Hey Bill,
You are right, Samsung supports a command to check the functions on the phone that there are less people known about this. Here I would like to instruct you to use this Test command on Samsung.
To use the test command Samsung smartphone you do as following:
Step 1: Open the call application.
Step 2: Type this:
*#0*#
Step 3: The test interface appears, you select each item to test for your smartphone.
Screen Check: Select Red, Green, Blue, Dimming.
Touch Sensation: Touch.
Speaker test: Receiver, Speaker.
Vibration test: Vibration.
Check camera: Front cam, Mega cam.
Check the function keys: Sub key.
Along with many other feature tests above. These are the main test items that you can try too.
So I have finished the test my Samsung smartphone and you can try yours and let us know if you see any issues with your smartphone after tested then.
Good luck!