Integration Testing

Integration Testing Overview

Integration Testing lets you structure single-spa work so it stays readable, testable, and easy to scale. Instead of ad-hoc code, you follow a clear pattern that other developers can recognise immediately.

The key is to keep integration testing focused and predictable. Start from the minimal example here, then layer in only the complexity your feature actually needs.

import * as app from './org-checkout.js';

test('exports single-spa lifecycles', () => {
  expect(typeof app.bootstrap).toBe('function');
  expect(typeof app.mount).toBe('function');
  expect(typeof app.unmount).toBe('function');
});

Verify each micro frontend exports valid single-spa lifecycle functions.

Integration Testing Example

registerApplication({
  name: '@org/app',
  app: () => System.import('@org/app'),
  activeWhen: ['/app'],
});
start();

• 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.

Single-SPA Cheatsheet

Core single-spa APIs related to integration testing.

How Integration Testing Works in Single-SPA

Integration Testing is part of how single-spa lets multiple applications — even in different frameworks — coexist on one page. A root config registers each app and controls when it is active.

Verify each micro frontend exports valid single-spa lifecycle functions.

• A root config registers apps and calls start().
• Each app exports bootstrap, mount, and unmount lifecycles.
• activeWhen decides which routes each app owns.
• Import maps resolve each app's bundle at runtime.

Practical Guidance for Integration Testing

For reliable micro frontends, integration testing should isolate failures and keep shared state minimal. Let each team own its app end to end while agreeing on a few shared contracts.

Common Mistakes

• 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.
• Ignoring documentation, which makes integration testing hard for the next developer to change.

Key Takeaways

• Integration Testing is a core part of working effectively with single-spa.
• 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.