you can test a puppy as early as eight or ten weeks. Take a quail wing with you and tie it to a string and drag it around past the puppies. The ones that chase it, go in a "maybe" crate. The ones that don't go back to mama for someone else to buy. One by one, try them out to see if they will make any attempt to bring it back to you if you toss it say, three feet or two feet away. It is amazing how much is hereditary and how early it shows in the ones with really strong hunting lines. Always go for a proven hunting line. The worst puppy from a great litter is way better than the best puppy from a mediocre litter.