It's interesting that many of those who question the effectiveness of TDD never seem to question the effectiveness of traditional methods, which are responsible for the dismal performance of the IT industry over the past few decades as documented in studies by Gartner, Forrester, Standish, and others. They demand newer methods like TDD prove themselves as compared with...well, with what, exactly? What's their baseline for comparison? Long lead times, high defect rates, untenable design debt, cost overruns? Rather than asking whether TDD really works, they ought to ask whether any other approach has really worked.