def METHOD_NAME(self):
    """Test calling update on the substs or defines pseudo dicts"""
    env = PartialConfigEnvironment(self._objdir())
    env.write_vars(config)
    mysubsts = {"NEW": "new"}
    mysubsts.update(env.substs.iteritems())
    self.assertEqual(mysubsts["NEW"], "new")
    self.assertEqual(mysubsts["CPP"], "cpp")
    mydefines = {"DEBUG": "1"}
    mydefines.update(env.defines.iteritems())
    self.assertEqual(mydefines["DEBUG"], "1")
    self.assertEqual(mydefines["MOZ_FOO"], "1")