In my case, it hooks into my editor or IDE. E.g. I don't need to have a "--watch" feature in my test-suite, because my Editor/IDE can fire the tests just fine.

In my case, it hooks into my editor or IDE. E.g. I don't need to have a "--watch" feature in my test-suite, because my Editor/IDE can fire the tests just fine. Same for (re-)starting webservices and such. And when not available or applicable in my editor, GNUtools, bash and unix offer plenty of tools to easily do this for me. E.g. https://linux.die.net/man/1/inotifywait https://linux.die.net/man/1/inotifywait to fire a command (e.g. restart a service) on changing files. I presumed these `--watch` where there to solve the slow-booting issues only (like in Rails) but maybe they are there because someone didn't know their OS and DE could do it for them already and decided to build it into the suite or tool instead of using existing tooling?