The utility of TDD varies tremendously from one language to another. Its biggest advocacy is usually associated with dynamically-typed languages, such as Ruby,

The utility of TDD varies tremendously from one language to another. Its biggest advocacy is usually associated with dynamically-typed languages, such as Ruby, Python, and Smalltalk, because TDD is a great workaround for mistakes that can easily occur in those languages. That doesn't mean it's a panacea for all programmers, though. For example, the type systems in OCaml and Haskell are effective for automatically verifying many of the same conditions. (Testing is used within those languages, but very differently -- Comparing TDD to Haskell's QuickCheck may prove enlightening.) Some day, better tools than the type systems in OCaml and Haskell and TDD will be invented. Let's not get so hung up on either as a solution that we miss out on even better ones (or fail to invent them).