I'll give you a suggestion. :) I am a programmer, but for many years I dabbled in electrical engineering and have done circuit design and stuff, mostly for digital electronics, and I'm actually super surprised to see that nowhere on DMCTalk.org has anyone mentioned a megger.
"What the heck is a megger?"
A 'megger', or "Meg-Ohm-Meter" is kind of like a regular ohm meter that you might have built into a typical multimeter - it tells you whether there is an electrical circuit present. Except instead of a regular ohm meter that uses just a tiny small voltage to determine how many ohms of resistance are between two points, a megger uses hundreds or even thousands of volts. It would be like the difference in using a smoke machine to blow a little bit of air to check for a leak vs using your air compressor at 100psi. It's super useful in finding ground faults that don't normally appear, because it has enough voltage to jump small gaps, or through broken insulation (hence why they are also called "insulation resistance testers").
While meggers are typically quite expensive (the one from Fluke is about $500) - you can find them cheap on eBay or Amazon - here's one for $50:
https://www.amazon.com/Digital-MegOh...604179&sr=8-17