def test_post_order_print_one_node(capsys):
root_node = BinaryTree(1)
root_node.post_order_print(root_node)
expected = "1 "
output = capsys.readouterr().out
assert output == expected
def test_post_order_print_multiple_nodes(capsys):
root_node = BinaryTree(4)
root_node.left_child = BinaryTree(1)
root_node.left_child.left_child = BinaryTree(7)
root_node.left_child.right_child = BinaryTree(9)
root_node.right_child = BinaryTree(5)
root_node.right_child.left_child = BinaryTree(2)
root_node.right_child.right_child = BinaryTree(6)
root_node.post_order_print(root_node)
expected = "7 9 1 2 6 5 4 "
output = capsys.readouterr().out
assert output == expected