Rami Alnawas has posted an interesting tutorial for the Phalcon users out there showing one way you can unit test your models. It's based on his own experience with the framework in a current project.

My first contribution to the PHP community in general, and Phalcon folks in particular, was the introduction of MVC Functional Testing with PHPUnit, this meant that Applications developed using Phalcon Framework could be unit tested by requesting a url then asserting that the response is handled by a specific action within the controller. [...] To date, my latest addition is an example of how to unit test code that utilises Phalcon models, mainly the various static find methods. The code is available on github and the coverage report is coveralls.io.

He shows it at work, creating a simple "Popup" model and a facade to help with making instances for testing. He also includes the code to test this facade, checking the results of methods like "fetchall", "select" and "execute".