Yeah, combining unit tests and written docs in various ways seems fine. My reading of the article was that the tests are the only documentation. Maybe that was not the intent but just a bad interpretation on my part.
Though some replies here seem to keep arguing for my interpretation, so it's not just me.
Combining is what TFA suggests. They even go as far as closing the article with:
> Note also that I’m not suggesting that unit tests should replace any form of documentation but rather that they should complement and enrich it.