Re: Non-aggressive way to test ability and level of understanding.
People internally make judgments about each other everyday, every moment. We gauge our world in this way. However, a student to go out with the intent to test his fellow class mate; IMO they are over stepping their boundaries. The teacher is the one with the experience and the credentials(at least she/he should have) to be putting tests upon their students. I truly feel deshi are over stepping their bounds to be testing their fellow students openly or intentionally. IMO, it goes into the category of; work on your issues before seeking out the issues in others.
For the student being "tested" by their fellow student I guess see it as a blessing that some one is "testing" you. Because, not only are YOU working on your issues, but your partner is too...all the training for you, and none for them! lol