About these testsI'm not a lens tester. I don't do systematic or scientific tests of lenses, and I don't claim that my results contain the full truth about a lens or indeed anything useful at all. I mostly do these for my own edification, and to gain a better understanding of lens performance on a given camera system.
Getting repeatable results is quite hard if you don't have your own testing lab. In real-world tests (i.e. actual photos) it is practically impossible - changes in light and atmospheric conditions can result in quite different image quality for the same subject with the same equipment. Because of this, I prefer not testing lenses in isolation, but comparing them against each other. That way, I get results that are valid to compare for a set of lenses at least.