At our airline we have a dedicated group of captains that do maintenance test flights. I did some on the Airbus before I moved over to the 757. It is very necessary to flight test after maintenance overhauls, we even do them for engine changes, which you would think would be a routine procedure for any airline's maintenence program.
You also get to ferry aircraft that the average line pilot won't want to deal with, like an A 320 I ferried back with a cracked P1 window. My seat was cranked down for that one!
It doesn't take a rocket scientist to run a test card. You just fly the profiles the manufacturers have developed. You just need the ability and knowledge to stay well ahead of the aircraft and to know thoroughly what the jet is doing and what it will be doing. Not an easy thing sometimes with the Airbus.
Cheers