Module Federation Testing

Testing Overview

Testing is a building block you will reach for often in Module Federation. It keeps related logic together and makes your intent obvious to reviewers and future maintainers.

When you learn testing properly, you avoid the guesswork that leads to bugs and rework. The example below shows the shape you will use in most real Module Federation projects.

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.

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

Module Federation Cheatsheet

Key Module Federation settings related to testing.

How Testing Works in Module Federation

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 Testing

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

Key Takeaways

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