'Check that a C{set} can contain a circular reference and be serialized
and unserialized without losing the reference.'

def test_set(self):

    s = set()
    a = SimpleJellyTest(s, None)
    s.add(a)
    res = jelly.unjelly(jelly.jelly(a))
    self.assertIsInstance(res.x, set)
    self.assertEqual(list(res.x), [res])
