This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
What methods are you wanting to test? What you are suggesting sounds more like an integration test than a unit test. If you are wanting to test the security mechisms or your configuration of them via the spring config files, you might want to use a browser based test tool like CubicTest/Selenium. This would allow you to test loging in with proper user, invalid user, etc.
Without more information, it's hard to make a better recommendation.