Mike, this is aimed at pilots, but try to do the basics like how a plane flies and what the controls do, don't know what they will ask, they probably are not after much to start but to basically know how it flies cannot be a bad thing.....
Technical stuff I don't know what they will ask, try to know a little bit about the aircraft you are going to work on, make of powerplant, how much thrust, has it been exported etc, just general stuff that shows you are keen and have an idea, also try to get a little background on the company.
Flight theory contents
as for the tests try the above mentioned....... good luck
Sample Airmen/Airwomen selection test