The answer to 'how to test light fixture' is to check if the light is receiving power and the bulb is working properly. First, make sure the light switch is turned on and the bulb is screwed in tightly. Then, use a voltage tester to check if there is power at the light fixture. If there is power but the light still isn't working, the bulb may be burned out and need to be replaced.
If the light fixture is wired directly to the electrical system, you'll need to turn off the power at the circuit breaker before testing or replacing the fixture. This ensures your safety when working with electricity. Once the power is off, you can remove the fixture and inspect the wiring connections to make sure they are secure and not damaged.