diff --git a/.github/workflows/dependencies.yml b/.github/workflows/dependencies.yml
new file mode 100644
index 0000000..d2ff329
--- /dev/null
+++ b/.github/workflows/dependencies.yml
@@ -0,0 +1,35 @@
+name: Dependencies
+
+permissions:
+    contents: read
+
+on:
+    push:
+        branches:
+            - master
+    pull_request:
+
+env:
+    PHP_VERSION: 7.4
+
+jobs:
+    composer-require-checker:
+        name: Check missing composer requirements
+        runs-on: ubuntu-20.04
+        steps:
+            -   uses: shivammathur/setup-php@v2
+                with:
+                  php-version: ${{ env.PHP_VERSION }}
+                  tools: composer:v2
+            -   uses: actions/checkout@v2
+            -   uses: actions/cache@v2
+                with:
+                    path: vendor
+                    key: composer-${{ runner.os }}-${{ env.PHP_VERSION }}-${{ hashFiles('composer.json') }}
+                    restore-keys: |
+                        composer-${{ runner.os }}-${{ env.PHP_VERSION }}-
+                        composer-${{ runner.os }}-
+            -   run: |
+                    composer install --no-interaction --no-progress --ansi --no-scripts
+                    composer show
+            -   uses: docker://webfactory/composer-require-checker:3.2.0
diff --git a/.github/workflows/fix-cs-php.yml b/.github/workflows/fix-cs-php.yml
index d6104aa..51cc369 100644
--- a/.github/workflows/fix-cs-php.yml
+++ b/.github/workflows/fix-cs-php.yml
@@ -1,6 +1,3 @@
-# Update this by running
-# curl https://gist.githubusercontent.com/mpdude/ca93a185bcbf56eb7e341632ad4f8263/raw/fix-cs-php.yml > .github/workflows/fix-cs-php.yml
-
 on:
     push:
         branches:
@@ -13,7 +10,6 @@ jobs:
     open-pr-for-cs-violations:
         name: PHP-CS-Fixer
         runs-on: ubuntu-20.04
-        if: github.actor != 'dependabot[bot]'
         steps:
             -   name: Checkout code
                 uses: actions/checkout@v2
diff --git a/.github/workflows/lock-symfony-version.sh b/.github/workflows/lock-symfony-version.sh
new file mode 100755
index 0000000..01405b2
--- /dev/null
+++ b/.github/workflows/lock-symfony-version.sh
@@ -0,0 +1,3 @@
+#!/bin/bash
+
+cat <<< $(jq --arg version $VERSION '.require  |= with_entries(if ((.key|test("^symfony/"))) then .value=$version else . end)' < composer.json) > composer.json
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 0000000..c856e59
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,40 @@
+name: Tests
+
+on:
+    push:
+        branches:
+            - master
+    pull_request:
+
+env:
+    SYMFONY_DEPRECATIONS_HELPER: weak
+
+jobs:
+    PHPUnit:
+        runs-on: ubuntu-20.04
+        strategy:
+            fail-fast: false
+            matrix:
+                include:
+                    - { php-version: 7.2, symfony-locked-version: none, dependency-version: prefer-lowest }
+                    - { php-version: 7.4, symfony-locked-version: none, dependency-version: prefer-lowest }
+                    - { php-version: 7.4, symfony-locked-version: none, dependency-version: prefer-stable }
+                    - { php-version: 8.1, symfony-locked-version: none, dependency-version: prefer-stable }
+        name: PHPUnit (PHP ${{matrix.php-version}}, Symfony Version Lock ${{ matrix.symfony-locked-version }}, ${{ matrix.dependency-version }})
+        steps:
+            -   uses: actions/checkout@v2
+            -   uses: shivammathur/setup-php@v2
+                with:
+                  php-version: ${{ matrix.php-version }}
+                  tools: composer:v2
+            -   uses: actions/cache@v2
+                with:
+                    path: vendor
+                    key: composer-${{ runner.os }}-${{ matrix.php-version }}-${{ matrix.symfony-locked-version }}-${{ matrix.dependency-version }}-${{ hashFiles('composer.json') }}
+                    restore-keys: |
+                        composer-${{ runner.os }}-${{ matrix.php-version }}-${{ matrix.symfony-locked-version }}-${{ matrix.dependency-version }}-
+            -   run: VERSION=${{ matrix.symfony-locked-version }} .github/workflows/lock-symfony-version.sh
+                if: matrix.symfony-locked-version != 'none'
+            -   run: composer update --${{ matrix.dependency-version }} --no-interaction --no-scripts --no-progress --ansi
+            -   run: composer show
+            -   run: vendor/bin/phpunit
diff --git a/.gitignore b/.gitignore
index de5b49d..326e565 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
 vendor/
 .php_cs.cache
+.phpunit.result.cache
+composer.lock
diff --git a/composer.json b/composer.json
index b6fab8d..2bbfe68 100644
--- a/composer.json
+++ b/composer.json
@@ -1,43 +1,49 @@
 {
-  "name": "webfactory/http-cache-bundle",
-  "description": "Symfony bundle to ease HTTP cache validation via last modified header",
-  "keywords": [
-    "caching",
-    "http",
-    "304",
-    "notmodified",
-    "ifnotmodifiedsince"
-  ],
-  "license": "MIT",
-  "authors": [
-    {
-      "name": "webfactory GmbH",
-      "email": "info@webfactory.de",
-      "homepage": "http://www.webfactory.de",
-      "role": "Developer"
-    }
-  ],
+    "name": "webfactory/http-cache-bundle",
+    "description": "Symfony bundle to ease HTTP cache validation via last modified header",
+    "keywords": [
+        "caching",
+        "http",
+        "304",
+        "notmodified",
+        "ifnotmodifiedsince"
+    ],
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "webfactory GmbH",
+            "email": "info@webfactory.de",
+            "homepage": "http://www.webfactory.de",
+            "role": "Developer"
+        }
+    ],
 
