The development team validates the design
One can create a culture where the quality of the system is constantly brought into focus before the whole team. Even before engaging QA, the development team, ideally including Customer, can validate the design.
Techniques such as CRC cards and group debugging help socialize and solve problems. Members of a validation team can also work with QA to fix root causes attributable to common classes of software faults. The group learning aspect of group validation has been recognized since structured walkthroughs of COBOL. Variants of this pattern include PeerReview, RecipientAlsoReviews; also instant design validation is one potential aspect of DevelopingInPairs.