Test breeding is, classically, the breeding of a suspected carrier to a dog known to have a certain trait, to determine IF the suspected carrier is a carrier. One pup affected is a definate yes answer. Less than ~8 pups without the trait, however, is little to no assurance the suspected carrier can be cleared of its suspect status. Very few breeders actually & deliberately keep & breed a dog with PRA or vWD, although this is exactly how English breeders of Labradors practically deleted the genes for PRA out of their bloodstock. Test breeding is a most effective tool & can also be used "retroactively" on any breeding you do. For example, when a dog at public stud develops PRA. If you bred to the dog & your stock remains clear, especially when it was suspect, then this can help provide info on the status of the dogs in question. The same sort of general information can be gathered and used when a breeding produces an affected individual to at least identify carriers. The trick is to USE the info, not to bury it, or condemn the breeder who cared enough about their breed to announce it publically when a dog of theirs is found to carry a serious defect. Thanking them would make more sense. This way, the next generation of breedings can be done with more information and, therefore, with potentially better results. As more & more genetic marker tests become available, we may more easily be able to identify carriers. What will we do then about the information we have?

.