public void register_user_should_invoke_service_new_user(
     [Frozen] IUserService service,
     UserController sut,
     User newUser)
 {
     sut.Post(newUser);
     service.Received()
         .RegisterUser(newUser);
 }
 public void register_user_should_return_http_status_created(
     [Frozen] IUserService service,
     UserController sut,
     User newUser)
 {
     ((HttpStatusCode)sut.Post(newUser))
         .Should()
         .Be(HttpStatusCode.Created);
 }
        public void register_existing_user_should_return_http_status_conflict(
            [Frozen] IUserService service,
            UserController sut,
            User newUser)
        {
            service.RegisterUser(newUser)
                .Returns(ServiceStatus.Conflict);

            ((HttpStatusCode)sut.Post(newUser))
                .Should()
                .Be(HttpStatusCode.Conflict);
        }