def test_shift(self):
     agenda = Agenda()
     shift = agenda.add_shift(9, 14)
     self.assertEqual(Interval(9, 14), agenda.get_shift(shift))
     shifts = list(agenda.get_shifts_iter())
     self.assertEqual(shifts, [(shift, Interval(9, 14)), ])
     agenda.del_shift(shift)
     shifts = list(agenda.get_shifts_iter())
     self.assertEqual(shifts, [])