KI on Aikiweb!
In our dojo, although we use and believe in ki, our sensei rarely refers to its existance. Since it's use is required to perform all of our techniques, we do not have specific testing.
Essentially a curious uke will "ki down" during static training to test the ki of a nage. Ki sensitivity will allow the uke to apply the right amount of "counter ki" to insure the that the technique is performed correctly. Once the motion begins the uke simply follows the connection to the end of the move. If the nage's connection falters anywhere along this path, the uke will feel this instantly.
I guess you could say that we build ki through our practice of the techniques. Kokuyo Doza is our biggest "ki exercise," and we seem to be doing fine.