def test_post_order():
tree = BinarySearchTree()
tree.add(50)
tree.add(25)
tree.add(75)
tree.add(20)
tree.add(80)
tree.add(40)
"""
50
25 75
20 40 80
"""
actual = tree.post_order()
expected = [20, 40, 25, 80, 75, 50]
assert actual == expected
def test_postorder():
tree = BinarySearchTree(5)
tree.add(3)
tree.add(19)
assert tree.post_order() == [3, 19, 5]
