vitest-dev/vitest

14 rules learned from 1,307 merged PRs: the files and habits in vitest-dev/vitest that kept needing a fix after merge.

Merged PRs read
1,307
Needed a fix
69 (5.3%)
Reverted
1
Merged between
2025-11-07 and 2026-11-10

Tested on PRs the rules had never seen

14 of the 73 code PRs that breached a rule needed a fix (19%), against 0 of the 29 that breached none (0%).

Rules were learned from older PRs, then tested on later PRs they hadn't seen. How we tested

PRTitle and the rule it breachedWhat happened
feat(browser): add failure-only trace view modeHotspot: packages/vitest/src/node/config/resolveConfig.ts (9 of 17 earlier PRs needed a fix) fixed in #11771, 3 days later
feat(browser): show trace steps timeline on terminal on test failureFragile area: packages/vitest/ (34 of 109 earlier PRs needed a fix) fixed in #11695, 3 days later
feat: introduce `--since-last-run` flagHotspot: packages/vitest/src/node/config/resolveConfig.ts (9 of 17 earlier PRs needed a fix) fixed in #11707, 7 days later

Fix-prone files and folders

PRs that touched these paths needed a follow-up fix more often than the 13% repo average. Counts are PRs that touched the path.

  1. Hotspot: packages/vitest/src/node/pools/browser.ts

    5 of 8 earlier PRs that changed this needed a fix.

    3 clean, 5 fixed (63%)
  2. Hotspot: packages/vitest/src/node/project.ts

    9 of 16 earlier PRs that changed this needed a fix.

    7 clean, 9 fixed (56%)
  3. Hotspot: packages/browser/src/client/orchestrator.ts

    6 of 11 earlier PRs that changed this needed a fix.

    5 clean, 6 fixed (55%)
  4. Hotspot: packages/vitest/src/node/core.ts

    12 of 24 earlier PRs that changed this needed a fix.

    12 clean, 12 fixed (50%)
  5. Hotspot: packages/vitest/src/node/config/resolveConfig.ts

    13 of 28 earlier PRs that changed this needed a fix.

    15 clean, 13 fixed (46%)
  6. Hotspot: packages/vitest/src/integrations/snapshot/chai.ts

    4 of 10 earlier PRs that changed this needed a fix.

    6 clean, 4 fixed (40%)
  7. Hotspot: packages/vitest/src/node/reporters/base.ts

    4 of 10 earlier PRs that changed this needed a fix.

    6 clean, 4 fixed (40%)
  8. Fragile area: packages/expect/

    8 of 21 earlier PRs that changed this needed a fix.

    13 clean, 8 fixed (38%)
  9. Hotspot: packages/vitest/src/node/cache/fsModuleCache.ts

    6 of 16 earlier PRs that changed this needed a fix.

    10 clean, 6 fixed (38%)
  10. Hotspot: packages/browser-playwright/src/playwright.ts

    3 of 9 earlier PRs that changed this needed a fix.

    6 clean, 3 fixed (33%)
  11. Fragile area: packages/mocker/

    6 of 20 earlier PRs that changed this needed a fix.

    14 clean, 6 fixed (30%)
  12. Fragile area: packages/utils/

    6 of 21 earlier PRs that changed this needed a fix.

    15 clean, 6 fixed (29%)
  13. Fragile area: packages/vitest/

    51 of 190 earlier PRs that changed this needed a fix.

    139 clean, 51 fixed (27%)
  14. Fragile area: packages/snapshot/

    4 of 15 earlier PRs that changed this needed a fix.

    11 clean, 4 fixed (27%)

Conventions

Habits most PRs here follow, where PRs that broke them needed a fix more often. Counts on each bar are the PRs that broke it.

No habit here made the list.

Recent PRs that needed a fix

Rules flagged 172 recent PRs, and 39 of those needed a fix (23%), against 12% of all recent PRs. These are the 15 with the strongest rule that needed a fix, with the PR that fixed each.

PRTitleSizeRule it breachedWhat happened
refactor!: separate config resolution from the server creation +3,485 -3,143 touches packages/vitest/src/node/project.ts7 clean, 9 fixed fixed in #10731, same day
fix: track project files and mocks with --changed +2,804 -229 touches packages/vitest/src/node/project.ts7 clean, 9 fixed fixed in #11593, 13 days later
feat(experimental): add an option to cache dependencies instead of statically parsing them +1,756 -32 touches packages/vitest/src/node/project.ts7 clean, 9 fixed fixed in #11596, 7 days later
feat!: share the Vite server between inline projects +1,270 -355 touches packages/vitest/src/node/project.ts7 clean, 9 fixed fixed in #10913, 1 day later
fix(browser): run browser instances as workers +1,194 -239 touches packages/vitest/src/node/project.ts7 clean, 9 fixed fixed in #11582, 6 days later
feat: support merge reports for non-sharded multi-environment runs (take 2) +902 -203 touches packages/vitest/src/node/project.ts7 clean, 9 fixed fixed in #10348, 14 days later
fix!: represent locator as an object instead of a string +638 -214 touches packages/browser/src/client/orchestrator.ts5 clean, 6 fixed fixed in #10227, 1 day later
feat(browser): add failure-only trace view mode +332 -60 touches packages/browser/src/client/orchestrator.ts5 clean, 6 fixed fixed in #11771, 3 days later
fix(browser): wait for orchestrator readiness before resolving browser sessions +114 -7 touches packages/browser/src/client/orchestrator.ts5 clean, 6 fixed fixed in #10555, 8 days later
feat: introduce `--since-last-run` flag +772 -91 touches packages/vitest/src/node/core.ts12 clean, 12 fixed fixed in #11707, 7 days later
fix: apply --shard before the test run starts +301 -44 touches packages/vitest/src/node/core.ts12 clean, 12 fixed fixed in #11924, 5 days later
feat!: parse files statically in vitest list by default +84 -31 touches packages/vitest/src/node/core.ts12 clean, 12 fixed fixed in #11146, 4 days later
chore(vitest): remove dead code that the "./src/*" export was hiding from knip +81 -178 touches packages/vitest/src/node/config/resolveConfig.ts15 clean, 13 fixed fixed in #10928, 3 days later
feat: support `test.ui.theme` option +193 -14 touches packages/vitest/src/node/config/resolveConfig.ts15 clean, 13 fixed fixed in #11517, 1 day later
feat(experimental/snapshot): support custom snapshot matcher +867 -151 touches packages/vitest/src/integrations/snapshot/chai.ts6 clean, 4 fixed fixed in #10042, 2 days later

Get this for your own repo

Precall reads your repo's history the same way and comments on new PRs that touch the spots that kept breaking.

Start freeGet a report for your repo