If you have obtained your Samsung Galaxy S7 and unpack it for the first time, then you should test after turning on the device various technical hardware components. This includes the display. This you should test for pixel errors.
How this works on the new Samsung Galaxy S7 we explain here:
Once you have completed the setup wizard on the Samsung Galaxy S7, you must now open the phone app. Tap on the “Keypad” Symbol, which can be found at the bottom right. Tap the button and enter now the following code on the keypad:
Open Service menu: *# 0*#
After you have typed in the code, the service menu opens automatically. In the top row you will now find three different tiles:
All three tiles you must now tap in a row and then check on the display with the eye whether a pixel errors exist. A pixel error occurs as a dark spot. If you see no black dot at one of the three colors, then your Samsung Galaxy S7 display is without technical errors. Now you know how to check on the Samsung Galaxy S7 if the screen has defect pixels.