-  "require": {
-    "php": "^7.1",
-    "symfony/config": "^2.8 || ^3.0 || ^4.0",
-    "symfony/dependency-injection": "^2.8 || ^3.0 || ^4.0",
-    "symfony/http-foundation": "^2.8 || ^3.0 || ^4.0",
-    "symfony/http-kernel": "^2.8 || ^3.0 || ^4.0",
-    "doctrine/annotations": "^1.0"
-  },
+    "require": {
+        "php": "^7.1|8.0.*|8.1.*",
+        "symfony/config": "^4.4 | ^5.0",
+        "symfony/dependency-injection": "^4.4 | ^5.0",
+        "symfony/http-foundation": "^4.4 | ^5.0",
+        "symfony/http-kernel": "^4.4 | ^5.0",
+        "doctrine/annotations": "^1.0"
+    },
 
-  "require-dev": {
-    "phpunit/phpunit": "^4.8.0"
-  },
+    "require-dev": {
+        "phpunit/phpunit": "^8.5|^9.0",
+        "symfony/phpunit-bridge": ">=5.0"
+    },
 
-  "suggest": {
-    "webfactory/wfdmeta-bundle": "Invalidate caches based on meta data tracked with wfDynamic"
-  },
+    "suggest": {
+        "webfactory/wfdmeta-bundle": "Invalidate caches based on meta data tracked with wfDynamic"
+    },
 
-  "autoload": {
-    "psr-4": {
-      "Webfactory\\HttpCacheBundle\\": ""
+    "autoload": {
+        "psr-4": {
+            "Webfactory\\HttpCacheBundle\\": "src"
+        }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "Webfactory\\HttpCacheBundle\\Tests\\": "tests"
+        }
     }
-  }
 }
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 8c665d6..b6cf515 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -4,7 +4,7 @@
          xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/4.8/phpunit.xsd">
     <testsuites>
         <testsuite name="Library Test Suite">
-            <directory>Tests</directory>
+            <directory>tests</directory>
         </testsuite>
     </testsuites>
 
