If you mean the large fuses, usually you can tell they are blown by looking, but they can fail at the ends of the strip and look okay.
The better way to test them is to use a test light. You connect the clamp end to a good ground. Then use the tip to probe the contacts on top of each fuse with the key in the on position, and the headlights on. You can run through every fuse on a typical car in about five minutes that way.
https://www.2carpros.com/articles/how-a-car-fuse-works
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Thursday, June 29th, 2017 AT 10:05 PM