test-file-split

Identify natural describe-block boundaries, group them by functional area, then move each group into a new file named with a suffix like module-area.test.ts. Extract shared fixtures into a tests/helpers utility, then verify both files pass isolated and co-run execution.

The check-test-file-cap.ts script fails PRs containing new or growing test files over 500 lines. Split the file using describe-block extraction, or set TEST_CAP_ENFORCE=0 to soft-warn temporarily while you reorganize.

Bun shares a single process across test files, so mock.module calls leak between files and cause co-run failures. Check for unmocked module leaks and use the _internals dependency-injection seam pattern to isolate mocks per file.

If a previously split file exceeds 500 lines again, the suite is structurally too large for one module. Reorganize tests by source module boundaries rather than splitting a third time, which produces fragmented, hard-to-navigate suites.

Use module-area.test.ts for functional-area splits, such as release-notes-fragments-sha.test.ts, or module-area.adversarial.test.ts when separating adversarial test cases into their own file.