The answer to 'how to test light fixture' is to first turn off the power to the fixture at the circuit breaker or light switch. Then, use a voltage tester to check for power at the fixture's wire connections. If there is power, the issue may be with the fixture itself. You can also try replacing the light bulb to see if that resolves the problem. If the fixture still doesn't work, you may need to replace the entire fixture or call an electrician for further inspection.
It's important to take safety precautions when testing light fixtures, such as turning off power, using insulated tools, and avoiding contact with live wires. Testing light fixtures should be done periodically, such as when a fixture stops working or during annual home maintenance checks.