def test_1element(self): a = ConstDom("") o = a.one() #self.assertEqual(str(o), # "{ ONE }") a = ConstDom("r1 = 3") #test that one is neutral for extend b = a.extend(o) self.assertEqual(str(b), str(a)) b = o.extend(a) self.assertEqual(str(b), str(a))