def test_find_max_root_is_max():
    tree = BinarySearchTree()
    tree.root = Node(23)
    tree.root.left = Node(19)
    tree.root.right = Node(7)
    tree.root.left.left = Node(5)
    tree.root.left.right = Node(8)

    assert tree.find_max_val(tree.root) == 23
def test_find_max_root_no_root():
    tree = BinarySearchTree()
    assert tree.find_max_val(tree.root) == None