- It is absolutely A MUST to do some sim beforehand...i did 4 hours in Gatwick at PMFlight, on the same aircraft. They know exactly how to prepare you for that...
To calm some people down... No it's not a must, you can pass anyway.
I bet many people have, myself included, this question in their mind before they go for the interview. Sometimes it's simply not practically possible to solve an hour in a 737 simulator before the assessment, considering time available, availability of sim, cost and much more...
Personally I only had a week notice, travelling 5000 miles for the interview, lots of paperwork to arrange beforehand, I did not get the opportunity. I sat in FS reviewing procedures, profiles etc. and it worked out just fine.
It's certainly a good idea to have some experience with a 737 cockpit and approximate flight characteristics, but don't feel your doomed to fail on beforehand just because you haven't.