diff --git a/.Build/phpunit/FunctionalTests.xml b/.Build/phpunit/FunctionalTests.xml
index 56618c733..bf3e76a05 100644
--- a/.Build/phpunit/FunctionalTests.xml
+++ b/.Build/phpunit/FunctionalTests.xml
@@ -2,17 +2,17 @@
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.3/phpunit.xsd"
          backupGlobals="true"
          bootstrap="../../.Build/vendor/typo3/testing-framework/Resources/Core/Build/FunctionalTestsBootstrap.php"
+         cacheDirectory=".phpunit.cache"
          cacheResult="false"
          colors="true"
-         stopOnError="false"
-         stopOnFailure="false"
-         stopOnIncomplete="false"
-         stopOnSkipped="false"
-         beStrictAboutTestsThatDoNotTestAnything="false"
-         failOnWarning="true"
+         displayDetailsOnTestsThatTriggerDeprecations="true"
+         displayDetailsOnTestsThatTriggerErrors="true"
+         displayDetailsOnTestsThatTriggerNotices="true"
+         displayDetailsOnTestsThatTriggerWarnings="true"
+         failOnDeprecation="true"
+         failOnNotice="true"
          failOnRisky="true"
-         cacheDirectory=".phpunit.cache"
-         requireCoverageMetadata="false"
+         failOnWarning="true"
 >
   <coverage/>
   <testsuites>
diff --git a/Classes/ViewHelpers/PrefillViewHelper.php b/Classes/ViewHelpers/PrefillViewHelper.php
index 326b080a0..4ac106e09 100644
--- a/Classes/ViewHelpers/PrefillViewHelper.php
+++ b/Classes/ViewHelpers/PrefillViewHelper.php
@@ -40,7 +40,7 @@ public function render(): string
             return $registrationData['registration'][$fieldname];
         }
 
-        $frontendUser = $this->getFrontendUser();
+        $frontendUser = $request->getAttribute('frontend.user');
         if (!$frontendUser->user || empty($prefillSettings) ||
             !array_key_exists($fieldname, $prefillSettings)
         ) {
@@ -49,9 +49,4 @@ public function render(): string
 
         return (string)($frontendUser->user[$prefillSettings[$fieldname]]);
     }
-
-    protected function getFrontendUser(): FrontendUserAuthentication
-    {
-        return $this->renderingContext->getAttribute(ServerRequestInterface::class)->getAttribute('frontend.user');
-    }
 }
diff --git a/Tests/Functional/ViewHelpers/PrefillViewHelperTest.php b/Tests/Functional/ViewHelpers/PrefillViewHelperTest.php
new file mode 100644
index 000000000..a8738c85f
--- /dev/null
+++ b/Tests/Functional/ViewHelpers/PrefillViewHelperTest.php
@@ -0,0 +1,227 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the Extension "sf_event_mgt" for TYPO3 CMS.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ */
+
+namespace DERHANSEN\SfEventMgt\Tests\Functional\ViewHelpers;
+
+use PHPUnit\Framework\Attributes\Test;
+use TYPO3\CMS\Core\Core\SystemEnvironmentBuilder;
+use TYPO3\CMS\Core\Http\ServerRequest;
+use TYPO3\CMS\Extbase\Mvc\ExtbaseRequestParameters;
+use TYPO3\CMS\Extbase\Mvc\Request;
+use TYPO3\CMS\Fluid\Core\Rendering\RenderingContextFactory;
+use TYPO3\CMS\Frontend\Authentication\FrontendUserAuthentication;
+use TYPO3\TestingFramework\Core\Functional\FunctionalTestCase;
+use TYPO3Fluid\Fluid\View\TemplateView;
+
+class PrefillViewHelperTest extends FunctionalTestCase
+{
+    protected array $testExtensionsToLoad = ['typo3conf/ext/sf_event_mgt'];
+
+    #[Test]
+    public function viewHelperReturnsEmptyStringIfFrontendUserNotAvailable(): void
+    {
+        $frontendUser = new FrontendUserAuthentication();
+        $extbaseRequestParameters = new ExtbaseRequestParameters();
+        $serverRequest = new ServerRequest();
