Until now, I used to test my pkgbuilds with GitHub actions and a custom script I wrote a couple of years ago to automatically install dependencies. After leaving GitHub in protest (see https://github.com/groctel/), it would have been extremely hypocritical to still use their compute time to test my packages.
I have struggled all these months to find a solution because, honestly, it takes a lot of work to set up a generic environment to test AUR installers. Today I have done just that!