In their interview of you the breeder should have tried to find out something about your life style. All of these things are going to factor into which puppy will fit best in your house. While within a breed you should be able to expect general trends in activity level, dominance and temperament, each puppy is an individual with its own unique style. Within a litter you will find puppies that are more or less dominant with more or less energy. Just as you wouldn't expect all your children to be cookie-cutter replicas of each other, don't expect this from the puppies either.
Some breeders rely heavily on various puppy temperament testing methods.
Some, like ourselves rely heavily on observing and interacting with the puppies to determine their individual personality traits. In order to be accurate, the puppy temperament testing, in our opinion, should be repeated several times. Whichever method your breeder uses, you should trust their judgement in evaluating the puppies. But bear in mind that what you see in a 5 to 8 week old puppy is just an indicator and is not an absolute. The experiences the puppy has once he goes to your home will also determine what the adult grows up to be.