Display gone dark, but computer still working

My Macbook has randomly lost its laptop display. The display remains dark, including the apple logo on the back. I have connected an external display to it, and the computer still functions correctly. I have reset the PRAM many times, along with trying to “reset” it back into single screen mode.

Based on another question I saw on this forum I tried shining a light through the computer, and did not see any indication of the LCD displaying anything.

I’m guessing that my logic-board doesn’t have problems, but is there a way to diagnose if the cable/connection is bad - instead of the full display assembly?