If you need to learn how to test a circuit breaker, there are important tools you can purchase to make the process much easier. When troubleshooting a circuit breaker problem, you may have a faulty device running on the circuit, or a bad circuit breaker. It all depends on the nature of the problem. Do you need to see if a device is attached to a particular circuit is faulty? A continuity tester is a simple device you can buy to help determine if a circuit can carry electricity.
Use the "live" probe on the "live" prong power cord and the ground probe on the ground part of the plug to see if it is able to carry current. The tester will respond positively (with a light or buzz depending on the model) if it is functioning properly. A multimeter is a more sophisticated tool you can use to test a circuit breaker. By putting the multimeter in "volts AC" mode and touching the hot prong to the breaker's screw you can see if the breaker has power. If there is no power, you need to replace that circuit breaker.