def test_is_empty(self):
     """Test is empty method."""
     d = Dequeue()
     self.assertTrue(d.is_empty())
     d.add_front(1)
     self.assertFalse(d.is_empty())
 def test_is_empty(self):
     d = Dequeue()
     self.assertEqual(d.is_empty(), True)
     d.add_front("apple")
     self.assertEqual(d.is_empty(), False)