+        $serverRequest = $serverRequest->withAttribute('extbase', $extbaseRequestParameters)
+            ->withAttribute('frontend.user', $frontendUser)
+            ->withAttribute('applicationType', SystemEnvironmentBuilder::REQUESTTYPE_FE);
+        $extbaseRequest = (new Request($serverRequest));
+        $context = $this->get(RenderingContextFactory::class)->create([], $extbaseRequest);
+        $context->getViewHelperResolver()->addNamespace('e', 'DERHANSEN\\SfEventMgt\\ViewHelpers');
+        $context->getTemplatePaths()->setTemplateSource('<e:prefill fieldname="firstname" prefillSettings="{settings.registration.prefillFields}" />');
+        $this->assertEquals('', (new TemplateView($context))->render());
+    }
+
+    #[Test]
+    public function viewHelperReturnsCurrentFieldValueIfValueInParsedBodyAvailable(): void
+    {
+        $submittedData = [
+            'tx_sfeventmgt_pieventregistration' => [
+                'registration' => ['firstname' => 'Torben'],
+            ],
+        ];
+
+        $frontendUser = new FrontendUserAuthentication();
+        $extbaseRequestParameters = new ExtbaseRequestParameters();
+        $extbaseRequestParameters->setPluginName('Pieventregistration');
+        $extbaseRequestParameters->setControllerExtensionName('SfEventMgt');
+        $serverRequest = new ServerRequest();
+        $serverRequest = $serverRequest->withAttribute('extbase', $extbaseRequestParameters)
+            ->withParsedBody($submittedData)
+            ->withAttribute('frontend.user', $frontendUser)
+            ->withAttribute('applicationType', SystemEnvironmentBuilder::REQUESTTYPE_FE);
+        $extbaseRequest = (new Request($serverRequest));
+        $context = $this->get(RenderingContextFactory::class)->create([], $extbaseRequest);
+        $context->getViewHelperResolver()->addNamespace('e', 'DERHANSEN\\SfEventMgt\\ViewHelpers');
+        $context->getTemplatePaths()->setTemplateSource('<e:prefill fieldname="firstname" prefillSettings="{settings.registration.prefillFields}" />');
+        $this->assertEquals('Torben', (new TemplateView($context))->render());
+    }
+
+    #[Test]
+    public function viewHelperReturnsEmptyStringIfPrefillSettingsEmpty(): void
+    {
+        $submittedData = [];
+        $settings = [];
+
+        $frontendUser = new FrontendUserAuthentication();
+        $frontendUser->user = [
+            'first_name' => 'John',
+        ];
+        $extbaseRequestParameters = new ExtbaseRequestParameters();
+        $extbaseRequestParameters->setPluginName('Pieventregistration');
+        $extbaseRequestParameters->setControllerExtensionName('SfEventMgt');
+        $serverRequest = new ServerRequest();
+        $serverRequest = $serverRequest->withAttribute('extbase', $extbaseRequestParameters)
+            ->withParsedBody($submittedData)
+            ->withAttribute('frontend.user', $frontendUser)
+            ->withAttribute('applicationType', SystemEnvironmentBuilder::REQUESTTYPE_FE);
+        $extbaseRequest = (new Request($serverRequest));
+        $context = $this->get(RenderingContextFactory::class)->create([], $extbaseRequest);
+        $context->getViewHelperResolver()->addNamespace('e', 'DERHANSEN\\SfEventMgt\\ViewHelpers');
+        $context->getTemplatePaths()->setTemplateSource('<e:prefill fieldname="firstname" prefillSettings="{settings.registration.prefillFields}" />');
+        $context->getVariableProvider()->add('settings', $settings);
+        $this->assertEquals('', (new TemplateView($context))->render());
