When told that they are ready to grade (you should never, ever, ask).....
When I was a young, wee thing - just starting aikido, I was at a dojo where we were taught that you should never, ever ask to test....
....but then I moved into a larger dojo where, if you wanted to test, you were expected to approach Sensei and ask permission at least two weeks prior to the test.
....to make matters worse. Sensei never, ever said 'no' to anyone asking. So, it was left up to the asker to differentiate the many ways he would answer 'yes'. I spent many hours (ok, maybe not HOURS) in the dressing room with sempai and kohai trying to interpret his 'yes' answer....Did he say, 'yes, of course you should test'....or did he say, 'well, do you think you are ready?'....or, like the last time I ask....'I thought you were going to test for Nidan over a year ago!')
It is a crazy world!