The rewards are great. Aikido tests are not only important for the individual student testing, but also for everyone else involved. The people sitting on the mat observing may be testing soon and learn something from watching. It goes without saying that the uke profits from the experience. The student's instructor profits from the experience by seeing what needs attention.
Spectators hopefully profit from the experience.
In fact, Aikido tests, which are demonstration in nature and frequently attended by spectators, singularly represent to many, what Aikido is. I believe the answer is everyone. Given this importance, tests need to be confronted with the utmost seriousness and honesty. It begins with preparation. Often students have not prepared properly.