Jimmy Sensei will not test you until you are ready, so when he says it's time, relax and test the same way you practice.
That's my understanding of Jimmy's appraoch as well. When I was freaking out about a test that I didn't feel ready for, several long-time students told me that Jimmy views "testing" more as a demonstration of what he's already seen on the mat than a one-time pass-fail type event. That being said, be prepared. I believe that a big part of testing is showing how you handle the pressure of the moment. If you are confident (or at least act that way) and stay calm, you will leave a positive impression even if you "mess up" in your technique.
See you on the mat!