def test_unconstructed_singleton(self): a = Objective() self.assertEqual(a._constructed, False) self.assertEqual(len(a), 0) try: a() self.fail("Component is unconstructed") except ValueError: pass try: a.expr self.fail("Component is unconstructed") except ValueError: pass try: a.sense self.fail("Component is unconstructed") except ValueError: pass a.construct() a.set_sense(minimize) self.assertEqual(len(a), 1) self.assertEqual(a(), None) self.assertEqual(a.expr, None) self.assertEqual(a.sense, minimize) a.sense = maximize self.assertEqual(len(a), 1) self.assertEqual(a(), None) self.assertEqual(a.expr, None) self.assertEqual(a.sense, maximize)