René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Test runner with isolation=none does not work in child process","articleBody":"### Version\n\nv24.9.0\n\n### Platform\n\n```text\nLinux 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\n```\n\n### Subsystem\n\n_No response_\n\n### What steps will reproduce the bug?\n\nrunner.js\n\n```js\nimport cluster from 'node:cluster';\nimport { run } from \"node:test\";\n\nif (cluster.isPrimary) {\n  cluster.fork();\n} else {\n  const stream = run({\n    isolation: \"none\",\n  });\n\n  stream.on(\"data\", (data) => {\n    console.log(\"on data\", data.type);\n  });\n\n  stream.on(\"end\", () => {\n    console.log(\"on end\")\n    process.exit(0);\n  });\n\n  stream.on(\"error\", (err) => {\n    console.log(\"on error\", err);\n  });\n}\n```\n\ndummy.test.js\n\n```js\nimport { describe, it } from \"node:test\";\nimport * as assert from \"node:assert\";\n\ndescribe(\"suite\", () => {\n  it(\"works\", ()  => {\n    assert.ok(true);\n  });\n});\n\n```\n\n### How often does it reproduce? Is there a required condition?\n\nAlways. No.\n\n### What is the expected behavior? Why is that the expected behavior?\n\nWith `isolation: \"process\"` (the default), here's the output:\n\n```\non data test:enqueue\non data test:dequeue\non data test:enqueue\non data test:dequeue\non data test:enqueue\non data test:dequeue\non data test:complete\non data test:start\non data test:start\non data test:pass\non data test:complete\non data test:plan\non data test:pass\non data test:summary\non data test:complete\non data test:plan\non data test:diagnostic\non data test:diagnostic\non data test:diagnostic\non data test:diagnostic\non data test:diagnostic\non data test:diagnostic\non data test:diagnostic\non data test:diagnostic\non data test:summary\non end\n\nProcess finished with exit code 0\n```\n\nThe process cleanly exits at the end of the tests.\n\n### What do you see instead?\n\nWith `isolation: \"none\"`, here's the output:\n\n```\non data test:enqueue\non data test:dequeue\non data test:enqueue\non data test:dequeue\non data test:complete\non data test:start\non data test:start\non data test:pass\non data test:complete\non data test:plan\non data test:pass\n```\n\nAnd the process hangs.\n\n### Additional information\n\nThe goal was to use the \"cluster\" module to run the tests in parallel with the `shard` option:\n\n```js\nimport { run } from \"node:test\";\nimport { spec } from \"node:test/reporters\";\nimport { PassThrough } from \"node:stream\";\nimport { availableParallelism } from \"node:os\";\nimport cluster from 'node:cluster';\n\nconst concurrency = availableParallelism();\nlet completed = 0;\n\nif (cluster.isPrimary) {\n  const mergedStream = new PassThrough({\n    objectMode: true\n  });\n\n  cluster.on(\"message\", (_worker, message) => {\n    mergedStream.emit(\"data\", message);\n  });\n\n  mergedStream\n    .compose(spec)\n    .pipe(process.stdout);\n\n  for (let i = 1; i \u003c= concurrency; i++) {\n    cluster.fork({\n      SHARD_INDEX: i,\n      SHARD_TOTAL: concurrency,\n    });\n  }\n\n  cluster.on(\"exit\", (worker, code, signal) => {\n    if (++completed === concurrency) {\n      mergedStream.end();\n    }\n  });\n} else {\n  const stream = run({\n    isolation: \"none\",\n    shard: {\n      index: parseInt(process.env.SHARD_INDEX, 10),\n      total: parseInt(process.env.SHARD_TOTAL, 10),\n    },\n  });\n\n  stream.on(\"data\", (chunk) => {\n    process.send(chunk);\n  });\n}\n```\n\n\nRelated: https://github.com/nodejs/node/issues/55939","author":{"url":"https://github.com/darrachequesne","@type":"Person","name":"darrachequesne"},"datePublished":"2025-09-26T06:09:43Z","url":"https://github.com/nodejs/node/issues/60020"}