E2E tests have been broken since upgrading TypeScript from 4 to 5. The reason is that between TypeScript 5.2.2 and TypeScript 5.3.3, an internal property on sourceFiles, resolvedModules was removed, and moved to Program. See PR: microsoft/TypeScript#55790 This caused karma-typescript, which we use for the karma tests, to break as it was depending on that field to find modules and determine if it should bundle files. karma-typescript is deprecated and no longer maintained so we can't get a fix from it even though we know the problem.

In light of this, I'm migrating our E2E tests from karma to Jest.

Pros:

• a lot of our users use Jest (in JSDOM mode) so this will catch SDK incompatibilities with it early
• it's maintained

Cons:

• Since Jest uses JSDOM and not a live headless browser, these tests don't catch any conflicts with real browser APIs
• Also due to some things missing in JSDOM, we need to do some patches, polyfills, and mocks, and reduce some functionality

Details

• Had to mock some browser APIs directly (service worker related) before calling getMessaging(), or else there would be an error
• Had to turn off useFetchStreams on Firestore tests as JSDOM does not handle fetch readable streams well. There's no public API to turn it off in compat so I had to do it pretty hacky.
• We had some special 5000ms timeouts on some tests because karma's default was 2000ms which wasn't enough. Jest's default is already 5000 so I got rid of the special settings on those tests.
• Jest running in Node allows it to easily read process.env.APP_CHECK_DEFAULT_TOKEN in the config so we don't have to do the convoluted custom context.html that karma required
• Did not touch the webpack build tests, those are still valuable as is, and still working (they test if the project builds in webpack without error)