E2E testing

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As microfrontends gain widespread adoption, testing tools will catch up and the testing story will improve.

End to End (E2E) testing a single-spa application, parcel, or utility is very similar to E2E testing in other architectures. Because you are testing in the browser you can even use tools like import-map-overrides to run your tests in a production or production like environment with an override before deploying to that environment.

In general we suggest only using E2E tests to test integration points between microfrontends and core functionality following principles of either the testing pyramid or the testing trophy.

In single-spa, there are more ways to test your code in a browser using tools like cypress. Two common approaches are to test individual applications by using standalone mode and testing everything together, both provide value in different ways.

While not perfect standalone mode offers a way to run individual single-spa applications and can be used to test a single-spa application. If the microfrontend relies upon configuration or initialization happening in your single-spa root-config you cannot test those areas in standalone mode without mocking. Standalone mode works by creating a custom single-spa root-config on the fly that will just render the one application, so the code is the same as if it were running in production but the configuration is different.

Much like E2E tests run in traditional SPA applications you can open a brower and run assertions using tools like Cypress. Taking this approach is mirroring a full end to end test. You are running the exact same code that is in the environment. With some configuration and tools like import-map-overrides you can set-up your testing environment to work with overrides to the import map and can run end-to-end tests before deploying your code changes to an environment.

At a high level you will need to do the following before your environment can utilize overrides in E2E tests

Use a tool like import-map-overrides
Get the built code on a publically accessible domain. Similar to a “review app”
Configure your E2E testing environment to set the override
Run the E2E tests

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