how to test christmas lights without a tester

Testing Christmas lights without a tester can be a bit tricky, but it's not impossible. One way to do it is to use your hands to check for heat coming from the bulb. If it's hot to the touch, then the light bulb is probably working. Another way is to use a multimeter, which is a device used to measure electrical current. Simply connect the multimeter to the plug and turn on the lights. If the multimeter shows a reading, then the lights are working. Finally, if you have a smartphone with a camera, you can use it to take a picture of the lights.