[bradknowles]

Many years ago, I did a six month contract for Apple Retail Software Engineering, to deliver a Jenkins CI/CD system for the code that was used to communicate with the employees in the stores, to allow those employees to communicate with each other, to deliver training to them, etc….

There were multiple major components. There was the back-end server system that ran on Linux. There was the content creation system that ran on MacOS. There was the end-user clients that ran on iOS and iPadOS. And there was an extensive array of QA processes that they ran.

I ended up making minor changes to the code base for each of those components, so that they could build on the Jenkins server that was running underneath my desk (on an old Mac Pro server that had been lying around).

And I can tell you that they had extensive regression tests — as of the time I was there, over five thousand of them. Those took a really long time to run, which is why they needed the Jenkins server instead of doing this stuff on their laptops.

Now, I can’t speak for developers anywhere else at Apple, but I believe that they are well acquainted with the concept of regression testing.