public void EachTestSetUp()
 {
     _passwordHashingService = Substitute.For<IPasswordHashingService>();
     _passwordHashingService.ComputeHash("somestring", new byte[4]).ReturnsForAnyArgs("hashedPassword");
     _userRepository = Substitute.For<ILinqRepository<User>>();
     _authService = new AuthenticationService(_userRepository, _passwordHashingService);
 }
        public void wrong_email_address_cannot_log_in()
        {
            _userRepository = Substitute.For<ILinqRepository<User>>();
            _authService = new AuthenticationService(_userRepository, _passwordHashingService);
               var result = _authService.Login("invalidAddress", "SomePassword");

            Assert.AreEqual(LoginResult.unsuccessful, result);
        }