Brian Marick - Test-driving GUIs (with RubyCocoa). Brian is a good, enjoyable presenter.

Objective-C is more like Ruby than it is like Java.

He tests apps written in Objective-C using Ruby. This works fairly well, with an occasional necessity to explicitly convert from a Ruby boolean to an Obj-C boolean type.

The danger of using mock objects is that they don't behave like the real world objects that they mock. Sometimes, he has the test verify the expected result, but runs the interaction with the application manually. He's the "mechanical turk".