I wouldn't know how to use a multimeter.. maybe one of those screwdriver looking things that light up if electricity is flowing. Luckily I have circuit breaker type fuses.
I do carry a basic tool kit (including electrical tape) & fix-a-flat. I need to add a couple larger size allens. Probably should add duct tape, cable ties (a metal one too) and some velcro.
It's funny, you look at the car... there's barely anything there, you can see everything and nuts have marks to show if they're coming loose, and you ask yourself "what could go wrong?" Then 50 miles from home, a fender bracket bolt vibrates loose/off, fuel hose in tank works it's way off, you hit a pothole and tear a suspension mount... hopefully not all on the same trip.