Currently, we automatically run tests on Ubuntu Linux provided by Travis and on Windows provided by AppVeyor. macOS is missing here. That is unfortunate for several reasons:

• macOS is rather popular for web development.
• The Symfony CLI webserver encourages developers to run Symfony applications natively on their dev machine.
• Console tools are often run on the dev machine rather than the (virtualized) target environment of an app.
• Especially the components Console, Process, Filesystem and Finder have some code in place to normalize quirky behavior of different operating systems.

Because of that, I think we should consider adding macOS to our CI as well.

GitHub actions for instance offers a runner with macOS Catalina: https://docs.github.com/en/free-pro-team@latest/actions/reference/workflow-syntax-for-github-actions#jobsjob_idruns-on