It's quite similar to the doctests ideas I guess - but not intended
to be documentation like them.
I ended up disliking docttests because of this doc+test duality by
the way: it often ends up as a
not so good documentation and not so good tests.
Anyways, having a dedicated keyword to append after a function some
tests as part of the language
has benefits imho:
- the scope is reduced to the function - so it helps making 'real'
isolated unit tests.
- we do have the unittest conventions, but here it make tests a
first class citizen in the language.