+    }
+
+    #[Test]
+    public function viewHelperReturnsEmptyStringIfFieldNotFoundInPrefillSettings(): void
+    {
+        $submittedData = [];
+        $settings = [
+            'registration' => [
+                'prefillFields' => [
+                    'lastname' => 'last_name',
+                ]
+            ],
+        ];
+
+        $frontendUser = new FrontendUserAuthentication();
+        $frontendUser->user = [
+            'first_name' => 'John',
+        ];
+        $extbaseRequestParameters = new ExtbaseRequestParameters();
+        $extbaseRequestParameters->setPluginName('Pieventregistration');
+        $extbaseRequestParameters->setControllerExtensionName('SfEventMgt');
+        $serverRequest = new ServerRequest();
+        $serverRequest = $serverRequest->withAttribute('extbase', $extbaseRequestParameters)
+            ->withParsedBody($submittedData)
+            ->withAttribute('frontend.user', $frontendUser)
+            ->withAttribute('applicationType', SystemEnvironmentBuilder::REQUESTTYPE_FE);
+        $extbaseRequest = (new Request($serverRequest));
+        $context = $this->get(RenderingContextFactory::class)->create([], $extbaseRequest);
+        $context->getViewHelperResolver()->addNamespace('e', 'DERHANSEN\\SfEventMgt\\ViewHelpers');
+        $context->getTemplatePaths()->setTemplateSource('<e:prefill fieldname="firstname" prefillSettings="{settings.registration.prefillFields}" />');
+        $context->getVariableProvider()->add('settings', $settings);
+        $this->assertEquals('', (new TemplateView($context))->render());
+    }
+
+    #[Test]
+    public function viewHelperReturnsEmptyStringIfFieldNotFoundInFeUser(): void
+    {
+        $submittedData = [];
+        $settings = [
+            'registration' => [
+                'prefillFields' => [
+                    'non_existing' => 'non_existing_field',
+                ]
+            ],
+        ];
+
+        $frontendUser = new FrontendUserAuthentication();
+        $frontendUser->user = [
+            'first_name' => 'John',
+        ];
+        $extbaseRequestParameters = new ExtbaseRequestParameters();
+        $extbaseRequestParameters->setPluginName('Pieventregistration');
+        $extbaseRequestParameters->setControllerExtensionName('SfEventMgt');
+        $serverRequest = new ServerRequest();
+        $serverRequest = $serverRequest->withAttribute('extbase', $extbaseRequestParameters)
+            ->withParsedBody($submittedData)
+            ->withAttribute('frontend.user', $frontendUser)
+            ->withAttribute('applicationType', SystemEnvironmentBuilder::REQUESTTYPE_FE);
+        $extbaseRequest = (new Request($serverRequest));
+        $context = $this->get(RenderingContextFactory::class)->create([], $extbaseRequest);
+        $context->getViewHelperResolver()->addNamespace('e', 'DERHANSEN\\SfEventMgt\\ViewHelpers');
+        $context->getTemplatePaths()->setTemplateSource('<e:prefill fieldname="non_existing" prefillSettings="{settings.registration.prefillFields}" />');
+        $context->getVariableProvider()->add('settings', $settings);
+        $this->assertEquals('', (new TemplateView($context))->render());
+    }
+
+    #[Test]
+    public function viewHelperReturnsFieldvalueIfFound(): void
+    {
+        $submittedData = [];
+        $settings = [
+            'registration' => [
+                'prefillFields' => [
+                    'firstname' => 'first_name',
+                ]
+            ],
