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Testing New Added 8 September 2026

Jest: SyntaxError: Cannot use import statement outside a module

Jest ran a file containing ES module syntax through a CommonJS pipeline. Either the transform does not cover that file, or it lives in node_modules, which Jest deliberately does not transform, and modern packages increasingly ship ESM only.

Quick fix

Read the commands before running them. Anything that restarts a service, deletes data or changes permissions should be tried on a non-production system first.

Quick fix
// Transform the ESM dependency that is failing
// jest.config.js
module.exports = {
  transform: { '^.+\\.[tj]sx?$': ['@swc/jest'] },
  transformIgnorePatterns: ['node_modules/(?!(nanoid|query-string)/)'],
};

# Or run Jest with real ESM support
node --experimental-vm-modules node_modules/.bin/jest
// package.json: "type": "module", and jest.config.mjs

# TypeScript users: ts-jest needs the same allowance
# Vitest handles ESM natively and is the lower friction option

How to diagnose Testing errors

Test errors divide into infrastructure problems (the framework cannot find or load your tests, fixtures or modules) and flakiness, which is the more expensive category. End-to-end timeouts are almost always a race between the test and the application, and the durable fix is to wait for a condition (an element, a network response, a state change) rather than for a duration.

If the quick fix above does not resolve it, work through these steps. They apply to this whole class of error, not just to this one message, which is usually what saves the time.

  1. Run a single failing test in isolation. If it passes alone but fails in the suite, you have shared state or test ordering dependence.
  2. For Cypress and Playwright timeouts, use the trace viewer or video to see what the page actually showed. The element usually exists but is covered, detached, or not yet interactive.
  3. Replace fixed waits with condition-based waits. waitForSelector and auto-retrying assertions eliminate an entire class of flakiness.
  4. For collection and module-resolution errors, check the framework's rootDir/testPaths configuration and the presence of __init__.py or conftest.py where the framework expects it.
  5. Review snapshot diffs rather than updating them reflexively. A changed snapshot is sometimes a real regression.

Tools worth reaching for

  • playwright show-trace
  • pytest -x -vv --tb=long
  • jest --runInBand
  • cypress open
  • test retry analytics

Authoritative references

Primary documentation for this error, worth reading before applying any fix in production.

jestjs.io

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