name : test_delegator.py import unittest from idlelib.Delegator import Delegator class DelegatorTest(unittest.TestCase): def test_mydel(self): # test a simple use scenario # initialize mydel = Delegator(int) self.assertIs(mydel.delegate, int) self.assertEqual(mydel._Delegator__cache, set()) # add an attribute: self.assertRaises(AttributeError, mydel.__getattr__, 'xyz') bl = mydel.bit_length self.assertIs(bl, int.bit_length) self.assertIs(mydel.__dict__['bit_length'], int.bit_length) self.assertEqual(mydel._Delegator__cache, {'bit_length'}) # add a second attribute mydel.numerator self.assertEqual(mydel._Delegator__cache, {'bit_length', 'numerator'}) # delete the second (which, however, leaves it in the name cache) del mydel.numerator self.assertNotIn('numerator', mydel.__dict__) self.assertIn('numerator', mydel._Delegator__cache) # reset by calling .setdelegate, which calls .resetcache mydel.setdelegate(float) self.assertIs(mydel.delegate, float) self.assertNotIn('bit_length', mydel.__dict__) self.assertEqual(mydel._Delegator__cache, set()) if __name__ == '__main__': unittest.main(verbosity=2, exit=2)