The answer to 'how to test GFCI outlet' is to regularly test your GFCI outlets to ensure they are working properly and protecting you from electrical shocks. GFCI outlets are designed to quickly shut off power if they detect a ground fault, which can happen if an electrical device is not properly grounded or if there is a problem with the wiring.
To test a GFCI outlet, first make sure the outlet is powered on. Then, locate the 'test' and 'reset' buttons on the outlet. Press the 'test' button - this should cause the outlet to trip and the power to shut off. Press the 'reset' button to restore power. If the outlet does not trip when you press the 'test' button, or if it does not reset properly, the GFCI outlet needs to be replaced.