Integration Testing

Integration Testing Overview

At its core, integration testing is about doing one thing well inside your Module Federation project. Once you understand the pattern, you can apply it consistently across features and teams.

Good integration testing pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

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

test('remote component renders products', () => {
  render(<ProductList products={[{ id: 1, name: 'Book' }]} />);
  expect(screen.getByText('Book')).toBeInTheDocument();
});

Test exposed components in isolation the same way you test any local component.

Integration Testing Example

new ModuleFederationPlugin({
  name: 'app',
  filename: 'remoteEntry.js',
  exposes: { './Widget': './src/Widget' },
  remotes: { other: 'other@http://host/remoteEntry.js' },
  shared: { react: { singleton: true } },
});

• Start from a minimal Integration Testing example and grow it only as needed.
• Keep configuration explicit so Integration Testing behaves the same in every environment.
• Name things clearly so teammates understand your Integration Testing at a glance.
• Add tests around Integration Testing early to lock in expected behaviour.

Module Federation Cheatsheet

Key Module Federation settings related to integration testing.

How Integration Testing Works in Module Federation

Integration Testing builds on Module Federation's ability to load code from another independently built and deployed application at runtime. Each app can be a host, a remote, or both.

Test exposed components in isolation the same way you test any local component.

• Remotes expose modules through a remoteEntry.js manifest.
• Hosts declare remotes and import exposed modules dynamically.
• Shared dependencies are deduplicated, ideally as singletons.
• Each micro frontend builds and deploys on its own schedule.

Practical Guidance for Integration Testing

In production, integration testing needs careful version management and graceful failure handling. Align shared dependency versions and always render a fallback when a remote cannot load.

Common Mistakes

• Copying integration testing snippets without understanding what each line does.
• Skipping error handling and edge cases when wiring up integration testing.
• Leaving integration testing untested, so regressions slip into production.
• Over-engineering integration testing before you actually need the extra flexibility.

Key Takeaways

• Integration Testing is a core part of working effectively with Module Federation.
• Start small and keep integration testing focused on a single responsibility.
• Apply consistent patterns so integration testing scales across your project.
• Test and document integration testing to keep it maintainable over time.