+        ];
+
+        $frontendUser = new FrontendUserAuthentication();
+        $frontendUser->user = [
+            'first_name' => 'John',
+        ];
+        $extbaseRequestParameters = new ExtbaseRequestParameters();
+        $extbaseRequestParameters->setPluginName('Pieventregistration');
+        $extbaseRequestParameters->setControllerExtensionName('SfEventMgt');
+        $serverRequest = new ServerRequest();
+        $serverRequest = $serverRequest->withAttribute('extbase', $extbaseRequestParameters)
+            ->withParsedBody($submittedData)
+            ->withAttribute('frontend.user', $frontendUser)
+            ->withAttribute('applicationType', SystemEnvironmentBuilder::REQUESTTYPE_FE);
+        $extbaseRequest = (new Request($serverRequest));
+        $context = $this->get(RenderingContextFactory::class)->create([], $extbaseRequest);
+        $context->getViewHelperResolver()->addNamespace('e', 'DERHANSEN\\SfEventMgt\\ViewHelpers');
+        $context->getTemplatePaths()->setTemplateSource('<e:prefill fieldname="firstname" prefillSettings="{settings.registration.prefillFields}" />');
+        $context->getVariableProvider()->add('settings', $settings);
+        $this->assertEquals('John', (new TemplateView($context))->render());
+    }
+
+    #[Test]
+    public function viewHelperReturnsSubmittedValueIfValidationError(): void
+    {
+        $submittedData = [
+            'tx_sfeventmgt_pieventregistration' => [
+                'registration' => ['firstname' => 'Torben'],
+            ],
+        ];
+
+        $settings = [
+            'registration' => [
+                'prefillFields' => [
+                    'firstname' => 'first_name',
+                ]
+            ],
+        ];
+
+        $frontendUser = new FrontendUserAuthentication();
+        $frontendUser->user = [
+            'first_name' => 'John',
+        ];
+        $extbaseRequestParameters = new ExtbaseRequestParameters();
+        $extbaseRequestParameters->setPluginName('Pieventregistration');
+        $extbaseRequestParameters->setControllerExtensionName('SfEventMgt');
+        $serverRequest = new ServerRequest();
+        $serverRequest = $serverRequest->withAttribute('extbase', $extbaseRequestParameters)
+            ->withParsedBody($submittedData)
+            ->withAttribute('frontend.user', $frontendUser)
+            ->withAttribute('applicationType', SystemEnvironmentBuilder::REQUESTTYPE_FE);
+        $extbaseRequest = (new Request($serverRequest));
+        $context = $this->get(RenderingContextFactory::class)->create([], $extbaseRequest);
+        $context->getViewHelperResolver()->addNamespace('e', 'DERHANSEN\\SfEventMgt\\ViewHelpers');
+        $context->getTemplatePaths()->setTemplateSource('<e:prefill fieldname="firstname" prefillSettings="{settings.registration.prefillFields}" />');
+        $context->getVariableProvider()->add('settings', $settings);
+        $this->assertEquals('Torben', (new TemplateView($context))->render());
+    }
+}
diff --git a/Tests/Unit/ViewHelpers/PrefillViewHelperTest.php b/Tests/Unit/ViewHelpers/PrefillViewHelperTest.php
deleted file mode 100644
index 962f57c30..000000000
--- a/Tests/Unit/ViewHelpers/PrefillViewHelperTest.php
+++ /dev/null
@@ -1,209 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-/*
- * This file is part of the Extension "sf_event_mgt" for TYPO3 CMS.
- *
- * For the full copyright and license information, please read the
- * LICENSE.txt file that was distributed with this source code.
