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

def test_frozenset(self):

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