A simple banking application that follows the OO design from 'Object Calisthenics by Jeff Bay, ThoughtWorks Anthology)' in Python.
Bank -> Customers
Customers -> Customer
Customer -> Accounts
Customer -> Name
Accounts -> Account
Account -> Balance
(At least for one class...)
$ nosetests -s -x
........
----------------------------------------------------------------------
Ran 8 tests in 0.005s
OK