I have a Lenovo IdeaTab A1000 with Android 4.1.2. System update was available and started it. After a few minutes screen was black and thought update was finished. By mistake pressed the volume button when picking up the pad and it started some short of a factory test procedure. In a first test screen was filled by circles which I was able reset one by one, next test followed, and an other one... I can't finish the tests. How to stop the test procedure? I tried to press power and volume buttons again, but no success. Should I wait until the battery is flat... Thanks for help.