diff --git a/Classes/AbstractClient.php b/Classes/AbstractClient.php
index 366de9ef..66aec7f3 100644
--- a/Classes/AbstractClient.php
+++ b/Classes/AbstractClient.php
@@ -22,6 +22,23 @@ abstract class AbstractClient implements ClientInterface
 
     protected LoggerInterface $logger;
 
+    /**
+     * Copied from TranslatorOptions
+     * for iterating over Client Configuration
+     * @see TranslatorOptions::OPTIONS_KEYS
+     */
+    private const OPTIONS_KEYS = [
+        TranslatorOptions::SERVER_URL,
+        TranslatorOptions::HEADERS,
+        TranslatorOptions::TIMEOUT,
+        TranslatorOptions::MAX_RETRIES,
+        TranslatorOptions::PROXY,
+        TranslatorOptions::LOGGER,
+        TranslatorOptions::HTTP_CLIENT,
+        TranslatorOptions::SEND_PLATFORM_INFO,
+        TranslatorOptions::APP_INFO,
+    ];
+
     public function __construct(ConfigurationInterface $configuration)
     {
         $this->configuration = $configuration;
@@ -46,6 +63,11 @@ protected function getTranslator(): Translator
             throw new ApiKeyNotSetException('The api key ist not set', 1708081233823);
         }
         $options[TranslatorOptions::HTTP_CLIENT] = GeneralUtility::makeInstance(GuzzleClientFactory::class)->getClient();
+        foreach (self::OPTIONS_KEYS as $option) {
+            if ($options[TranslatorOptions::HTTP_CLIENT]->getConfig($option) !== null) {
+                $options[$option] = $options[TranslatorOptions::HTTP_CLIENT]->getConfig($option);
+            }
+        }
         $this->translator = new Translator($this->configuration->getApiKey(), $options);
         return $this->translator;
     }
diff --git a/Classes/Client.php b/Classes/Client.php
index ffe2fe6e..30538470 100644
--- a/Classes/Client.php
+++ b/Classes/Client.php
@@ -12,11 +12,13 @@
 use DeepL\TextResult;
 use DeepL\TranslateTextOptions;
 use DeepL\Usage;
+use Symfony\Component\DependencyInjection\Attribute\AsAlias;
 use WebVision\Deepltranslate\Core\Exception\ApiKeyNotSetException;
 
 /**
  * @internal No public usage
  */
+#[AsAlias(id: ClientInterface::class, public: true)]
 final class Client extends AbstractClient
 {
     /**
diff --git a/Tests/Functional/AbstractDeepLTestCase.php b/Tests/Functional/AbstractDeepLTestCase.php
index 24c4acaf..ca51e3f7 100644
--- a/Tests/Functional/AbstractDeepLTestCase.php
+++ b/Tests/Functional/AbstractDeepLTestCase.php
@@ -4,25 +4,17 @@
 
 namespace WebVision\Deepltranslate\Core\Tests\Functional;
 
-use Closure;
-use DeepL\Translator;
 use DeepL\TranslatorOptions;
 use Exception;
-use phpmock\phpunit\PHPMock;
-use Psr\Log\NullLogger;
 use Ramsey\Uuid\Uuid;
 use RuntimeException;
 use SBUERK\TYPO3\Testing\TestCase\FunctionalTestCase;
-use Symfony\Component\DependencyInjection\Container;
 use TYPO3\CMS\Core\Information\Typo3Version;
+use TYPO3\CMS\Core\Utility\ArrayUtility;
 use TYPO3\CMS\Core\Utility\StringUtility;
-use WebVision\Deepltranslate\Core\Client;
-use WebVision\Deepltranslate\Core\ClientInterface;
-use WebVision\Deepltranslate\Core\ConfigurationInterface;
 
 abstract class AbstractDeepLTestCase extends FunctionalTestCase
 {
-    use PHPMock;
 
     /**
      * @var string
@@ -112,7 +104,6 @@ abstract class AbstractDeepLTestCase extends FunctionalTestCase
     protected array $testExtensionsToLoad = [
         'web-vision/deepl-base',
         'web-vision/deepltranslate-core',
-        __DIR__ . '/Fixtures/Extensions/test_services_override',
     ];
 
     protected const EXAMPLE_DOCUMENT_INPUT = AbstractDeepLTestCase::EXAMPLE_TEXT['en'];
@@ -152,13 +143,13 @@ protected function setUp(): void
             }
             $this->authKey = getenv('DEEPL_AUTH_KEY');
         }
-        parent::setUp();
         $this->instantiateMockServerClient();
+        parent::setUp();
     }
 
     private function makeSessionName(): string
     {
-        return sprintf('%s/%s', self::getInstanceIdentifier(), StringUtility::getUniqueId());
+        return sprintf('%s/%s', self::getInstanceIdentifier(), StringUtility::getUniqueId('deepl-mock-'));
     }
 
