diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..2c1bae6
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,11 @@
+Tests export-ignore
+.github export-ignore
+
+.gitattributes export-ignore
+.gitignore export-ignore
+
+.php-cs-fixer.dist.php export-ignore
+phpstan.neon export-ignore
+phpunit.xml.dist export-ignore
+
+shell.nix export-ignore
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index e6e7aff..04665e5 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -20,11 +20,9 @@ jobs:
     strategy:
       matrix:
         php-version:
-          - 7.3
-          - 7.4
-          - 8.0
           - 8.1
           - 8.2
+          - 8.3
     steps:
       - name: Checkout
         uses: actions/checkout@v3
@@ -78,13 +76,42 @@ jobs:
         with:
           coverage: none
           tools: composer:v2
-          php-version: "8.2"
+          php-version: "8.3"
 
       - name: Install dependencies
         run: composer install --prefer-dist --no-progress --no-suggest
 
       - name: Coding Guideline
-        run: ./vendor/bin/ecs
+        run: ./vendor/bin/php-cs-fixer fix --dry-run
+
+  phpstan:
+    runs-on: ubuntu-latest
+    needs:
+      - xml-linting
+    strategy:
+      matrix:
+        include:
+          - php-version: '8.1'
+            typo3-version: '^12.4'
+          - php-version: '8.2'
+            typo3-version: '^12.4'
+          - php-version: '8.3'
+            typo3-version: '^12.4'
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Install PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          coverage: none
+          tools: composer:v2
+          php-version: "${{ matrix.php-version }}"
+
+      - name: Install dependencies
+        run: composer req "typo3/cms-core:${{ matrix.typo3-version }}" --prefer-dist --no-progress --no-interaction
+
+      - name: PHPStan
+        run: ./vendor/bin/phpstan
 
   tests:
     runs-on: ubuntu-latest
@@ -93,16 +120,12 @@ jobs:
     strategy:
       matrix:
         include:
-          - php-version: '7.3'
-            typo3-version: '^10.4'
-          - php-version: '7.4'
-            typo3-version: '^10.4'
-          - php-version: '7.4'
-            typo3-version: '^11.5'
           - php-version: '8.1'
-            typo3-version: '^11.5'
+            typo3-version: '^12.4'
           - php-version: '8.2'
-            typo3-version: '^11.5'
+            typo3-version: '^12.4'
+          - php-version: '8.3'
+            typo3-version: '^12.4'
     steps:
       - uses: actions/checkout@v3
 
@@ -114,7 +137,7 @@ jobs:
           php-version: "${{ matrix.php-version }}"
 
       - name: Install dependencies
-        run: composer install --prefer-dist --no-progress --no-suggest
+        run: composer req "typo3/cms-core:${{ matrix.typo3-version }}" --prefer-dist --no-progress --no-interaction
 
       - name: PHPUnit Tests
         run: ./vendor/bin/phpunit --testdox
diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
new file mode 100644
index 0000000..86849bd
--- /dev/null
+++ b/.php-cs-fixer.dist.php
@@ -0,0 +1,63 @@
+<?php
+
+$finder = (new PhpCsFixer\Finder())
+    ->ignoreVCSIgnored(true)
+    ->in(realpath(__DIR__));
+
+return (new \PhpCsFixer\Config())
+    ->setRiskyAllowed(true)
+    ->setRules([
+        '@DoctrineAnnotation' => true,
+        '@PSR2' => true,
+        'array_syntax' => ['syntax' => 'short'],
+        'blank_line_after_opening_tag' => true,
+        'braces' => ['allow_single_line_closure' => true],
+        'cast_spaces' => ['space' => 'none'],
+        'compact_nullable_typehint' => true,
+        'concat_space' => ['spacing' => 'one'],
+        'declare_equal_normalize' => ['space' => 'none'],
+        'dir_constant' => true,
+        'function_to_constant' => ['functions' => ['get_called_class', 'get_class', 'get_class_this', 'php_sapi_name', 'phpversion', 'pi']],
+        'function_typehint_space' => true,
+        'lowercase_cast' => true,
+        'method_argument_space' => ['on_multiline' => 'ensure_fully_multiline'],
+        'modernize_strpos' => true,
+        'modernize_types_casting' => true,
+        'native_function_casing' => true,
+        'new_with_braces' => true,
+        'no_alias_functions' => true,
+        'no_blank_lines_after_phpdoc' => true,
+        'no_empty_phpdoc' => true,
+        'no_empty_statement' => true,
+        'no_extra_blank_lines' => true,
+        'no_leading_import_slash' => true,
+        'no_leading_namespace_whitespace' => true,
+        'no_null_property_initialization' => true,
+        'no_short_bool_cast' => true,
+        'no_singleline_whitespace_before_semicolons' => true,
+        'no_superfluous_elseif' => true,
+        'no_trailing_comma_in_singleline_array' => true,
+        'no_unneeded_control_parentheses' => true,
+        'no_unused_imports' => true,
+        'no_useless_else' => true,
+        'no_whitespace_in_blank_line' => true,
+        'ordered_imports' => true,
+        'php_unit_construct' => ['assertions' => ['assertEquals', 'assertSame', 'assertNotEquals', 'assertNotSame']],
+        'php_unit_mock_short_will_return' => true,
+        'php_unit_test_case_static_method_calls' => ['call_type' => 'self'],
+        'phpdoc_no_access' => true,
+        'phpdoc_no_empty_return' => true,
+        'phpdoc_no_package' => true,
+        'phpdoc_scalar' => true,
+        'phpdoc_trim' => true,
+        'phpdoc_types' => true,
+        'phpdoc_types_order' => ['null_adjustment' => 'always_last', 'sort_algorithm' => 'none'],
+        'return_type_declaration' => ['space_before' => 'none'],
+        'single_quote' => true,
+        'single_line_comment_style' => ['comment_types' => ['hash']],
+        'single_trait_insert_per_statement' => true,
+        'trailing_comma_in_multiline' => ['elements' => ['arrays']],
+        'whitespace_after_comma_in_array' => true,
+        'yoda_style' => ['equal' => false, 'identical' => false, 'less_and_greater' => false],
+    ])
+    ->setFinder($finder);
diff --git a/Classes/Controller/Frontend/CalendarController.php b/Classes/Controller/Frontend/CalendarController.php
index 1be5855..21f349c 100644
--- a/Classes/Controller/Frontend/CalendarController.php
+++ b/Classes/Controller/Frontend/CalendarController.php
@@ -21,11 +21,14 @@
  * 02110-1301, USA.
  */
 
