Should I comment out the code for what I am not testing when loading the test firmware for Ramps 1.4? You may want to use this code to test all the electronics before
  installing any of the suggested firmwares.


I'm planning on:


Flashing the test firmware onto the Arduino Mega 2560, then unplugging it from the USB.
Connecting RAMPS 1.4
Connecting all 3 jumpers under the X-Axis (leaving the other jumpers disconnected).
Connecting a stepper driver to the X-Axis on the board.
Turning the trimpot down all the way, and then back up 1/4th of the way.
Plugging in 1 NEMA 17 motor to the X-Axis.
Connecting 5A DC input into RAMPS 1.4 (not plugged in).
Finally plugging it in and seeing if the motor moves for 5 seconds.


Now my question is, if I'm going to do this to test out a single NEMA 17 motor, do I need to comment out the rest of the test code before loading the firmware?
There's no reason to comment anything out. It will work just fine without any modification, even if you're just testing a single motor. That said, I don't see the value of this "test firmware" over just installing Marlin.