def METHOD_NAME(self):
    """
    Test cancelling does cancel (relatively quickly)
    """
    bl = self.light
    ccd = mock.FakeCCD(self.img_ccd_loff)
    f = turnOnLight(bl, ccd)
    time.sleep(1)
    cancelled = f.cancel()
    self.assertTrue(cancelled)
    self.assertTrue(f.cancelled())
    with self.assertRaises(CancelledError):
        f.result(5)