What questions should I expect during an EASA skill test?
Goodness, the best not guess, since the amount of information an ATPL candidate must master is just massive. Could be anything from the smallest detail to broad concepts. Anything to make you uncomfortable and see if you are willing to admit that you might not yet know everything, or whether are you the kind of guy who takes the best guess and hopes it's the right one...

For your sake I hope all goes well, and for everybody elses, I hope you know everything needed to become a safe professional airline pilot. Godspeed.