This tests that font features are able to be turned on and off as desired. It uses a special font designed specifically for this purpose. The test passes if you see a sequence of alternating check marks and X below.
AB
AB
BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA
BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA
BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA
BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA BA