$ python machine_spec.py
test_MachineShouldInitiallyHaveStateOfTheFirstState (__main__.machine_spec) ... ok
test_MachineShouldRememberListOfEventsWithTransitions (__main__.machine_spec) ... ok
test_MachineShouldRememberListOfValidStates (__main__.machine_spec) ... ok
test_MachineShouldTransitionToCheckingOutUponTriggerCheckOutEvent (__main__.machine_spec) ... ok

----------------------------------------------------------------------
Ran 4 tests in 0.008s

OK
$