How to Reconcile Webpack and Jest in a Node.js Project Using Imports

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The Problem

Webpack, generally operates on CommonJS modules.

Jest enforces ES module syntax when "type": "module" is declared.

As a result, you may encounter frustrating error messages when trying to execute your tests, such as:

SyntaxError: Cannot use import statement outside a module

You’ve tried various workarounds, including modifying the test script and using .mjs file extensions, yet the errors persist. So what should you do?

The Solution

1. Renaming Webpack Configuration File

The key to reconciling this issue lies in a simple yet effective workaround: rename your Webpack configuration file.

Steps to Fix:

This might seem like a trivial change at first, but it has significant implications for your setup:

Important Message

You might encounter the following warning after this change:

[webpack-cli] ReferenceError: require is not defined in ES module scope, you can use import instead

This indicates that your Webpack configuration file is correctly treated as a CommonJS script and resolves the previous import errors you encountered.

2. Review Use of Imports/Exports

Now that your Webpack configuration can properly handle modules, ensure your project is using consistent import/export syntax across all files.

Key Points:

Use ES modules for your application code.

3. Modify Jest Configuration (If Necessary)

Conclusion

This solution not only unblocks your testing process but ensures a smoother workflow moving forward. Remember, the key to mastering these tools lies in understanding how they interact with module systems—once you grasp this, you’ll navigate through future conflicts with ease.