Problem/Motivation
In #2925064: [1/2] JS codestyle: no-restricted-syntax we broke Drupal.behaviors.copyFieldValue(). It was fixed in #2941106: Site email address in the install profile form is no longer copied to the user email address but we should add test coverage so we don't break it again.
Proposed resolution
Add test coverage.
Remaining tasks
User interface changes
None
API changes
None
Data model changes
None