from tensorflow.python.platform import gfile

      self.assertEqual([], save.last_checkpoints)

      s1 = save.save(sess, os.path.join(save_dir, "s1"))
      self.assertEqual([s1], save.last_checkpoints)
      self.assertTrue(gfile.Exists(s1))

      s2 = save.save(sess, os.path.join(save_dir, "s2"))
      self.assertEqual([s1, s2], save.last_checkpoints)
