Sadly, I *really* dislike that. To me, "where" has absolutely nothing to do with testing. I see that Pyret also includes a "check" keyword which also does testing. That seems like a more sensible keyword.

"where" seems like it would implement argument constraints. I don't think you want the (necessary) mess of comprehensive unit test code embedded in the source, so nix on the "check" keyword too. It would just obscure the structure of the code. Skip