Use async-await with done does not work since v27.

[infacto]

💥 Regression Report

Test functions cannot both take a 'done' callback and return something. Either use a 'done' callback, or return a promise.

Last working version

26 (latest)

Stopped working in version:

27 (next)

Expected behavior

I just wonder why this is dropped since 27? Not sure if just the detection is new (never worked) or not.
But in some cases we may use both. The advantage of async-await and e.g. setTimeout. But since async transforms the return type from void to Promise<void> Jest 27 detects it as returned value.

I could wrap the window.setTimeout into a Promise but what do you think about this issue?

Here's a test demo.

test('something', async (done) => {
  await something();
  setTimeout(() => {
    expect(another).toBe(42);
    done();
  }, 2000);
});

I also wondering if Jest already supports an own sleep method like jest.sleep(ms) or jest.wait(ms) or jest.delay(ms) (Promise). Maybe a good feature request? Otherwise I could wrap the timeout like:

export const wait = async (ms: number): Promise<void> => {
  return new Promise<void>((resolve) => {
    window.setTimeout(resolve, ms);
  });
}

But I would prefer a jest.wait function, instead of importing my own. But it's another issue.

Jest Envinfo

System:
  OS: Windows 10 10.0.19042
  CPU: (12) x64 Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz
Binaries:
  Node: 14.15.1 - C:\Program Files\nodejs\node.EXE
  npm: 6.14.8 - C:\Program Files\nodejs\npm.CMD
npmPackages:
  jest: ^27.0.0-next.9 => 27.0.0-next.9

[ahnpnl]

You need to use jest runner jest-jasmine2, v27 default uses jest-circus which doesn’t support done callback, see https://jestjs.io/blog/2020/05/05/jest-26 and #10529

[ozluy]

Override with react-app-rewired worked for me

// config-overrides.js
module.exports.jest = (config) => {
  config.testRunner = 'jest-jasmine2';
 return config;
};

[dhull]

Here is a workaround to allow a "done" function to be used with an async test. Change

  const functionUnderTest = (arg: any, callback: any) => { callback(arg); };

  test("my async test using done", async (done) => {
    const callback = jest.fn((result) => {
      expect(result).toBe("expected value");
      done();
    });

    const input = await Promise.resolve("expected value");

    functionUnderTest(input, callback);
  });

to

  test("my async test using done", async () => {
    let done: () => void;
    const callbackResolved = new Promise((resolve) => { done = resolve; });

    const callback = jest.fn((result) => {
      expect(result).toBe("expected value");
      done();
    });

    const input = await Promise.resolve("expected value");

    functionUnderTest(input, callback);

    await callbackResolved;
  });

You could also do the following but for a reason I don't understand this causes the test to also time out when the test fails. (When the test passes it's fine.)

  test("my async test using done", async () => {
    await new Promise(async (done) => {
      const callback = jest.fn(async (result) => {
        expect(result).toBe("expected value");
        done();
      });

      const input = await Promise.resolve("expected value");

      functionUnderTest(input, callback);
    });
  });

[spieIbug]

Put in your jest.config.js

module.exports = {
  // ... other settings,
  testRunner: 'jest-jasmine2' 
};

I had the issue with an angular project, solved it by setting the testRunner to jest-jasmine2

[github-actions]

This issue is stale because it has been open for 1 year with no activity. Remove stale label or comment or this will be closed in 30 days.

[SimenB]

Yeah, this is by design. You can use promises to handle anything the done callback does.

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.
Please note this issue tracker is not a help forum. We recommend using StackOverflow or our discord channel for questions.