[Bug]: "Outdated snapshot: No snapshot header found." error on Windows with Jest v30.1.0

[martincostello]

Version

30.1.0

Steps to reproduce

1. Clone martincostello/benchmarkdotnet-results-publisher@493a56c on Windows
2. Run npm install
3. Run npm test

Expected behavior

Tests pass.

Actual behavior

Tests fail:

 FAIL  tests/main.test.ts
  ● Test suite failed to run

    Outdated snapshot: No snapshot header found. Jest 19 introduced versioned snapshots to ensure all developers on a project are using the same version of Jest. Please update all snapshots during this upgrade of Jest.
    
    Warning: Before you upgrade snapshots, we recommend that you revert any local changes to tests or other code, to ensure that you do not store invalid state.

      at validateSnapshotHeader (node_modules/@jest/snapshot-utils/build/index.js:91:12)
      at getSnapshotData (node_modules/@jest/snapshot-utils/build/index.js:156:28)

Additional context

Likely caused by #15787.

Environment

Current runner version: '2.328.0'
Runner Image Provisioner
  Hosted Compute Agent
  Version: 20250812.370
  Commit: 4a2b2bf7520004e3e907c2150c8cabe342a3da32
  Build Date: 2025-08-12T16:08:14Z
Operating System
  Microsoft Windows Server 2022
  10.0.20348
  Datacenter
Runner Image
  Image: windows-2022
  Version: 20250817.1.0
  Included Software: https://github.com/actions/runner-images/blob/win22/20250817.1/images/windows/Windows2022-Readme.md
  Image Release: https://github.com/actions/runner-images/releases/tag/win22%2F20250817.1

[fredrikcarlbom]

It's very strange, those snapshot tests works on my windows machine. In our project, our snapshot tests works on our windows developer machines but not in our dockerized CI environment, also using jest 30.1.0.

[fredrikcarlbom]

I expect it to be related to line endings and the auto.crlf setting combined with this regex:
const SNAPSHOT_HEADER_REGEXP = /^// Jest Snapshot v(.+), (.+)\n/;. Matching \n instead of $ is likely the problem...

[Mlocik97]

Hit exact same issue on Linux in CI. Now all PR pipelines are failing in our company.

[martincostello]

Looking to do a PR to fix it now.

[martincostello]

#15800

[cpojer]

Shipped 30.1.1 with the fix.

[hainenber]

Hi, im the PR's author there. Apologies for causing mayhem in the CI realm! 🙇

Lesson learnt: Always test with Windows 🪟

[hainenber]

@Mlocik97 other folks are affected in their Windows-based CI except you. Might I know if 30.1.1 managed to fix your issue? If not, I can open another one for resolution

[Mlocik97]

@hainenber yes, we can still reproduce with 30.1.1 in Github pipeline with configuration:

runs-on: ubuntu-latest
steps:
    - uses: actions/setup-node@v4
      with:
        node-version: 22
        cache: npm

[cpojer]

@hainenber could you investigate and send a PR with a fix?