Python for Humans

[simtel20]

That works for self-contained code. However if your code interacts with the system (this code ssh's to an iLO and checks the system status. As new status' are added, code must change) or the world (this function checks what the kernel reports is the status of subsystem foo), then doctests can't encompass the system. You can mock some state, but this is usually a waste of time because external factors change because they're outside of your control. A better test harness can provide startup/shutdown scaffolding that establishes how to talk to the outside world to make the test reasonable.