How do you know if fuses are bad?

Sometimes something goes wrong with an electrical part, and it starts to draw too much electricity. When this happens, the circuit is protected by a fuse. The fuse is the weak link in the circuit, so when a problem occurs, the fuse blows, and the electricity stops flowing. This is a safety feature to protect the wiring and the rest of the car from catching fire. Many mechanics will tell you that all you have to do to check a fuse is to look at it. . I have seen fuses that visually looked perfectly OK, but were, in fact, blown. The only sure way to tell if a fuse is good is with a test light or an ohmmeter.