGeneratedEnum()
+    public function testGeneratedEnum(): void
     {
         $outputDir = __DIR__.'/../../build/enum';
         $config = __DIR__.'/../config/enum.yaml';
@@ -401,7 +401,7 @@ public function testGeneratedEnum()
         $this->assertNotContains('function setId(', $gender);
     }
 
-    public function testSupersededProperties()
+    public function testSupersededProperties(): void
     {
         $outputDir = __DIR__.'/../../build/superseded-properties';
         $config = __DIR__.'/../config/superseded-properties.yaml';
diff --git a/tests/TypesGeneratorTest.php b/tests/TypesGeneratorTest.php
index 04601020..29465374 100644
--- a/tests/TypesGeneratorTest.php
+++ b/tests/TypesGeneratorTest.php
@@ -390,7 +390,7 @@ private function getClasses(): array
      *
      * @return \Closure
      */
-    private function getContextMatcher(array $class)
+    private function getContextMatcher(array $class): \Closure
     {
         $config = $this->getConfig();