jest-worker fails with "Do not know how to serialize a BigInt" in `messageParent.ts` instead of showing the actual assertion error message when there are 2 or more test suite files executing in parallel

Link to repl or repo (highly encouraged)

Minimal reproduction repo: jest-bigint-worker-issue

🐛 Bug Report

When you have multiple test suite files executing in parallel, and some of the tests are asserting values with bigint numbers in them and the assertion fails, instead of showing this assertion error message, jest-worker fails itself on attempt to serialise this value during the call to the:

parentProcess.send([_types().PARENT_MESSAGE_CUSTOM, message]);

(in messageParent.js)

I assume that’s because message includes failureDetails.matcherResult holding the compared bigint values that can’t be passed to process.send(), as unlike worker_threads it does not support non-json values out of the box.

To Reproduce

Steps to reproduce the behavior:

git clone [e-mail]:klesun-productions/jest-bigint-worker-issue.git # clone minimal reproduction repo
cd jest-bigint-worker-issue
npm ci # install jest dependency
npm test # run the test that reproduces the issue

Expected behavior

You should have seen the assertion error informing you that expect(1n).toEqual(2n); expectation failed

Actual behavior

But instead you get following output due to an internal jest-worker error:

 PASS  tests/some-other.test.js
  ✓ should succeed (2 ms)

 FAIL  tests/bigint.test.js
  ● Test suite failed to run

    TypeError: Do not know how to serialize a BigInt
        at stringify (<anonymous>)

      at messageParent (node_modules/jest-worker/build/workers/messageParent.js:42:19)

Test Suites: 1 failed, 1 passed, 2 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        0.777 s

With no details of what the actual error that jest-worker tried to report was in tests/bigint.test.js.

envinfo

  System:
    OS: macOS 11.3.1
    CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
  Binaries:
    Node: 14.17.0 - /usr/local/bin/node
    Yarn: 1.22.10 - /usr/local/bin/yarn
    npm: 6.14.13 - /usr/local/bin/npm
  npmPackages:
    jest: ^27.0.5 => 27.0.5

Misc

I assume that’s a transport issue that user of jest is not supposed to be aware of. One thing I did that at least somehow solved the absence of the real message was patching the jest-worker wrapping the call to parentProcess.send() in a try-catch and console.log-ing the message whose serialisation failed:

try {
  parentProcess.send([_types().PARENT_MESSAGE_CUSTOM, message]);
} catch (error) {
  console.error('jest-worker message serialisation failed', error);
  console.dir(message, {depth: 10});
  throw error;
}

There is likely a number of ways how to better address this problem…

[kaptainkommie]

Any update?

[gomain]

For those of you that got here because a failing test involves some BigInt, you can temporarily circumvent this issue by setting maxWorkers: 1 in your jest configuration.