- */
-
-namespace DERHANSEN\SfEventMgt\Tests\Unit\ViewHelpers;
-
-use PHPUnit\Framework\Attributes\Test;
-use DERHANSEN\SfEventMgt\ViewHelpers\PrefillViewHelper;
-use stdClass;
-use TYPO3\CMS\Extbase\Mvc\Request;
-use TYPO3\CMS\Fluid\Core\Rendering\RenderingContext;
-use TYPO3\CMS\Frontend\Authentication\FrontendUserAuthentication;
-use TYPO3\TestingFramework\Core\Unit\UnitTestCase;
-
-use function PHPUnit\Framework\any;
-
-/**
- * Test case for prefill viewHelper
- */
-class PrefillViewHelperTest extends UnitTestCase
-{
-    #[Test]
-    public function viewHelperReturnsEmptyStringIfFrontendUserNotAvailable(): void
-    {
-        $frontendUser = $this->createMock(FrontendUserAuthentication::class);
-        $request = $this->createMock(Request::class);
-        $request->expects(self::any())->method('getAttribute')->with('frontend.user')->willReturn($frontendUser);
-        $renderingContext = $this->createMock(RenderingContext::class);
-        $renderingContext->expects(self::any())->method('getAttribute')->willReturn($request);
-
-        $viewHelper = new PrefillViewHelper();
-        $viewHelper->setRenderingContext($renderingContext);
-        $viewHelper->setArguments([
-            'fieldname' => 'a field',
-            'prefillSettings' => [],
-        ]);
-        $actual = $viewHelper->render();
-        self::assertSame('', $actual);
-    }
-
-    #[Test]
-    public function viewHelperReturnsCurrentFieldValueIfValueInParsedBodyAvailable(): void
-    {
-        $submittedData = [
-            'tx_sfeventmgt_pieventregistration' => [
-                'registration' => ['firstname' => 'Torben'],
-            ],
-        ];
-
-        $frontendUser = $this->createMock(FrontendUserAuthentication::class);
-        $request = $this->createMock(Request::class);
-        $request->expects(self::any())->method('getControllerExtensionName')->willReturn('SfEventMgt');
-        $request->expects(self::any())->method('getPluginName')->willReturn('Pieventregistration');
-        $request->expects(self::any())->method('getParsedBody')->willReturn($submittedData);
-        $request->expects(self::any())->method('getAttribute')->with('frontend.user')->willReturn($frontendUser);
-        $renderingContext = $this->createMock(RenderingContext::class);
-        $renderingContext->expects(self::any())->method('getAttribute')->willReturn($request);
-
-        $viewHelper = new PrefillViewHelper();
-        $viewHelper->setRenderingContext($renderingContext);
-        $viewHelper->setArguments([
-            'fieldname' => 'firstname',
-            'prefillSettings' => [],
-        ]);
-        $actual = $viewHelper->render();
-        self::assertSame('Torben', $actual);
-    }
-
-    #[Test]
-    public function viewHelperReturnsEmptyStringIfPrefillSettingsEmpty(): void
-    {
-        $submittedData = [];
-
-        $frontendUser = $this->createMock(FrontendUserAuthentication::class);
-        $frontendUser->user = [
-            'first_name' => 'John',
-        ];
-        $request = $this->createMock(Request::class);
-        $request->expects(self::any())->method('getControllerExtensionName')->willReturn('SfEventMgt');
-        $request->expects(self::any())->method('getPluginName')->willReturn('Pieventregistration');
-        $request->expects(self::any())->method('getParsedBody')->willReturn($submittedData);
-        $request->expects(self::any())->method('getAttribute')->with('frontend.user')->willReturn($frontendUser);
-        $renderingContext = $this->createMock(RenderingContext::class);
-        $renderingContext->expects(self::any())->method('getAttribute')->willReturn($request);
-
-        $viewHelper = new PrefillViewHelper();
-        $viewHelper->setRenderingContext($renderingContext);
-        $viewHelper->setArguments([
-            'fieldname' => 'firstname',
-            'prefillSettings' => [],
-        ]);
-        $actual = $viewHelper->render();
-        self::assertSame('', $actual);
-    }
-
-    #[Test]
-    public function viewHelperReturnsEmptyStringIfFieldNotFoundInPrefillSettings(): void
-    {
-        $submittedData = [];
-        $frontendUser = $this->createMock(FrontendUserAuthentication::class);
-        $frontendUser->user = [
-            'first_name' => 'John',
-        ];
-        $request = $this->createMock(Request::class);
-        $request->expects(self::any())->method('getControllerExtensionName')->willReturn('SfEventMgt');
-        $request->expects(self::any())->method('getPluginName')->willReturn('Pieventregistration');
