diff --git a/Tests/CacheWarmer/SerializerCacheWarmerTest.php b/Tests/CacheWarmer/SerializerCacheWarmerTest.php
index 85dbd8810..5feb0c8ec 100644
--- a/Tests/CacheWarmer/SerializerCacheWarmerTest.php
+++ b/Tests/CacheWarmer/SerializerCacheWarmerTest.php
@@ -40,7 +40,7 @@ public function testWarmUp(array $loaders)
         $this->assertTrue($arrayPool->getItem('Symfony_Bundle_FrameworkBundle_Tests_Fixtures_Serialization_Author')->isHit());
     }
 
-    public static function loaderProvider()
+    public static function loaderProvider(): array
     {
         return [
             [
diff --git a/Tests/Command/CachePoolClearCommandTest.php b/Tests/Command/CachePoolClearCommandTest.php
index cc4573faf..08e2766d9 100644
--- a/Tests/Command/CachePoolClearCommandTest.php
+++ b/Tests/Command/CachePoolClearCommandTest.php
@@ -44,7 +44,7 @@ public function testComplete(array $input, array $expectedSuggestions)
         $this->assertSame($expectedSuggestions, $suggestions);
     }
 
-    public static function provideCompletionSuggestions()
+    public static function provideCompletionSuggestions(): iterable
     {
         yield 'pool_name' => [
             ['f'],
diff --git a/Tests/Command/CachePoolDeleteCommandTest.php b/Tests/Command/CachePoolDeleteCommandTest.php
index 7cd236670..41f7b6643 100644
--- a/Tests/Command/CachePoolDeleteCommandTest.php
+++ b/Tests/Command/CachePoolDeleteCommandTest.php
@@ -98,7 +98,7 @@ public function testComplete(array $input, array $expectedSuggestions)
         $this->assertSame($expectedSuggestions, $suggestions);
     }
 
-    public static function provideCompletionSuggestions()
+    public static function provideCompletionSuggestions(): iterable
     {
         yield 'pool_name' => [
             ['f'],
diff --git a/Tests/Command/EventDispatcherDebugCommandTest.php b/Tests/Command/EventDispatcherDebugCommandTest.php
index 9bc054f22..61c50a7bc 100644
--- a/Tests/Command/EventDispatcherDebugCommandTest.php
+++ b/Tests/Command/EventDispatcherDebugCommandTest.php
@@ -31,7 +31,7 @@ public function testComplete(array $input, array $expectedSuggestions)
         $this->assertSame($expectedSuggestions, $suggestions);
     }
 
-    public static function provideCompletionSuggestions()
+    public static function provideCompletionSuggestions(): iterable
     {
         yield 'event' => [[''], ['Symfony\Component\Mailer\Event\MessageEvent', 'console.command']];
         yield 'event for other dispatcher' => [['--dispatcher', 'other_event_dispatcher', ''], ['other_event', 'App\OtherEvent']];
diff --git a/Tests/Command/SecretsRemoveCommandTest.php b/Tests/Command/SecretsRemoveCommandTest.php
index 88c247ec6..2c12b6128 100644
--- a/Tests/Command/SecretsRemoveCommandTest.php
+++ b/Tests/Command/SecretsRemoveCommandTest.php
@@ -37,7 +37,7 @@ public function testComplete(bool $withLocalVault, array $input, array $expected
         $this->assertSame($expectedSuggestions, $suggestions);
     }
 
-    public static function provideCompletionSuggestions()
+    public static function provideCompletionSuggestions(): iterable
     {
         yield 'name' => [true, [''], ['SECRET', 'OTHER_SECRET']];
         yield '--local name (with local vault)' => [true, ['--local', ''], ['SECRET']];
diff --git a/Tests/Command/SecretsSetCommandTest.php b/Tests/Command/SecretsSetCommandTest.php
index 8e8e968c8..678fb417c 100644
--- a/Tests/Command/SecretsSetCommandTest.php
+++ b/Tests/Command/SecretsSetCommandTest.php
@@ -32,7 +32,7 @@ public function testComplete(array $input, array $expectedSuggestions)
         $this->assertSame($expectedSuggestions, $suggestions);
     }
 