@@ -12,10 +12,10 @@
     <filter>
         <whitelist processUncoveredFilesFromWhitelist="true">
             <directory suffix=".php">src/</directory>
-            <exclude>
-                <directory>vendor</directory>
-                <directory>Tests</directory>
-            </exclude>
         </whitelist>
     </filter>
+
+    <listeners>
+        <listener class="\Symfony\Bridge\PhpUnit\SymfonyTestsListener" />
+    </listeners>
 </phpunit>
diff --git a/DependencyInjection/WebfactoryHttpCacheExtension.php b/src/DependencyInjection/WebfactoryHttpCacheExtension.php
similarity index 100%
rename from DependencyInjection/WebfactoryHttpCacheExtension.php
rename to src/DependencyInjection/WebfactoryHttpCacheExtension.php
diff --git a/NotModified/Annotation/ReplaceWithNotModifiedResponse.php b/src/NotModified/Annotation/ReplaceWithNotModifiedResponse.php
similarity index 100%
rename from NotModified/Annotation/ReplaceWithNotModifiedResponse.php
rename to src/NotModified/Annotation/ReplaceWithNotModifiedResponse.php
diff --git a/NotModified/EventListener.php b/src/NotModified/EventListener.php
similarity index 94%
rename from NotModified/EventListener.php
rename to src/NotModified/EventListener.php
index 5110e00..24d7ddf 100644
--- a/NotModified/EventListener.php
+++ b/src/NotModified/EventListener.php
@@ -14,8 +14,8 @@
 use SplObjectStorage;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Response;
-use Symfony\Component\HttpKernel\Event\FilterControllerEvent;
-use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
+use Symfony\Component\HttpKernel\Event\ControllerEvent;
+use Symfony\Component\HttpKernel\Event\ResponseEvent;
 use Webfactory\HttpCacheBundle\NotModified\Annotation\ReplaceWithNotModifiedResponse;
 
 /**
@@ -58,7 +58,7 @@ public function __construct(Reader $reader, ContainerInterface $container, bool
      * header in the request, replace the determined controller action with a minimal action that just returns an
      * "empty" response with a 304 Not Modified HTTP status code.
      */
-    public function onKernelController(FilterControllerEvent $event)
+    public function onKernelController(ControllerEvent $event)
     {
         $annotation = $this->findAnnotation($event->getController());
         if (!$annotation) {
@@ -94,7 +94,7 @@ public function onKernelController(FilterControllerEvent $event)
      * If a last modified date was determined for the current (master or sub) request, set it to the response so the
      * client can use it for the "If-Modified-Since" header in subsequent requests.
      */
-    public function onKernelResponse(FilterResponseEvent $event)
+    public function onKernelResponse(ResponseEvent $event)
     {
         $request = $event->getRequest();
         $response = $event->getResponse();
diff --git a/NotModified/LastModifiedDeterminator.php b/src/NotModified/LastModifiedDeterminator.php
similarity index 100%
rename from NotModified/LastModifiedDeterminator.php
rename to src/NotModified/LastModifiedDeterminator.php
diff --git a/NotModified/services.xml b/src/NotModified/services.xml
similarity index 100%
rename from NotModified/services.xml
rename to src/NotModified/services.xml
diff --git a/WebfactoryHttpCacheBundle.php b/src/WebfactoryHttpCacheBundle.php
similarity index 100%
rename from WebfactoryHttpCacheBundle.php
rename to src/WebfactoryHttpCacheBundle.php
diff --git a/Tests/NotModified/Annotation/ReplaceWithNotModifiedResponseTest.php b/tests/NotModified/Annotation/ReplaceWithNotModifiedResponseTest.php
similarity index 76%
rename from Tests/NotModified/Annotation/ReplaceWithNotModifiedResponseTest.php
rename to tests/NotModified/Annotation/ReplaceWithNotModifiedResponseTest.php
index 3053528..70ed4b3 100644
--- a/Tests/NotModified/Annotation/ReplaceWithNotModifiedResponseTest.php
+++ b/tests/NotModified/Annotation/ReplaceWithNotModifiedResponseTest.php
@@ -10,8 +10,8 @@
 namespace Webfactory\HttpCacheBundle\Tests\NotModified\Annotation;
 
