Wordpress is massively popular. If you live and breath PHP then great, but if you don't, what if I told you of an approach that provides an MVC'ish style experience to build themes?
A framework called Timber can help! coupled up with a templating engine called Twig makes for just a lovely experience!
Built by an agency (https://www.upstatement.com) and open source:
https://www.upstatement.com/timber/#whats-timber
Yes! you can also apply testing too: https://timber.github.io/docs/guides/testing/
Episode 5 - Wordpress Timber and Twig