Jest react is not defined

The error “jest react is not defined” occurs when the Jest testing framework is unable to find the React library. This can happen due to multiple reasons, and I’ll explain a few common causes along with examples.

Possible Causes:

1. Missing npm packages: Ensure that you have installed the required packages for Jest and React in your project. If you haven’t already, install them using the following commands:

    $ npm install --save-dev jest
    $ npm install react react-dom
  

2. Incorrect configuration: Verify that your Jest configuration is set up correctly in your project’s package.json file. Ensure that you have specified the correct entry point for your tests and the relevant setup files. Here’s an example:

    "jest": {
      "testEnvironment": "jsdom",
      "roots": [
        "/src"
      ],
      "setupFilesAfterEnv": [
        "/src/setupTests.js"
      ]
    }
  

3. Missing Babel configuration: If you are using JSX syntax in your tests, make sure you have configured Babel properly to transform JSX code. Install the required Babel packages and create a .babelrc file with the following content:

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

Example:

Let’s say you have a basic component named “Button” in a file called Button.js, and you want to write a Jest test for it:

    // Button.js
    import React from 'react';

    const Button = ({ text }) => {
      return {text};
    };

    export default Button;
  

Your test file, Button.test.js, should import the required packages and the component you want to test:

    // Button.test.js
    import React from 'react';
    import { render, screen } from '@testing-library/react';
    import Button from './Button';

    describe('Button', () => {
      test('renders button with given text', () => {
        render();
        const buttonElement = screen.getByText(/Click me/);
        expect(buttonElement).toBeInTheDocument();
      });
    });
  

Make sure that you have the necessary packages installed and the Jest configuration set up correctly to run the tests. You can then run the tests using a command like this:

    $ jest Button.test.js
  

If everything is set up properly, Jest should be able to find the React library, and the test should run without the “jest react is not defined” error.

I hope this helps! Let me know if you have any further questions.