Michael Bolton recently pointed out on an agile testing list that few people think of
Testing as questioning the product in order to evaluate it or
Testing as an empirical, technical investigation of the product, done on behalf of stakeholders, with the intention of revealing quality-related information of the kind that they seek.
This is interesting to me because the Testing as finding defects is not very high value and test driven development is a technique to allow developers to think through issues, rather than something that protects the stakeholders interests.
Yes Testing-as-design and Testing-as-confirmation are interesting, but they are not typically the things that make or break a project.