Finally, there's tooling for #androiddev to test backup and restore of apps: https://developer.android.com/studio/preview/backup-restore-testing
This is an area which was neglected by Google and app devs alike. Hope this will help to improve the backup situation on Android.
@grote
Of course android doesn't have a proper backup system at all.
All of the apps are backed up together and you can't restore a single app.
Only one copy of the app data is saved. It's impossible to restore to a previous working state after it is overwritten state.