def test_remove_root():
root = BinarySearchTree(4)
root.insert(2)
root.insert(6)
root.insert(1)
root.insert(3)
root.insert(5)
root.insert(7)
assert list(root.levelorder()) == [4, 2, 6, 1, 3, 5, 7]
root.remove(4)
assert list(root.levelordernested()) == [[5], [2, 6], [1, 3, 7]]
def test_remove_twochildren():
root = BinarySearchTree(4)
root.insert(2)
root.insert(6)
root.insert(1)
root.insert(3)
root.insert(5)
root.insert(7)
assert list(root.levelorder()) == [4, 2, 6, 1, 3, 5, 7]
root.remove(7)
root.remove(6)
root.remove(2)
assert list(root.levelordernested()) == [[4], [3, 5], [1]]