def test_rotate_left():
from bst import Node
node1 = Node()
node2 = Node()
node2.right = node1
node1.rotate_right()
assert node1.right == node2
assert not node2.left
def test_rotate_left():
from bst import Node
node1 = Node()
node2 = Node()
node2.right = node1
node1.rotate_right()
assert node1.right == node2
assert not node2.left
