Como mockar a ServerRequestInterface | MVC com PHP: entenda o padrão Model-View-Controller

Tentei criar o seguinte teste

    public function test_should_return_400_if_no_name_is_provided()
    {
        $this->expectError();

        $this->sut = new SignUpController();

        $body = [
            'body' => [
                'email' => 'any@email.com',
                'password' => 'any_password',
                'passwordConfirmation' => 'any_password'
            ]
        ];

        $this->withHeaders();

        $psr17Factory = new Psr17Factory();

        $creator = new ServerRequestCreator(
                $psr17Factory,
                $psr17Factory,
                $psr17Factory,
                $psr17Factory
        );

        $request = $creator->fromGlobals();
        $request->withBody($psr17Factory->createStream(json_encode($body)));

        $response = $this->sut->handle($request);
    }

para o nosso controller em questão , porém ao tentar pegar os valores na controller

    public function handle(ServerRequestInterface $httpRequest): ResponseInterface
    {
        var_dump($httpRequest->getBody()->getContents()); exit;
    }

recebo o seguinte

Sign Up Controller
 ✘ Should return 400 if no name is provided
   ┐
   ├ PHPUnit\Framework\Exception: string(0) ""

O que estou errando? Obrigado!

public function test_should_return_400_if_no_name_is_provided() { $this->sut = new SignUpController(); $body = json_encode([ 'email' => 'any@email.com', 'password' => 'any_password', 'passwordConfirmation' => 'any_password' ]); $reflection = new \ReflectionClass(ServerRequestInterface::class); $methods = []; foreach($reflection->getMethods() as $method) { $methods[] = $method->name; } $stub = $this->getMockBuilder(ServerRequestInterface::class) ->setMethods($methods) ->getMock(); $stub->method('getBody')->willReturn($body); $response = $this->sut->handle($stub); $this->assertEquals($response->getStatusCode(), 400); $this->assertEquals($response->getBody(), 'Missing param: name'); }