When tests run under process isolation, output from the built-in global console reaches the parent through the child process's stdout and stderr streams. By the time the parent emits test:stdout or test:stderr, it no longer knows which test produced the write. Custom reporters therefore cannot associate the output with a test, and it can arrive before the matching test:dequeue. Depending on how the pipe is drained, writes from different tests can also be combined into a single raw event.

The test runner installs an internal write hook on the built-in global console in child processes that use the V8 serializer. While a non-root test or suite is active, the formatted message is emitted through its TestsStream with testId, parentId, name, nesting, and source location metadata. These events bypass the per-file declaration-order buffer, so they stay in execution order after the matching test:dequeue.

This follows the approach suggested by cjihrig in #53103 (comment).

context.log() and context.diagnostic() remain the explicit reporting APIs. The hook also covers global console calls made by code under test or third-party modules, without requiring those callers to use the test context APIs. The existing test:stdout and test:stderr event types are preserved.

Scope

• Only test runner child processes that use the V8 serializer install the hook. Ordinary Node.js processes do not.
• Output that the hook does not attribute keeps its existing file-scoped path: direct process.stdout and process.stderr writes, native output, separately constructed Console instances, top-level and root-hook output, output written while suites are being defined, and asynchronous output after a test has finished.
• Suite-owned hooks follow the existing hook-context ownership, so output from a suite's beforeEach() is attributed to that suite.
• If the source location of an attributed test or suite is unavailable, file falls back to the child's entry file and remains a string.

Tests

• test/parallel/test-runner-console-output-attribution.mjs
• all test/parallel/test-runner-* tests
• make test-only
• make lint
• make test-doc

Fixes: #53103