[!IMPORTANT]

For ember-intl@v6 users:

Before updating @ember/test-helpers to v4, please update ember-intl to 6.5.6 or higher. Otherwise, you will encounter the following error message in tests:

ember-intl tried to import "@ember/test-helpers" in "ember-intl/test-support/..." from addon code, but "@ember/test-helpers" is a devDependency. You may need to move it into dependencies.

Thanks to @wozny1989 for reporting the issue, and @NullVoxPopuli for helping me fix the failing ember-try scenarios.