Re: Poll: How often do you get to choose your uke(s) for your rank testing at your aikido dojo?
We start to have taigi (set-piece series of techniques, usually six techniques per taigi) on our tests around second kyu, and by shodan the tester is choosing a couple of taigi from numbers 1-15. This means that uke has to be able to produce, on demand, the correct six attacks for any of those taigi. We don't practice taigi often enough for this to come naturally even to yudansha....
The upshot is, shodan candidates pick their ukes months in advance and the whole dojo spends time coaching both people on taigi! (And there was still a taigi with only five techniques in it, last testing. Nage passed anyway, with compliments on "keeping calm in difficult situations.")
For kyu tests we usually pick, but sensei is free to call in someone else, and occasionally does. I think if you don't seem rattled enough by the normal course of testing, he may try to rattle you a bit more.
At one of our sibling schools I saw a shodan test where sensei suddenly called for a folding chair. It was placed in the center of the mat, and the candidate sat down on it, visibly wondering what was coming. "Three techniques from ryote dori, without getting up." He did it nicely, too--not the wrist controls that it turns out sensei was expecting, but zenpo-nage, kiri-kaeishi, and something whose name I don't know that took uke right over the back of the chair into a roll. Mmm.