def test_postorder():
tree = BinaryTree()
tree.root = Node(50)
tree.root.left = Node(30)
tree.root.right = Node(70)
tree.root.left.left = Node(20)
tree.root.left.right = Node(40)
actual = tree.post_order()
expected = [20, 40, 30, 70, 50]
assert actual == expected
def test_tree_postorder():
tree = BinaryTree()
tree.root = Node(1)
tree.root.left = Node(11)
tree.root.right = Node(2)
tree.root.left.left = Node(111)
tree.root.left.right = Node(112)
actual = tree.post_order()
expected = [111, 112, 11, 2, 1]
assert actual == expected