Fuse Testing

I don't know for sure about trucks but in the automotive word a test light or volt meter are not valid tests. There can be voltage on both sides of a fuse. The way they wire things up you can get voltage back feeding on the "down stream" side of a fuse. There won't be any amperage to speak of but enough to light a test light and read on a volt meter.
Back in the 90s I worked on a Cadillac that every time you opened the door the radio would go haywire. The guy said he was ready to start going dukes of hazard style so he did not have to reset his radio every time he got in the car. He had it to multiple shops and had spent over a 1000 bucks trying to figure it out. It was a blown fuse. I'm guessing everyone missed it because the fuse looked good to a test light. But did not pass the best test.... a visual inspection.

 

I just use a conduit test with a multi meter. Works on bulbs also.

 

Fuse may protect circuit relatad with other and when it is not removed from panel - u can be sure, it is OK ore not.

Other way - use circuit brakers instead of fuses. In case of overload it click and small reset button pops up and u can see broken circuit.

 

as an example - Volvo LCM has power supply fuse check, but only six LCM fuses

Really, if u wanna dupm money in cool truck fuse panel - build circut braker panel like in planes. When braker pops up u can see what braker is off. U can easily reset it and u can pull small knob to turn circuit off