Unit Testing a Login in ASP.NET

Question

I'm very new to TDD and I'm having trouble with one of my unit tests. I just can't seem to understand what to do next. :( I'm trying to unit test a service of mine called AccountService and I'm testing a method called DoLogin(username, password). Here's some example code:

    [Test]
    public void User_With_Correct_Username_And_Pass_Should_Login_Successfully()
    {
        // Arrange
        var accountService = new AccountService();

        // Act
        bool result = accountService.DoLogin("test", "test");

        // Assert
        Assert.IsTrue(result);
    }

    public class AccountService : IAccountService
    {
      public bool DoLogin(string username, string password)
      {
        if (string.IsNullOrEmpty(username) || string.IsNullOrEmpty(password))
            return false;

        return true;
      }
    }

So this test pasts but now what do I do?! How do I really test if a valid login occured? Do I need to implement an integration test and test the login against a real or in-memory DB? Sorry if I'm doing things totally incorrect. I really hope one day to get this TDD stuff down. Thanks

Answer 1

You should have a test that an invalid username or invalid password causes DoLogin() to fail.

Given the name of the function, (DoLogin() rather then CheckLogin()) I'd think the function should have some side effect as well. The test should verify that side affect. Really need to clarify what that is before someone can clarify how it should be verified.

Answer 2

Pass what you know to be valid and invalid credentials to DoLogin, and then compare the results to what you expect. Try to imagine every possible (read: reasonable) combination/input of the "username" and "password" parameters the user will provide, and create a test for each.

If your DoLogin business logic is to be believed, we're defining a "valid" username (and a "valid" password) to be anything that's populated. Fair enough, for discussion's sake.

Some simple tests come to mind:

Login_With_Null_UserName_Fails()
Login_With_Populated_UserName_Succeeds()
Login_With_Empty_UserName_Fails()
Login_With_Null_Password_Fails()
Login_With_Populated_Password_Succeeds()
Login_With_Empty_Password_Fails()

Or, consider combinations:

Login_With_Null_UserName_And_Populated_Password_Fails()
Login_With_Populated_UserName_And_Populated_Password_Succeeds()
Login_With_Empty_UserName_And_Null_Password_Fails()
etc
etc