def test_breadth_first_traversal(self):
     print("Running test_breadth_first_traversal")
     airport = Airport(100)
     a1 = airport.bounded_insert(2000, "TOP")
     a2 = airport.bounded_insert(1000, "TIP")
     a3 = airport.bounded_insert(2500, "RIC")
     a4 = airport.bounded_insert(500, "KRO")
     a5 = airport.bounded_insert(1800, "LLE")
     b = airport.breadth_first_traversal()
     ground_truth = [a1, a2, a3, a4, a5, None, None, None, None, None, None]
     for layer in b:
         for element in layer:
             # Check if there are still elements that could be processed
             self.assertTrue(len(ground_truth) > 0)
             gt = ground_truth.pop(0)
             self.assertEqual(element, gt)
     # All elements should have been processed.
     self.assertTrue(len(ground_truth) == 0)