Add `--collect-only` flag to list tests without running them by alexander-turner · Pull Request #16006 · jestjs/jest

alexander-turner · 2026-03-25T19:53:22Z

Summary

The --collect-tests flag discovers and reports all test cases without executing any test callbacks — similar to pytest's --collect-only. Complements the existing --list-tests (which lists test files) by looking inside files to list individual test cases.

Running jest --collect-tests loads test files and registers all describe/test/it blocks, then prints a tree of discovered tests and exits with code 0:

src/tests/math.test.ts
  add
    adds positive numbers
    adds negative numbers
  subtract
    subtracts positive numbers

With --json, it outputs the standard formatTestResults JSON format with all tests marked as pending. Works with --testNamePattern and --testPathPatterns for filtering.

Implementation

jest-cli / jest-config / jest-types / jest-schemas: Thread collectTests as a GlobalConfig boolean option
jest-circus: After loading test files, the adapter calls collectTestsWithoutRunning() which walks the describe tree recursively, filters by testNamePattern using the existing getTestID utility, and returns all matching tests as pending assertion results
jest-jasmine2: Equivalent support — walks the jasmine suite tree via env.topSuite(), collects specs with ancestor titles, and filters by testNamePattern
jest-core: runJest schedules tests with reporters suppressed and coverage disabled, prints the tree via VerboseReporter.groupTestsBySuites, and delegates JSON/file output to the existing processResults helper
jest-circus/utils: Exports the previously-private getTestNamesPath for use by the collection function

Testing

E2e tests (e2e/__tests__/collectTests.test.ts) using the existing e2e/each fixture verify: tree output, valid JSON structure, --testNamePattern filtering, empty result handling, and that deliberately failing tests still exit 0 (confirming no execution). Pass under both jest-circus and jest-jasmine2.
Unit tests (collectTestsWithoutRunning.test.ts) verify: flat/nested collection, ancestor titles, source order preservation across describe blocks, testNamePattern filtering, and empty results
Updated logDebugMessages snapshot for the new config key

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linux-foundation-easycla · 2026-03-25T19:53:29Z

The committers listed above are authorized under a signed CLA.

✅ login: alexander-turner / name: Alex Turner (06b748f)

pkg-pr-new · 2026-03-27T15:42:42Z

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commit: 06b748f

- Fix bug: stack-based (LIFO) traversal reversed describe block order; switch back to recursive traversal to preserve source order - Fix CHANGELOG link: point to jestjs#16006 not fork PR - Disable coverage collection in collectOnly mode (wasted work) - Add "preserves source order" regression test - Tighten unit tests: simplify helper, remove over-assertions, extract collect() shorthand, reduce from 111 to 96 lines https://claude.ai/code/session_018SbTXFCAujDRRjBFtMTFXU

SimenB · 2026-03-27T16:54:10Z

Thanks for the PR!

we have --list-tests already (which just lists the test files, doesn't look in them). should this be --collect-tests to keep somewhat the same name?

alexander-turner · 2026-04-01T01:02:07Z

@SimenB Thanks for the feedback; integrated. Thoughts?

https://claude.ai/code/session_01QZMfWaN6e1W1ExV78YLUrw

alexander-turner force-pushed the claude/add-jest-collect-only-2ea6Q branch from fc5fefe to 44b35ce Compare March 27, 2026 16:52

alexander-turner force-pushed the claude/add-jest-collect-only-2ea6Q branch from a0e9f1d to 129e6a1 Compare March 31, 2026 17:22

alexander-turner changed the title ~~Add --collectOnly flag to list tests without running them~~ Add --collect-only flag to list tests without running them Mar 31, 2026

alexander-turner force-pushed the claude/add-jest-collect-only-2ea6Q branch 4 times, most recently from 2d2a5b3 to de23b06 Compare April 1, 2026 01:01

alexander-turner force-pushed the claude/add-jest-collect-only-2ea6Q branch from 2020562 to 5d6726d Compare April 1, 2026 17:16

feat: add --collect-tests flag to discover tests without executing them

06b748f

https://claude.ai/code/session_01QZMfWaN6e1W1ExV78YLUrw

alexander-turner force-pushed the claude/add-jest-collect-only-2ea6Q branch from 5d6726d to 06b748f Compare April 1, 2026 17:22

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Add `--collect-only` flag to list tests without running them#16006

Add `--collect-only` flag to list tests without running them#16006
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