How do I check if my Audi A2's alternator is faulty?

I have noticed that my Audi A2's battery is draining faster than usual and the headlights seem to flicker. Is there a way to check if the alternator is causing the issue?

To check if your alternator is faulty, start your car and disconnect the negative terminal of the battery. If the car continues to run, your alternator is working properly.

You can also use a voltmeter to test the voltage output of your alternator. If it reads below 13 volts, then your alternator may be faulty.