The Volhart Test has its merits, though I don't use it per se. I rather trust my own gut instincts in looking at prospects. For me, if you're selecting a guard dog from puppyhood, I believe it's better to look at the performance and abilities of the parents first. Do they have to working qualities you want? Then look at the puppy. At 6weeks or even less, you will be able to see the characteristics and proper temperament you want. I believe that drives are hereditary. They cannot be trained into the dog if the genes for the ability is simply not there....
So, for me, the most important thing in choosing a pup to be guard dog is genetic.
Volhart Test, to me is only as good as the tester, and consequently, not very useful to me at all. If I know someone, and know the type of dogs they like, and they know what I like, then sometimes.......maybe.
Also there is research out there somewhere.......sorry really bad at losing interesting sites............that shows that testing done at something like 9 months and 18 months showed the test to be wrong often enough to render it useless. Again, who were the testers? Just random people??? I do remember how nuts the article made me, as they were kinda just winging it, and didn't know enough about dogs to write about them. LOL
If you are doing this with your own pups, then take a look at all the tests, and make up your own to see what you see. Video your test, and have people come up with their answers and you will see just how far off we can be. Most arguements on boards start from different words and opinions for the same things.