 use DateTime;
+use PHPUnit\Framework\TestCase;
 use PHPUnit_Framework_MockObject_MockObject;
-use PHPUnit_Framework_TestCase;
 use RuntimeException;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Request;
@@ -21,24 +21,24 @@
 /**
  * Tests for the ReplaceWithNotModifiedResponse annotation.
  */
-final class ReplaceWithNotModifiedResponseTest extends PHPUnit_Framework_TestCase
+final class ReplaceWithNotModifiedResponseTest extends TestCase
 {
     /**
      * @test
      */
     public function lastModifiedDescriptionsCannotBeEmpty()
     {
-        $this->setExpectedException(RuntimeException::class);
+        $this->expectException(RuntimeException::class);
         $annotation = new ReplaceWithNotModifiedResponse(['value' => []]);
         $annotation->determineLastModified(new Request());
     }
 
     /**
      * @test
+     * @doesNotPerformAssertions
      */
     public function stringAsSimpleLastModifiedDescription()
     {
-        $this->setExpectedException(null);
         $annotation = new ReplaceWithNotModifiedResponse(['value' => [MyLastModifedDeterminator::class]]);
         $annotation->determineLastModified(new Request());
     }
@@ -49,7 +49,7 @@ public function stringAsSimpleLastModifiedDescription()
     public function serviceNameAsLastModifiedDescription()
     {
         /** @var ContainerInterface|PHPUnit_Framework_MockObject_MockObject $container */
-        $container = $this->getMock(ContainerInterface::class);
+        $container = $this->createMock(ContainerInterface::class);
         $container->expects($this->once())
             ->method('get')
             ->with('my.service')
@@ -58,16 +58,15 @@ public function serviceNameAsLastModifiedDescription()
         $annotation = new ReplaceWithNotModifiedResponse(['value' => ['@my.service']]);
         $annotation->setContainer($container);
 
-        $this->setExpectedException(null);
         $annotation->determineLastModified(new Request());
     }
 
     /**
      * @test
+     * @doesNotPerformAssertions
      */
     public function arrayAslastModifiedDeterminatorDescriptionWithConstructorArguments()
     {
-        $this->setExpectedException(null);
         $annotation = new ReplaceWithNotModifiedResponse(['value' => [[MyLastModifedDeterminator::class => new DateTime('2000-01-01')]]]);
         $annotation->determineLastModified(new Request());
     }
@@ -77,23 +76,22 @@ public function arrayAslastModifiedDeterminatorDescriptionWithConstructorArgumen
      */
     public function lastModifiedDeterminatorsHaveToImplementInterface()
     {
-        $this->setExpectedException(RuntimeException::class);
+        $this->expectException(RuntimeException::class);
         $annotation = new ReplaceWithNotModifiedResponse(['value' => [FakeLastModifiedDeterminatorWithoutInterface::class]]);
         $annotation->determineLastModified(new Request());
     }
 
     /**
      * @test
+     * @group time-sensitive
      */
     public function determineLastModifiedDeterminesLastModifiedOfOneDeterminator()
     {
         $annotation = new ReplaceWithNotModifiedResponse(['value' => [MyLastModifedDeterminator::class]]);
-        $this->assertEquals(
-            new DateTime(),
-            $annotation->determineLastModified(new Request()),
-            '',
-            $allowedDeltaInSeconds = 3
-        );
+
+        $lastModified = $annotation->determineLastModified(new Request());
+
+        self::assertEquals(DateTime::createFromFormat('U', time()), $lastModified);
     }
 
