Testing a fuse can be done a few ways. A visual inspection is not always accurate. If you find a blown fuse the diagnostic isn’t over. Why did it blow is the next question.

One option is a test light or multimeter. You should have power on both sides or neither side. Only one is a blown fuse. Firmly connect or clamp a lead or test lamp to battery negative or a known good ground. Apply a known good power. This is a baseline showing the setup works. apply the other lead or tip of the light to the fuse on both prongs while the fuse is installed. Do both sides have the same reading? If they do the fuse is good.

Another option is a multimeter on ohms or continuity. Zero out the meter by connecting the leads and watching the reading turn form OFL to 0.00. This is the change you want to see when you test the fuse as well. This test can be done with the fuse in or out of the fusebox. If the fuse is out test on the legs of the fuse. If the fuse is in test on both top openings.

Less reliable but would work in an absolute pinch. Pull the fuse and look at it. Does it look blown? You are inspecting in the plastic. There is a thin metal connection between the two legs. If it doesn’t look blown swap the fuse with another fuse thats the same amperage.