Ah, ignore my last comment's 2nd point. I didn't go through the code properly...

Ah, ignore my last comment's 2nd point. I didn't go through the code properly. I see how this works now.

Still, I am thinking if we should mock the drupal user information service. That is not what we are testing and relying on an API makes our test fragile. That could be more relevant for a functional test later. Let's keep this kernel test tiny, fast, and reliable.

Once we remove the HTTP request, you can then ignore my previous comment's 1st point as well as you would be able to service alter for the alter method. You might still need that method to mock the drupal user information service.