How to get GUI tests to run on Mac?

I may have asked this before, but forgotten how to make things work. My main environment is a M1 MacBook Pro. If I make test in a Terminal window, it fails to run the tkinter and ttk tests with this message:

test_ttk skipped -- cannot run without OS X gui process

I have an XQuartz server running and a valid DISPLAY environment variable. In fact, when I ssh -X ... into my Ubuntu laptop and run tests there, the tkinter and ttk tests happily provide me with a bunch of pop-up window entertainment.

Why doesn’t this work on my Mac? Clearly, I have a graphical user interface running on my Mac. I do not create framework builds. Is that what I’m missing? If so, why can’t the system fall back to X for these tests?