To run the test, simply change from the default (English) keyboard to the "Special" keyboard.
When things are working properly, the base keys on the "Special" keyboard should contain evenly-sized dots. On touch devices, they should be fairly large.
If the dots are small and unevenly-sized instead, key-cap scaling is occurring before the keyboard's font has loaded. (Pay special attention to the QWERTY-layout 'w' and 'm' keys.)