     /**
@@ -101,11 +99,13 @@ public function determineLastModifiedDeterminesLastModifiedOfOneDeterminator()
      */
     public function determineLastModifiedDeterminesLastModifiedOfMultipleDeterminators()
     {
-        $annotation = new ReplaceWithNotModifiedResponse(['value' => [
-            [MyLastModifedDeterminator::class => new DateTime('2001-01-01')],
-            [MyLastModifedDeterminator::class => new DateTime('2003-01-01')],
-            [MyLastModifedDeterminator::class => new DateTime('2002-01-01')],
-        ]]);
+        $annotation = new ReplaceWithNotModifiedResponse([
+            'value' => [
+                [MyLastModifedDeterminator::class => new DateTime('2001-01-01')],
+                [MyLastModifedDeterminator::class => new DateTime('2003-01-01')],
+                [MyLastModifedDeterminator::class => new DateTime('2002-01-01')],
+            ],
+        ]);
         $this->assertEquals(new DateTime('2003-01-01'), $annotation->determineLastModified(new Request()));
     }
 }
@@ -121,7 +121,7 @@ final class MyLastModifedDeterminator implements LastModifiedDeterminator
 
     public function __construct(DateTime $lastModified = null)
     {
-        $this->lastModified = $lastModified ?: new DateTime();
+        $this->lastModified = $lastModified ?: DateTime::createFromFormat('U', time());
     }
 
     public function getLastModified(Request $request)
diff --git a/Tests/NotModified/EventListenerTest.php b/tests/NotModified/EventListenerTest.php
similarity index 62%
rename from Tests/NotModified/EventListenerTest.php
rename to tests/NotModified/EventListenerTest.php
index f0a7a85..cf9e8ba 100644
--- a/Tests/NotModified/EventListenerTest.php
+++ b/tests/NotModified/EventListenerTest.php
@@ -9,23 +9,28 @@
 
 namespace Webfactory\HttpCacheBundle\Tests\NotModified;
 
+use Closure;
 use DateTime;
 use Doctrine\Common\Annotations\Reader;
-use PHPUnit_Framework_MockObject_MockObject;
-use PHPUnit_Framework_TestCase;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
-use Symfony\Component\HttpKernel\Event\FilterControllerEvent;
-use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
+use Symfony\Component\HttpKernel\Event\ControllerEvent;
+use Symfony\Component\HttpKernel\Event\ResponseEvent;
+use Symfony\Component\HttpKernel\HttpKernelInterface;
+use Symfony\Component\HttpKernel\KernelInterface;
 use Webfactory\HttpCacheBundle\NotModified\Annotation\ReplaceWithNotModifiedResponse;
 use Webfactory\HttpCacheBundle\NotModified\EventListener;
 use Webfactory\HttpCacheBundle\NotModified\LastModifiedDeterminator;
 
 /**
  * Tests for the EventListener.
+ *
+ * @group time-sensitive
  */
-final class EventListenerTest extends PHPUnit_Framework_TestCase
+final class EventListenerTest extends TestCase
 {
     /**
      * System under test.
@@ -34,13 +39,13 @@ final class EventListenerTest extends PHPUnit_Framework_TestCase
      */
     private $eventListener;
 
-    /** @var Reader|PHPUnit_Framework_MockObject_MockObject */
+    /** @var Reader|MockObject */
     private $reader;
 
-    /** @var ContainerInterface|PHPUnit_Framework_MockObject_MockObject */
+    /** @var ContainerInterface|MockObject */
     private $container;
 
-    /** @var FilterControllerEvent|PHPUnit_Framework_MockObject_MockObject */
+    /** @var ControllerEvent|MockObject */
     private $filterControllerEvent;
 
     /** @var Request */
@@ -49,87 +54,105 @@ final class EventListenerTest extends PHPUnit_Framework_TestCase
     /** @var Response */
     private $response;
 
