Kind of an SOP one should follow in order to figure out whether one has a good or a bad copy. let's answer the question how to test a lens without spending a tremendous amount of time and effort. I mean you just have your own copy! Non-symmetrical issues like decentration are relatively easy to detect. Usually, you are in lack of a benchmark.Front/backfocus - is this a lens or a body issue?.I wonder whether we could collect tips what tests to do? It seems we can agree on the fact that there is a certain copy to copy variation (maybe within spec, maybe due to a QC issue) and that one is better off to do a few but thorough tests after purchase in order not to miss out the warranty period. Honestly speaking, I was a bit shocked that I never noticed before!! So ' just go out and take pictures' may not be sufficient after having made a purchase. I recently noticed a certain decentration with my 55-200 mm 15 (!) months after purchase (see here) and now sent it to Fuji's repair center. In this forum, we quite often encounter lens quality discussions, like 'do I have a bad copy of this or that lens?'

Zeiss modified siemens star chart