如何在iOS单元测试中公开私有属性？

I am trying to test a method of a class that uses some of the class' private properties. I looked around for best practices on how to access them in a unit test and decided on adding a category for the class in my test implementation file. It still won't let me access them though, I get "unrecgonized selector sent to instance" errors.I am trying to test a method of a class that us