+    private $callable;
+
+    /** @var KernelInterface|MockObject */
+    private $kernel;
+
     /**
      * @see \PHPUnit_Framework_TestCase::setUp()
      */
-    protected function setUp()
+    protected function setUp(): void
     {
+        $this->kernel = $this->createMock(KernelInterface::class);
+        $this->callable = [DummyController::class, 'action'];
         $this->request = new Request();
         $this->response = new Response();
-        $this->filterControllerEvent = $this->getMockBuilder(FilterControllerEvent::class)->disableOriginalConstructor()->getMock();
-        $this->filterControllerEvent->expects($this->any())
-            ->method('getController')
-            ->willReturn([DummyController::class, 'action']);
-        $this->filterControllerEvent->expects($this->any())
-            ->method('getRequest')
-            ->willReturn($this->request);
-
-        $this->reader = $this->getMock(Reader::class);
-        $this->container = $this->getMock(ContainerInterface::class);
+        $this->filterControllerEvent = new ControllerEvent($this->kernel, $this->callable, $this->request, HttpKernelInterface::MASTER_REQUEST);
+        $this->reader = $this->createMock(Reader::class);
+        $this->container = $this->createMock(ContainerInterface::class);
         $this->eventListener = new EventListener($this->reader, $this->container);
     }
 
     /** @test */
-    public function onKernelControllerDoesNoHarmForMissingAnnotation()
+    public function onKernelControllerDoesNoHarmForMissingAnnotation(): void
     {
-        $this->expectRegularControllerResponse();
         $this->setUpAnnotationReaderToReturn(null);
 
         $this->eventListener->onKernelController($this->filterControllerEvent);
+
+        $this->assertRegularControllerResponse();
     }
 
     /** @test */
-    public function onKernelControllerDoesNoHarmForNoDeterminedLastModified()
+    public function onKernelControllerDoesNoHarmForNoDeterminedLastModified(): void
     {
         $this->setUpAnnotationReaderToReturn(new ReplaceWithNotModifiedResponse(['value' => [AbstainingLastModifiedDeterminator::class]]));
-        $this->expectRegularControllerResponse();
 
         $this->eventListener->onKernelController($this->filterControllerEvent);
+
+        $this->assertRegularControllerResponse();
     }
 
     /** @test */
-    public function onKernelControllerDoesNoHarmIfNotModifiedSinceHeaderIsNotInRequest()
+    public function onKernelControllerDoesNoHarmIfNotModifiedSinceHeaderIsNotInRequest(): void
     {
         $this->setUpAnnotationReaderToReturn(new ReplaceWithNotModifiedResponse(['value' => [OneDayAgoModifiedLastModifiedDeterminator::class]]));
-        $this->expectRegularControllerResponse();
 
         $this->eventListener->onKernelController($this->filterControllerEvent);
+
+        $this->assertRegularControllerResponse();
     }
 
     /** @test */
-    public function onKernelControllerSkipsToModifiedResponseIfLastModifiedIsSmallerThanIfNotModifiedSinceHeader()
+    public function onKernelControllerSkipsToModifiedResponseIfLastModifiedIsSmallerThanIfNotModifiedSinceHeader(): void
     {
         $this->setUpAnnotationReaderToReturn(new ReplaceWithNotModifiedResponse(['value' => [OneDayAgoModifiedLastModifiedDeterminator::class]]));
         $this->request->headers->set('If-Modified-Since', '-1 hour');
-        $this->expectNotModifiedResponse();
 
         $this->eventListener->onKernelController($this->filterControllerEvent);
+
+        $this->assertNotModifiedResponse();
     }
 
