My master teaches two arts - Taekwondo and Hapkido. In our Taekwondo class, there are lots of requirements for each belt test, and at several points there exist a "brain dump" where certain techniques are no longer tested. For example, earlier forms, simpler punch and kick combinations, and previous self defense drills that were tested on. These are of course replaced by newer forms, more complicated combinations, and new defense drills that use different situations and usually higher difficulty.
There ends up being more on the Red belt test than the Purple belt test, and while the degree of difficulty and the complexity are higher, the number of tested items remains relatively the same.
On the other hand (pun unintended), the hapkido class is cumulative, in that we are tested on 27 techniques at White belt, learn 7 new ones for yellow belt (total of 34 for that test), 4 new ones (38 total) for our next belt, and by the time you get to black belt, you have over 90 things to remember on the test.
I'm a 2nd degree black belt (getting close to 3rd) in Taekwondo, and an orange belt in Hapkido. It's interesting to see that in Taekwondo, very few people remember ALL of the test requirements. Every black belt can provide advice on individual techniques and assist with class, but very few could lead a class and say "this is your form, this is your combinations," etc. In fact, I think I'm one of the only black belts that does remember ALL of the testing requirements for every test.
Now, if we were to change that, and require everyone to remember everything, then we'd have to truncate our curriculum, or the tests would take several hours to go through everything, so I understand the reason for this. However, in our Hapkido class, anyone can teach the requirements to a lower belt, because we need to know it for our next test. We have 7 keub ranks, and a 1st or 2nd keub will know the 7th and 6th keub requirements very well, because they're still practicing them.
I'd like to hear your thoughts. If you have tests, does your school do a brain dump, or do you have cumulative requirements? How well do you feel it would work if you switched? If you don't have tests, which style would you prefer if your school introduced a testing system?