Google has its own robot testing Android phones and reveals shortcomings.
From the appearance of Android, there was always the concern in relation to lagging the system at certain moments. Enough reviews from that time shows that the people who tested the phones switch between the two screens to see if it appears lag.
Even today, when Android phones come with more powerful hardware and software that is constantly updated, this problem was not resolved until the end. As reported by Francois Bufort, Google uses robots Finnish company called OptoFidelity to measure extremely late for Android and Chrome devices. As you can see in the video, the robot constantly pressing the screen in order to measure how the screen reacts. It should be noted that the robot can identify the hardware and software problems.