     /** @test */
-    public function onKernelControllerSkipsToNotModifiedResponseIfLastModifiedIsEqualToIfNotModifiedSinceHeader()
+    public function onKernelControllerAlwaysRunsControllerInKernelDebugMode(): void
+    {
+        $this->eventListener = new EventListener($this->reader, $this->container, true);
+        $this->setUpAnnotationReaderToReturn(new ReplaceWithNotModifiedResponse(['value' => [OneDayAgoModifiedLastModifiedDeterminator::class]]));
+        $this->request->headers->set('If-Modified-Since', '-1 hour');
+
+        $this->eventListener->onKernelController($this->filterControllerEvent);
+
+        $this->assertRegularControllerResponse();
+    }
+
+    /** @test */
+    public function onKernelControllerSkipsToNotModifiedResponseIfLastModifiedIsEqualToIfNotModifiedSinceHeader(): void
     {
         $this->setUpAnnotationReaderToReturn(new ReplaceWithNotModifiedResponse(['value' => [FixedDateAgoModifiedLastModifiedDeterminator::class]]));
         $this->request->headers->set('If-Modified-Since', '2000-01-01');
-        $this->expectNotModifiedResponse();
 
         $this->eventListener->onKernelController($this->filterControllerEvent);
+
+        $this->assertNotModifiedResponse();
     }
 
     /** @test */
-    public function onKernelControllerDoesNotReplaceDeterminedControllerIfLastModifiedIsGreaterThanIfNotModifiedSinceHeader()
+    public function onKernelControllerDoesNotReplaceDeterminedControllerIfLastModifiedIsGreaterThanIfNotModifiedSinceHeader(): void
     {
         $this->setUpAnnotationReaderToReturn(new ReplaceWithNotModifiedResponse(['value' => [OneDayAgoModifiedLastModifiedDeterminator::class]]));
         $this->request->headers->set('If-Modified-Since', '-2 day');
-        $this->expectRegularControllerResponse();
 
         $this->eventListener->onKernelController($this->filterControllerEvent);
+
+        $this->assertRegularControllerResponse();
     }
 
     /**
      * @test
      */
-    public function onKernelResponseSetsLastModifiedHeaderToResponseIfAvailable()
+    public function onKernelResponseSetsLastModifiedHeaderToResponseIfAvailable(): void
     {
         $this->setUpAnnotationReaderToReturn(new ReplaceWithNotModifiedResponse(['value' => [OneDayAgoModifiedLastModifiedDeterminator::class]]));
         $this->eventListener->onKernelController($this->filterControllerEvent);
@@ -137,11 +160,11 @@ public function onKernelResponseSetsLastModifiedHeaderToResponseIfAvailable()
         $filterResponseEvent = $this->createFilterResponseEvent($this->filterControllerEvent->getRequest(), $this->response);
         $this->eventListener->onKernelResponse($filterResponseEvent);
 
-        $this->assertNotNull($this->response->getLastModified());
+        self::assertEquals(DateTime::createFromFormat('U', time() - 86400), $this->response->getLastModified());
     }
 
     /** @test */
-    public function onKernelResponseDoesNotSetLastModifiedHeaderToResponseIfNotAvailable()
+    public function onKernelResponseDoesNotSetLastModifiedHeaderToResponseIfNotAvailable(): void
     {
         $this->setUpAnnotationReaderToReturn(new ReplaceWithNotModifiedResponse(['value' => [AbstainingLastModifiedDeterminator::class]]));
         $this->eventListener->onKernelController($this->filterControllerEvent);
@@ -149,11 +172,11 @@ public function onKernelResponseDoesNotSetLastModifiedHeaderToResponseIfNotAvail
         $filterResponseEvent = $this->createFilterResponseEvent($this->filterControllerEvent->getRequest(), $this->response);
         $this->eventListener->onKernelResponse($filterResponseEvent);
 
-        $this->assertNull($this->response->getLastModified());
+        self::assertNull($this->response->getLastModified());
     }
 
