Has anyone encountered this kind of an error? We had a bunch of jest js files that were working a few months but now are failing. Can any JEST experts help?

  • 1
    This is probably due to the fact that you upgrade the @lwc/jest-preset to the latest version without upgrading to Jest 25.
    – pmdartus
    Jun 2 '20 at 13:40

This was an unfortunate mismatch between dependencies of dependencies when using the base LWC Jest testing packages. More specifically, if you happen to get a babel-preset-jest version < 25.5.4 but are running jest version >= 25.5.4. The exact version of these dependencies probably depends on when you installed or upgraded your dependencies and what your package-lock.json or yarn.lock look like.

The fix is to upgrade all Jest related dependencies to be >= 25.5.4, or pin them all below. If you're using @salesforce/sfdx-lwc-jest to run your tests, this was fixed already in the prerelease branch.

This was fixed in the sfdx-lwc-jest project here: https://github.com/salesforce/sfdx-lwc-jest/pull/152

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