def test_peek_front_rear(self):
d = Dequeue()
d.add_front("apple")
d.add_front("banana")
d.add_front("cherry")
self.assertEqual(d.items, ["cherry", "banana", "apple"])
self.assertEqual(d.peek_front(), "cherry")
self.assertEqual(d.peek_rear(), "apple")
def test_peek_empty(self):
d = Dequeue()
self.assertEqual(d.peek_front(), None)
self.assertEqual(d.peek_rear(), None)