The answer to 'how to test generator' is to perform a load test to ensure the generator is working properly. This involves connecting a load to the generator and measuring the voltage, frequency, and current output. Start by turning off all circuit breakers or loads connected to the generator, then connect a portable load bank or other electrical load. Run the generator under load for 30 minutes to an hour, monitoring the output to ensure it stays within the manufacturer's specifications.
It's also important to check the fuel, oil, and coolant levels, and inspect the generator for any signs of damage or wear. If you notice any issues, it's best to have a professional technician inspect and service the generator.