Test runner with isolation=none does not work in child process #60020
Description
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: #55939