The normal thing is the depth of the fillet on a point that bisects the joint, the sides are different.

Normal welding practice is to test parts to destruction. It isn't just what some book says it is, but whether you can actually pull off that dimension. The normal simple destruction test would be an unsupported t type joint, but that is obviously a very severe test relative to a triangulated frame, still can't hurt. Might also explain why the fillets are the size they are.

There is a lot of talk in certain circles about certification for frame builders, but it would be a useful step before getting to that point to just have some simple answers to questions like this so that people who want to develop their skills have something to shoot for.