Cannot make Rhino Mocks return the correct type

Question

I just started a new job and one of the first things I've been asked to do is build unit tests for the code base (the company I now work for is committed to automated testing but they do mostly integration tests and the build takes forever to complete).

So everything started nicely, I started to break dependencies here and there and started writing isolated unit tests but now I'm having an issue with rhino mocks not being able to handle the following situation:

//authenticationSessionManager is injected through the constructor.  
var authSession = authenticationSessionManager.GetSession(new Guid(authentication.SessionId));

((IExpirableSessionContext)authSession).InvalidateEnabled = false;

The type that the GetSession method returns is SessionContext and as you can see it gets casted into the IExpirableSessionContext interface.

There is also an ExpirableSessionContext object that inherits from SessionContext and implements the IExpirableSessionContext interface.

The way the session object is stored and retrieved is shown in the following snippet:

private readonly Dictionary<Guid, SessionContext<TContent>> Sessions= new Dictionary<Guid, SessionContext<TContent>>(); 

public override SessionContext<TContent> GetSession(Guid sessionId)
{
    var session = base.GetSession(sessionId);

    if (session != null)
    {
        ((IExpirableSessionContext)session).ResetTimeout();
    }

    return session;
}

public override SessionContext<TContent> CreateSession(TContent content)
{
    var session = new ExpirableSessionContext<TContent>(content, SessionTimeoutMilliseconds, new TimerCallback(InvalidateSession));

    Sessions.Add(session.Id, session);            

    return session;
}

Now my problem is when I mock the call to GetSession, even though I'm telling rhino mocks to return an ExpirableSessionContext<...> object, the test throws an exception on the line where it's being casted into the IExpirableSession interface, here is the code in my test (I know I'm using the old syntax, please bear with me on this one):

Mocks = new MockRepository();
IAuthenticationSessionManager AuthenticationSessionMock;
AuthenticationSessionMock = Mocks.DynamicMock<IAuthenticationSessionManager>();

var stationAgentManager = new StationAgentManager(AuthenticationSessionMock);

var authenticationSession = new ExpirableSessionContext<AuthenticationSessionContent>(new AuthenticationSessionContent(AnyUserName, AnyPassword), 1, null);

using (Mocks.Record())  
{
   Expect.Call(AuthenticationSessionMock.GetSession(Guid.NewGuid())).IgnoreArguments().Return(authenticationSession);  
}

using (Mocks.Playback())  
{  
    var result = stationAgentManager.StartDeploymentSession(anyAuthenticationCookie);
    Assert.IsFalse(((IExpirableSessionContext)authenticationSession).InvalidateEnabled);  
}

I think it makes sense the cast fails since the method returns a different kind of object and the production code works since the session is being created as the correct type and stored in a dictionary which is code the test will never run since it is being mocked.

How can I set this test up to run correctly?

Thank you for any help you can provide.

Answer 1

Turns out everything is working fine, the problem was that on the setup for each test there is an expectation on that method call:

Expect.Call(AuthenticationSessionMock.GetSession(anySession.Id)).Return(anySession).Repeat.Any();

So this expectation was overriding the one I set on my own test. I had to take this expectation out of the setup method, include it on a helper method and have all the other tests use this one instead.

Once out of the way, my test started working.