Cannot run Jest (27.4.6) tests: defaultResolver is not defined by export

The error message "defaultResolver is not defined by export" in Jest usually occurs when there is a version mismatch between the Jest version and the Babel version you are using in your project. This can happen when you upgrade Jest without updating Babel and its plugins.

To resolve this issue, you can try the following steps:

1. Update Dependencies: Ensure that you have the latest versions of Jest, Babel, and other related packages installed. Check your package.json file and update the Jest and Babel packages to the latest versions:

   jsonCopy code
   {
     "devDependencies": {
       "jest": "^27.4.6",
       "babel-jest": "^27.4.6",
       // Other dependencies...
     }
   }
   

   Run npm install or yarn install to update the packages.

2. Clear Jest Cache: Sometimes, Jest caches old versions of modules, which can cause issues. Clear the Jest cache by running the following command:

   bashCopy code
   npx jest --clearCache
   

3. Check Babel Configuration: Verify that your Babel configuration is correctly set up. Ensure that Babel is correctly transpiling your code, especially if you are using any experimental features or custom configurations.

   For example, if you have a .babelrc file or Babel settings in your package.json, check if it includes the necessary presets and plugins. Make sure you are using compatible versions of Babel plugins with your current Babel version.

4. Check Jest Configuration: Review your Jest configuration (usually in your jest.config.js or package.json). Ensure that the resolver option is set correctly.

   For example, in jest.config.js, you should have something like:

   javascriptCopy code
   module.exports = {
     // Other Jest configurations...
     resolver: 'jest-resolve',
   };
   

   If you are using a custom resolver or have modified the resolver configuration, ensure that it is defined and working correctly.

5. Verify Test Files: Check your test files to ensure that they are written correctly and don't contain any syntax errors or other issues that might affect Jest's ability to run them.

6. Downgrade Jest: If the issue persists and you have recently upgraded Jest, you can try temporarily downgrading to a previous version that worked without the error. However, this is not a recommended long-term solution, and it's better to resolve version conflicts properly.

If you still encounter the error after trying these steps, double-check your project's Jest and Babel configuration for any conflicts or errors that might be causing the issue. Additionally, check the Jest documentation and GitHub repository for any reported issues related to your specific Jest and Babel versions.