I'm afraid that most of the mock questions out on the net are poor examples of what the SCEA requires for JEE 5 knowledge. Most of the mock tests I've seen dwell on trivia questions about EJB 2.
The SCEA exam doesn't require an intimate knowledge of the APIs and low-level details, but you will absolutely need to know all the general concepts, properties, and behavior of EJB 3 development. I read EJB 3 in Action prior to taking the test. It is a good source of what you need to know.