Not working on some Androids

[vganin]

I tested on AVDs with API 21 and 29 and this method didn't work for me.

The issue is that the test runs under the permissions of your app under test. And it requires android.permission.SET_ANIMATION_SCALE to make such changes to global settings. And this permission is signature and system which means that only system apps can have it. That's why it works when using adb shell and rooted device (or emulator).

On API 21 the additional issue is present. adb shell settings put global requires device reboot. So even if you make such change to settings, you still need to kill all processes to reboot.