即使断言不正确，模拟和单元测试也会通过

我对单元测试和TDD整体上很陌生。

我的服务层 （WCF） 中有以下登录方法，该方法作为 Windows 服务托管。我的服务层遵循外观模式，对服务层的所有调用都是使用请求对象进行的，并返回相应的响应对象。

public LoginResponse Login(LoginRequest request)
{
    var response = new LoginResponse(request.RequestId);
    try
    {
        if (!ValidRequest(request, response, Validate.ClientTag))
            return response;
        var user = userDao.GetByUserId(request.UserId);
        if (user != null)
        {                   
            if (request.Password != "")
            {
                var authenticationService = new AuthenticationService();
                if (authenticationService.Authenticate(user, request.Password))
                {                          
                    return response;
                }                        
                response.ErrorCode = "IncorrectPassword";
            }
            else
            {                       
                response.ErrorCode = "PasswordNotFound";
            }
        }
        else
        {
            response.ErrorCode = "UserNotFound";
        }
        response.Acknowledge = AcknowledgeType.Failure;
        return response;
    }
    catch (Exception ex)
    {
        Log.Error(ex);
        response.Acknowledge = AcknowledgeType.Failure;
        response.ErrorCode = "Exception";
        return response;
    }
}

两行都在这里：

userDao.GetByUserId(request.UserId);

和

authenticationService.Authenticate(user, request.Password);

正在调用数据库。

这是我用xUnit和JustMock编写的测试：

    [Theory]
    [InlineData("manager", "manager")]
    public void LoginTest(string userId, string password)
    {
        //Arrange
        var userServiceMock = Mock.Create<IUserManagementService>();
        var request = new LoginRequest().Prepare();
        request.UserId = userId;
        request.Password = password;
        var response = new LoginResponse(request.RequestId);
        Mock.Arrange(() => userServiceMock.Login(request)).Returns(response).OccursOnce();
        //Act
        userServiceMock.Login(request);
        //Assert
        Mock.Assert(userServiceMock);            
    }

我遇到的问题是，即使我将服务方法更改为

public LoginResponse Login(LoginRequest request)
{
    return null;
}

我的测试仍然通过。我做错了什么？

[Theory]
[InlineData("manager", "manager")]
public void LoginTest(string userId, string password)
{
    // Arrange
    // System under test
    IUserManagementService userService = new UserManagementService();
    var request = new LoginRequest().Prepare();
    request.UserId = userId;
    request.Password = password;
    var expectedResponse = new LoginResponse(request.RequestId);
    //Act
    var actualResponse = userService.Login(request);
    //Assert
    Assert.AreEqual(actualResponse.Something, expectedResponse.Something);            
}

Mock.Arrange(() => userServiceMock.Login(request)).Returns(response).OccursOnce();