[Pharo-users] Pyret: adding tests directly into classes

I have just come across the Pyret language. It looks interesting, but the part which particularly caught my interest was the way that they had built the unit tests directly into the classes, rather than having separate test classes. I think this is an interesting idea. It seems as though it would be easier to manage writing tests if everything were in one location. And this - might - mean that people were more likely to write tests. Has anyone else looked at this, and have an opinion on whether it would be a good addition to Pharo 4/5/X? Cheers Andy