'L{task.react} returns quickly if the L{Deferred} returned by the
function it is passed has already been called back at the time it is
returned.'

def test_runsUntilSyncCallback(self):

    def main(reactor):
        return defer.succeed(None)
    r = _FakeReactor()
    exitError = self.assertRaises(SystemExit, task.react, main, _reactor=r)
    self.assertEqual(0, exitError.code)
    self.assertEqual(r.seconds(), 0)