+use Psr\Http\Message\ResponseInterface;
+use RuntimeException;
 use TYPO3\CMS\Core\TypoScript\TypoScriptService;
 use TYPO3\CMS\Core\Utility\GeneralUtility;
 use TYPO3\CMS\Extbase\Annotation as Extbase;
 use TYPO3\CMS\Extbase\Mvc\Controller\ActionController;
 use TYPO3\CMS\Extbase\Property\TypeConverter\DateTimeConverter;
+use TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer;
 use WerkraumMedia\Calendar\Domain\Model\Context;
 use WerkraumMedia\Calendar\Domain\Model\ContextSpecificFactory;
 use WerkraumMedia\Calendar\Domain\Model\Day;
@@ -35,7 +38,7 @@
 use WerkraumMedia\Calendar\Domain\Model\Year;
 use WerkraumMedia\Calendar\Events\AssignTemplateVariables;
 
-class CalendarController extends ActionController
+final class CalendarController extends ActionController
 {
     /**
      * @var ForeignDataFactory
@@ -55,19 +58,19 @@ public function __construct(
         $this->typoScriptService = $typoScriptService;
     }
 
-    public function initializeAction()
+    public function initializeAction(): void
     {
         if ($this->foreignDataFactory instanceof ContextSpecificFactory) {
             $this->foreignDataFactory->setContext(
-                Context::createFromContentObjectRenderer($this->configurationManager->getContentObject())
+                Context::createFromContentObjectRenderer($this->getContentObjectRenderer())
             );
         }
     }
 
-    public function initializeYearAction()
+    public function initializeYearAction(): void
     {
         if ($this->request->hasArgument('year') === false) {
-            $this->request->setArguments([
+            $this->request = $this->request->withArguments([
                 'year' => [
                     'year' => $this->getDefaultArgumentValue('year'),
                 ],
@@ -82,17 +85,19 @@ public function initializeYearAction()
     /**
      * @Extbase\IgnoreValidation("year")
      */
-    public function yearAction(Year $year)
+    public function yearAction(Year $year): ResponseInterface
     {
         $this->assignVariables([
             'year' => $year,
         ]);
+
+        return $this->htmlResponse();
     }
 
-    public function initializeMonthAction()
+    public function initializeMonthAction(): void
     {
         if ($this->request->hasArgument('month') === false) {
-            $this->request->setArguments([
+            $this->request = $this->request->withArguments([
                 'month' => [
                     'month' => $this->getDefaultArgumentValue('month'),
                     'year' => $this->getDefaultArgumentValue('year'),
@@ -108,17 +113,19 @@ public function initializeMonthAction()
     /**
      * @Extbase\IgnoreValidation("month")
      */
-    public function monthAction(Month $month)
+    public function monthAction(Month $month): ResponseInterface
     {
         $this->assignVariables([
             'month' => $month,
         ]);
+
+        return $this->htmlResponse();
     }
 
-    public function initializeWeekAction()
+    public function initializeWeekAction(): void
     {
         if ($this->request->hasArgument('week') === false) {
-            $this->request->setArguments([
+            $this->request = $this->request->withArguments([
                 'week' => [
                     'week' => $this->getDefaultArgumentValue('week'),
                     'year' => $this->getDefaultArgumentValue('year'),
@@ -134,17 +141,19 @@ public function initializeWeekAction()
     /**
      * @Extbase\IgnoreValidation("week")
      */
-    public function weekAction(Week $week)
+    public function weekAction(Week $week): ResponseInterface
     {
         $this->assignVariables([
             'week' => $week,
         ]);
+
+        return $this->htmlResponse();
     }
 
-    public function initializeDayAction()
+    public function initializeDayAction(): void
     {
         if ($this->request->hasArgument('day') === false) {
-            $this->request->setArguments([
+            $this->request = $this->request->withArguments([
                 'day' => [
                     'day' => $this->getDefaultArgumentValue('day'),
                 ],
@@ -167,11 +176,13 @@ public function initializeDayAction()
     /**
      * @Extbase\IgnoreValidation("day")
      */
-    public function dayAction(Day $day)
+    public function dayAction(Day $day): ResponseInterface
     {
         $this->assignVariables([
             'day' => $day,
         ]);
+
+        return $this->htmlResponse();
     }
 
     private function assignVariables(array $variables): void
@@ -202,12 +213,23 @@ private function getDefaultArgumentValue(string $argumentName): string
             'day' => date('Y-m-d'),
         ];
 
-        $value = $this->configurationManager->getContentObject()->stdWrapValue(
+        $value = $this->getContentObjectRenderer()->stdWrapValue(
             $argumentName,
             $arguments,
             $fallbackValues[$argumentName]
         );
 
-        return $value;
+        return (string)$value;
+    }
+
+    private function getContentObjectRenderer(): ContentObjectRenderer
+    {
+        $contentObjectRenderer = $this->request->getAttribute('currentContentObject');
+
+        if (! $contentObjectRenderer instanceof ContentObjectRenderer) {
+            throw new RuntimeException('Could not fetch currentContentObject from request.', 1726490796);
+        }
+
+        return $contentObjectRenderer;
     }
 }
diff --git a/Classes/Domain/Model/Day.php b/Classes/Domain/Model/Day.php
index 43991cd..6a84679 100644
--- a/Classes/Domain/Model/Day.php
+++ b/Classes/Domain/Model/Day.php
@@ -22,7 +22,6 @@
  */
 
 use TYPO3\CMS\Core\Utility\GeneralUtility;
-use TYPO3\CMS\Extbase\Persistence\ObjectStorage;
 
 class Day
 {
@@ -44,7 +43,6 @@ class Day
     public function __construct(
         \DateTime $day
     ) {
-        $this->periods = new ObjectStorage();
         $this->day = \DateTimeImmutable::createFromMutable($day)->modify('midnight');
     }
 
@@ -58,7 +56,7 @@ public function isActive(): bool
         return false;
     }
 
-    public function getForeignData()
+    public function getForeignData(): mixed
     {
         $this->initializeForeignData();
 
diff --git a/Classes/Domain/Model/ForeignDataFactory.php b/Classes/Domain/Model/ForeignDataFactory.php
index f47b4c4..cc8a5d3 100644
--- a/Classes/Domain/Model/ForeignDataFactory.php
+++ b/Classes/Domain/Model/ForeignDataFactory.php
@@ -27,5 +27,5 @@ interface ForeignDataFactory
      * Receives a specific day and may return arbirtrary data.
      * This data is attached to the day and available through getter.
      */
-    public function getData(Day $day);
+    public function getData(Day $day): mixed;
 }
diff --git a/Classes/Domain/Model/Month.php b/Classes/Domain/Model/Month.php
index 04a6143..bbf9bfb 100644
--- a/Classes/Domain/Model/Month.php
+++ b/Classes/Domain/Model/Month.php
@@ -21,9 +21,6 @@
  * 02110-1301, USA.
  */
 
-use TYPO3\CMS\Core\Utility\GeneralUtility;
-use TYPO3\CMS\Extbase\Persistence\ObjectStorage;
-
 class Month
 {
     /**
@@ -77,8 +74,8 @@ public function getWeeks(): array
 
         while ($currentDay <= $lastDay) {
             $this->weeks[] = new Week(
-                (int) $currentDay->format('W'),
-                (int) $currentDay->format('o')
+                (int)$currentDay->format('W'),
+                (int)$currentDay->format('o')
             );
 
