Well, my surgeon hasn't required me to get the endoscopy test, but I do know that the psych eval is a pretty common exam. They basically want to make sure that you're psychologically sound and have a firm grasp on what it means to go through with this surgery as it's a life changing (and diet changing!) operation. Not all surgeons require the same tests for everyone as my father (who just had the surgery) had to have a sleep test, EKG, chest xray, etc while I only had to get blood work as I'm younger with less health problems.
Hope that helped!
~Lyra