'Attributes names that start with a double underscore get
mangled when an instance is created.'

def test_double_underscore_attribute_prefixes_cause_name_mangling(self):

    rover = self.Dog()
    try:
        password = rover.__password()
    except Exception as ex:
        self.assertEqual(__, ex.__class__.__name__)
    self.assertEqual(__, rover._Dog__password())
