Our school is informal. It wasn't really a test per say, but a right of passage that had to be to receive the rank.
I survived, so I passed,lol.
I have taught goju for several years. When a student is ready for their next rank you will know it. I simply gave students their next rank when they were ready. The 'testing' is in the everyday dedication to training and learning.
I understand how some martial arts schools do business though. They give little Johnny Firecracker a test every few months with the flavor of the month belt and a hefty "testing fee" lol.There are no testing fees and it isn't a commercial school.
That's why you see soke's and grandmasters on every corner, not to mention 25yr old 5th and 6th dans,lol.
I like it the way we do it.