"So how do you write a test for a case you couldn't foresee?"

"You don't, but once you discover it, you write a regression test to make sure it doesn't come back."

Sure, that's SOP in any good dev. house that does testing. But you've failed to address a key weakness in TDD. The real question is how do you discover these sorts of defects given that a single developer writing in a TDD style is unlikely to do so? TDD is clearly not a cure all, and this is a major weakness of it. Other development techniques, many of which can complement TDD, such as formal code reviews and beta testing can do a better job of getting you to higher product quality than TDD alone.

"TDD is clearly not a cure all"

Who said it was?

Exactly!! There is no such thing as a cure all. Anybody angry over a technique that does not solve all problems is clearly suffering from the Silver Bullet Syndrome.

What? Why does something have to be perfect for somebody to get angry over it?

Not exactly sure what you are asking. I mainly meant any tool you use will not solve all of your problems. Pretty basic common sense, IMO.