🧪 React Unit Testing with RTL & Enzyme – Compare Testing Approaches (2025 Guide)

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🧲 Introduction – Why Unit Test React Components?

Unit testing React.js components ensures that individual pieces of your UI work correctly in isolation. Whether you’re validating a button click or input behavior, solid unit tests give you confidence and catch regressions early.

Two popular libraries for unit testing React components are:

• React Testing Library (RTL) – modern, user-centric testing
• Enzyme – legacy, implementation-focused testing (no longer actively maintained)

🎯 In this guide, you’ll learn:

• How to write unit tests using RTL and Enzyme
• Key differences and real-world examples
• Best practices for modern React component testing
• Which library to prefer in 2025 (hint: it’s RTL)

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⚙️ 1. Setup – Installing RTL & Enzyme

✅ React Testing Library (recommended)

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

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✅ Enzyme (legacy)

npm install --save-dev enzyme enzyme-adapter-react-16

Then configure the adapter:

import Enzyme from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

Enzyme.configure({ adapter: new Adapter() });

📌 Enzyme does not fully support React 18+
⚠️ Prefer RTL for modern projects

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📦 2. Sample Component – Button

// Button.jsx
export default function Button({ onClick, label }) {
  return <button onClick={onClick}>{label}</button>;
}

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🧪 3. Unit Testing with React Testing Library

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

test('renders button and handles click', () => {
  const handleClick = jest.fn();
  render(<Button label="Click Me" onClick={handleClick} />);

  const button = screen.getByText('Click Me');
  fireEvent.click(button);

  expect(button).toBeInTheDocument();
  expect(handleClick).toHaveBeenCalledTimes(1);
});

✅ Focuses on user behavior
✅ Queries DOM the way a user would (getByText, getByRole)
✅ Works seamlessly with @testing-library/jest-dom

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🔍 4. Unit Testing with Enzyme (Shallow Rendering)

// Button.enzyme.test.js
import { shallow } from 'enzyme';
import Button from './Button';

test('renders and triggers click event', () => {
  const handleClick = jest.fn();
  const wrapper = shallow(<Button label="Click Me" onClick={handleClick} />);

  wrapper.find('button').simulate('click');

  expect(wrapper.text()).toBe('Click Me');
  expect(handleClick).toHaveBeenCalledTimes(1);
});

✅ More implementation-focused
✅ Relies on component structure (e.g., find('button'))
⚠️ Tests may break during refactoring even if behavior is unchanged

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⚖️ 5. RTL vs Enzyme – Feature Comparison

Feature	React Testing Library	Enzyme (legacy)
Focus	User behavior (black-box)	Internal implementation (white-box)
React 18+ support	✅ Fully supported	⚠️ Limited or broken
Active maintenance	✅ Yes	❌ No
Testing philosophy	“Test what users see”	“Test component structure”
Encourages accessibility	✅ getByRole, getByLabelText	❌ Manual queries only
Simulate events	✅ fireEvent()	✅ simulate()
Learning curve	⭐⭐ Easy	⭐⭐ Easy

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💡 6. Best Practices for Unit Testing

✅ Prefer RTL for new projects
✅ Test user interactions rather than implementation details
✅ Use screen.getByRole() or getByText() over getByTestId()
✅ Use jest.fn() to mock handlers
✅ Avoid Enzyme for React 18+ unless stuck in legacy code

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📌 Summary – Recap & Next Steps

Both RTL and Enzyme can be used for unit testing React components, but React Testing Library is the modern standard. It aligns with how users interact with your app and avoids fragile, structure-based tests.

🔍 Key Takeaways:

• RTL promotes accessible, user-focused testing
• Enzyme encourages structure-dependent tests (deprecated)
• Use fireEvent (RTL) or simulate (Enzyme) to test interactions
• Prefer RTL + Jest for React 18+ and future-proof testing

⚙️ Real-World Relevance:
React Testing Library powers the testing setups of apps like Vercel, Shopify, and Netlify, and is supported by the React core team.

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❓ FAQ Section

❓ Should I migrate from Enzyme to RTL?
✅ Yes. RTL is actively maintained, React-18-ready, and aligned with best practices.

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❓ What’s the difference between shallow and render in Enzyme?
✅ shallow() renders only one level deep. render() does full static rendering. mount() renders the full component tree.

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❓ Can I test class components with RTL?
✅ Yes. RTL works with both function and class components.

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❓ How do I test component props with RTL?
✅ Pass props when rendering and test output, not props directly:

render(<MyComponent title="Test" />);
expect(screen.getByText('Test')).toBeInTheDocument();

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❓ What if my team still uses Enzyme?
✅ Use it only for legacy support. Begin migrating to RTL for future components.

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