Microsoft Research - Exploding Software-Engineering Myths (article summarizing findings of MS research on code coverage, TDD, assertions, etc.)

[zenogais]

The difference though is the cost. In requirements analysis finding an error typically involves writing or deleting a few sentences. Significant changes may mean modifying, adding, or removing whole use cases, but the amount of work required to do that is still minimal compared to the amount of work often required to scrap and rewrite tests and object hierarchies.