Designing a cable tester
Instead of having dedicated circuitry that lights a LED for each wire, I'd test the whole thing with a microcontroller.

The microcontroller would be capable of driving each line high or low at one end, although small series resistors should be used to prevent damage in case lines of the cable are shorted to each other.  At the other end it can apply either a pullup or pulldown and read the state of each line.  A walking 0s and walking 1s pattern should be all you need to check for any opens or cross-conductor shorts.  That's only twice as many tests as there are conductors in the cable.

The whole test would be instantaneous in human time, and you'd get a single simple good/bad indication immediately.  That's a lot better than a bunch of individual good/bad indications.  People get tired and make mistakes.  Asking production techs to look at a bunch of different indicators to ultimately get a single yes/no answer is not a good idea.  Make it simple, and thereby difficult to mess up.