def test_derive(self):
takeoff_gross_weight = TakeoffGrossWeight()
takeoff_gross_weight.set_flight_attr = Mock()
liftoff_gross_weight = KPV('Gross Weight At Liftoff',
items=[KeyPointValue(5, 135, 'a'),
KeyPointValue(12, 120, 'b')])
takeoff_gross_weight.derive(liftoff_gross_weight)
takeoff_gross_weight.set_flight_attr.assert_called_once_with(135)
def test_can_operate(self):
self.assertEqual(TakeoffGrossWeight.get_operational_combinations(),
[('Gross Weight At Liftoff',)])
