[Bug] Could not find module ember-testing imported from @ember/test/index on ember 3.27.0

[sinankeskin]

🐞 Describe the Bug

Updating ember app to v3.27.0 causing an error: Could not find module ember-testing imported from @ember/test/index

🔬 Minimal Reproduction

Create an app with latest ember-cli. Update ember-source to v3.27.0
Build the app with npm run build. Go to dist folder. Serve the folder. In my case, I'm using python -m "http.server"
You'll see the error message as: Uncaught Error: Could not find module ember-testing imported from @ember/test/index

I'm seeing the same error with my production app.

Here is the sample repo.

😕 Actual Behavior

App successfully built but when I run and reach to main route I'm seeing this error and app doesn't work.

🤔 Expected Behavior

App should be working.

🌍 Environment

• Ember: - 3.26.1
• Node.js/npm: - v14.16.1/7.6.3
• OS: - Windows 10
• Browser: - Microsoft Edge 90.0.818.51 x64

➕ Additional Context

Add any other context about the problem here.

[kpfefferle]

We are also seeing this error when we try to run our production app builds.

[runspired]

We also hit this in production with EmberData. Removing all usage of registerWaiter and unregisterWaiter fixes production builds.

I think the issue is this import is likely dropped from production builds since it is only used for test builds. This went unnoticed when it was transpiled into Ember.registerWaiter because typically usage of it is wrapped in an if (DEBUG) {} but now that it's an import the import is missing.

cc @rwjblue @igorT @ef4

A failed app boot due to this can be seen in the relationship-performance check suite here: emberjs/data#7520

Failed check: https://github.com/emberjs/data/pull/7520/checks?check_run_id=2551009597

[runspired]

cc @Turbo87 I'm fairly sure this is what you hit in crates

[elwayman02]

embroider-build/embroider#805 seems to be related as well. I encountered the exact same error on Ember 3.26, but when upgrading @embroider/test-setup instead.

[runspired]

@elwayman02 most of the embroider ones are due to a bad fix in ember-cli-babel for ember-polyfills/ember-cached-decorator-polyfill#70 but yeah, this one might be this issue.

[pzuraq]

This should be fixed in 3.27.1, let us know if there are any issues!

[sinankeskin]

I confirm, this issue fixed with 3.27.1

Thanks a lot.