-    public static function provideCompletionSuggestions()
+    public static function provideCompletionSuggestions(): iterable
     {
         yield 'name' => [[''], ['SECRET', 'OTHER_SECRET']];
         yield '--local name (with local vault)' => [['--local', ''], ['SECRET', 'OTHER_SECRET']];
diff --git a/Tests/Command/TranslationDebugCommandTest.php b/Tests/Command/TranslationDebugCommandTest.php
index 846abd445..e3ac1066a 100644
--- a/Tests/Command/TranslationDebugCommandTest.php
+++ b/Tests/Command/TranslationDebugCommandTest.php
@@ -269,7 +269,7 @@ function ($path, $catalogue) use ($extractedMessagesWithDomains) {
         $this->assertSame($expectedSuggestions, $suggestions);
     }
 
-    public static function provideCompletionSuggestions()
+    public static function provideCompletionSuggestions(): iterable
     {
         yield 'locale' => [
             [''],
diff --git a/Tests/Command/TranslationUpdateCommandCompletionTest.php b/Tests/Command/TranslationUpdateCommandCompletionTest.php
index 91999d288..6992ade4d 100644
--- a/Tests/Command/TranslationUpdateCommandCompletionTest.php
+++ b/Tests/Command/TranslationUpdateCommandCompletionTest.php
@@ -42,7 +42,7 @@ public function testComplete(array $input, array $expectedSuggestions)
         $this->assertSame($expectedSuggestions, $suggestions);
     }
 
-    public static function provideCompletionSuggestions()
+    public static function provideCompletionSuggestions(): iterable
     {
         $bundle = new ExtensionPresentBundle();
 
diff --git a/Tests/Controller/AbstractControllerTest.php b/Tests/Controller/AbstractControllerTest.php
index d8dc199d8..2de0f7c91 100644
--- a/Tests/Controller/AbstractControllerTest.php
+++ b/Tests/Controller/AbstractControllerTest.php
@@ -409,7 +409,7 @@ public function testdenyAccessUnlessGrantedSetsAttributesAsArray($attribute, $ex
         }
     }
 
-    public static function provideDenyAccessUnlessGrantedSetsAttributesAsArray()
+    public static function provideDenyAccessUnlessGrantedSetsAttributesAsArray(): array
     {
         $obj = new \stdClass();
         $obj->foo = 'bar';
diff --git a/Tests/Controller/RedirectControllerTest.php b/Tests/Controller/RedirectControllerTest.php
index de72396df..b2da9ef58 100644
--- a/Tests/Controller/RedirectControllerTest.php
+++ b/Tests/Controller/RedirectControllerTest.php
@@ -103,7 +103,7 @@ public function testRoute($permanent, $keepRequestMethod, $keepQueryParams, $ign
         $this->assertEquals($expectedCode, $returnResponse->getStatusCode());
     }
 
-    public static function provider()
+    public static function provider(): array
     {
         return [
             [true, false, false, false, 301, ['additional-parameter' => 'value']],
@@ -210,7 +210,7 @@ public function testUrlRedirectDefaultPorts()
         $this->assertRedirectUrl($returnValue, $expectedUrl);
     }
 
-    public static function urlRedirectProvider()
+    public static function urlRedirectProvider(): array
     {
         return [
             // Standard ports
@@ -262,7 +262,7 @@ public function testUrlRedirect($scheme, $httpPort, $httpsPort, $requestScheme,
         $this->assertRedirectUrl($returnValue, $expectedUrl);
     }
 
-    public static function pathQueryParamsProvider()
+    public static function pathQueryParamsProvider(): array
     {
         return [
             ['http://www.example.com/base/redirect-path', '/redirect-path',  ''],
diff --git a/Tests/Controller/TemplateControllerTest.php b/Tests/Controller/TemplateControllerTest.php
index e567342ec..c403a4c59 100644
--- a/Tests/Controller/TemplateControllerTest.php
+++ b/Tests/Controller/TemplateControllerTest.php
@@ -32,13 +32,23 @@ public function testTwig()
         $this->assertEquals('bar', $controller('mytemplate')->getContent());
     }
 
