def test_link_left(self):
n1 = Node(2)
n2 = Node(3)
self.assertIsNone(n1.left)
self.assertIsNone(n1.right)
n1.link_left(n2)
self.assertEqual(n1.left, n2)
self.assertIsNone(n1.right)
self.assertEqual(n2.parent, n1)
def test_link_left_fails(self):
n1 = Node(2)
with self.assertRaises(Exception):
n1.link_left(n1)
n2 = Node(5)
n1.link_left(n2)
with self.assertRaises(Exception):
n2.link_left(n1)
