diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..4283b9a
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,64 @@
+name: CI
+
+on: [push, pull_request]
+
+jobs:
+  testsuite:
+
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        TYPO3: [ '11' , '12', '13']
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Set up PHP Version
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 8.1
+          tools: composer:v2
+
+      - name: Start MySQL
+        run: sudo /etc/init.d/mysql start
+
+      - name: Validate composer.json and composer.lock
+        run: composer validate
+
+      - name: Cache dependencies
+        uses: actions/cache@v1
+        with:
+          path: ~/.composer/cache
+          key: dependencies-composer-${{ hashFiles('composer.json') }}
+
+      - name: Install composer dependencies TYPO3 13
+        if: matrix.TYPO3 == '13'
+        run: |
+          composer install --no-progress --no-interaction
+
+      - name: Install composer dependencies TYPO3 12
+        if: matrix.TYPO3 == '12'
+        run: |
+          composer require typo3/cms-core:^12.4 --no-progress --no-interaction --dev -W
+      - name: Install composer dependencies TYPO3 11
+        if: matrix.TYPO3 == '11'
+        run: |
+          composer require typo3/cms-core:^11.5 --no-progress --no-interaction --dev -W
+      - name: Phpstan 12/13
+        if: matrix.TYPO3 != '11'
+        run: .Build/bin/phpstan analyze -c Build/phpstan.neon
+      - name: Phpstan 11
+        if: matrix.TYPO3 == '11'
+        run: .Build/bin/phpstan analyze -c Build/phpstan11.neon
+      - name: Phpcsfix
+        run: .Build/bin/php-cs-fixer fix --config=Build/php-cs-fixer.php --dry-run --stop-on-violation --using-cache=no
+      - name: Unit Tests
+        run: .Build/bin/phpunit -c Build/phpunit/UnitTests.xml Tests/Unit
+      - name: Functional Tests
+        run: |
+          export typo3DatabaseName="typo3";
+          export typo3DatabaseHost="127.0.0.1";
+          export typo3DatabaseUsername="root";
+          export typo3DatabasePassword="root";
+          .Build/bin/phpunit -c Build/phpunit/FunctionalTests.xml Tests/Functional
diff --git a/.gitignore b/.gitignore
index a1ee133..ebbd882 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,4 @@
-/build/
 /composer.lock
-/.php_cs.cache
-/public/
\ No newline at end of file
+/Build/phpunit/.phpunit.*
+/public/
+/.Build/
diff --git a/Build/php-cs-fixer.php b/Build/php-cs-fixer.php
new file mode 100644
index 0000000..6ee0307
--- /dev/null
+++ b/Build/php-cs-fixer.php
@@ -0,0 +1,5 @@
+<?php
+
+$config = \TYPO3\CodingStandards\CsFixerConfig::create();
+$config->getFinder()->exclude(['var'])->in(__DIR__ . '/..');
+return $config;
diff --git a/Build/phpstan.neon b/Build/phpstan.neon
new file mode 100644
index 0000000..457f990
--- /dev/null
+++ b/Build/phpstan.neon
@@ -0,0 +1,6 @@
+includes:
+  - ../.Build/vendor/saschaegerer/phpstan-typo3/extension.neon
+parameters:
+  level: 5
+  paths:
+    - %currentWorkingDirectory%/Classes
\ No newline at end of file
diff --git a/Build/phpstan11.neon b/Build/phpstan11.neon
new file mode 100644
index 0000000..649a756
--- /dev/null
+++ b/Build/phpstan11.neon
@@ -0,0 +1,8 @@
+includes:
+  - ../.Build/vendor/saschaegerer/phpstan-typo3/extension.neon
+parameters:
+  level: 5
+  paths:
+    - %currentWorkingDirectory%/Classes
+  excludePaths:
+      - %currentWorkingDirectory%/Classes/Listener/AfterCacheableContentIsGenerated.php
diff --git a/Build/phpunit/FunctionalTests.xml b/Build/phpunit/FunctionalTests.xml
new file mode 100644
index 0000000..3c32aa4
--- /dev/null
+++ b/Build/phpunit/FunctionalTests.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.3/phpunit.xsd" backupGlobals="true" bootstrap="FunctionalTestsBootstrap.php" colors="true" stopOnError="false" stopOnFailure="false" stopOnIncomplete="false" stopOnSkipped="false" beStrictAboutTestsThatDoNotTestAnything="false" failOnWarning="true" cacheDirectory=".phpunit.cache" requireCoverageMetadata="false">
+  <testsuites>
+    <testsuite name="Functional tests">
+      <directory>../../Tests/Functional/</directory>
+    </testsuite>
+  </testsuites>
+  <php>
+    <ini name="display_errors" value="1"/>
+    <env name="TYPO3_CONTEXT" value="Testing"/>
+  </php>
+</phpunit>
diff --git a/Build/phpunit/FunctionalTestsBootstrap.php b/Build/phpunit/FunctionalTestsBootstrap.php
new file mode 100644
index 0000000..443197d
--- /dev/null
+++ b/Build/phpunit/FunctionalTestsBootstrap.php
@@ -0,0 +1,20 @@
+<?php
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+call_user_func(function () {
+    $testbase = new \TYPO3\TestingFramework\Core\Testbase();
