def test_derive(self): landing_datetime = LandingDatetime() landing_datetime.set_flight_attr = Mock() start_datetime = A('Start Datetime', datetime(1970, 1, 1)) touchdown = KTI('Touchdown', items=[KeyTimeInstance(12, 'a'), KeyTimeInstance(30, 'b')]) touchdown.frequency = 0.5 landing_datetime.derive(start_datetime, touchdown) expected_datetime = datetime(1970, 1, 1, 0, 1) landing_datetime.set_flight_attr.assert_called_once_with( expected_datetime) touchdown = KTI('Touchdown') landing_datetime.set_flight_attr = Mock() landing_datetime.derive(start_datetime, touchdown) landing_datetime.set_flight_attr.assert_called_once_with(None)