             $currentDay = $currentDay->modify('+7 days');
diff --git a/Classes/Domain/Model/NullDataFactory.php b/Classes/Domain/Model/NullDataFactory.php
index 0b55153..713bb98 100644
--- a/Classes/Domain/Model/NullDataFactory.php
+++ b/Classes/Domain/Model/NullDataFactory.php
@@ -23,7 +23,7 @@
 
 class NullDataFactory implements ForeignDataFactory
 {
-    public function getData(Day $day)
+    public function getData(Day $day): mixed
     {
         return null;
     }
diff --git a/Classes/Domain/Model/Week.php b/Classes/Domain/Model/Week.php
index 81e1c65..14fb692 100644
--- a/Classes/Domain/Model/Week.php
+++ b/Classes/Domain/Model/Week.php
@@ -79,8 +79,8 @@ public function getPreviousWeek(): Week
         $newDay = $this->getWeek()->modify('-1 week');
 
         return new self(
-            (int) $newDay->format('W'),
-            (int) $newDay->format('o')
+            (int)$newDay->format('W'),
+            (int)$newDay->format('o')
         );
     }
 
@@ -89,8 +89,8 @@ public function getNextWeek(): Week
         $newDay = $this->getWeek()->modify('+1 week');
 
         return new self(
-            (int) $newDay->format('W'),
-            (int) $newDay->format('o')
+            (int)$newDay->format('W'),
+            (int)$newDay->format('o')
         );
     }
 
diff --git a/Classes/Domain/Model/Year.php b/Classes/Domain/Model/Year.php
index 88f005f..dda2281 100644
--- a/Classes/Domain/Model/Year.php
+++ b/Classes/Domain/Model/Year.php
@@ -21,9 +21,6 @@
  * 02110-1301, USA.
  */
 
-use TYPO3\CMS\Core\Utility\GeneralUtility;
-use TYPO3\CMS\Extbase\Persistence\ObjectStorage;
-
 class Year
 {
     /**
@@ -64,7 +61,7 @@ public function getMonths(): array
 
         while ($currentMonth <= $lastMonth) {
             $this->months[] = new Month(
-                (int) $currentMonth->format('n'),
+                (int)$currentMonth->format('n'),
                 $this->year
             );
 
diff --git a/Documentation/Changelog/2.0.0.rst b/Documentation/Changelog/2.0.0.rst
new file mode 100644
index 0000000..d4ee2c9
--- /dev/null
+++ b/Documentation/Changelog/2.0.0.rst
@@ -0,0 +1,36 @@
+2.0.0
+=====
+
+Breaking
+--------
+
+* Drop support for TYPO3 v10.4 LTS and PHP 7.3, 7.4, 8.0.
+
+Features
+--------
+
+* Add compatibility for TYPO3 v12.4.0 and PHP 8.3.
+
+Fixes
+-----
+
+Nothing
+
+Tasks
+-----
+
+* Switch CGL from ecs to php-cs-fixer.
+
+  As that's the tool we use everywhere else.
+  Use the same config as well.
+
+* Add PHPStan
+
+  As we always add that tool.
+  It helps us to find bugs and keep code clean.
+
+Deprecation
+-----------
+
+Nothing
+
diff --git a/Tests/Fixtures/BasicDatabase.php b/Tests/Fixtures/BasicDatabase.php
new file mode 100644
index 0000000..fee9931
--- /dev/null
+++ b/Tests/Fixtures/BasicDatabase.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+return [
+    'pages' => [
+        0 => [
+            'uid' => 1,
+            'pid' => 0,
+            'doktype' => 1,
+            'is_siteroot' => 1,
+            'slug' => '/',
+            'title' => 'Page Title',
+        ],
+    ],
+    'sys_template' => [
+        0 => [
+            'uid' => 1,
+            'pid' => 1,
+            'root' => 1,
+            'clear' => 3,
+            'constants' => 'databasePlatform = mysql',
+            'config' => '
+                <INCLUDE_TYPOSCRIPT: source="FILE:EXT:calendar_example/Configuration/TypoScript/Setup.typoscript">
+                <INCLUDE_TYPOSCRIPT: source="FILE:EXT:fluid_styled_content/Configuration/TypoScript/setup.typoscript">
+            ',
+        ],
+    ],
+];
diff --git a/Tests/Fixtures/BasicDatabase.xml b/Tests/Fixtures/BasicDatabase.xml
deleted file mode 100644
index e62ccec..0000000
--- a/Tests/Fixtures/BasicDatabase.xml
+++ /dev/null
@@ -1,22 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<dataset>
-    <pages>
-        <uid>1</uid>
-        <pid>0</pid>
-        <doktype>1</doktype>
-        <is_siteroot>1</is_siteroot>
-        <slug>/</slug>
-        <title>Page Title</title>
-    </pages>
-    <sys_template>
-        <uid>1</uid>
-        <pid>1</pid>
-        <root>1</root>
-        <clear>3</clear>
-        <constants>databasePlatform = mysql</constants>
-        <config><![CDATA[
-            <INCLUDE_TYPOSCRIPT: source="FILE:EXT:calendar_example/Configuration/TypoScript/Setup.typoscript">
-            <INCLUDE_TYPOSCRIPT: source="FILE:EXT:fluid_styled_content/Configuration/TypoScript/setup.typoscript">
-        ]]></config>
-    </sys_template>
-</dataset>
diff --git a/Tests/Fixtures/calendar_example/Classes/Domain/ExampleDataFactory.php b/Tests/Fixtures/calendar_example/Classes/Domain/ExampleDataFactory.php
index 0ec0fc9..e7e4c1a 100644
--- a/Tests/Fixtures/calendar_example/Classes/Domain/ExampleDataFactory.php
+++ b/Tests/Fixtures/calendar_example/Classes/Domain/ExampleDataFactory.php
@@ -40,7 +40,7 @@ public function setContext(Context $context): void
         $this->context = $context;
     }
 
-    public function getData(Day $day)
+    public function getData(Day $day): mixed
     {
         return [
             'exampleKey' => 'exampleValue',
diff --git a/Tests/Fixtures/calendar_example/Configuration/TypoScript/Setup.typoscript b/Tests/Fixtures/calendar_example/Configuration/TypoScript/Setup.typoscript
index 9031a3e..c0613c8 100644
--- a/Tests/Fixtures/calendar_example/Configuration/TypoScript/Setup.typoscript
+++ b/Tests/Fixtures/calendar_example/Configuration/TypoScript/Setup.typoscript
@@ -11,7 +11,7 @@ page {
     10 =< tt_content.calendar_example.20
 }
 
