I'm glad your doctor isn't just prescribing by the "seat of his pants" :-) but wants you to get evaluated. It's usually several word-type oral and written tests; nothing with right/wrong replies, just how you think and feel. You can't fail or have anything horrible happen as a result.

I noticed you're in the UK, here's a UK explanation:

http://www.ehow.co.uk/how-does_66495...nsist-of_.html