Thanks for your interest in contributing to Polyglot!
If you have an idea for a feature, I prefer that you open an issue first before going to the trouble of writing code. I welcome your ideas, but I'd like to work with you first to come up with solutions that work well for the project as a whole. I'm relatively responsive, so it shouldn't take us long to figure out whether and how best to implement your idea.
I use Orchestra Testbench as my base Phpunit TestCase for testing PHP and Jest for testing my JavaScript.
If you need any help with this please don't hesitate to ask.