def test_errorReplace(self):
        """
        Test an erroneous replace: if a L{MemCacheProtocol.replace} is called
        but the key doesn't exist on the server, it returns a B{NOT STORED}
        answer, which calls back the resulting L{Deferred} with C{False}.
        """
        return self._test(
            self.proto.replace(b"foo", b"bar"),
            b"replace foo 0 0 3\r\nbar\r\n", b"NOT STORED\r\n", False)

        Test an erroneous replace: if a L{MemCacheProtocol.replace} is called
        but the key doesn't exist on the server, it returns a B{NOT STORED}
        answer, which calls back the resulting L{Deferred} with C{False}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_memcache.py