-[request.getQueryParams()['typoScriptDefaults'] == 1]
+[traverse(request.getQueryParams(), 'typoScriptDefaults') == 1]
     plugin.tx_calendar_example {
         settings {
             arguments {
diff --git a/Tests/ForcePropertyTrait.php b/Tests/ForcePropertyTrait.php
index 1af013f..543b5c9 100644
--- a/Tests/ForcePropertyTrait.php
+++ b/Tests/ForcePropertyTrait.php
@@ -23,7 +23,7 @@
 
 trait ForcePropertyTrait
 {
-    protected function forceProperty($subject, string $name, $value)
+    protected function forceProperty(object $subject, string $name, mixed $value): void
     {
         $objectReflection = new \ReflectionObject($subject);
         $property = $objectReflection->getProperty($name);
diff --git a/Tests/Functional/CalendarControllerTest.php b/Tests/Functional/CalendarControllerTest.php
index c412cc6..fdfb58f 100644
--- a/Tests/Functional/CalendarControllerTest.php
+++ b/Tests/Functional/CalendarControllerTest.php
@@ -23,30 +23,32 @@
 
 namespace WerkraumMedia\Calendar\Tests\Functional;
 
+use Codappix\Typo3PhpDatasets\TestingFramework;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\Attributes\TestDox;
+use TYPO3\CMS\Core\Localization\DateFormatter;
 use TYPO3\TestingFramework\Core\Functional\Framework\Frontend\InternalRequest;
 use TYPO3\TestingFramework\Core\Functional\FunctionalTestCase;
-use WerkraumMedia\Calendar\Controller\Frontend\CalendarController;
 
-/**
- * @coversNothing
- * @testdox Calendar controller renders with
- */
+#[TestDox('Calendar controller renders with')]
 class CalendarControllerTest extends FunctionalTestCase
 {
-    protected $coreExtensionsToLoad = [
+    use TestingFramework;
+
+    protected array $coreExtensionsToLoad = [
         'fluid_styled_content',
     ];
 
-    protected $testExtensionsToLoad = [
+    protected array $testExtensionsToLoad = [
         'typo3conf/ext/calendar',
         'typo3conf/ext/calendar/Tests/Fixtures/calendar_example',
     ];
 
-    protected $pathsToLinkInTestInstance = [
+    protected array $pathsToLinkInTestInstance = [
         'typo3conf/ext/calendar/Tests/Fixtures/Sites' => 'typo3conf/sites',
     ];
 
-    protected $configurationToUseInTestInstance = [
+    protected array $configurationToUseInTestInstance = [
         'FE' => [
             'cacheHash' => [
                 'excludedParameters' => [
@@ -61,45 +63,39 @@ protected function setUp(): void
     {
         parent::setUp();
 
-        $this->importDataSet(__DIR__ . '/../Fixtures/BasicDatabase.xml');
+        $this->importPHPDataSet(__DIR__ . '/../Fixtures/BasicDatabase.php');
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function modifiedVariablesForCurrentDay(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('modifiedVariable', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function pluginNameForCurrentDay(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('PluginName: Example', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function contextForCurrentDay(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
@@ -107,14 +103,12 @@ public function contextForCurrentDay(): void
         self::assertStringContainsString('Title: Page Title', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function customDataForCurrentDay(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
@@ -122,75 +116,65 @@ public function customDataForCurrentDay(): void
         self::assertStringContainsString('exampleValue', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function configuredDay(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('typoScriptDefaults', '1');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('03.11.1988', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providedDay(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[day][day]', '2020-11-03');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('03.11.2020', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function modifiedVariablesForCurrentWeek(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'week');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('modifiedVariable', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function pluginNameForCurrentWeek(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'week');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('PluginName: Example', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function contextForCurrentWeek(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'week');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
@@ -198,15 +182,13 @@ public function contextForCurrentWeek(): void
         self::assertStringContainsString('Title: Page Title', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function customDataForCurrentWeek(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'week');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
@@ -214,25 +196,21 @@ public function customDataForCurrentWeek(): void
         self::assertStringContainsString('exampleValue', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function configuredWeek(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'week');
         $request = $request->withQueryParameter('typoScriptDefaults', '1');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('12 1988', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providedWeek(): void
     {
         $request = new InternalRequest();
@@ -240,52 +218,46 @@ public function providedWeek(): void
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'week');
         $request = $request->withQueryParameter('tx_calendar_example[week][week]', '02');
         $request = $request->withQueryParameter('tx_calendar_example[week][year]', '2020');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('02 2020', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function modifiedVariablesForCurrentMonth(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'month');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('modifiedVariable', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function pluginNameForCurrentMonth(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'month');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('PluginName: Example', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function contextForCurrentMonth(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'month');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
@@ -293,41 +265,35 @@ public function contextForCurrentMonth(): void
         self::assertStringContainsString('Title: Page Title', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function customDataForCurrentMonth(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'month');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
-        self::assertStringContainsString(strftime('%B %Y'), $html);
+        self::assertStringContainsString((new DateFormatter())->strftime('%B %Y', 'now', 'de-DE'), $html);
         self::assertStringContainsString('exampleValue', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function configuredMonth(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'month');
         $request = $request->withQueryParameter('typoScriptDefaults', '1');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('November 1988', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providedMonth(): void
     {
         $request = new InternalRequest();
@@ -335,7 +301,7 @@ public function providedMonth(): void
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'month');
         $request = $request->withQueryParameter('tx_calendar_example[month][month]', '11');
         $request = $request->withQueryParameter('tx_calendar_example[month][year]', '2020');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
@@ -343,45 +309,39 @@ public function providedMonth(): void
         self::assertStringContainsString('exampleValue', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function modifiedVariablesForCurrentYear(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'year');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('modifiedVariable', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function pluginNameForCurrentYear(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'year');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('PluginName: Example', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function contextForCurrentYear(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'year');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
@@ -389,15 +349,13 @@ public function contextForCurrentYear(): void
         self::assertStringContainsString('Title: Page Title', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function customDataForCurrentYear(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'year');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
@@ -405,32 +363,28 @@ public function customDataForCurrentYear(): void
         self::assertStringContainsString('exampleValue', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function configuredYear(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'year');
         $request = $request->withQueryParameter('typoScriptDefaults', '1');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
         self::assertStringContainsString('1988', $html);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providedYear(): void
     {
         $request = new InternalRequest();
         $request = $request->withPageId(1);
         $request = $request->withQueryParameter('tx_calendar_example[action]', 'year');
         $request = $request->withQueryParameter('tx_calendar_example[year][year]', '2020');
-        $result = $this->executeFrontendRequest($request);
+        $result = $this->executeFrontendSubRequest($request);
 
         self::assertSame(200, $result->getStatusCode());
         $html = $result->getBody()->__toString();
diff --git a/Tests/Unit/Domain/Model/ContextTest.php b/Tests/Unit/Domain/Model/ContextTest.php
index 380822d..c7cbfd4 100644
--- a/Tests/Unit/Domain/Model/ContextTest.php
+++ b/Tests/Unit/Domain/Model/ContextTest.php
@@ -23,32 +23,14 @@
 
 namespace WerkraumMedia\Calendar\Tests\Unit\Domain\Model;
 
