Are you just arguing for fun now? A testing best practice is to control your environment as much as possible. What's more reliable, using a fresh sdcard for every test or removing all files in the sdcard before a test? You'll probably also find minor performance improvements in using a fresh sdcard too. We can't do this on devices because we can't automate physically replacing the sdcard. Anway, I give up, if you insist on not following a practice that's recommended and easy to implement, then go ahead.