Sphinx Doctest: test the code without comparing the output.

[Luca Cerone]

> but if you're using this for a
> 
> tutorial, you risk creating a breed of novice programmers who believe
> 
> their first priority is to stop the program crashing. Smoke testing is

Hi Chris,
actually my priority is to check that the code is correct. I changed the syntax 
during the development, and I want to be sure that my tutorial is up to date.

The user will only see the examples that, after testing with doctest, will
run. They won't know that I used doctests for the documentation..

How can I do what you call smoke tests in my Sphinx documentation?