+use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
 use TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer;
 use WerkraumMedia\Calendar\Domain\Model\Context;
 
-/**
- * @covers \WerkraumMedia\Calendar\Domain\Model\Context
- */
 class ContextTest extends TestCase
 {
-    /**
-     * @test
-     */
-    public function canNotBeCreatedViaNew(): void
-    {
-        $this->expectError();
-        if (version_compare(PHP_VERSION, '8.0', '>=')) {
-            $this->expectErrorMessage('Call to private WerkraumMedia\Calendar\Domain\Model\Context::__construct() from scope WerkraumMedia\Calendar\Tests\Unit\Domain\Model\ContextTest');
-        } else {
-            $this->expectErrorMessage('Call to private WerkraumMedia\Calendar\Domain\Model\Context::__construct() from context \'WerkraumMedia\Calendar\Tests\Unit\Domain\Model\ContextTest\'');
-        }
-        $subject = new Context();
-    }
-
-    /**
-     * @test
-     */
+    #[Test]
     public function canBeCreatedFromContentObjectRenderer(): void
     {
         $contentObjectRenderer = $this->createStub(ContentObjectRenderer::class);
@@ -57,9 +39,7 @@ public function canBeCreatedFromContentObjectRenderer(): void
         self::assertInstanceOf(Context::class, $subject);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providesTableNameInheritedFromContentObjectRenderer(): void
     {
         $contentObjectRenderer = $this->createStub(ContentObjectRenderer::class);
@@ -69,9 +49,7 @@ public function providesTableNameInheritedFromContentObjectRenderer(): void
         self::assertSame('tx_calendar_example_table', $subject->getTableName());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providesDatabaseRowInheritedFromContentObjectRenderer(): void
     {
         $contentObjectRenderer = $this->createStub(ContentObjectRenderer::class);
diff --git a/Tests/Unit/Domain/Model/DayTest.php b/Tests/Unit/Domain/Model/DayTest.php
index 7bfc028..5177f05 100644
--- a/Tests/Unit/Domain/Model/DayTest.php
+++ b/Tests/Unit/Domain/Model/DayTest.php
@@ -21,19 +21,16 @@
  * 02110-1301, USA.
  */
 
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\Attributes\TestDox;
 use PHPUnit\Framework\TestCase;
 use TYPO3\CMS\Core\Utility\GeneralUtility;
-use TYPO3\CMS\Extbase\Persistence\ObjectStorage;
 use WerkraumMedia\Calendar\Domain\Model\Day;
 use WerkraumMedia\Calendar\Domain\Model\ForeignDataFactory;
 use WerkraumMedia\Calendar\Domain\Model\IsDayActive;
-use WerkraumMedia\Calendar\Domain\Model\NullDataFactory;
 use WerkraumMedia\Calendar\Tests\ForcePropertyTrait;
 
-/**
- * @covers WerkraumMedia\Calendar\Domain\Model\Day
- * @testdox A day
- */
+#[TestDox('A day')]
 class DayTest extends TestCase
 {
     use ForcePropertyTrait;
@@ -44,9 +41,7 @@ public function tearDown(): void
         parent::tearDown();
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function canBeCreated(): void
     {
         $subject = new Day(
@@ -56,9 +51,7 @@ public function canBeCreated(): void
         self::assertInstanceOf(Day::class, $subject);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providesDateTimeInstance(): void
     {
         $dateTimeInstance = new \DateTime();
@@ -69,9 +62,7 @@ public function providesDateTimeInstance(): void
         self::assertInstanceOf(\DateTimeImmutable::class, $subject->getDateTimeInstance());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providedDateTimeInstanceHasExpectedDay(): void
     {
         $dateTimeInstance = new \DateTime();
@@ -82,9 +73,7 @@ public function providedDateTimeInstanceHasExpectedDay(): void
         self::assertSame($dateTimeInstance->format('d.m.Y'), $subject->getDateTimeInstance()->format('d.m.Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providedDateTimeInstanceHasMidnight(): void
     {
         $dateTimeInstance = new \DateTime();
@@ -95,9 +84,7 @@ public function providedDateTimeInstanceHasMidnight(): void
         self::assertSame('00:00:00', $subject->getDateTimeInstance()->format('H:i:s'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providesItselfAsUrlArgument(): void
     {
         $subject = new Day(new \DateTime('2020-10-19'));
@@ -105,9 +92,7 @@ public function providesItselfAsUrlArgument(): void
         self::assertSame(['day' => '2020-10-19'], $subject->getAsUrlArgument());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function isNotActiveIfNoForeignDataWithInterfaceExists(): void
     {
         $subject = new Day(new \DateTime('2020-10-19'));
@@ -117,9 +102,7 @@ public function isNotActiveIfNoForeignDataWithInterfaceExists(): void
         self::assertFalse($subject->isActive());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function isNotActiveIfForeignDataIsNotActive(): void
     {
         $subject = new Day(new \DateTime('2020-10-19'));
@@ -133,9 +116,7 @@ public function isNotActiveIfForeignDataIsNotActive(): void
         self::assertFalse($subject->isActive());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function initializesForeignDataViaFactory(): void
     {
         $subject = new Day(new \DateTime('2020-10-19'));
diff --git a/Tests/Unit/Domain/Model/MonthTest.php b/Tests/Unit/Domain/Model/MonthTest.php
index f214f63..5e8c81b 100644
--- a/Tests/Unit/Domain/Model/MonthTest.php
+++ b/Tests/Unit/Domain/Model/MonthTest.php
@@ -21,22 +21,19 @@
  * 02110-1301, USA.
  */
 
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\Attributes\TestDox;
 use PHPUnit\Framework\TestCase;
 use WerkraumMedia\Calendar\Domain\Model\Month;
 use WerkraumMedia\Calendar\Domain\Model\Week;
 use WerkraumMedia\Calendar\Tests\ForcePropertyTrait;
 
-/**
- * @covers WerkraumMedia\Calendar\Domain\Model\Month
- * @testdox A month
- */
+#[TestDox('A month')]
 class MonthTest extends TestCase
 {
     use ForcePropertyTrait;
 