+    $testbase->defineOriginalRootPath();
+    $testbase->createDirectory(ORIGINAL_ROOT . 'typo3temp/var/tests');
+    $testbase->createDirectory(ORIGINAL_ROOT . 'typo3temp/var/transient');
+});
diff --git a/Build/phpunit/UnitTests.xml b/Build/phpunit/UnitTests.xml
new file mode 100644
index 0000000..380f48d
--- /dev/null
+++ b/Build/phpunit/UnitTests.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd" backupGlobals="true" bootstrap="UnitTestsBootstrap.php" colors="true" processIsolation="false" stopOnError="false" stopOnFailure="false" stopOnIncomplete="false" stopOnSkipped="false" beStrictAboutTestsThatDoNotTestAnything="false" failOnWarning="true" cacheDirectory=".phpunit.cache" requireCoverageMetadata="false">
+  <testsuites>
+    <testsuite name="Unit tests">
+      <directory>../../Tests/Unit/</directory>
+    </testsuite>
+  </testsuites>
+  <php>
+    <ini name="display_errors" value="1"/>
+    <env name="TYPO3_CONTEXT" value="Testing"/>
+  </php>
+</phpunit>
diff --git a/Build/phpunit/UnitTestsBootstrap.php b/Build/phpunit/UnitTestsBootstrap.php
new file mode 100644
index 0000000..b12ccf0
--- /dev/null
+++ b/Build/phpunit/UnitTestsBootstrap.php
@@ -0,0 +1,74 @@
+<?php
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+use TYPO3\CMS\Core\Information\Typo3Version;
+
+call_user_func(function () {
+    $testbase = new \TYPO3\TestingFramework\Core\Testbase();
+
+    // These if's are for core testing (package typo3/cms) only. cms-composer-installer does
+    // not create the autoload-include.php file that sets these env vars and sets composer
+    // mode to true. testing-framework can not be used without composer anyway, so it is safe
+    // to do this here. This way it does not matter if 'bin/phpunit' or 'vendor/phpunit/phpunit/phpunit'
+    // is called to run the tests since the 'relative to entry script' path calculation within
+    // SystemEnvironmentBuilder is not used. However, the binary must be called from the document
+    // root since getWebRoot() uses 'getcwd()'.
+    if (!getenv('TYPO3_PATH_ROOT')) {
+        putenv('TYPO3_PATH_ROOT=' . rtrim($testbase->getWebRoot(), '/'));
+    }
+    if (!getenv('TYPO3_PATH_WEB')) {
+        putenv('TYPO3_PATH_WEB=' . rtrim($testbase->getWebRoot(), '/'));
+    }
+
+    $testbase->defineSitePath();
+
+    $requestType = \TYPO3\CMS\Core\Core\SystemEnvironmentBuilder::REQUESTTYPE_BE | \TYPO3\CMS\Core\Core\SystemEnvironmentBuilder::REQUESTTYPE_CLI;
+    \TYPO3\CMS\Core\Core\SystemEnvironmentBuilder::run(0, $requestType);
+
+    $testbase->createDirectory(\TYPO3\CMS\Core\Core\Environment::getPublicPath() . '/typo3conf/ext');
+    $testbase->createDirectory(\TYPO3\CMS\Core\Core\Environment::getPublicPath() . '/typo3temp/assets');
+    $testbase->createDirectory(\TYPO3\CMS\Core\Core\Environment::getPublicPath() . '/typo3temp/var/tests');
+    $testbase->createDirectory(\TYPO3\CMS\Core\Core\Environment::getPublicPath() . '/typo3temp/var/transient');
+
+    // Retrieve an instance of class loader and inject to core bootstrap
+    $classLoader = require $testbase->getPackagesPath() . '/autoload.php';
+    \TYPO3\CMS\Core\Core\Bootstrap::initializeClassLoader($classLoader);
+
+    // Initialize default TYPO3_CONF_VARS
+    $configurationManager = new \TYPO3\CMS\Core\Configuration\ConfigurationManager();
+    $GLOBALS['TYPO3_CONF_VARS'] = $configurationManager->getDefaultConfiguration();
+
+    $cache = new \TYPO3\CMS\Core\Cache\Frontend\PhpFrontend(
+        'core',
+        new \TYPO3\CMS\Core\Cache\Backend\NullBackend('production', [])
+    );
+    // Set all packages to active
+    if (version_compare((new Typo3Version())->getVersion(), '11.3.0', '>')) {
+        $packageManager = \TYPO3\CMS\Core\Core\Bootstrap::createPackageManager(
+            \TYPO3\CMS\Core\Package\UnitTestPackageManager::class,
+            \TYPO3\CMS\Core\Core\Bootstrap::createPackageCache($cache)
+        );
+    } else {
+        $packageManager = \TYPO3\CMS\Core\Core\Bootstrap::createPackageManager(
+            \TYPO3\CMS\Core\Package\UnitTestPackageManager::class,
+            $cache
+        );
+    }
+    \TYPO3\CMS\Core\Utility\GeneralUtility::setSingletonInstance(\TYPO3\CMS\Core\Package\PackageManager::class, $packageManager);
+    \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::setPackageManager($packageManager);
+
+    $testbase->dumpClassLoadingInformation();
+
+    \TYPO3\CMS\Core\Utility\GeneralUtility::purgeInstances();
+});
diff --git a/Classes/AssetCollector.php b/Classes/AssetCollector.php
index 770730f..880d9df 100644
--- a/Classes/AssetCollector.php
+++ b/Classes/AssetCollector.php
@@ -1,6 +1,7 @@
 <?php
 
