HowTo: test with Jest or Vitest

[ilteoood]

Hi everyone,
in these days I'm facing the following problem: writing good tests for a host which is importing a federated remote components library.

As you may already know, when you execute a test with jest (or vitest), this results in an error like:
Cannot find module remote/component

To avoid this, I initially found a pretty bad solution: virtual mocking the federated module. This could be done using a syntax like:

jest.mock(remote/component, function componentFactory() {...}, {virtual: true})

The current solution that I'm using is the following: I've created the native-federation-tests plugins, following the same idea of the typescript variant.
In short, the NativeFederationTestsRemote:

1. uses esbuild under the hood to concat in a single file the exposed module;
2. creates a zip containing all the exposed modules.

While the NativeFederationTestsHost just downloads the zip files and extract its content in the __mocks__ folder.

Since jest is able to automatically mock everything it recognises as external module, now the tests are ready to work.

I know that there is also the reunited solution provided by @ScriptedAlchemy, but sometimes do a full build for tests is slow.

What you think about this idea? Could it make sense or should I just drop it?

[ilteoood]

@viktoriialurie since this has been included in the universe repo, IMO this discussion could be closed.

What do you think?

[viktoriialurie]

@ilteoood agree, makes sense