I had a lot of fun welding and worked as a welder/fabricator for a few years after attending tech school.
All of our certifications would only pass if the weld was as strong as the parent metal. They would take a 1" strip and bend it in a U shape. If the weld held and was clean of pitting, debris, etc., it passed. If it broke or was flawed, it failed. Fortunately, all of my samples passed (I had an excellent teacher).
Slightly OT:
I held 13 certifications in MIG, TIG, ARC (including pipefitting) and welded everything from 1/8"+ stainless steel, 1/4"+ aluminum to 1" mild steel, but got sick of 55-60 hour work weeks. Every shop I worked in had mandatory OT, often mandatory Saturdays. And the pay wasn't that great (I made much more waiting tables soon after).
Anyway, my interest in a sculpture class sparked (sorry, had to) my interest in welding and I hope to work again in a studio some day.