To perform fluorescent ballast testing, turn off the power to the lights at the circuit breaker, remove the bulb and ballast cover, and use a multimeter to perform the test. If there is an issue, it is time to replace the ballast.
Begin the testing by turning off the circuit breaker inside the home's breaker panel. Remove the lens cover and the bulbs from the fixture, making sure to remove the bulb correctly based on the type of bulb it is. For instance, to release a U-shaped bulb, release the tension springs. Remove the cover of the ballast from the fixture if not seen, and if the ballast looks swollen, has burn marks or is leaking oil, replace the ballast without testing.
If the ballast looks good, set the multimeter to an ohm setting, and if there is an option, choose the X1K setting before moving on. Insert one of the probes of the multimeter into the connector that holds the white wires close. Touch the other probe to the ends of the red, blue and yellow wire, though some only have blue and red wires. If the multimeter does not respond, the ballast is bad.
Replace the ballast if necessary, and work in reverse to put the light back together before turning the power back on. If the ballast is working correctly, there is another issue with the lighting.