Symfony 4 Mock service in functional test

I am testing a service which essentially is mostly serializing an object and sending it via a service to an external system.

If I create the typical unittest I would mock the response of the serializer and of the service, which contacts the external system. In fact there would be not much left to test except calling a bunch of setter Methods in my object.

The alternative would be using a KernelTestCase and creating a functional test, which would be fine except I don't want to contact the external system, but to use a mock only for this "external" service.

Is there any possibility to achieve this in Symfony 4?Or is there another approach to this?

What I am doing now is the following:

<?phpnamespace App\Tests\Service;use App\Service\MyClassService;use App\Service\ExternalClient\ExternalClient;use JMS\Serializer\Serializer;use JMS\Serializer\SerializerInterface;use Psr\Http\Message\RequestInterface;use Psr\Log\LoggerInterface;use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;use Symfony\Component\HttpFoundation\Request;class MyClassServiceTest extends KernelTestCase{    /** @var LoggerInterface */    private $logger;    /** @var Serializer */    private $serializer;    /** @var ExternalClient */    private $externalClient;    /** @var RequestInterface */    private $request;    /** @var MyClassService */    private $myClassService;    public function setUp()    {        $kernel = self::bootKernel();        $this->logger = $kernel->getContainer()->get(LoggerInterface::class);        $this->serializer = $kernel->getContainer()->get(SerializerInterface::class);        $this->externalClient = $this->createMock(ExternalClient::class);    }    public function testPassRegistrationData()    {        $getParams = ['amount'          => '21.56','product_id'      => 867,'order_id'        => '47t34g','order_item_id'   => 2,'email'           => 'kiki%40bubu.com',        ];        $this->generateMyClassService($getParams);        $userInformation = $this->myClassService->passRegistrationData();        var_dump($userInformation);    }    /**    * generateMyClassService    *    * @param $getParams    *    * @return MyClass    */    private function generateMyClassService($getParams)    {        $this->request = new Request($getParams, [],  [], [], [], [], null);        $this->myClassService = new MyClassService(            $this->logger,            $this->serializer,            $this->externalClient,            $this->request        );    }}

give back this error:

Symfony\Component\DependencyInjection\Exception\RuntimeException: Cannot autowire service "App\Service\MyClassConfirmationService": argument "$request" of method "__construct()" references class "Symfony\Component\HttpFoundation\Request" but no such service exists.