Ability to use `reactively()` in Node.js unit tests

[rjhuijsman]

Is your feature request related to a problem? Please describe.
In our Discord, a customer reports that they're writing extensive Node.js unit tests for their Reboot backend, but they struggle to write -ergonomic tests because their ExternalContext does not support .reactively() calls.

Describe the solution you'd like
Ideally, ExternalContext would be able to call .reactively(). Alternatively, the WebContext that can call .reactively() would become available in Node.js unit tests.

Describe alternatives you've considered
Manually making calls when data is known to have changed via some external notification mechanism, or alternatively polling, "is funny but gets old fast".

Additional context
In terms of priority: this isn't blocking progress, but it would make life easier.

[benh]

WebContext is in fact usable in Node.js unit tests. The trick, however, is that it is making good old HTTP fetches, and thus you need to bring up your app using Reboot with { localEnvoy: true }, for example:

test("Using `WebContext`", async (t) => {
  await t.test("Basic", async (t) => {
    const application = new Application({
      servicers: [GreeterServicer],
    });

    const rbt = new Reboot();
    await rbt.start();

    t.after(async () => {
      await rbt.stop();
    });

    await rbt.up(application, { localEnvoy: true });

    const context = new WebContext({
      url: rbt.url(),
    });

    const [greeter] = await Greeter.create(context, {
      title: "Dr",
      name: "Jonathan",
      adjective: "Best",
    });

    await greeter.setAdjective(context, {
      adjective: "Friendly",
    });

    const response = await greeter.greet(context, {});

    assert(response.message == "Hi , I am Dr Jonathan the Friendly");
  });
});

[rjhuijsman]

@benh is there a design reason why .reactively() isn't available for ExternalContext? Or has there simply not been a use-case for it so far?

[benh]

@benh is there a design reason why .reactively() isn't available for ExternalContext? Or has there simply not been a use-case for it so far?

Simply not been a use-case yet, let's build it!