Testing in React 19

Testing ensures your React 19 application is reliable, maintainable, and bug-free. Use a combination of unit, integration, and end-to-end tests.

Unit Testing

• Use Jest, Vitest, or React Testing Library for unit tests.
• Test components, hooks, and context in isolation.

Example: Component Unit Test (React Testing Library)

import { render, screen, fireEvent } from '@testing-library/react';
import Counter from './Counter';
test('increments value on click', () => {
  render(<Counter />);
  fireEvent.click(screen.getByText('Increment'));
  expect(screen.getByText('1')).toBeInTheDocument();
});

Integration Testing

• Test interactions between components and services.
• Mock API calls and external dependencies.

End-to-End (E2E) Testing

• Use Cypress or Playwright for E2E tests.
• Simulate real user flows (navigation, form submission, etc.).

Best Practices

• Write tests for critical logic and user flows.
• Run tests in CI pipelines for every commit/PR.
• Use coverage tools to monitor test completeness.

References

• React Testing Library
• Jest Docs
• Cypress Docs
• Playwright Docs