hope - the thing with tests is they only really evaluate how good a person is at taking tests. It's a test-specific kind of stress, not a realistic kind of stress. If you want to test a person's skills under stress you should jump out at them from behind a corner and gauge their response
I'm more inclined to agree with Dereck that everyday in class should be a test. If one has demonstrated regularly in class that they deserve to move forward, just present the new belt to them at the end of class. People will also work harder in each individual class because day to day performance matters more in this kind of setting compared to when advancement depends on a finite test in time.