I have a differing opinion and I know i'll get shouted down but i'll make it anyway.
I believe belt testing is important. The more afraid you are testing the better is for you to do it. I believe everyone has a fear of testing, some more than others. As a result, testing would force you to face your fear, to challange it and eventually with persistance overcome it. Facing your fears is one way to remind you that you are still alive. It gets you out of that "comfort zone" and challanges you. If you never get out of the "comfort zone" have you really lived.
If successful the euphoria experienced is overwhelming and is a part of what enjoying life is about, isn't it? However I admit if unsuccessful the depression can be just as overwhelming, but to overcome that depression can only make you stronger in character. Then hopefully next time you will experience the euphoria.
As for the sempai/kohai problem, if you "leap frog" someone becasue they missed a test and they're jealous or annoyed at you, then that is their problem. They have to learn to deal with it, not you.
those are my thoughts.