Our tests are rather short, even our dan tests. Actually, the dan tests are really short if you test in front of the shihans, because we have a lot of people testing at once. Four groups go up at a time with the test taker as nage and his/her uke. It can take about two hours to test everyone. Sometimes we can have up to 15-20 people going just for shodan. I couldn't imagine two hours for each person as we usually test a seminars -- although most sensei in our association can test their own students at thier own dojo most give deference to the shihan (you know Yamada, Sugano, and formerly Kanai Sensei). But kyu tests are not in front of the shihan just our sensei.
BUT, the test isn't the test, it's what you do to get there that matters. For the dan ranks, my sensei conducts advanced classes and if you're planning to test for shodan and up your expected to attended, and 2nd kyu and up are allowed as the 1st kyu test is very similar to the dan test. It's in these classes that we are put through the paces, and at which time you'll be told you'll be permitted to test.
For 5th kyu through 2nd kyu we have a list of techniques to perform. These are not real long tests either and take around 20 minutes for the nage to complete. I don't remember my 5th kyu test that much. I just remember learning the techniques and demonstrating them. Now my 4th kyu test stamina-wise was the hardest. I was really out of shape at the time and I was partnered with another test taker which means I would both "nage" and "uke". Well, fortunately I got to be nage first, but as uke -- I couldn't finish because I was close to passing out, and they had to switch ukes. Pretty embarrasing. I was told to "work on your stamina" after that test, which meant lose weight in my case.
With my 3rd kyu test, I got an uke who I really wasn't familiar with and his ukemi was really different. He would attack so hard I'd evade and he would just just fall over. Fine for effectiveness but not fine for demonstrating the techniques. I had to really slow down my throws so I could control him. As a result my test wasn't the "prettiest" but as Penny said it was "good" in that I didn't freak out, as some people would, and that I demonstrated control over my uke. Sometimes your test is as much as how well you respond to your uke as you perform your techniques because you don't always get your favorite uke that might make you look good.
My 2nd kyu test was fun. I was in shape by this time and got to do randori (2 person) on my test for the first time. I was really thankful for all that jiyuwaza I did for the past few years the randori just flowed although it wasn't perfect, but was evading people and throwing them into the other attacker. I wasn't intentionally doing that -- I just did. Nice to know that all that training has been ingrained into my body memory.
Now, I'm approaching my 1st kyu test, and that will be different because we don't have a list of techniques to memorize rather you do jiyuwaza (in our dojo that is more like a controlled randori where one attack is called and you perform a variety of techniques). I have to perform at least 5 techniques demonstrating variety of openings and variations. I just can't repeat the same 5 over and over again with each attack. Also we do suwari waza, handmi handachi, tanto tori and a 3 person randori. The 1st kyu test can take anywhere from 20-40 minutes depending on sensei's mood that day. 1st kyu for me will be the longest test, and it will probably my hardest test not test anxiety-wise but just personal expectation-wise.