I always tell my friends (and myself) when we are preparing for a test: Donīt try to look better than you really are.
Sadly, I've seen three very adept aikidoka failed because they were arrogant. Just be respectful to everyone involved, answer questions straightforwardly (no matter how simple! No smirking and eye rolling!) and take the prodeedings seriously, and you'll do fine.
On the other side of the coin, there are some folks that failed because they didn't have the technical ability or didn't know the material well enough. While they failed the test, they earned the respect of their peers (and their sensei) because they didn't quit, no matter how much they were struggling.
Those uke that give you a bit of a hard time are the ones that are showing Sensei what you're really made of. If your sensei is anything like mine, he WANTS to see how you act under stress.
Best of luck to you.