It is my understanding a tank has to be in VERY bad condition to fail testing. Fibre has to be peeling, and even then I believe they can epoxy the fiber back onto the tank in some instances.
People FREAK out when there's a dinky tiny nick or scratch in a tank. I was selling a Nitroduck Tuffskin tank, had a handful of nicks in the Tuffskin (not even in the actual tank, mind you) and people were freaking out about it.
Obviously the best thing to do is keep a cover on the tank and don't let it get nicks/scratches, but if you do I wouldn't sweat it.