How To Test a React App with Jest and React Testing Library

Testing a React app with Jest and React Testing Library involves setting up a testing environment and writing test cases to ensure your components work as expected. Here's a step-by-step guide:

  1. Install Jest and React Testing Library:

                        npm install --save-dev jest @testing-library/react @testing-library/jest-dom

  2. Configure Jest:

    Create a jest.config.js file at the root of your project or add configurations in package.json:

                            "jest": {
                              "preset": "react-scripts"

Writing Tests:
  1. Create a Test File:

    For a component named ExampleComponent, create a ExampleComponent.test.js file.

  2. Import Required Dependencies:

                        import React from 'react';
                        import { render, screen } from '@testing-library/react';
                        import ExampleComponent from './ExampleComponent'; // Import the component to be tested                    

  3. > Write Test Cases:
    • Render Test:

      Test if the component renders properly:

                                  test('renders ExampleComponent', () => {
                                      render(<ExampleComponent />);
                                      const componentElement = screen.getByTestId('example-component'); // Use appropriate selector

    • Interaction Test:

      Test user interaction:

                                  test('clicking button changes text', () => {
                                      render(<ExampleComponent />);
                                      const buttonElement = screen.getByRole('button');
                                      const textElement = screen.getByTestId('text-element');
                                      expect(textElement).toHaveTextContent('Initial Text');
                                      expect(textElement).toHaveTextContent('Updated Text');

  4. Run Tests:

    Execute tests using the Jest CLI or through your package.json script:

                        npm test

  • Queries: Use screen from @testing-library/react to query elements by text, role, label, or any other accessible way.
  • Assertions: Leverage expect from Jest to make assertions about the DOM elements.
  • Async Testing: For async code, use async/await or return Promises within your tests.
  • Mocking Dependencies: Use jest.mock() to mock external dependencies like API calls or modules.
  • Mock Functions: Use jest.fn() to create mock functions and spy on function calls.
  • Cleanup After Tests: If your tests render components that might affect other tests, use cleanup() from @testing-library/react to clean up after each test.

This setup and structure provide a solid foundation for testing React components. React Testing Library focuses on testing components as users would interact with them, promoting good testing practices and maintainable tests.

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