def test_stop(self):
        removed = []
        observer = object()
        def remove(observer):
            removed.append(observer)
        self.patch(log, 'removeObserver', remove)
        logger = app.AppLogger({})
        logger._observer = observer
        logger.stop()
        self.assertEquals(removed, [observer])
        logger.stop()
        self.assertEquals(removed, [observer])
        self.assertIdentical(logger._observer, None)
L{app.AppLogger.stop} removes the observer created in C{start}, and
dataset/ETHPy150Open kuri65536/python-for-android/python-modules/twisted/twisted/test/test_twistd.py/AppLoggerTestCase.test_stop