FakeItEasy Login Service Example Series – Part 6

This is the sixth part in the series of posts where I’m porting Brett Schucherts excelent demo of Mockito in Java to C# and FakeItEasy.

The source for this example series can be found in a Mercurial repository at Google code. Each test implementation and following code update is a separate commit so you can easily update your repository to look at the full code at any given state. Find the repository here.

Part 1 can be found here.

Part 2 can be found here.

Part 3 can be found here.

Part 4 can be found here.

Part 5 can be found here.

Test 6 – Exception thrown when account is not found

This is a final test to make sure the code handles the case of an account not getting found. This is not too hard to write:

The test

[Test]
public void Should_throw_when_account_does_not_exist()
{
    // Arrange
    A.CallTo(() => this.accountRepository.Find(A<string>.Ignored)).ReturnsNull();

    // Act, Assert
    Assert.Throws<AccountNotFoundException>(() =>
        this.service.Login("username", "password"));
}

Test Description

This test takes advantage of the fact that later configurations of a fake object takes precedence over earlier configurations, this differs from the way that Rhino Mocks works where earlier configurations has precedence.

A login is attempted which should fail.

Things Created for Compilation

To get this test to compile, you'll need to add a new exception class:
AccountNotFoundException.

namespace FakeItEasy.Examples.LoginService
{
    using System;

    public class AccountNotFoundException
        : Exception
    {
    }
}

Code Updated to get Test to turn Green

The test currently fails with a null reference exception, a quick fix is needed at the top of the method.

namespace FakeItEasy.Examples.LoginService
{
    using System;

    public class LoginService
    {
        private IAccountRepository accountRepository;
        private int numberOfFailedAttempts;
        private string previousUsername;

        public LoginService(IAccountRepository accountRepository)
        {
            this.accountRepository = accountRepository;
            this.previousUsername = string.Empty;
        }

        public void Login(string username, string password)
        {
            var account = this.accountRepository.Find(username);

            if (account == null)
            {
                throw new AccountNotFoundException();
            }

            if (account.IsLoggedIn)
            {
                throw new AccountLoginLimitReachedException();
            }

            if (account.PasswordMatches(password))
            {
                account.SetLoggedIn(true);
            }
            else
            {
                if (this.previousUsername.Equals(username))
                {
                    this.numberOfFailedAttempts++;
                }
                else
                {
                    this.numberOfFailedAttempts = 1;
                    this.previousUsername = username;
                }
            }

            if (this.numberOfFailedAttempts == 3)
            {
                account.SetRevoked(true);
            }
        }
    }
}