Enable testServer usage with

Currently the `testServer` helper only works with declaratively register functions. We should find a way to make it work with the old background functions as well.

One idea is to have it accept a function as an argument instead of the registered name...

从 testServer 辅助程序的入口点开始，跟踪它如何解析以声明方式注册的函数与旧的后台函数。完成标准是 testServer 能够执行后台函数，同时保留其对声明式注册的现有行为。

由索引模型根据 Issue 内容生成。