public async Task RegisterUser_WhenCorrectData_ShouldReturnOkStatus()
        {
            var    mockUserService = new Mock <IUserService>();
            UserVm userVm          = new UserVm
            {
                username  = "******",
                firstName = "John",
                lastName  = "Doe",
                email     = "*****@*****.**"
            };

            mockUserService.Setup(x => x.AddOrUpdate(userVm, null)).Returns(userVm);
            var signInController = new SignInController(mockUserService.Object);

            ActionResult <UserVm> result = await signInController.RegisterUser(userVm);

            var createdResult = result.Result as ObjectResult;

            Assert.IsNotNull(createdResult);
            Assert.AreEqual(201, createdResult.StatusCode);
        }