     /**
@@ -210,29 +201,12 @@ protected function instantiateMockServerClient(array $options = []): void
         if ($this->serverUrl !== false) {
             $mergedOptions[TranslatorOptions::SERVER_URL] = $this->serverUrl;
         }
-        $mockConfiguration = $this
-            ->getMockBuilder(ConfigurationInterface::class)
-            ->getMock();
-        $mockConfiguration
-            ->method('getApiKey')
-            ->willReturn(self::getInstanceIdentifier());
-
-        $client = new Client($mockConfiguration);
-        $client->setLogger(new NullLogger());
-
-        // use closure to set private option for translation
-        $translator = new Translator(self::getInstanceIdentifier(), $mergedOptions);
-        Closure::bind(
-            function (Translator $translator) {
-                $this->translator = $translator;
-            },
-            $client,
-            Client::class
-        )->call($client, $translator);
-
-        /** @var Container $container */
-        $container = $this->getContainer();
-        $container->set(ClientInterface::class, $client);
+        ArrayUtility::mergeRecursiveWithOverrule(
+            $this->configurationToUseInTestInstance,
+            [
+                'HTTP' => $mergedOptions,
+            ],
+        );
     }
 
     public static function readFile(string $filepath): string
@@ -301,20 +275,4 @@ public function assertExceptionClass(string $class, callable $function): Excepti
         }
         static::fail("Expected exception of class '$class' but nothing was thrown");
     }
-
-    /**
-     * This is necessary due to https://github.com/php-mock/php-mock-phpunit#restrictions
-     * In short, as these methods can be called by other tests before UserAgentTest and other
-     * tests that use their mocks are executed, we need to call `defineFunctionMock` before
-     * calling the unmocked function, or the mock will not work.
-     * Otherwise the tests will fail with:
-     *     Expectation failed for method name is "delegate" when invoked 1 time(s).
-     *     Method was expected to be called 1 times, actually called 0 times.
-     */
-    public static function setUpBeforeClass(): void
-    {
-        self::defineFunctionMock(__NAMESPACE__, 'curl_exec');
-        self::defineFunctionMock(__NAMESPACE__, 'curl_getinfo');
-        self::defineFunctionMock(__NAMESPACE__, 'curl_setopt_array');
-    }
 }
diff --git a/Tests/Functional/Container/ContentElementsInContainerTest.php b/Tests/Functional/Container/ContentElementsInContainerTest.php
index 640908b2..35f65fa8 100644
--- a/Tests/Functional/Container/ContentElementsInContainerTest.php
+++ b/Tests/Functional/Container/ContentElementsInContainerTest.php
@@ -23,7 +23,6 @@ final class ContentElementsInContainerTest extends AbstractDeepLTestCase
         'b13/container',
         'web-vision/deepl-base',
         'web-vision/deepltranslate-core',
-        __DIR__ . '/../Fixtures/Extensions/test_services_override',
         __DIR__ . '/Fixtures/Extensions/test_container',
     ];
 
