Call to undefined method setParameter() into my PHPUnit Test

Beginner in tests, I search the way to test my function which consists to check existence of my file and download it. At each test, I receive this error :

Error: Call to undefined method AppBundle\Controller\DownloadUserGuideController::setParameter()

My test :

public function testDownloadAction()
{
    $DownloadUserGuideController = new DownloadUserGuideController();
    $DownloadUserGuideController->setParameter('path_to_file','%kernel.root_dir%/data/User_Guide.pdf');
    $result_response = $DownloadUserGuideController->downloadAction();
    $this->assertSame(Response::HTTP_OK, $result_response->getStatusCode());
}

My function:

public function downloadAction()
{
    $filePath = $this->getParameter('path_to_file');

    if (!file_exists($filePath)) {
        throw $this->createNotFoundException();
    }

    $response = new BinaryFileResponse($filePath);
    $response->setContentDisposition(ResponseHeaderBag::DISPOSITION_ATTACHMENT);

    return $response;
}