It would seem that putting the aircraft in the air mode would be the best way to check the whole system in a running environment. I have some doubts on trusting "Built In Test" as a means of system verification.
The one that really bothers me is the Auto-Land Test to say the aircraft is Cat-3B. Shouldn't an actual auto-land in good weather conditions be the safest way to say the aircraft can land itself???
I agree! Being that I am CAT certified on the Bus, that test is easy money as opposed to the MD. To your point, the crews do an Auto-Land test after heavy MX; otherwise, it's on my back to bless them!!!