-    /**
-     * @test
-     */
+    #[Test]
     public function canBeCreated(): void
     {
         $subject = new Month(1, 2020);
@@ -44,9 +41,7 @@ public function canBeCreated(): void
         self::assertInstanceOf(Month::class, $subject);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsPreviousMonthForSameYear(): void
     {
         $subject = new Month(2, 2020);
@@ -55,9 +50,7 @@ public function returnsPreviousMonthForSameYear(): void
         self::assertSame('2020', $subject->getPreviousMonth()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsPreviousMonthForPreviousYear(): void
     {
         $subject = new Month(1, 2020);
@@ -66,9 +59,7 @@ public function returnsPreviousMonthForPreviousYear(): void
         self::assertSame('2019', $subject->getPreviousMonth()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsNextMonthForSameYear(): void
     {
         $subject = new Month(1, 2020);
@@ -77,9 +68,7 @@ public function returnsNextMonthForSameYear(): void
         self::assertSame('2020', $subject->getNextMonth()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsNextMonthForNextYear(): void
     {
         $subject = new Month(12, 2020);
@@ -88,9 +77,7 @@ public function returnsNextMonthForNextYear(): void
         self::assertSame('2021', $subject->getNextMonth()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsFiveWeeksForDecember2020(): void
     {
         $subject = new Month(12, 2020);
@@ -101,9 +88,7 @@ public function returnsFiveWeeksForDecember2020(): void
         self::assertSame('2021-01-03', $weeks[4]->getDays()[6]->getDateTimeInstance()->format('Y-m-d'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsSixWeeksForNovember2020(): void
     {
         $subject = new Month(11, 2020);
@@ -114,9 +99,7 @@ public function returnsSixWeeksForNovember2020(): void
         self::assertSame('2020-12-06', $weeks[5]->getDays()[6]->getDateTimeInstance()->format('Y-m-d'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsSameWeeksOnSecondCall(): void
     {
         $subject = new Month(11, 2020);
@@ -124,9 +107,7 @@ public function returnsSameWeeksOnSecondCall(): void
         self::assertSame($subject->getWeeks(), $subject->getWeeks());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsAllDaysOfTheFebruaryMonth2021(): void
     {
         $subject = new Month(02, 2021);
@@ -138,9 +119,7 @@ public function returnsAllDaysOfTheFebruaryMonth2021(): void
         self::assertSame('2021-02-28', $result[27]->getDateTimeInstance()->format('Y-m-d'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsWeeksIfLastDecemberWeekIsInNextYear(): void
     {
         $subject = new Month(12, 2024);
@@ -160,9 +139,7 @@ public function returnsWeeksIfLastDecemberWeekIsInNextYear(): void
         self::assertSame('2024-12-29', $days[6]->getDateTimeInstance()->format('Y-m-d'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsAllDaysOfTheJuneMonth2021(): void
     {
         $subject = new Month(06, 2021);
@@ -174,9 +151,7 @@ public function returnsAllDaysOfTheJuneMonth2021(): void
         self::assertSame('2021-06-30', $result[29]->getDateTimeInstance()->format('Y-m-d'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsSameDaysOnSecondCall(): void
     {
         $subject = new Month(06, 2021);
@@ -184,9 +159,7 @@ public function returnsSameDaysOnSecondCall(): void
         self::assertSame($subject->getDays(), $subject->getDays());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providesDateTimeInstance(): void
     {
         $subject = new Month(02, 2018);
@@ -194,9 +167,7 @@ public function providesDateTimeInstance(): void
         self::assertSame('2018-02-01', $subject->getDateTimeInstance()->format('Y-m-d'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsAsUrlArguments(): void
     {
         $subject = new Month(02, 2018);
@@ -207,9 +178,7 @@ public function returnsAsUrlArguments(): void
         ], $subject->getAsUrlArgument());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsNotActiveIfAllWeeksAreInactive(): void
     {
         $subject = new Month(02, 2018);
@@ -222,9 +191,7 @@ public function returnsNotActiveIfAllWeeksAreInactive(): void
         self::assertFalse($subject->isActive());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsActiveIfASingleWeekIsActive(): void
     {
         $subject = new Month(02, 2018);
diff --git a/Tests/Unit/Domain/Model/NullDataFactoryTest.php b/Tests/Unit/Domain/Model/NullDataFactoryTest.php
index 90106bc..3e54ebe 100644
--- a/Tests/Unit/Domain/Model/NullDataFactoryTest.php
+++ b/Tests/Unit/Domain/Model/NullDataFactoryTest.php
@@ -21,18 +21,14 @@
  * 02110-1301, USA.
  */
 
+use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
 use WerkraumMedia\Calendar\Domain\Model\Day;
 use WerkraumMedia\Calendar\Domain\Model\NullDataFactory;
 
-/**
- * @covers WerkraumMedia\Calendar\Domain\Model\NullDataFactory
- */
 class NullDataFactoryTest extends TestCase
 {
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsNull(): void
     {
         $subject = new NullDataFactory();
diff --git a/Tests/Unit/Domain/Model/WeekTest.php b/Tests/Unit/Domain/Model/WeekTest.php
index afee954..4368e9e 100644
--- a/Tests/Unit/Domain/Model/WeekTest.php
+++ b/Tests/Unit/Domain/Model/WeekTest.php
@@ -21,22 +21,19 @@
  * 02110-1301, USA.
  */
 
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\Attributes\TestDox;
 use PHPUnit\Framework\TestCase;
 use WerkraumMedia\Calendar\Domain\Model\Day;
 use WerkraumMedia\Calendar\Domain\Model\Week;
 use WerkraumMedia\Calendar\Tests\ForcePropertyTrait;
 
-/**
- * @covers WerkraumMedia\Calendar\Domain\Model\Week
- * @testdox A week
- */
+#[TestDox('A week')]
 class WeekTest extends TestCase
 {
     use ForcePropertyTrait;
 
