What would you like to do with PHP/Laravel that isn't unit testable? Laravel is, from my experience, written in a way that specifically makes testing of most things very easy.
Yeah, I'd like to know, too. I've done laravel + TDD for almost a decade and I can't think of anything you can't test or mock. Emails, Queues, Guzzle requests, AWS SDK, events, grammers, sessions, etc.. You name it, I've probably done extreme TDD to it.