Modern mobile devices are smart and complex machines. Unlike personal computers, they use different sensors.

Information captured by the sensors triggers various processes on the tablet or smartphone. One should find out during web site testing on mobile devices or mobile application testing how the system reacts on various modes of the device.

Common Modes of Tablets and Smartphones:

• battery saving mode; when the battery is low
  a mobile device tries to diminish usage of the battery and turns off
  some functions;
• countermeasures to overheating of the device; there are no working
  parts for cooling in mobile devices; that is why when they get hot they
  disable some affordances, slow down CPU; when the smartphone or tablet
  gets too overheated it may turn itself off in order to prevent breaking.

Experts in manual and automated testing of mobile software know that mobile devices always try to save battery,
if possible. Among the most energy consuming activities is lighting up
the screen.

That is why smartphones and tablets use proximity sensors and detect
if the user is interacting with the device. If nobody’s interacting with
the smartphone or tablet, or proximity sensors do not notice the user
near the device, the screen automatically turns off.

A software testing company advises its testers to find out during mobile testing how these processes influence functioning of the program under test.

http://qatestlab.com/