If you’ve seen the error “ReferenceError jest is not defined” while using Jest.
Indeed, it can be really frustrating, especially when you’re trying to run tests or use Jest’s powerful testing features.
In this article, we’ll explain, what the ReferenceError means, common reasons why you might see the “ReferenceError jest is not defined” message, and we’ll give you solutions to help you fix the problem.
What is referenceerror jest is not defined?
The error “ReferenceError: Jest is not defined,” means that the Jest library or module is not accessible or loaded properly in your code.
This could happen few possible reasons:
- Jest is not installed.
- Incorrect import statement
- Configuration issue
- Build or bundling issue
By addressing these potential causes, it could help in resolving the “ReferenceError: Jest is not defined” error and successfully run your Jest tests.
How to fix referenceerror jest is not defined
Since we already know the factors why we get this referenceerror jest is not defined error, now the following are the solutions you can try.
- Verify Jest installation
Double-check that you have Jest installed as a development dependency in your project.
To ensure that the Jest is installed correctly, run the commands:
npm install jest –save-dev
yarn add jest –dev
- Check import statement
Confirm that the import statement for Jest is correct in the test file where the error occurs. Make sure it matches the correct syntax.
For example, you can use this import statement:
import jest from ‘jest’;
const jest = require(‘jest’);
- Verify build/bundling configuration
If you’re using a build or bundling tool like Webpack or Babel, ensure that your Jest configuration is correctly integrated.
Make sure that the Jest package is included in the build process and properly resolved in your bundling configuration.
- Clear cache and node_modules
Sometimes, issues can arise due to a corrupted cache or conflicting dependencies.
Try clearing your package manager’s cache (npm cache clean or yarn cache clean) and then delete the node_modules directory.
Afterward, reinstall your project dependencies with npm install or yarn install.
- Upgrade Jest
If you have an older version of Jest, it’s possible that the error is due to a bug that has been fixed in a newer version.
Upgrade Jest to the latest version by running npm update jest or yarn upgrade jest.
- Check test script
If you’re running Jest through a script in your package.json file, ensure that the script is correctly configured.
Check that the command to run Jest is accurate and without any typos.
Anyway, here are other fixed errors you can refer to when you might encounter them.
It can be caused by various factors such as Jest not being installed, incorrect import statements, misconfigured Jest configuration files, build or bundling issues, or other related issues.
We hope this guide has assisted you in resolving the error effectively.
Until next time! 😊