### Describe the bug 在上文中有调用到`app.start()`, 但在下文没有在`after`注册对应的`app.stop()`, 看起来和其他测试文件不一致. https://github.com/koishijs/koishi/blob/cbc18a1d1a240ab96704dc04bcb30ad080e25a96/packages/core/tests/middleware.spec.ts#L14