How to do mocks when testing a nodejs custom environment to test a fastify server?

[akhilmhdh]

Hey everyone,

We are using vitest to test our fastify nodejs server. How we do is that is using the vitest custom environment option.

So our custom environment file would looks like this

// load environment
export default {
  name: "env",
  transformMode: "ssr",
  async setup() {
    // connect with db

    try {
      // do migration
     // do seeding

      const server = await main({ db, smtp, logger, queue, keyStore });
      // @ts-expect-error type
      globalThis.testServer = server;
    } catch (error) {
      console.log("[TEST] Error setting up environment", error);
      await db.destroy();
      throw error;
    }

    console.log("ended environment");
    // custom setup
    return {
      async teardown() {
        await globalThis.testServer.close();
        await db.destroy();
      }
    };
  }
};

A simple spec file would look like this

describe("Org V1 Router", async () => {
  test("GET Org list", async () => {
    const res = await testServer.inject({
      method: "GET",
      url: "",
      headers: {
        authorization: `Bearer ${<valid token>}`
      }
    });
    expect(res.statusCode).toBe(200);
    const payload = JSON.parse(res.payload);
    expect(payload).toHaveProperty("organizations");
  });
});

This seems to be working really well for us. Until we wanted some mocking to do on testing on endpoints. Like axios as an example.

For some reason none of mocks are working. Like ones setup in setupFiles nor anywhere in spec? I do think i am making a mistake in doing mocking (as i am mainly amateur in test frameworks and my experience in mocking is not that great 😅 ) or is mocking not possible with this way?

Any insights would be helpful!

[hi-ogawa]

I think environment loading happens before any module graph setup (namely VitestExecutor), so probably that's why vi.mock wouldn't work.

Probably you had some reasons to choose custom environment approach, but just in case, sharing another way to achieve similar server setup using higher level API (so it should compose better with other APIs like vi.mock).
Have you considered something like this using beforeAll in setupFiles?

beforeAll(async () => {
  // connect with db

  try {
    // do migration
    // do seeding

    const server = await main({ db, smtp, logger, queue, keyStore });
    globalThis.testServer = server;
  } catch (error) {
    console.log("[TEST] Error setting up environment", error);
    await db.destroy();
    throw error;
  }

  console.log("ended environment");
  // custom setup
  return async () => {
    await globalThis.testServer.close();
    await db.destroy();
  }
})

[akhilmhdh]

Yes it seems your right. The environment as I guessed doesn't allow mocking to work due to module loading. I guess that's why .resetModule is also not working.

We went for custom environment because we wanted to do the process only once and not for each test suite. Something like the globalSetup. But globalSetup doesn't allow the globalThis because i think its run on a different context and the inject from vitest only allows JSON serializable.

[hi-ogawa]

We went for custom environment because we wanted to do the process only once and not for each test suite.

By default, environment setup is isolated for each test file, so I was assuming that beforeAll would mostly work same, but perhaps you disable isolation by isolate: false? Sharing your config would help to understand your use case better.

[akhilmhdh]

Sure,
Here you go: vitest config

Yes we have single thread and isolate as false. Because the issue is migration as multiple entity cannot run it at the same time.

We thought of making it as start of the script but the issue is cleanup causes conflict too.

[hi-ogawa]

Thanks for sharing the full repo, that's even better 👍

It might be too simplistic, but maybe you can still delay db/server setup till setupFiles + beforeAll by checking globalThis.testServer?

beforeAll(async () => {
  if (globalThis.testSever) return;

  // then setup db / server only on first setup
});

[akhilmhdh]

Yes I need to rethink our implementation once again but i think i now have a better understanding of vitest.

I did try the setupFiles way and the mocks were indeed working. So marking above as the answer indeed. Thank you so much for your valuable time and insight. Have a good day.