Install Nokia Care Suite on your PC,install all the drivers that come with the program. Connect your Lumia to the PC.Open the program.Once your phone is identified where it says normal change it to test.Phone will reboot and the screen will change.On the program at the bottom go to test and select the test you want to perform or all. Once done it shows the results.To take the phone out of test mode,change back where you choose test to normal.Phone will reboot in normal mode.Hope it helps.You just need a little basic knowledge and common sense. ;-)