My instructor never tested us until he thought we were ready, or we told him we were ready.
Once, another student was testing, but I still had to do everything I knew as though I was being tested. Since I still felt uncomfortable about a few of my requirements, I had elected not to be tested. My instructor graded me anyway without telling me. After the test was over (the other fella passed), my instructor told me he graded me and asked me if I considered what I had just done was a test. If I answered no, the results would be ignored and he wouldn't let me know how bad or good I performed. If I answered yes, he'd tell me how I had done. For the hell of it, I answered yes and was surprised that I had done better than I had on previous tests. Guess the luxury of 'not testing' helped me perform without any anxiety which led to a better performance.
By the way, that TKD organization I mentioned? $45 per test every 8 weeks. They have their rainbow of belt colors, as well as 'senior' grades for each belt color. In my system, we had our belt colors, with two stripes per belt. However, belt tests were only $20 (whenever we were ready) and stripe tests were only $5. If you did well enough on a stripe test (essentially earning the next full belt rank), you just paid for the belt test ($20) and didn't have to pay for the two stripe tests you'd normally have to take. I seem to recall my instructor waiving the fee for one of my belt tests. Can't remember why. Our black belt test was free. The mentality was that you didn't pay for your black belt, you earned it, dagnabbit!
Which reminds me...I seem to remember reading that JKA Shotokan charges black belt candidates for each dan test, the costs (supposedly for registration and other fees...what, I have no idea) going up quite a bit for each dan rank. According to this source, pretty much anyone could take a dan test as long as they could prove they had been training for at least three years. I find that rather...odd. I dunno...maybe I'm just old, crotchety, and set in my ways.
Dammit, I've rambled again. So sorry.
Cthulhu