Here be dragons: testing your error handling code

Who tests the error handling parts of their code?  You might want to start doing this after watching this very interesting video from Goto Conference 2016.  Among other things, the speaker summarises a paper that investigates catastrophic failures in things like MapReduce, Cassandra etc.

58% of the catastrophic failures could have been prevented by testing error handling code because the error handling was just a comment saying TODO, or the error was logged but not handled etc.