I had trained for a year before I took my 5th kyu (I wasn't in a hurry to get tested and changed a few dojos). I felt that I was ready for it when it came and not really nervous. For my 4th kyu, I wasn't nervous, but I forgot what shomen uchi ikkyo ura was!
Now, that's pretty bad. I had to get thrown and shown before my brain went back into place.
Now, I'm getting close to taking my 3rd kyu and I've watched a few more tests since my last test.
But more importantly, I've
actively studied what it is I need to do. I've put in a lot of time with the Jo and Bokken, for the foot work. I've seen myself on a few tapes that we've shot in the dojo (painful to watch, very painful
). I've though about testing while training in the dojo. And I've spent a lot of time doing 'shadow giawaza' in my head with 2-3 imaginary foes.
Now, I feel much more confident about taking my test. And as a few have said above, if your sensei feels that you're ready to test, then you probably are. Most won't test you just to get the money.
I work offshore and have missed a lot of classes because of that. But my Sensei has been telling me that I'm ready. Now I feel he is right and feel that, in my mind, I
am already a 3rd kyu, wheather I pass my next test, or not.
Write down what will be required of you in the test. Have 2 moves for each attack AND one back up, because, you may very well brain lock when asked to do a technique. Practice those everyday, even if it's just you in a room or going over it in your head. Follow those two things and you'll do well enough.