Basically the tests measure how broadly competent you are. Tatsuya's magic (outside the Fast Casting thing the anime hasn't gone into detail with) is very, very focused. And REALLY POWERFUL. Basically his sister in an emergency can create a hammer or a screwdriver or a drill, or whatever. Which is what they measure, a broad competence with changing Eidos and speed at that. Tatsuya can create a hammer. A BIG HAMMER.
And yeah, the anime mentioned it. The guns are special, not 'normal' guns. They didn't go into detail on how so I can't comment further.
