def METHOD_NAME(self, ref=None, itr=None):
    # Test the indexing functionality of CountingIterator
    if ref is None:
        assert itr is None
        ref = list(range(10))
        itr = iterators.CountingIterator(ref)
    else:
        assert len(ref) == 10
        assert itr is not None
    self.assertTrue(itr.has_next())
    self.assertEqual(itr.n, 0)
    self.assertEqual(next(itr), ref[0])
    self.assertEqual(itr.n, 1)
    self.assertEqual(next(itr), ref[1])
    self.assertEqual(itr.n, 2)
    itr.skip(3)
    self.assertEqual(itr.n, 5)
    self.assertEqual(next(itr), ref[5])
    itr.skip(2)
    self.assertEqual(itr.n, 8)
    self.assertEqual(list(itr), [ref[8], ref[9]])
    self.assertFalse(itr.has_next())