When I did my Multi exam, I was told that the school had the responsibility of writing the exam which had to approved my the CAA. It is nothing nasty, just stuff that was covered in the ATPL, and a few questions specific to the aircraft you will be training on, mostly performance.
I seem to recall questions on the different speeds, what happens to Vyse with altitude, assymetric blade effect, critical engines, thrust line changes etc. Your instructor should give you a thorough briefing of what is expected of you.
All the best.