The answer to 'how to test lighting installation' is to use a multimeter to check for proper voltage and circuit continuity. First, turn off the power to the lighting circuit at the circuit breaker or light switch. Then, use the multimeter to test the voltage at the light fixture or outlet where the new lighting was installed. You should see the expected voltage (e.g. 120V for standard household circuits). Next, check for continuity by placing the multimeter probes on the hot and neutral wires - you should see a complete circuit. This ensures the wiring is properly connected. Finally, turn the power back on and test the new lighting to ensure it is working correctly.
It's important to take safety precautions when testing electrical circuits, such as wearing insulated gloves and turning off power before making any connections. Testing lighting installations should be done periodically, such as when adding new fixtures or after any electrical work in the home. If you are uncomfortable performing these tests or find any issues, it's best to consult a licensed electrician.