On the QaFoo blog they've posted an article sharing a quick testing tip when using Phake to test APIs where the calls don't return any data.

Today I want to share a simple trick for the excellent Mocking library Phake (I wrote about it before) when testing state on APIs that don't return values.

Testing becomes harder when you are using command / query separation in your code and service operations don't return values anymore. If your command method creates objects and passes them down the stack, then you usually want to make assertions on the nature of the changes.

He gives an example of a class that creates an Order object and saves it but doesn't return a value. He shows how to update this with Phake in the test to capture and verify that the calls are correctly made and the number of products on the order is correct.