Jest 'SyntaxError: Cannot use import statement outside a module' when a package in node_modules ships only ES modules. How do I fix it?

Cause: Jest, by default, does not run code transforms on anything under node_modules (the default transformIgnorePatterns skips it). If a dependency is published as untranspiled ESM, Jest loads it as CommonJS and the first import statement is a syntax error. The same message appears for your own ESM files when Jest is not configured for ESM. Fix (best first): 1. Let Jest transform the offending package. Keep babel-jest (or your own transformer) and narrow the ignore pattern with a negative lookahead, replacing the package names with yours: transformIgnorePatterns: ['<rootDir>/node_modules/(?!(some-esm-pkg|@scope/other-pkg)/)'] Make sure a Babel config exists that converts ESM to CommonJS (for example @babel/preset-env targeting the current node). If you list other entries under "transform", list babel-jest explicitly or it stops applying. 2. With pnpm, packages are symlinks into node_modules/.pnpm, so the simple pattern does not match. Point the pattern at the .pnpm folder and separate name and version with @ instead of /, for example '<rootDir>/node_modules/.pnpm/(?!(some-esm-pkg)@)'. 3. Note that a file is ignored if it matches any pattern in the array, so a second pattern like '/some-esm-pkg/' would undo the exception. 4. Alternative: run Jest's experimental native ESM mode. Disable transforms ("transform": {}), run node with --experimental-vm-modules (for example NODE_OPTIONS="$NODE_OPTIONS --experimental-vm-modules" npx jest), and mark files as ESM through "type": "module" in the nearest package.json, .mjs files, or extensionsToTreatAsEsm. In ESM mode jest.mock is not hoisted; use jest.unstable_mockModule and a dynamic import(). Jest documents this support as experimental, so prefer option 1 for stable suites. 5. If the package has a CommonJS entry, you can also point Jest at it with moduleNameMapper, anchoring the regex with ^ and $. Verify: rerun the failing test file; the syntax error should be gone. If another package then fails the same way, add it to the lookahead list. Sources: https://jestjs.io/docs/ecmascript-modules https://jestjs.io/docs/configuration