     /** @test */
-    public function eventListenerDifferentiatesBetweenMultipleRequests()
+    public function eventListenerDifferentiatesBetweenMultipleRequests(): void
     {
         $this->setUpAnnotationReaderToReturn(new ReplaceWithNotModifiedResponse(['value' => [OneDayAgoModifiedLastModifiedDeterminator::class]]));
         $this->eventListener->onKernelController($this->filterControllerEvent);
@@ -161,58 +184,49 @@ public function eventListenerDifferentiatesBetweenMultipleRequests()
         // first request - should get a last modified
         $filterResponseEvent = $this->createFilterResponseEvent($this->filterControllerEvent->getRequest(), $this->response);
         $this->eventListener->onKernelResponse($filterResponseEvent);
-        $this->assertNotNull($this->response->getLastModified());
+        self::assertNotNull($this->response->getLastModified());
 
         // event for another request - it's response should not get a last modified
         $anotherRequest = new Request();
         $anotherResponse = new Response();
         $anotherFilterResponseEvent = $this->createFilterResponseEvent($anotherRequest, $anotherResponse);
         $this->eventListener->onKernelResponse($anotherFilterResponseEvent);
-        $this->assertNull($anotherResponse->getLastModified());
+        self::assertNull($anotherResponse->getLastModified());
     }
 
     /**
      * @param object|null $annotation
      */
-    private function setUpAnnotationReaderToReturn($annotation = null)
+    private function setUpAnnotationReaderToReturn($annotation = null): void
     {
-        $this->reader->expects($this->any())
-            ->method('getMethodAnnotation')
-            ->willReturn($annotation);
+        $this->reader->method('getMethodAnnotation')->willReturn($annotation);
     }
 
-    private function expectRegularControllerResponse()
+    private function assertRegularControllerResponse(): void
     {
-        $this->filterControllerEvent->expects($this->never())
-            ->method('setController');
+        self::assertSame($this->callable, $this->filterControllerEvent->getController());
     }
 
-    private function expectNotModifiedResponse()
+    private function assertNotModifiedResponse(): void
     {
-        $this->filterControllerEvent->expects($this->once())
-            ->method('setController');
+        $closure = $this->filterControllerEvent->getController();
+
+        self::assertInstanceOf(Closure::class, $closure);
+
+        $response = $closure();
+        self::assertInstanceOf(Response::class, $response);
+        self::assertSame(304, $response->getStatusCode());
     }
 
-    /**
-     * @return PHPUnit_Framework_MockObject_MockObject|FilterResponseEvent
-     */
-    private function createFilterResponseEvent(Request $request, Response $response)
+    private function createFilterResponseEvent(Request $request, Response $response): ResponseEvent
     {
-        $filterResponseEvent = $this->getMockBuilder(FilterResponseEvent::class)->disableOriginalConstructor()->getMock();
-        $filterResponseEvent->expects($this->any())
-            ->method('getRequest')
-            ->willReturn($request);
-        $filterResponseEvent->expects($this->any())
-            ->method('getResponse')
-            ->willReturn($response);
-
-        return $filterResponseEvent;
+        return new ResponseEvent($this->kernel, $request, HttpKernelInterface::MASTER_REQUEST, $response);
     }
 }
 
 final class DummyController
 {
-    public function action()
+    public static function action(): Response
     {
         return new Response();
     }
@@ -220,7 +234,7 @@ public function action()
 
 final class AbstainingLastModifiedDeterminator implements LastModifiedDeterminator
 {
-    public function getLastModified(Request $request)
+    public function getLastModified(Request $request): ?DateTime
     {
         return null;
     }
@@ -228,15 +242,15 @@ public function getLastModified(Request $request)
 
 final class OneDayAgoModifiedLastModifiedDeterminator implements LastModifiedDeterminator
 {
-    public function getLastModified(Request $request)
+    public function getLastModified(Request $request): DateTime
     {
-        return new DateTime('-1 day');
+        return DateTime::createFromFormat('U', time() - 86400);
     }
 }
 
 final class FixedDateAgoModifiedLastModifiedDeterminator implements LastModifiedDeterminator
 {
-    public function getLastModified(Request $request)
+    public function getLastModified(Request $request): DateTime
     {
         return new DateTime('2000-01-01');
     }