Off the car you need a special tester that is powered. So the short answer is, off the car, no.
On the car it's pretty easy. Procedure is in the shop manual.
Charge the battery fully.
Place positve probe or clip of the voltmeter onto the ignition circuit some place close to the regulator. The 'run' terminal at the ballast resistor is a good location.
Connect the negative probe to a good ground.
View attachment 1715605734
Start the car.
View attachment 1715605717
With nothing else turned on and the battery charging done, voltage should stay pretty steady regardless of rpm.
That still leaves the possibility of resistance in the wiring, but the regulator itself is working.
