Increase test coverage (depends on travis & appveyor)

[SailReal]

At the moment it is not possible to start an android emulator on appveyor in general and on Travis only, if the project target is Android. On the other side, travis doesn't support multy targets right now so if we choose android, we can not build rust applications.
It is realy sad that it is not possible with this setting, to execute all adbackup commands and check the results withoud having an Android device on the server side.

This issue should remind us to periodically check, if travis and appveyor changed the Android emulator support.
If so, increase coverage in

• blackbox
• integration
• unit