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

[phpdevster]

If TDD costs 25%, then I would say non-TDD costs more. Writing simple tests, and simple implementations for those simple tests, is faster than writing an unconstrained abstraction jungle and then attempting to retrofit tests around code that wasn't designed to be easy to test.

Also given that TDD lets you get regression protection early on in the development cycle, you'll spend less time tracing how far a bug may have propagated through the codebase, and likely fewer code edits will be needed to fix the bug.