Mix/Gulp: how to use Mix to create new Gulp tasks?

I am interested in adding some automations to my deve environment.

I see that I can use npm run watch-poll to auto-recompile assets on dev and this is great.

But, for example, I'de like a task that execute a PHP Linter, and phpunit tests so I can attach this to git commit via hooks... Actually I'm running a LOT of command manually