def test_add_zone(self):
        cluster = Cluster()
        self.assertEqual(0, len(cluster.nodes))
        self.assertEqual([], cluster.zones)
        self.assertEqual(0, len(cluster.zone_members))
        self.assertEqual(0, len(cluster.rings))

        cluster.add_zone('b')
        self.assertEqual(0, len(cluster.nodes))
        self.assertEqual(['b'], cluster.zones)
        self.assertEqual(0, len(cluster.zone_members['b']))
        self.assertEqual(0, len(cluster.rings))

        cluster.add_zone('b')
        self.assertEqual(0, len(cluster.nodes))
        self.assertEqual(['b'], cluster.zones)
        self.assertEqual(0, len(cluster.zone_members['b']))
        self.assertEqual(0, len(cluster.rings))

        cluster.add_zone('a')
        self.assertEqual(0, len(cluster.nodes))
        self.assertEqual(['a', 'b'], cluster.zones)
        self.assertEqual(0, len(cluster.zone_members['a']))
        self.assertEqual(0, len(cluster.zone_members['b']))
        self.assertEqual(0, len(cluster.rings))