How do you test alternator if ok?

To test if an alternator is functioning properly, start by checking the battery voltage with a multimeter; it should read around 12.6 volts when the car is off. Next, start the engine and measure the voltage again; it should increase to between 13.7 to 14.7 volts, indicating the alternator is charging the battery. Additionally, you can look for any unusual noises or signs of wear, and confirm that the alternator belt is tight and in good condition. If the voltage does not increase, the alternator may need repair or replacement.