Here is my test with a new Mock and its setup:

[Fact]
    public async Task RegisterUser_MustReturnPhoneNumberError2()
    {

        var userRepository = new Mock<IUserRepository>()
            .Setup(_ => _.GetUserByUsernameAndPassword(It.IsAny<string>(), It.IsAny<string>()))
            .Returns(new User
            {
                Password = "b",
                EmailAddress = "asdadsa!yaho",
                Name = "asa"
            });

        var userService = new UserService(new Mock<IUserRepository>().Object);

        var expectation = new UserResponseDto
        {
            Status = new StatusMaker().ErrorStatus("TEXT")
        };

        var a = new UserCredentialRequestDto
        {
            EmailAddress = "a",
            Password = "b",
            PhoneNumber = "c"
        };

        

        var res = await userService.LoginUser(a);

        Assert.Equal(expectation.Status.Message, res.Status.Message);
        
    }

and here is the real method:

public async Task<UserResponseDto> LoginUser(UserCredentialRequestDto userCredential)
    {
        var user = _userRepository.GetUserByUsernameAndPassword(userCredential.PhoneNumber,
            userCredential.Password.DoHash());

        // If user is Null
        #region Error Status

        if (user is null)
        {
            return new UserResponseDto
            {
                Status = new StatusMaker().ErrorStatus("ABCD")
            };
        }else{
            return new UserResponseDto
           {
            Status = new StatusMaker().ErrorStatus("TEXT")
           };

     }

After I run debug the test, the GetUserByUsernameAndPassword() function would be null again. Why the return of GetUserByUsernameAndPassword() would be null even after Mock Setup?

CodePudding user response：

You're passing a newly instantiated Mock of IUserRepository.

Try the following

var userRepository = new Mock<IUserRepository>()
        .Setup(_ => _.GetUserByUsernameAndPassword(It.IsAny<string>(), It.IsAny<string>()))
        .Returns(new User
        {
            Password = "b",
            EmailAddress = "asdadsa!yaho",
            Name = "asa"
        });

    var userService = new UserService(userRepository.Object);