But test against what? This only makes sense for the property based testing, but then random sampling should give the same result up to a statistical margin of

But test against what? This only makes sense for the property based testing, but then random sampling should give the same result up to a statistical margin of error (unless there's some specific pathological case). I suppose this is good for extremely critical routines, kind of like the modified condition/decision coverage safe critical flight software has to undergo.