ReactiveCocoa: How do you unit test a RACCommand?

In MVVM pattern, ViewModel give out a RACCommand and View bind a button with the RACCommand, but how to test the RACCommand?

I have two aspects that needs to be tested:

• under some conditions, the RACCommand should be enabled
• fire that command and see if the ViewModel does its job when the command fires

How to test these cases?