PHP | check which classes / methods don't have tests setup

I'm using codeigniter / codeigniter-phpunit / phpunit and it's all working great.

I'm currently going through and adding tests for my models and their methods but it's all getting quite big now, especially when new methods are being added to classes that already have tests configured.

Other than TDD (Test Drive Development) as I still have a lot of existing code I need to build tests for, is there a tool that I can use that will scan all my classes/methods and then show which ones do not have a corresponding test written for it?

Then I can slowly work my way through the the classes/methods that have missing tests.

I appreciate this isn't a belt a braces solution as it can't quantify the quality of my existing tests or anything like that, but it would be nice to have a list of methods which are missings tests for a starting point.

Thanks All R