> It seems obvious that the answer to that rather depends on how well you actually understand the problem space you're trying to solve. An advocate for TDD (as

> It seems obvious that the answer to that rather depends on how well you actually understand the problem space you're trying to solve. An advocate for TDD (as in “red > green > refactor”) might say that writing the spec upfront is an excellent way to understand the problem space, or at least to help achieve that understanding. At least when I’ve been fortunate enough to work on projects where such a TDD approach is possible, I’ve found that to be the case. I’ve also often found it harder to gain that understanding when testing lags development.