The answer to 'how to test circuit breaker' is to regularly test your home's circuit breakers to ensure they are functioning properly. This involves turning the circuit breaker off and on to make sure it trips and resets as expected.
Start by locating the circuit breaker box, usually in the basement, garage, or utility room. Identify the specific circuit breaker you want to test. Turn the breaker fully to the 'off' position, then back to the 'on' position. The breaker should trip and reset properly. You may also want to test the breaker by plugging in a device and intentionally overloading the circuit to ensure the breaker trips as designed.