I've discovered that mf2py not only allows me to parse people's h-cards, but to parse my own website in unit testing to see if the renderer outputs stuff correctly. #IndieWeb has some unexpected benefits!
State is not your friend, state is your enemy. Changes to state make programs harder to reason about, harder to test and harder to debug. Stateful programs are harder to parallelize, and this is important in a world moving towards more units, more cores and more work.