How to Resolve “Cannot use import statement outside a module” from Jest when Running Tests?

If you’re working with JavaScript and using Jest for testing, you might have encountered the error message “Cannot use import statement outside a module” when running your tests. This error occurs when you try to use the import statement in a file that is not recognized as a module by Jest.

Fortunately, there are a few solutions to resolve this issue:

Solution 1: Configure Jest to Handle ES Modules

Jest, by default, does not handle ES modules. To enable support for ES modules, you can add the following configuration to your jest.config.js file:

  module.exports = {
    // Other Jest configurations...
    transform: {
      "^.+\.jsx?$": "babel-jest",
    },
    transformIgnorePatterns: [
      "/node_modules/(?!(module-to-ignore)/)",
    ],
    moduleNameMapper: {
      "\.(css|less|scss|sass)$": "identity-obj-proxy",
    },
    globals: {
      "ts-jest": {
        babelConfig: true,
      },
    },
  };
  

This configuration tells Jest to use Babel for transforming JavaScript files and handle ES modules. Make sure you have Babel and the necessary presets and plugins installed in your project.

Solution 2: Use CommonJS Syntax Instead of ES Modules

If you prefer not to configure Jest for ES modules, you can convert your import statements to use CommonJS syntax instead. CommonJS is the default module system in Node.js and is supported by Jest out of the box.

Here’s an example of how you can convert an ES module import statement to CommonJS:

  // ES module import
  import { myFunction } from './myModule';
  
  // CommonJS import
  const { myFunction } = require('./myModule');
  

By using CommonJS syntax, Jest will be able to recognize and handle the import statements correctly.

Solution 3: Use a Transpiler like Babel

If you want to continue using ES modules in your code and have Jest handle them, you can use a transpiler like Babel. Babel can transform your ES modules into CommonJS modules that Jest can understand.

First, install the necessary Babel packages:

  npm install --save-dev @babel/core @babel/preset-env babel-jest
  

Then, create a .babelrc file in your project’s root directory with the following configuration:

  {
    "presets": ["@babel/preset-env"]
  }
  

Now, Jest will be able to handle your ES modules by transpiling them into CommonJS modules using Babel.

These are the three main solutions to resolve the “Cannot use import statement outside a module” error from Jest when running tests. Choose the solution that best fits your project’s requirements and configuration.

Happy testing!