def test_insert_top(self):
     linked = LinkedList(['two', 3])
     linked.insert_to_the_top(1)
     self.assertEqual(1, linked.first_node.data)
     self.assertEqual('two', linked.first_node.next.data)
 def test_insert_top_empty_list(self):
     linked = LinkedList([])
     linked.insert_to_the_top('first')
     self.assertEqual('first', linked.first_node.data)
     self.assertEqual(None, linked.first_node.next)