public async Task AuthenticateReturnsNullIfCredentialsAreMissingOrIncorrect(string username, string password)
        {
            //Arrange
            var service = new DummyAuthenticationService();

            //Act
            var result = await service.Authenticate(username, password);

            //Assert
            Assert.IsNull(result);
        }
        public async Task AuthenticateReturnsUserIfCredentialsAreCorrect()
        {
            //Arrange
            var service      = new DummyAuthenticationService();
            var expectedUser = new User()
            {
                Username = "******",
                Password = "******"
            };

            //Act
            var result = await service.Authenticate("testuser", "password1");

            //Assert
            Assert.IsNotNull(result);
            Assert.AreEqual(expectedUser.Username, result.Username);
            Assert.AreEqual(expectedUser.Password, result.Password);
        }