IntelliJ 2016 how to create separate project to test PHP application

I have a project that is written in PHP with IntelliJ. I need to create a new IntelliJ project that contains only tests for the PHP application. I can't use classes from the application in the tests project. How can I add other project as a dependency for my project that contains the tests?

I have tried using IntelliJ module settings but I don't see the dependencies tab.