Hi,
I did the assesment recently, they will send a briefing package a few days before which will mostly cover the sim part. Expect loss of engine after v1, then manual one engine ils approaches with and without flight director. Also some failures during climb to check how you deal with control and communication handover, checklist reading, I think these are required skills elsewhere too and they are not trying to overwhelm you, just stay relaxed and safe.
The interview was very nice, with two captains from the company, they were asking questions about my personality, how do I resolve problems and conflicts, and to share some examples. I hope it helped. Good luck!