 declare(strict_types=1);
+
 namespace B13\Assetcollector;
 
 /*
@@ -137,6 +138,7 @@ public function buildInlineCssTag(): string
 
     protected function cssContentWithResolvedPaths(string $cssFile): string
     {
+        $content = '';
         $absoluteFile =  GeneralUtility::getFileAbsFileName($cssFile);
         if (file_exists($absoluteFile)) {
             $content = $this->removeUtf8Bom(file_get_contents($absoluteFile));
@@ -183,7 +185,7 @@ public function buildJavaScriptIncludes(): string
                     $attributeCode[] = htmlspecialchars($name);
                 }
             }
-            $webPath = (strpos($file['fileName'], 'EXT:') === 0)
+            $webPath = (str_starts_with($file['fileName'], 'EXT:'))
                 ? PathUtility::getAbsoluteWebPath(GeneralUtility::getFileAbsFileName(($file['fileName'])))
                 : $file['fileName'];
             $includes .= '<script src="' . htmlspecialchars($webPath) . '"' . (!empty($attributeCode) ? ' ' . implode(' ', $attributeCode) : '') . '></script>';
diff --git a/Classes/Hooks/AssetRenderer.php b/Classes/Hooks/AssetRenderer.php
index 96b7d60..a98d87a 100644
--- a/Classes/Hooks/AssetRenderer.php
+++ b/Classes/Hooks/AssetRenderer.php
@@ -1,6 +1,7 @@
 <?php
 
 declare(strict_types=1);
+
 namespace B13\Assetcollector\Hooks;
 
 /*
diff --git a/Classes/Middleware/InlineSvgInjector.php b/Classes/Middleware/InlineSvgInjector.php
index 36da02c..dffa05a 100644
--- a/Classes/Middleware/InlineSvgInjector.php
+++ b/Classes/Middleware/InlineSvgInjector.php
@@ -1,6 +1,7 @@
 <?php
 
 declare(strict_types=1);
+
 namespace B13\Assetcollector\Middleware;
 
