It's less about testing your code with your documentation, but more the other way around. Make sure that the examples in your documentation stay current with your code. If you've spent any time working in Python, then you are probably familiar with doctest. The examples you add to document your project are like a map to the secret treasure that your users will find when they are able to easily use your library/API/tool/etc. But if the examples are wrong, it's like labeling the map with "promised land" right over the spot where it should say, "there be dragons".