Module Federation, How do we create unit tests for distributed code?!

The curious case of Module Federation and how do we write tests for federated applications.

If you haven't heard by now — Module Federation is a way to simply import() other modules/files between independently compiled and deployed bundles at runtime.

Possibilities are endless, especially after working with it for over a year. Before there was even an npm release, it was in production, installing directly from a branch on GitHub. It’s immensely more powerful then most think

With this new at-runtime orchestration and code sharing, a big question loomed.

How on earth will I test this?

Over a year later, I think I've found a potential solution…

Federated Unit Tests

If i can federate my features, why not federate them into unit tests as well?

Let us take an example:

I have a file with a form on it. It imports a federated button.

import React,{Suspense} from "react";
import lazy from 'react-lazy-ssr';
const Button = lazy(
  ()=>import('federated/Button'),{chunkId:"federated/Button"}
)
// this will…