I have been seeing this warning recently as well when doing some build and runs on different projects.
I think the test runner is a package for unit testing in Unity. But since we are not using that in the course, I can’t figure out why the compiler is looking for it, or why it would be missing even if it was.
I think this is just an open bug on Unity’s end.
https://issuetracker.unity3d.com/issues/unable-to-find-player-assembly-testrunner-dot-dll-warning-appears-in-the-console-after-building-standalone?page=2#comments
Anyhow, similar for both of these, they are just warnings not errors. Meaning they are there to inform you, but don’t necessarily effect the functionality of your game.