'When L{MemCacheProtocol.checkAndSet} response is C{EXISTS}, the
resulting L{Deferred} fires with C{False}.'

def test_casUnknowKey(self):

    return self._test(self.proto.checkAndSet('foo', 'bar', cas='1234'), 'cas    foo    0    0    3    1234\r\nbar\r\n', 'EXISTS\r\n', False)
