I'm not even close to being an instructor, but I've seen a few methods tried, and know what I tell folks who are scared: one sensei went to 12 kyus, so your first one was rolls, standing in hanmi, and sitting in seiza, the next was the basic attacks, etc, with the idea that those who had anxiety wouldn't mind how little and how easy the first few tests were and as they went along develop confidence. While it seemed like a good idea to me, those who were afraid just saw it as 12 tests rather than 5 or 6. I hear he's gone back to the 6 test version. When i hear someone who is anxious (and i will admit it is often a female while we are dressing, but it could just be women admit fear more readily), I point out how much we all care about her and eachother, so it is really like just practicing with one person while her friends cheer her on, that they wouldn't let her test if she didn't already know it, that it is just a formality and a chance for her to shine. I contrast what they do for a living (PhD, marketing exec, raising four boys, etc) and how hard that really is, "and this is, after all, just Aikido" and besides "if you REALLY screw up, or sensei gets up on the wrong side of bed, and you actually don't pass, what is the worst thing that happens--they call it practice and you take it again in a week or two. One woman, who liked the keeping Aikido tests in perspective with the rest of life thought was heard repeating to herself before her last test "world hunger, global warming, poor little Elian!"
I wonder how students who get promoted without testing (when testing is usually done) feel about that: I know that on one test when sensei skipped me a rank, I felt uncomfortable about it, even though he'd had me do the next kyu's techniques as well as the one for which I was testing.