🧪 Testing React Apps

Jest test runner, React Testing Library (RTL), screen queries, and fireEvent / userEvent.

React Testing Philosophy

React Testing Library focuses on testing components from the perspective of real users rather than implementation details.

Writing Component Unit Tests

Using Jest matchers and RTL `render` & `screen` utilities.

Button.test.jsx JSX

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

test('increments counter on button click', () => {
  render(<CounterApp />);
  const button = screen.getByText('+1');
  fireEvent.click(button);
  expect(screen.getByText('Count: 1')).toBeInTheDocument();
});

Redux Toolkit