-    public function testNoTwig()
+    public function testNoTwigTemplateActionMethod()
     {
+        $controller = new TemplateController();
+
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('You cannot use the TemplateController if the Twig Bundle is not available.');
-        $controller = new TemplateController();
 
         $controller->templateAction('mytemplate')->getContent();
+    }
+
+    public function testNoTwigInvokeMethod()
+    {
+        $controller = new TemplateController();
+
+        $this->expectException(\LogicException::class);
+        $this->expectExceptionMessage('You cannot use the TemplateController if the Twig Bundle is not available.');
+
         $controller('mytemplate')->getContent();
     }
 
diff --git a/Tests/DependencyInjection/ConfigurationTest.php b/Tests/DependencyInjection/ConfigurationTest.php
index 47b66baf3..41f3d7482 100644
--- a/Tests/DependencyInjection/ConfigurationTest.php
+++ b/Tests/DependencyInjection/ConfigurationTest.php
@@ -113,7 +113,7 @@ public function testValidAssetsPackageNameConfiguration($packageName)
         $this->assertArrayHasKey($packageName, $config['assets']['packages']);
     }
 
-    public static function provideValidAssetsPackageNameConfigurationTests()
+    public static function provideValidAssetsPackageNameConfigurationTests(): array
     {
         return [
             ['foobar'],
@@ -139,7 +139,7 @@ public function testInvalidAssetsConfiguration(array $assetConfig, $expectedMess
             ]);
     }
 
-    public static function provideInvalidAssetConfigurationTests()
+    public static function provideInvalidAssetConfigurationTests(): iterable
     {
         // helper to turn config into embedded package config
         $createPackageConfig = function (array $packageConfig) {
@@ -192,7 +192,7 @@ public function testValidLockConfiguration($lockConfig, $processedConfig)
         $this->assertEquals($processedConfig, $config['lock']);
     }
 
-    public static function provideValidLockConfigurationTests()
+    public static function provideValidLockConfigurationTests(): iterable
     {
         yield [null, ['enabled' => true, 'resources' => ['default' => [class_exists(SemaphoreStore::class) && SemaphoreStore::isSupported() ? 'semaphore' : 'flock']]]];
 
diff --git a/Tests/Functional/ContainerDebugCommandTest.php b/Tests/Functional/ContainerDebugCommandTest.php
index 63c717b7b..01d0727a2 100644
--- a/Tests/Functional/ContainerDebugCommandTest.php
+++ b/Tests/Functional/ContainerDebugCommandTest.php
@@ -204,7 +204,7 @@ public function testGetDeprecationNoFile()
         $this->assertStringContainsString('[WARNING] The deprecation file does not exist', $tester->getDisplay());
     }
 
-    public static function provideIgnoreBackslashWhenFindingService()
+    public static function provideIgnoreBackslashWhenFindingService(): array
     {
         return [
             [BackslashClass::class],
@@ -232,7 +232,7 @@ public function testComplete(array $input, array $expectedSuggestions, array $no
         }
     }
 
-    public static function provideCompletionSuggestions()
+    public static function provideCompletionSuggestions(): iterable
     {
         $serviceId = 'console.command.container_debug';
         $hiddenServiceId = '.console.command.container_debug.lazy';
diff --git a/Tests/Functional/RouterDebugCommandTest.php b/Tests/Functional/RouterDebugCommandTest.php
index 6b8eb6b7f..58130ad42 100644
--- a/Tests/Functional/RouterDebugCommandTest.php
+++ b/Tests/Functional/RouterDebugCommandTest.php
@@ -100,7 +100,7 @@ public function testComplete(array $input, array $expectedSuggestions)
         $this->assertSame($expectedSuggestions, $tester->complete($input));
     }
 
-    public static function provideCompletionSuggestions()
+    public static function provideCompletionSuggestions(): iterable
     {
         yield 'option --format' => [
             ['--format', ''],