They're really quite nice. My son has seen various doctors while he's been going through the process of being diagnosed, and they just talk to you... ask you questions about your life, your routine, how you feel about things. My son actually found it really helpful to talk about the bullying and teasing that he experiences. He was also tested for dyspraxia, which involved trying to do a few simple physical things like standing on one leg, walking toe to heel and so on, but I think that had nothing to do with the aspergers.
He's also been asked to look at pictures people, and identify what they were feeling... he said he found it "quite interesting". And he's listened to recorded dialogues in various tones of voice, and been asked to describe what the actors etc were doing.
Don't worry, it's not threatening or anything.
It's so long since I was diagnosed that I can't even remember it happening, but it seems that things have changed a lot for the better in the last thirty odd years.