diff --git a/Tests/Functional/Fixtures/Extensions/test_services_override/Configuration/Services.php b/Tests/Functional/Fixtures/Extensions/test_services_override/Configuration/Services.php
deleted file mode 100644
index 7cf0d4b7..00000000
--- a/Tests/Functional/Fixtures/Extensions/test_services_override/Configuration/Services.php
+++ /dev/null
@@ -1,21 +0,0 @@
-<?php
-
-namespace Symfony\Component\DependencyInjection\Loader\Configurator;
-
-use Symfony\Component\DependencyInjection\ContainerBuilder;
-use WebVision\Deepltranslate\Core\ClientInterface;
-
-return function (ContainerConfigurator $containerConfigurator, ContainerBuilder $containerBuilder) {
-    $services = $containerConfigurator->services();
-    $services
-        ->defaults()
-        ->autowire()
-        ->autoconfigure();
-
-    // Set the ClientInterface to public for testing purpose only. This is needed, that
-    // functional testcases can set a special configured or mocked service
-    // instance for the alias. No need to have it public in general.
-    $services
-        ->set(ClientInterface::class)
-        ->public();
-};
diff --git a/Tests/Functional/Fixtures/Extensions/test_services_override/composer.json b/Tests/Functional/Fixtures/Extensions/test_services_override/composer.json
deleted file mode 100644
index 47962c4f..00000000
--- a/Tests/Functional/Fixtures/Extensions/test_services_override/composer.json
+++ /dev/null
@@ -1,15 +0,0 @@
-{
-	"name": "web-vision/test-services-override",
-	"type": "typo3-cms-extension",
-	"description": "Change service registrations for testing purposes.",
-	"license": ["GPL-2.0-or-later"],
-	"extra": {
-		"typo3/cms": {
-			"extension-key": "test_services_override"
-		}
-	},
-	"require": {
-		"typo3/cms-core": "*",
-		"web-vision/deepltranslate-core": "*"
-	}
-}
diff --git a/Tests/Functional/Fixtures/Extensions/test_services_override/ext_emconf.php b/Tests/Functional/Fixtures/Extensions/test_services_override/ext_emconf.php
deleted file mode 100644
index 3d611e8c..00000000
--- a/Tests/Functional/Fixtures/Extensions/test_services_override/ext_emconf.php
+++ /dev/null
@@ -1,30 +0,0 @@
-<?php
-
-/***************************************************************
- * Extension Manager/Repository config file for ext: "deepltranslate"
- *
- * Auto generated by Extension Builder 2020-04-18
- *
- * Manual updates:
- * Only the data in the array - anything else is removed by next write.
- * "version" and "dependencies" must not be touched!
- ***************************************************************/
-
-$EM_CONF[$_EXTKEY] = [
-    'title' => 'DeepL Translate - Test Overrides',
-    'description' => 'Change service registrations for testing purposes.',
-    'category' => 'backend',
-    'author' => 'web-vision GmbH Team',
-    'author_company' => 'web-vision GmbH',
-    'author_email' => 'hello@web-vision.de',
-    'state' => 'stable',
-    'version' => '1.0.0.',
-    'constraints' => [
-        'depends' => [
-            'typo3' => '12.4.0-12.4.99',
-            'deepltranslate_core' => '*',
-        ],
-        'conflicts' => [],
-        'suggests' => [],
-    ],
-];
diff --git a/Tests/Functional/Hooks/TranslationWithModifiedTcaConfigurationTest.php b/Tests/Functional/Hooks/TranslationWithModifiedTcaConfigurationTest.php
index cb8524a0..d7a3500c 100644
--- a/Tests/Functional/Hooks/TranslationWithModifiedTcaConfigurationTest.php
+++ b/Tests/Functional/Hooks/TranslationWithModifiedTcaConfigurationTest.php
@@ -68,7 +68,6 @@ final class TranslationWithModifiedTcaConfigurationTest extends AbstractDeepLTes
     protected array $testExtensionsToLoad = [
         'web-vision/deepl-base',
         'web-vision/deepltranslate-core',
-        __DIR__ . '/../Fixtures/Extensions/test_services_override',
         __DIR__ . '/Fixtures/Extensions/test_tca_override',
     ];
 
diff --git a/Tests/Functional/Regression/LocalizationInlineRegressionTest.php b/Tests/Functional/Regression/LocalizationInlineRegressionTest.php
index a8aafb96..efa4a246 100644
--- a/Tests/Functional/Regression/LocalizationInlineRegressionTest.php
+++ b/Tests/Functional/Regression/LocalizationInlineRegressionTest.php
@@ -14,15 +14,6 @@ final class LocalizationInlineRegressionTest extends AbstractDeepLTestCase
 {
     use SiteBasedTestTrait;
 
