Testing in React

Tests are essential for ensuring the quality and maintainability of your React applications. We'll explore the different types of tests and the tools available.

Basic setup

Create React App already includes Jest and React Testing Library. For existing projects:

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

Unit tests

Testing a simple component

// Button.js
function Button({ onClick, children }) {
  return <button onClick={onClick}>{children}</button>;
}

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

test('rendre le bouton avec le bon texte', () => {
  render(<Button>Cliquez-moi</Button>);
  expect(screen.getByText('Cliquez-moi')).toBeInTheDocument();
});

test('appeler onClick quand le bouton est cliqué', () => {
  const handleClick = jest.fn();
  render(<Button onClick={handleClick}>Cliquez-moi</Button>);
  
  fireEvent.click(screen.getByText('Cliquez-moi'));
  expect(handleClick).toHaveBeenCalledTimes(1);
});