Oh, the recruitment test.  I thought you meant the test after learning to use ki.  Too many tests, I guess.

For recruitment it can be anything that shows you are strong willed enough to learn to use magic, as it has to be controlled with Will.  In the old days they would just wait for people to show it, maybe by them enduring something extremely trying without breaking, or standing up to an authority figure, or getting them (or waiting for them) to knowingly risk their life, liberty, or property to do something that they want to do even more.  In modern times, though, they are usually given a task which gets them to do one of these, or a task that requires perseverance, to prove that they have the will to do what they set their mind to, which would be joining the college.