-    /**
-     * @test
-     */
+    #[Test]
     public function canBeCreated(): void
     {
         $subject = new Week(1, 2020);
@@ -44,9 +41,7 @@ public function canBeCreated(): void
         self::assertInstanceOf(Week::class, $subject);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsSevenDays(): void
     {
         $subject = new Week(1, 2020);
@@ -54,9 +49,7 @@ public function returnsSevenDays(): void
         self::assertCount(7, $subject->getDays());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsSameDaysOnSecondCall(): void
     {
         $subject = new Week(1, 2020);
@@ -64,9 +57,7 @@ public function returnsSameDaysOnSecondCall(): void
         self::assertSame($subject->getDays(), $subject->getDays());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsDaysForWeek1(): void
     {
         $subject = new Week(1, 2020);
@@ -81,9 +72,7 @@ public function returnsDaysForWeek1(): void
         self::assertSame('2020-01-05', $days[6]->getDateTimeInstance()->format('Y-m-d'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsDaysForWeek53(): void
     {
         $subject = new Week(53, 2020);
@@ -98,9 +87,7 @@ public function returnsDaysForWeek53(): void
         self::assertSame('2021-01-03', $days[6]->getDateTimeInstance()->format('Y-m-d'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsPreviousWeekForSameYear(): void
     {
         $subject = new Week(2, 2020);
@@ -109,9 +96,7 @@ public function returnsPreviousWeekForSameYear(): void
         self::assertSame('2020', $subject->getPreviousWeek()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsPreviousWeekForYearSwitchFrom2019To2018(): void
     {
         $subject = new Week(1, 2019);
@@ -120,9 +105,7 @@ public function returnsPreviousWeekForYearSwitchFrom2019To2018(): void
         self::assertSame('2018', $subject->getPreviousWeek()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsPreviousWeekForYearSwitchFrom2018To2017(): void
     {
         $subject = new Week(1, 2018);
@@ -131,9 +114,7 @@ public function returnsPreviousWeekForYearSwitchFrom2018To2017(): void
         self::assertSame('2017', $subject->getPreviousWeek()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsPreviousWeekForPreviousYear(): void
     {
         $subject = new Week(1, 2021);
@@ -142,9 +123,7 @@ public function returnsPreviousWeekForPreviousYear(): void
         self::assertSame('2020', $subject->getPreviousWeek()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsNextWeekForSameYear(): void
     {
         $subject = new Week(1, 2020);
@@ -153,9 +132,7 @@ public function returnsNextWeekForSameYear(): void
         self::assertSame('2020', $subject->getNextWeek()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsNextWeekForNextYear(): void
     {
         $subject = new Week(53, 2020);
@@ -164,9 +141,7 @@ public function returnsNextWeekForNextYear(): void
         self::assertSame('2021', $subject->getNextWeek()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsNextWeekForNextYearFrom2018To2019(): void
     {
         $subject = new Week(52, 2018);
@@ -175,9 +150,7 @@ public function returnsNextWeekForNextYearFrom2018To2019(): void
         self::assertSame('2019', $subject->getNextWeek()->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providesDateTimeInstance(): void
     {
         $subject = new Week(52, 2018);
@@ -186,9 +159,7 @@ public function providesDateTimeInstance(): void
         self::assertSame('2018-12-27 Thursday', $subject->getDateTimeInstance()->format('Y-m-d l'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function providesItselfAsUrlArgument(): void
     {
         $subject = new Week(52, 2018);
@@ -199,9 +170,7 @@ public function providesItselfAsUrlArgument(): void
         ], $subject->getAsUrlArgument());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsNotActiveIfAllDaysAreInactive(): void
     {
         $subject = new Week(02, 2018);
@@ -214,9 +183,7 @@ public function returnsNotActiveIfAllDaysAreInactive(): void
         self::assertFalse($subject->isActive());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsActiveIfASingleDayActive(): void
     {
         $subject = new Week(02, 2018);
diff --git a/Tests/Unit/Domain/Model/YearTest.php b/Tests/Unit/Domain/Model/YearTest.php
index c55c65a..4af88e6 100644
--- a/Tests/Unit/Domain/Model/YearTest.php
+++ b/Tests/Unit/Domain/Model/YearTest.php
@@ -21,22 +21,19 @@
  * 02110-1301, USA.
  */
 
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\Attributes\TestDox;
 use PHPUnit\Framework\TestCase;
 use WerkraumMedia\Calendar\Domain\Model\Month;
 use WerkraumMedia\Calendar\Domain\Model\Year;
 use WerkraumMedia\Calendar\Tests\ForcePropertyTrait;
 
-/**
- * @covers WerkraumMedia\Calendar\Domain\Model\Year
- * @testdox A year
- */
+#[TestDox('A year')]
 class YearTest extends TestCase
 {
     use ForcePropertyTrait;
 
-    /**
-     * @test
-     */
+    #[Test]
     public function canBeCreated(): void
     {
         $subject = new Year(2020);
@@ -44,9 +41,7 @@ public function canBeCreated(): void
         self::assertInstanceOf(Year::class, $subject);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsPreviousYear(): void
     {
         $subject = new Year(2020);
@@ -57,9 +52,7 @@ public function returnsPreviousYear(): void
         self::assertSame('2019', $result->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsNextYear(): void
     {
         $subject = new Year(2020);
@@ -70,9 +63,7 @@ public function returnsNextYear(): void
         self::assertSame('2021', $result->getDateTimeInstance()->format('Y'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsAsUrlArguments(): void
     {
         $subject = new Year(2020);
@@ -82,9 +73,7 @@ public function returnsAsUrlArguments(): void
         ], $subject->getAsUrlArgument());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsMonthsForYear2020(): void
     {
         $subject = new Year(2020);
@@ -96,13 +85,11 @@ public function returnsMonthsForYear2020(): void
         foreach ($result as $index => $month) {
             self::assertInstanceOf(Month::class, $month);
             $monthNumber = $index + 1;
-            self::assertSame((string) $monthNumber, $month->getDateTimeInstance()->format('n'));
+            self::assertSame((string)$monthNumber, $month->getDateTimeInstance()->format('n'));
         }
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsSameMonthsOnSecondCall(): void
     {
         $subject = new Year(2020);
@@ -110,9 +97,7 @@ public function returnsSameMonthsOnSecondCall(): void
         self::assertSame($subject->getMonths(), $subject->getMonths());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsAllDaysFor2020(): void
     {
         $subject = new Year(2020);
@@ -124,9 +109,7 @@ public function returnsAllDaysFor2020(): void
         self::assertSame('2020-12-31', $result[365]->getDateTimeInstance()->format('Y-m-d'));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsNotActiveIfAllMonthsAreInactive(): void
     {
         $subject = new Year(2020);
@@ -139,9 +122,7 @@ public function returnsNotActiveIfAllMonthsAreInactive(): void
         self::assertFalse($subject->isActive());
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsActiveIfASingleMonthIsActive(): void
     {
         $subject = new Year(2020);
diff --git a/Tests/Unit/Events/AssignTemplateVariablesTest.php b/Tests/Unit/Events/AssignTemplateVariablesTest.php
index f5d738b..35b4d34 100644
--- a/Tests/Unit/Events/AssignTemplateVariablesTest.php
+++ b/Tests/Unit/Events/AssignTemplateVariablesTest.php
@@ -21,17 +21,13 @@
  * 02110-1301, USA.
  */
 
+use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
 use WerkraumMedia\Calendar\Events\AssignTemplateVariables;
 