-        $request->expects(self::any())->method('getParsedBody')->willReturn($submittedData);
-        $request->expects(self::any())->method('getAttribute')->with('frontend.user')->willReturn($frontendUser);
-        $renderingContext = $this->createMock(RenderingContext::class);
-        $renderingContext->expects(self::any())->method('getAttribute')->willReturn($request);
-
-        $viewHelper = new PrefillViewHelper();
-        $viewHelper->setRenderingContext($renderingContext);
-        $viewHelper->setArguments([
-            'fieldname' => 'lastname',
-            'prefillSettings' => ['firstname' => 'first_name'],
-        ]);
-        $actual = $viewHelper->render();
-        self::assertSame('', $actual);
-    }
-
-    #[Test]
-    public function viewHelperReturnsEmptyStringIfFieldNotFoundInFeUser(): void
-    {
-        $frontendUser = $this->createMock(FrontendUserAuthentication::class);
-        $frontendUser->user = [
-            'first_name' => 'John',
-        ];
-        $request = $this->createMock(Request::class);
-        $request->expects(self::any())->method('getControllerExtensionName')->willReturn('SfEventMgt');
-        $request->expects(self::any())->method('getPluginName')->willReturn('Pieventregistration');
-        $request->expects(self::any())->method('getAttribute')->with('frontend.user')->willReturn($frontendUser);
-        $renderingContext = $this->createMock(RenderingContext::class);
-        $renderingContext->expects(self::any())->method('getAttribute')->willReturn($request);
-
-        $viewHelper = new PrefillViewHelper();
-        $viewHelper->setRenderingContext($renderingContext);
-        $viewHelper->setArguments([
-            'fieldname' => 'lastname',
-            'prefillSettings' => ['firstname' => 'first_name'],
-        ]);
-        $actual = $viewHelper->render();
-        self::assertSame('', $actual);
-    }
-
-    #[Test]
-    public function viewHelperReturnsFieldvalueIfFound(): void
-    {
-        $frontendUser = $this->createMock(FrontendUserAuthentication::class);
-        $frontendUser->user = [
-            'first_name' => 'John',
-            'last_name' => 'Doe',
-        ];
-        $request = $this->createMock(Request::class);
-        $request->expects(self::any())->method('getControllerExtensionName')->willReturn('SfEventMgt');
-        $request->expects(self::any())->method('getPluginName')->willReturn('Pieventregistration');
-        $request->expects(self::any())->method('getAttribute')->with('frontend.user')->willReturn($frontendUser);
-        $renderingContext = $this->createMock(RenderingContext::class);
-        $renderingContext->expects(self::any())->method('getAttribute')->willReturn($request);
-
-        $viewHelper = new PrefillViewHelper();
-        $viewHelper->setRenderingContext($renderingContext);
-        $viewHelper->setArguments([
-            'fieldname' => 'lastname',
-            'prefillSettings' => ['lastname' => 'last_name'],
-        ]);
-        $actual = $viewHelper->render();
-        self::assertSame('Doe', $actual);
-    }
-
-    #[Test]
-    public function viewHelperReturnsSubmittedValueIfValidationError(): void
-    {
-        $submittedData = [
-            'tx_sfeventmgt_pieventregistration' => [
-                'registration' => ['firstname' => 'Torben'],
-            ],
-        ];
-
-        $frontendUser = $this->createMock(FrontendUserAuthentication::class);
-        $frontendUser->user = [
-            'first_name' => 'John',
-            'last_name' => 'Doe',
-        ];
-        $request = $this->createMock(Request::class);
-        $request->expects(self::any())->method('getControllerExtensionName')->willReturn('SfEventMgt');
-        $request->expects(self::any())->method('getPluginName')->willReturn('Pieventregistration');
-        $request->expects(self::any())->method('getParsedBody')->willReturn($submittedData);
-        $request->expects(self::any())->method('getAttribute')->with('frontend.user')->willReturn($frontendUser);
-        $renderingContext = $this->createMock(RenderingContext::class);
-        $renderingContext->expects(self::any())->method('getAttribute')->willReturn($request);
-
-        $viewHelper = new PrefillViewHelper();
-        $viewHelper->setRenderingContext($renderingContext);
-        $viewHelper->setArguments([
-            'fieldname' => 'firstname',
-            'prefillSettings' => ['firstname' => 'first_name'],
-        ]);
-        $actual = $viewHelper->render();
-        self::assertSame('Torben', $actual);
-    }
-}