Question

Disclaimer: This is my first time writing unit tests…be gentle! 🙂

I am trying to write a test for the following method and would like people’s thoughts an whether I am thinking about this the correct way. I have an interface called IAuthenticationProvider with the following method:

bool Authenticate(string username, string password)

I also have a class called UserAccountService that has the following method:

bool SignIn(string username, string password)

The UserAccountService takes a IAuthenticationProvider interface as part of the constructor and is used within the SignIn method. The SignIn method looks a little like:

public bool SignIn(string username, string password)
{
    // _provider is of type IAuthenticationProvider
    bool result = _provider.Authenticate( username, password );  
    // ....
    return result;
}

Initially when I thought of tests such as “signing in with unknown username”, “signing in with an invalid password”, etc. But, I then began to think that I don’t really want to test the “authentication” aspect, i.e. _provider.Authenticate, but I want to test the actual signing in. So, I thought tests such as “signining in while already signed in”, “signing in when the user cannot be authenticated”, etc, would make more sense.

Would this be the right way of approaching this these type of tests?

Kind Regards

Michael

Answer 1

You can use a mock-based test. This would setup a UserAccountService with a mock implementation of IAuthenticationProvider.

//happy case provider return true
mock = createMock(IAuthenticationProvider, true);
service = new UserAccountService(mock).SignIn(..);
...

//provider will return false
mock = createMock(IAuthenticationProvider, false);
service = new UserAccountService(mock).SignIn(..);
...

You can write your own mock implementations if you like. Most of the time it is easier to use a mock library as easymock:

//same as above
mock = createMock(IAuthenticationProvider.class)
expect(mock.Authenticate(...)).andReturn(true);
replay(mock)
service = new UserAccountService(mock).SignIn(..);
//test here

Mock tests have their own cost and should only be used when a state-based test is not possible. Your application design should be in a way that classes depend on as few classes as possible and can be ideally work on their own (plus your runtime).