I attended the last black belt test and I’ve seen a few stripe tests online, so I’ll do my best to explain the basic idea. Again, I train under one of this school’s instructors on home mats, not at this school (except when I make the trip to drop in). I’m probably missing some details, but I get the gist of it.
At that school you test for stripes. White belt stripes are looking for technically-sound execution of the techniques on the curriculum.
You don’t test for blue belt. You get it after you’ve tested for all of your stripes and the instructor decides you’re a blue belt now. Some combination of proficiency on the mats, technical competency and whatever secret sauce they look for, seemingly weighted for age/sex and athletic ability/potential.
At blue you also test for stripes, but here the stripes are for varying degrees of technical responses of techniques that are on the curriculum. Give-and-take drills, complete sequences from takedown to finish and that sort of thing. In simple terms, it is navigating from position-to-position and building your conditional responses across the curriculum.
Then someone says you’re a purple belt.
Purple belt is where you repeat the same structure of the blue belt stripes, but with techniques that are NOT on the curriculum. They must be incorporated into your game and conditional responses and technical pathways built off of them. Doesn’t matter if you learn them in the gym, off of youtube, at another gym, wherever. The emphasis here is to push you away from the curriculum into whatever suits your game.
Then someone says you’re a brown belt.
Brown belt is where you repeat the same structure of the last two belt’s stripes, but with innovations you’ve developed that suit your own game. Brown belt is also where you must begin teaching. The stripes demonstrate the same conditional responses, if/then pathways and competence in navigating the landscape of your personal jiu jitsu game.
At all points from blue through brown you can and will be asked to demonstrate techniques from previous stripes, going all the way back to white belt 1. The idea is that you always revisit the curriculum as you progress. The techniques are that valuable and fundamental. You may have a purple belt Americana but a white belt kimura, after all.
Black belt IS tested, unlike the other belt promotions. I watched the last one and participated in the shark tank, and it was an incredible display of martial arts skill, endurance and toughness.
The first hour+ was a complete demonstration of the entire white belt curriculum. The next two hours took us through the blue, purple and brown belt curriculum, as demonstrated by the candidate being tested.
The final 45 min or so was a shark tank. Non-stop rolling with the entire room from white-to-black. I’ve never seen anything like it before or since.
My instructor is probably due to test for his sometime this year, assuming the whole virus thing blows over and people keep training.