HOLIDAY PRECAUTIONS: How to properly test a GFCI outlet while plugging in christmas lights: The GFCI outlet will have 2 buttons one will say test and one reset, press test and reset button will pop out and power will shut off then press reset in and it will hold turning power back on. While hanging christmas lights this year make sure lights work before hanging, and visually inspect lights for knicks and cuts for safetys sake.If using outdoors always make sure you are plugged into a GFCI protected device. Also with all these lights plugged in make sure all smoke detectors are fully functional by doing a test on each device per manufactures specs. Remember to annually change batterys in detectors and alarm panels. While testing check date stamped on back of detector, most detectors have a 5 year lifespan. Emergency power equipment seasonal check-up