Years ago, our Lab breeder/vet had our litter temperament tested and she invited us to watch. We picked our female based on the outcome of the test and we were also able to follow the rest of the litter since most went to people we knew and the rest we followed through the breeder. They really did seem to mature just like the tester said they would. It kind of got me hooked on researching the issue and testing it. We had two litters of pups out of that female and followed almost all of the pups for years. As a matter of fact, I am still friends with many of the people who owned those dogs though there are few left at this point. The traits we saw in the puppies really did follow them all the way through their life. The problem is that many breeders don't spend enough time with the litter to know the individual personalities of their pups. Those that do are able to tell you what each individual is like, their strengths and weaknesses and which one might be the best fit for your personality.Nice site on the temperament test!! We did that with a litter of border collie pups last year. It was interesting to see how each pup matured and changed over time. All the pups except 1 out of 5 were very middle of the road, not too dominant, and not too timid. All but one showed interest in a toy, but none would bring it back. None were sound sensitive , or aggressive . The 4 pups I've kept in close touch with have turned out to be nice level headed biddable working dogs.
That test is nice because you can see a pup's tendencies and spend a little more time on certain things a pup might have trouble with.