It's exactly the same test given to potential pilot candidates in the RAF, RN and Army. I did one while I was still in the RAF so it didn't cost me anything, but as a civvy you will have to pay, not sure how much. There's several tests for measuring your aptitude for interpreting instruments and picking the correct statement, another one has you pick the most appropriate attitude picture for a given set of instruments.
Another one has you control a cursor with a built in lag trying to move it over a stream of dots flowing down the screen. There's a couple of other ones as well using the joystick/cursor and also some pedals which are slightly offset. As always there are time constraints.
They're not too difficult really, as a GAPAN bloke you'll get a certificate rating your chances of success in pilot training, rather than a pass fail like the military. I think they make military candidates do the nav test as well which is probably more reasoning + maths rather than hand eye.
I wouldn't put too much faith in the test, I heard of several UAS Studes who were highly rated on the UAS but couldn't pass the selection test and therfore couldn't get selected.
If you have no flying experience at all, get some lessons with and experienced FI, you'll soon know whether you have the aptitude and desire to carry on.