The corrolary is that you must have a specification in order to test comprehensively. Either you use some form of TDD and your tests are your specification (and

The corrolary is that you must have a specification in order to test comprehensively. Either you use some form of TDD and your tests are your specification (and any behavior not under test is undefined), or you have exact and complete specifications that the as-built software can be compared to, and any hehavior not in the specficiation is undefined.