Test runner with isolation=none does not work in child process

Version

v24.9.0

Platform

Linux home 5.15.0-153-generic #163-Ubuntu SMP Thu Aug 7 16:37:18 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

runner.js

import cluster from 'node:cluster';
import { run } from "node:test";

if (cluster.isPrimary) {
  cluster.fork();
} else {
  const stream = run({
    isolation: "none",
  });

  stream.on("data", (data) => {
    console.log("on data", data.type);
  });

  stream.on("end", () => {
    console.log("on end")
    process.exit(0);
  });

  stream.on("error", (err) => {
    console.log("on error", err);
  });
}

dummy.test.js

import { describe, it } from "node:test";
import * as assert from "node:assert";

describe("suite", () => {
  it("works", ()  => {
    assert.ok(true);
  });
});

How often does it reproduce? Is there a required condition?

Always. No.

What is the expected behavior? Why is that the expected behavior?

With isolation: "process" (the default), here's the output:

on data test:enqueue
on data test:dequeue
on data test:enqueue
on data test:dequeue
on data test:enqueue
on data test:dequeue
on data test:complete
on data test:start
on data test:start
on data test:pass
on data test:complete
on data test:plan
on data test:pass
on data test:summary
on data test:complete
on data test:plan
on data test:diagnostic
on data test:diagnostic
on data test:diagnostic
on data test:diagnostic
on data test:diagnostic
on data test:diagnostic
on data test:diagnostic
on data test:diagnostic
on data test:summary
on end

Process finished with exit code 0

The process cleanly exits at the end of the tests.

What do you see instead?

With isolation: "none", here's the output:

on data test:enqueue
on data test:dequeue
on data test:enqueue
on data test:dequeue
on data test:complete
on data test:start
on data test:start
on data test:pass
on data test:complete
on data test:plan
on data test:pass

And the process hangs.

Additional information

The goal was to use the "cluster" module to run the tests in parallel with the shard option:

import { run } from "node:test";
import { spec } from "node:test/reporters";
import { PassThrough } from "node:stream";
import { availableParallelism } from "node:os";
import cluster from 'node:cluster';

const concurrency = availableParallelism();
let completed = 0;

if (cluster.isPrimary) {
  const mergedStream = new PassThrough({
    objectMode: true
  });

  cluster.on("message", (_worker, message) => {
    mergedStream.emit("data", message);
  });

  mergedStream
    .compose(spec)
    .pipe(process.stdout);

  for (let i = 1; i <= concurrency; i++) {
    cluster.fork({
      SHARD_INDEX: i,
      SHARD_TOTAL: concurrency,
    });
  }

  cluster.on("exit", (worker, code, signal) => {
    if (++completed === concurrency) {
      mergedStream.end();
    }
  });
} else {
  const stream = run({
    isolation: "none",
    shard: {
      index: parseInt(process.env.SHARD_INDEX, 10),
      total: parseInt(process.env.SHARD_TOTAL, 10),
    },
  });

  stream.on("data", (chunk) => {
    process.send(chunk);
  });
}

Related: https://github.com/nodejs/node/issues/55939

Bắt đầu với việc tái hiện trong runner.js và dummy.test.js, sau đó lần theo điểm vào run() của node:test với isolation được đặt thành "none" khi được gọi từ một tiến trình con của cluster. So sánh vòng đời stream của nó với isolation mặc định "process" và issue liên quan 55939. Hoàn thành khi stream của tiến trình con phát ra các event còn lại, kết thúc và thoát sạch sẽ, đồng thời vẫn giữ hỗ trợ shard.