Add phpunit-watcher for more convenient testing

[iandunn]

This is an alternative approach for a test watcher to the Grunt approach in 6382.6.patch. phpunit-watcher is used in Gutenberg, wordcamp.org, and several other wporg repos.

Pest may be a better alternative long term, but that might require a more substantial migration. There isn't any watcher right now, which makes testing less convenient (and therefore less likely). The ticket has been dormant for a long time, and this only took a few minutes to set up, so it seems like a good short/medium-term solution to me, even if folks eventually want to switch to Pest or something else. IMO it'd also be fine as a long-term solution.

To test, run composer update, then something like composer run test:watch -- --group=groups,cache. It should re-run the selected tests automatically when any PHP files in src or tests change.

Trac ticket: https://buddypress.trac.wordpress.org/ticket/6382

[renatonascalves]

I like this. I use phpunit-watcher locally, but using a different configuration.

@iandunn Would you be willing to resolve the conflicts and make sure this file is not bundled to wp?

@imath any objection adding this to core plugin? It's mostly developer focused.

[imath]

@renatonascalves sure no problem. Sorry @iandunn it got out of my radar 😞

[renatonascalves]

Closing it in favor of #233