[Miniflare] Cloudflare Pages Support for unit testing

[uhthomas]

I saw cloudflare/miniflare#113, but I am interested in using miniflare with Jest to test Cloudflare Pages Functions.

It doesn't seem possible to create a mock EventContext with Miniflare at current.

[mrbbot]

Hey! 👋 Thanks for raising this issue, and apologies for the delayed response. I'm going to transfer this to workers-sdk as that's the new home for Miniflare 3, and that will make it easier for us to track this. We're planning to revamp Miniflare's unit testing environments for Miniflare 3 soon, and will consider Pages Functions support when we're implementing this. For now, since EventContext is just a plain-object (https://workers-types.pages.dev/#EventContext), you should be able to create a mock context with something like...

const ctx = new ExecutionContext();
const context: EventContext<Env, string, Record<string, unknown>> = {
  request: new Request("http://localhost"),
  functionPath: "",
  waitUntil: ctx.waitUntil.bind(ctx),
  passThroughOnException: ctx.passThroughOnException.bind(ctx),
  async next(input) {
    return new Response();
  },
  env: {
    ...getMiniflareBindings(),
    ASSETS: {
      async fetch(input, info) {
        const request = new Request(input, info);
        const url = new URL(request.url);
        if (url.pathname === "/index.html") {
          return new Response("<h1>Hello!</h1>");
        } else {
          return new Response(null, { status: 404 });
        }
      }
    }
  },
  params: {},
  data: {}
};

// ...do something with `context`...

await getMiniflareWaitUntil(ctx);

[penalosa]

Since this issue was opened, we've released the revamped Vitest work for Miniflare 3, which should work with Pages Functions: https://developers.cloudflare.com/workers/testing/unit-testing/