-    /**
-     * @var non-empty-string[]
-     */
-    protected array $testExtensionsToLoad = [
-        'web-vision/deepl-base',
-        'web-vision/deepltranslate-core',
-        __DIR__ . '/../Fixtures/Extensions/test_services_override',
-    ];
-
     protected const LANGUAGE_PRESETS = [
         'EN' => [
             'id' => 0,
diff --git a/Tests/Functional/Services/UsageServiceTest.php b/Tests/Functional/Services/UsageServiceTest.php
index db040d91..f05ecc7a 100644
--- a/Tests/Functional/Services/UsageServiceTest.php
+++ b/Tests/Functional/Services/UsageServiceTest.php
@@ -6,7 +6,9 @@
 
 use DeepL\Usage;
 use DeepL\UsageDetail;
+use PHPUnit\Framework\Attributes\RunClassInSeparateProcess;
 use PHPUnit\Framework\Attributes\Test;
+use WebVision\Deepltranslate\Core\Domain\Dto\TranslateContext;
 use WebVision\Deepltranslate\Core\Service\DeeplService;
 use WebVision\Deepltranslate\Core\Service\ProcessingInstruction;
 use WebVision\Deepltranslate\Core\Service\UsageService;
@@ -35,7 +37,7 @@ public function classLoadable(): void
     {
         $usageService = $this->get(UsageService::class);
 
-        static::assertInstanceOf(UsageService::class, $usageService);
+        self::assertInstanceOf(UsageService::class, $usageService);
     }
 
     #[Test]
@@ -46,7 +48,7 @@ public function usageReturnsValue(): void
 
         $usage = $usageService->getCurrentUsage();
 
-        static::assertInstanceOf(Usage::class, $usage);
+        self::assertInstanceOf(Usage::class, $usage);
     }
 
     #[Test]
@@ -55,13 +57,13 @@ public function limitExceedReturnsFalse(): void
         /** @var UsageService $usageService */
         $usageService = $this->get(UsageService::class);
 
-        static::assertFalse($usageService->checkTranslateLimitWillBeExceeded(''));
+        self::assertFalse($usageService->checkTranslateLimitWillBeExceeded(''));
     }
 
     #[Test]
     public function limitExceedReturnsTrueIfLimitIsReached(): void
     {
-        $translateContent = 'proton beam';
+        $translateContent = self::EXAMPLE_TEXT['en'];
 
         /** @var UsageService $usageService */
         $usageService = $this->get(UsageService::class);
@@ -70,20 +72,20 @@ public function limitExceedReturnsTrueIfLimitIsReached(): void
         $deeplService = $this->get(DeeplService::class);
 
         // Execute translation to check translation limit
-        $responseObject = $deeplService->translateRequest(
-            $translateContent,
-            'DE',
-            'EN'
-        );
+        $translateContext = new TranslateContext($translateContent);
+        $translateContext->setSourceLanguageCode('EN');
+        $translateContext->setTargetLanguageCode('DE');
+        $translatedContent = $deeplService->translateContent($translateContext);
 
+        self::assertEquals(self::EXAMPLE_TEXT['de'], $translatedContent);
         $isLimitExceeded = $usageService->checkTranslateLimitWillBeExceeded($translateContent);
-        static::assertTrue($isLimitExceeded);
+        self::assertTrue($isLimitExceeded);
     }
 
     #[Test]
     public function checkHTMLMarkupsIsNotPartOfLimit(): void
     {
-        $translateContent = 'proton beam';
+        $translateContent = self::EXAMPLE_TEXT['en'];
 
         /** @var UsageService $usageService */
         $usageService = $this->get(UsageService::class);
@@ -91,17 +93,21 @@ public function checkHTMLMarkupsIsNotPartOfLimit(): void
         /** @var DeeplService $deeplService */
         $deeplService = $this->get(DeeplService::class);
 
+        $translateContext = new TranslateContext('<p>' . $translateContent . '</p>');
+        $translateContext->setSourceLanguageCode('EN');
+        $translateContext->setTargetLanguageCode('DE');
         // Execute translation to check translation limit
-        $responseObject = $deeplService->translateRequest(
-            '<p>' . $translateContent . '</p>',
-            'DE',
-            'EN'
-        );
+        // @todo at the moment the mock server returns an empty result, when the
+        //       translation string is given with HTML tags, but increases character
+        //       usage. I have no idea, why this is happening, but with this behaviour
+        //       there is no possibility checking the response onto valid value.
+        $response = $deeplService->translateContent($translateContext);
+
 
         $usage = $usageService->getCurrentUsage();
-        static::assertInstanceOf(Usage::class, $usage);
+        self::assertInstanceOf(Usage::class, $usage);
         $character = $usage->character;
-        static::assertInstanceOf(UsageDetail::class, $character);
-        static::assertEquals(strlen($translateContent), $character->count);
+        self::assertInstanceOf(UsageDetail::class, $character);
+        self::assertEquals(strlen($translateContent), $character->count);
     }
 }