I'm glad you're excited about it. Work on Arduino hardware packages was what got me initially interested in testing automation because it was just such a huge amount of work just to compile all the possible combinations manually that the job of testing was sometimes ending up getting put on the users. That's fine with willing beta testers but it's a bad experience for unsuspecting beginners who probably assume the bug they ran across is something they are doing wrong.
Generally a hardware package repository will be structured so that it can just be directly copied into the hardware subfolder of the Arduino sketchbook folder for manual installation. The folder structure required for Boards Manager installation is a little bit different in that there is no architecture folder so everything is moved up one folder level. Some repositories do have the Boards Manager installation structure, for example: ESP8266, ESP-32, nRF-52. All three of those require toolchain installation so they would need to go through some extra package installation steps anyway and thus structuring the repo for easy manual installation is not really beneficial.
Robin2:
It strikes me that that is quite a distance beyond the market that the Arduino system is aimed at.
I do agree that the target Arduino user would only be overwhelmed by the concept of unit testing. However, I think it is reasonably in reach for the average 3rd party Arduino library or hardware package developer, especially if people like ifreecarve help to make it more accessible. I've been noticing compilation tests using services like Travis CI becoming more common in the Arduino world but unit tests are pretty rare. I think the entire Arduino community would benefit tremendously from easier automated testing of 3rd party projects. One of the best things about Arduino is the huge number of libraries and hardware packages available but it can be a bit hit and miss. Being able to check the results of the Travis CI build is a great way for a potential user to do a quick initial evaluation.