René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Test runner with isolation=none does not work with coverage","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 { run } from \"node:test\";\nimport { spec } from \"node:test/reporters\";\n\nconst stream = run({\n  isolation: \"none\",\n  coverage: true,\n});\n\nstream.compose(spec).pipe(process.stdout);\n```\n\ndummy.test.js\n\n```js\nimport { describe, it } from \"node:test\";\nimport * as assert from \"node:assert\";\n\ndescribe(\"suite\", () =\u003e {\n  it(\"works\", ()  =\u003e {\n    assert.ok(true);\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```\n▶ suite\n  ✔ works (0.789789ms)\n✔ suite (2.636181ms)\nℹ tests 1\nℹ suites 1\nℹ pass 1\nℹ fail 0\nℹ cancelled 0\nℹ skipped 0\nℹ todo 0\nℹ duration_ms 77.285385\nℹ start of coverage report\nℹ -----------------------------------------------------------------\nℹ file             | line % | branch % | funcs % | uncovered lines\nℹ -----------------------------------------------------------------\nℹ test             |        |          |         | \nℹ  dummy.test.js   | 100.00 |   100.00 |  100.00 | \nℹ -----------------------------------------------------------------\nℹ all files        | 100.00 |   100.00 |  100.00 | \nℹ -----------------------------------------------------------------\nℹ end of coverage report\n```\n\n### What do you see instead?\n\nWith `isolation: \"none\"`, here's the output:\n\n```\n▶ suite\n  ✔ works (0.979666ms)\n✔ suite (2.172736ms)\nℹ tests 1\nℹ suites 1\nℹ pass 1\nℹ fail 0\nℹ cancelled 0\nℹ skipped 0\nℹ todo 0\nℹ duration_ms 28.684242\nℹ start of coverage report\nℹ ----------------------------------------------------------\nℹ file      | line % | branch % | funcs % | uncovered lines\nℹ ----------------------------------------------------------\nℹ ----------------------------------------------------------\nℹ all files | 100.00 |   100.00 |  100.00 | \nℹ ----------------------------------------------------------\nℹ end of coverage report\n```\n\n(empty coverage)\n\nThe test stream emits a \"test:coverage\" event, but it is empty:\n\n```js\n[Object: null prototype] {\n  nesting: 0,\n  summary: [Object: null prototype] {\n    workingDirectory: '/home/damien/git/socket.io/tmp',\n    files: [],\n    totals: [Object: null prototype] {\n      totalLineCount: 0,\n      totalBranchCount: 0,\n      totalFunctionCount: 0,\n      coveredLineCount: 0,\n      coveredBranchCount: 0,\n      coveredFunctionCount: 0,\n      coveredLinePercent: 100,\n      coveredBranchPercent: 100,\n      coveredFunctionPercent: 100\n    },\n    thresholds: [Object: null prototype] { line: 0, branch: 0, function: 0 }\n  }\n}\n```\n\n### Additional information\n\n_No response_","author":{"url":"https://github.com/darrachequesne","@type":"Person","name":"darrachequesne"},"datePublished":"2025-09-26T08:56:04.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/60023/node/issues/60023"}