迁移至Babel 7 Beta后测试报错：需Babel ^7.0.0-0却加载6.26.0

Hey there, let's break down why you're hitting this "Requires Babel ^7.0.0-0, but was loaded with 6.26.0" error in your tests. The core issue is Jest is still trying to load the Babel 6.x version of babel-core, even though your project's fully migrated to Babel 7 Beta. Here's how to fix it step by step:

1. Install Jest Packages Compatible with Babel 7 #

Jest needs an updated babel-jest to work with Babel 7's renamed package structure (where babel-core became @babel/core). You already have the official bridge package babel-core@7.0.0-0 installed, but you might be missing the matching babel-jest version.

Run this to install the right packages:

npm install --save-dev babel-jest@^24.0.0 @babel/preset-env@^7.0.0-beta.49

Stick to versions that match your existing Babel Beta release to avoid mismatches.

2. Update Jest Config to Point to Babel 7 #

Tell Jest explicitly to use babel-jest and recognize your Babel 7 setup by adding a transform block to your jest.config.js:

module.exports = {
  rootDir: '<rootDir>/../../',
  collectCoverageFrom: ['src/**/*.(jsx|js)'],
  moduleNameMapper: {
    '\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$': '<rootDir>/tests/fileMock.js',
  },
  setupTestFrameworkScriptFile: '<rootDir>/tests/setupTests.js',
  // Add these lines
  transform: {
    '^.+\\.(js|jsx)$': 'babel-jest',
  },
  transformIgnorePatterns: [
    '/node_modules/'
  ],
};

3. Clear Caches & Reinstall Dependencies #

Old cached packages are often the culprit here. Let's wipe them out:

• Delete your node_modules folder: rm -rf node_modules (use rmdir /s /q node_modules on Windows)
• Remove your lock file: rm package-lock.json (or yarn.lock if you use Yarn)
• Reinstall dependencies: npm install
• Clear Jest's cache: jest --clearCache

4. Verify babel-plugin-module-resolver Compatibility #

Your config uses babel-plugin-module-resolver@3.1.1 which supports Babel 7, but updating to the latest version can rule out any edge cases:

npm update babel-plugin-module-resolver --save-dev

5. Test with No Cache (Temporary) #

Add the --no-cache flag to your test command to bypass any leftover cached data while troubleshooting:

"test": "jest --no-cache --config tests/jest.config.js",

After going through these steps, run your tests again—this should resolve the version mismatch and get your test suites passing.

内容的提问来源于stack exchange，提问作者Tomasz Mularczyk