I don't like TDD, I find it focuses too much on ceremony and too little on practical issues. However, writing new code by using a single test as a workbench seems like a huge win.

When you're adding a new feature, you need to get the current system up to a certain state(e.g. I'm adding a new action page only for users with a specific history...), you want a fast turnover tweaking the feature(push 1 button to reload), and you want to verify quickly that the feature is running correctly. In other words, you need a test.

I usually throw away the first "workbench" test and proceed to write tests for specific cases after laying the groundwork for the feature. Using this approach also "primes" my code for testability, which means I'm getting most of the TDD benefits without the necessary ceremony.