I don’t have a multimeter but happy to buy one if you let me know how to use it and perform the test. -Alex
Alex - It is a simple continuity check you want to test between each pin of each connector. Any cheap multimeter that you can get at Home Depot or Lowes or possibly even WalMart will do a simple continuity check. Usually they have tone confirmation for continuity check so I usually try to get one that has that at a minimum.
I just tested two different C19 cables I have and found the following results. I held both plugs in my hand so the male/female ends were pointing at me with the two pins on top and the single pin on the bottom. On each the same position pin on each plug had continuity to the respective pin on the other connector. Top right was connected to top right on each connector. The only thing that could get reversed is the top two pins to give you the off reading. The single pin should always be ground.