 /*
@@ -35,7 +36,7 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
                 $body = $response->getBody();
                 $body->rewind();
                 $contents = $response->getBody()->getContents();
-                if (strpos($contents, '</body>') !== false) {
+                if (str_contains($contents, '</body>')) {
                     $content = str_ireplace(
                         '</body>',
                         $svgAsset . '</body>',
diff --git a/Classes/Resource/ResourceCompressor.php b/Classes/Resource/ResourceCompressor.php
index 7be6119..914625d 100644
--- a/Classes/Resource/ResourceCompressor.php
+++ b/Classes/Resource/ResourceCompressor.php
@@ -1,6 +1,7 @@
 <?php
 
 declare(strict_types=1);
+
 namespace B13\Assetcollector\Resource;
 
 /*
diff --git a/Classes/ViewHelpers/CssViewHelper.php b/Classes/ViewHelpers/CssViewHelper.php
index 8946ace..ad57188 100644
--- a/Classes/ViewHelpers/CssViewHelper.php
+++ b/Classes/ViewHelpers/CssViewHelper.php
@@ -1,6 +1,7 @@
 <?php
 
 declare(strict_types=1);
+
 namespace B13\Assetcollector\ViewHelpers;
 
 /*
diff --git a/Classes/ViewHelpers/JsViewHelper.php b/Classes/ViewHelpers/JsViewHelper.php
index a473647..e2eee78 100644
--- a/Classes/ViewHelpers/JsViewHelper.php
+++ b/Classes/ViewHelpers/JsViewHelper.php
@@ -1,6 +1,7 @@
 <?php
 
 declare(strict_types=1);
+
 namespace B13\Assetcollector\ViewHelpers;
 
 /*
diff --git a/Classes/ViewHelpers/SvgViewHelper.php b/Classes/ViewHelpers/SvgViewHelper.php
index 4c25fc7..a0ff30c 100644
--- a/Classes/ViewHelpers/SvgViewHelper.php
+++ b/Classes/ViewHelpers/SvgViewHelper.php
@@ -1,6 +1,7 @@
 <?php
 
 declare(strict_types=1);
+
 namespace B13\Assetcollector\ViewHelpers;
 
 /*
diff --git a/Configuration/Services.yaml b/Configuration/Services.yaml
index 4e58af3..cc8c83d 100644
--- a/Configuration/Services.yaml
+++ b/Configuration/Services.yaml
@@ -11,4 +11,3 @@ services:
     tags:
       - name: event.listener
         identifier: 'b13-assetcollector-after-cacheable-content-is-generated'
-        event: TYPO3\CMS\Frontend\Event\AfterCacheableContentIsGeneratedEvent
\ No newline at end of file
diff --git a/Tests/Functional/Frontend/AbstractFrontendTest.php b/Tests/Functional/Frontend/AbstractFrontendTest.php
deleted file mode 100644
index f130ff9..0000000
--- a/Tests/Functional/Frontend/AbstractFrontendTest.php
+++ /dev/null
@@ -1,33 +0,0 @@
-<?php
-
-namespace B13\Assetcollector\Tests\Functional\Functional;
-
-/*
- * This file is part of TYPO3 CMS-based extension "assetcollector" by b13.
- *
- * It is free software; you can redistribute it and/or modify it under
- * the terms of the GNU General Public License, either version 2
- * of the License, or any later version.
- */
-
-use Psr\Http\Message\ResponseInterface;
-use TYPO3\CMS\Core\Information\Typo3Version;
-use TYPO3\CMS\Core\Utility\GeneralUtility;
-use TYPO3\TestingFramework\Core\Functional\Framework\Frontend\InternalRequest;
-use TYPO3\TestingFramework\Core\Functional\Framework\Frontend\InternalRequestContext;
-use TYPO3\TestingFramework\Core\Functional\FunctionalTestCase;
-
-abstract class AbstractFrontendTest extends FunctionalTestCase
-{
-    protected array $testExtensionsToLoad = ['typo3conf/ext/assetcollector'];
-    protected array $coreExtensionsToLoad = ['core', 'frontend'];
-    protected array $pathsToLinkInTestInstance = ['typo3conf/ext/assetcollector/Build/sites' => 'typo3conf/sites'];
-
-    protected function executeFrontendRequestWrapper(InternalRequest $request, InternalRequestContext $context = null, bool $followRedirects = false): ResponseInterface
-    {
-        if ((GeneralUtility::makeInstance(Typo3Version::class))->getMajorVersion() < 11) {
-            return $this->executeFrontendRequest($request, $context, $followRedirects);
-        }
-        return $this->executeFrontendSubRequest($request, $context, $followRedirects);
-    }
-}
diff --git a/Tests/Functional/Frontend/InlineCssTest.php b/Tests/Functional/Frontend/InlineCssTest.php
index 812ba32..96da362 100644
--- a/Tests/Functional/Frontend/InlineCssTest.php
+++ b/Tests/Functional/Frontend/InlineCssTest.php
@@ -11,16 +11,21 @@
  */
 
