Given_a_login_request_is_missing_UserCredentials_fields_then_when_validated_returns_false_and_correct_error(string userEmail, string userPassword) { //Arrange var payload = new UserCredentials() { Email = userEmail, Password = userPassword }; //Act ErrorMessage error; var result = _sut.IsValid(payload, out error); //Assert Assert.IsFalse(result); Assert.AreEqual(error.Code, ErrorCode.MissingField); if (string.IsNullOrEmpty(userEmail)) { StringAssert.Contains(nameof(payload.Email), error.Message); } if (string.IsNullOrEmpty(userPassword)) { StringAssert.Contains(nameof(payload.Password), error.Message); } }