Single-SPA Testing

Testing Overview

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

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

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.

Testing Example

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

• 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.

Single-SPA Cheatsheet

Core single-spa APIs related to testing.

How Testing Works in Single-SPA

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 Testing

For reliable micro frontends, 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 testing.
• Leaving testing untested, so regressions slip into production.
• Over-engineering testing before you actually need the extra flexibility.
• Ignoring documentation, which makes testing hard for the next developer to change.

Key Takeaways

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