 use TYPO3\TestingFramework\Core\Functional\Framework\Frontend\InternalRequest;
+use TYPO3\TestingFramework\Core\Functional\FunctionalTestCase;
 
-class InlineCssTest extends AbstractFrontendTest
+class InlineCssTest extends FunctionalTestCase
 {
+    protected array $testExtensionsToLoad = ['typo3conf/ext/assetcollector'];
+    protected array $coreExtensionsToLoad = ['core', 'frontend'];
+    protected array $pathsToLinkInTestInstance = ['typo3conf/ext/assetcollector/Build/sites' => 'typo3conf/sites'];
+
     /**
      * @test
      */
     public function scriptTagForInlineCssIsRendered(): void
     {
-        $this->importCSVDataSet(ORIGINAL_ROOT . 'typo3conf/ext/assetcollector/Tests/Functional/Frontend/Fixtures/inline_css.csv');
-        $response = $this->executeFrontendRequestWrapper(new InternalRequest('http://localhost/'));
+        $this->importCSVDataSet(__DIR__ . '/Fixtures/inline_css.csv');
+        $response = $this->executeFrontendSubRequest(new InternalRequest('http://localhost/'));
         $expected = '<style class="tx_assetcollector">h1{color:red;}';
         $body = (string)$response->getBody();
         self::assertStringContainsString($expected, $body);
diff --git a/composer.json b/composer.json
index 9d6d55f..ed0f0c0 100644
--- a/composer.json
+++ b/composer.json
@@ -4,16 +4,23 @@
 	"description": "Add CSS and SVG files and strings as inline style tag/inline svg to the html code.",
 	"license": "GPL-2.0-or-later",
 	"config": {
-		"vendor-dir": "build/vendor"
+		"vendor-dir": ".Build/vendor",
+		"bin-dir": ".Build/bin",
+		"allow-plugins": {
+			"typo3/cms-composer-installers": true,
+			"typo3/class-alias-loader": true
+		}
 	},
 	"require": {
 		"php": "^7.4 || ^8.0",
-		"typo3/cms-core": "^10.4 || ^11.5 || ^12.0",
-		"typo3/cms-frontend": "^10.4 || ^11.5 || ^12.0"
+		"typo3/cms-core": "^11.5 || ^12.0 || ^13.0",
+		"typo3/cms-frontend": "^11.5 || ^12.0 || ^13.0"
 	},
 	"extra": {
 		"typo3/cms": {
-			"extension-key": "assetcollector"
+			"extension-key": "assetcollector",
+			"web-dir": ".Build/Web",
+			"app-dir": ".Build"
 		}
 	},
 	"autoload": {
@@ -21,8 +28,15 @@
 			"B13\\Assetcollector\\": "Classes/"
 		}
 	},
+	"autoload-dev": {
+		"psr-4": {
+			"B13\\Assetcollector\\Tests\\": "Tests/"
+		}
+	},
 	"require-dev": {
-		"typo3/coding-standards": "^0.5",
-		"typo3/tailor": "^1.1"
+		"saschaegerer/phpstan-typo3": "^1.8",
+		"typo3/coding-standards": "^0.7",
+		"typo3/tailor": "^1.1",
+		"typo3/testing-framework": "^7.0 || ^8.0"
 	}
 }
diff --git a/ext_emconf.php b/ext_emconf.php
index 02ca027..2204884 100644
--- a/ext_emconf.php
+++ b/ext_emconf.php
@@ -8,10 +8,10 @@
     'author' => 'b13 GmbH',
     'author_email' => 'typo3@b13.com',
     'author_company' => 'b13 GmbH, Stuttgart',
-    'version' => '2.0.2',
+    'version' => '3.0.0',
     'constraints' => [
         'depends' => [
-            'typo3' => '10.4.0-12.9.99',
+            'typo3' => '11.5.0-13.9.99',
         ],
     ],
 ];