-/**
- * @covers WerkraumMedia\Calendar\Events\AssignTemplateVariables
- */
 class AssignTemplateVariablesTest extends TestCase
 {
-    /**
-     * @test
-     */
+    #[Test]
     public function canBeCreated(): void
     {
         $subject = new AssignTemplateVariables(
@@ -42,9 +38,7 @@ public function canBeCreated(): void
         self::assertInstanceOf(AssignTemplateVariables::class, $subject);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsPluginName(): void
     {
         $subject = new AssignTemplateVariables(
@@ -57,9 +51,7 @@ public function returnsPluginName(): void
         self::assertSame('Example', $result);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function returnsVariables(): void
     {
         $subject = new AssignTemplateVariables(
@@ -76,9 +68,7 @@ public function returnsVariables(): void
         ], $result);
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function newVariablesOverwriteExistingVariables(): void
     {
         $subject = new AssignTemplateVariables(
diff --git a/composer.json b/composer.json
index 7dc5dda..294cc84 100644
--- a/composer.json
+++ b/composer.json
@@ -11,16 +11,21 @@
     ],
     "config": {
         "sort-packages": true,
+        "lock": false,
         "allow-plugins": {
             "typo3/class-alias-loader": true,
             "typo3/cms-composer-installers": true
         }
     },
+    "minimum-stability": "dev",
+    "prefer-stable": true,
     "require": {
-        "php": "^7.3.0 || ^7.4.0 || ^8.0.0 || ^8.1.0 || ^8.2.0",
-        "typo3/cms-core": "^10.4 || ^11.5",
-        "typo3/cms-extbase": "^10.4 || ^11.5",
-        "typo3/cms-frontend": "^10.4 || ^11.5"
+        "php": "~8.1.0 || ~8.2.0 || ~8.3.0",
+        "typo3/cms-backend": "^12.4",
+        "typo3/cms-core": "^12.4",
+        "typo3/cms-extbase": "^12.4",
+        "typo3/cms-fluid-styled-content": "^12.4",
+        "typo3/cms-frontend": "^12.4"
     },
     "autoload": {
         "psr-4": {
@@ -34,14 +39,16 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.5",
-        "symplify/easy-coding-standard": "^9.2",
-        "typo3/cms-fluid-styled-content": "^10.4 || ^11.5",
-        "typo3/testing-framework": "^6.6"
+        "codappix/typo3-php-datasets": "^1.5",
+        "friendsofphp/php-cs-fixer": "^3.11",
+        "phpstan/phpstan": "^1.12",
+        "phpstan/phpstan-phpunit": "^1.0",
+        "phpunit/phpunit": "^10.5 || ^11.3",
+        "saschaegerer/phpstan-typo3": "^1.10",
+        "typo3/testing-framework": "^8.2"
     },
     "extra": {
         "typo3/cms": {
-            "cms-package-dir": "{$vendor-dir}/typo3/cms",
             "extension-key": "calendar",
             "web-dir": ".Build/web"
         }
diff --git a/ecs.php b/ecs.php
deleted file mode 100644
index 379a801..0000000
--- a/ecs.php
+++ /dev/null
@@ -1,35 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use PhpCsFixer\Fixer\ArrayNotation\ArraySyntaxFixer;
-use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
-use Symplify\EasyCodingStandard\ValueObject\Option;
-use Symplify\EasyCodingStandard\ValueObject\Set\SetList;
-
-return static function (ContainerConfigurator $containerConfigurator): void {
-    $parameters = $containerConfigurator->parameters();
-    $parameters->set(Option::PATHS, [
-        __DIR__ . '/Classes',
-        __DIR__ . '/Tests',
-        __DIR__ . '/ext_emconf.php',
-        __DIR__ . '/ecs.php',
-    ]);
-
-    $parameters->set(Option::SETS, [
-        // run and fix, one by one
-        // SetList::SPACES,
-        // SetList::ARRAY,
-        // SetList::DOCBLOCK,
-        // SetList::NAMESPACES,
-        // SetList::CONTROL_STRUCTURES,
-        // SetList::CLEAN_CODE,
-        SetList::PSR_12,
-    ]);
-
-    $services = $containerConfigurator->services();
-    $services->set(ArraySyntaxFixer::class)
-        ->call('configure', [[
-            'syntax' => 'short',
-        ]]);
-};
diff --git a/ext_emconf.php b/ext_emconf.php
index 80d6d14..19cc470 100644
--- a/ext_emconf.php
+++ b/ext_emconf.php
@@ -10,7 +10,7 @@
     'state' => 'alpha',
     'uploadfolder' => 0,
     'clearCacheOnLoad' => 0,
-    'version' => '1.1.1',
+    'version' => '2.0.0',
     'constraints' => [
         'depends' => [
             'typo3' => '*',
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 0000000..28e3f34
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,10 @@
+parameters:
+  level: 'max'
+  paths:
+    - 'Classes'
+    - 'Configuration'
+    - 'Tests'
+  reportUnmatchedIgnoredErrors: true
+  ignoreErrors:
+    -
+      identifier: 'missingType.iterableValue'
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 858b92f..50b1459 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,21 +1,25 @@
 <?xml version="1.0"?>
 <phpunit
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd"
+    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/11.3/phpunit.xsd"
     backupGlobals="false"
-    backupStaticAttributes="false"
     bootstrap="vendor/typo3/testing-framework/Resources/Core/Build/FunctionalTestsBootstrap.php"
     colors="true"
-    convertErrorsToExceptions="true"
-    convertWarningsToExceptions="true"
-    forceCoversAnnotation="false"
     processIsolation="false"
     stopOnError="false"
     stopOnFailure="false"
     stopOnIncomplete="false"
     stopOnSkipped="false"
-    verbose="false"
-    >
+    cacheDirectory=".phpunit.cache"
+    backupStaticProperties="false"
+    requireCoverageMetadata="false"
+>
+
+    <source>
+        <include>
+            <directory suffix=".php">Classes</directory>
+        </include>
+    </source>
 
     <testsuites>
         <testsuite name="unit">
@@ -26,12 +30,6 @@
         </testsuite>
     </testsuites>
 
-    <coverage>
-        <include>
-            <directory suffix=".php">Classes</directory>
-        </include>
-    </coverage>
-
     <php>
         <env name="typo3DatabaseDriver" value="pdo_sqlite"/>
     </php>
diff --git a/shell.nix b/shell.nix
new file mode 100644
index 0000000..2e5e12d
--- /dev/null
+++ b/shell.nix
@@ -0,0 +1,52 @@
+{ pkgs ? import <nixpkgs> { } }:
+
+let
+  php = pkgs.php82.buildEnv {
+    extensions = { enabled, all }: enabled ++ (with all; [
+      xdebug
+    ]);
+    extraConfig = ''
+      xdebug.mode = debug
+      memory_limit = 4G
+    '';
+  };
+  inherit (php.packages) composer;
+
+  projectInstall = pkgs.writeShellApplication {
+    name = "project-install";
+    runtimeInputs = [
+      php
+      composer
+    ];
+    text = ''
+      rm -rf vendor/ .Build/
+      composer install --prefer-dist --no-progress --working-dir="$PROJECT_ROOT"
+    '';
+  };
+
+  projectValidateComposer = pkgs.writeShellApplication {
+    name = "project-validate-composer";
+    runtimeInputs = [
+      php
+      composer
+    ];
+    text = ''
+      composer validate
+    '';
+  };
+
+in pkgs.mkShell {
+  name = "TYPO3 Extension Watchlist";
+  buildInputs = [
+    projectInstall
+    projectValidateComposer
+    php
+    composer
+  ];
+
+  shellHook = ''
+    export PROJECT_ROOT="$(pwd)"
+
+    export typo3DatabaseDriver=pdo_sqlite
+  '';
+}