def test_post_order_three():
tree = BinarySearchTree()
tree.add(5)
tree.add(3)
tree.add(15)
expected = [3, 15, 5]
actual = tree.post_order()
assert actual == expected
def test_in_order_more():
tree = BinarySearchTree()
tree.add(20)
tree.add(5)
tree.add(10)
tree.add(15)
tree.add(25)
tree.add(35)
tree.add(40)
tree.add(23)
tree.add(45)
expected = [15, 10, 5, 23, 45, 40, 35, 25, 20]
actual = tree.post_order()
assert actual == expected