Unit testing and PInvoking pt. 2

In part one of this series of posts I explained how I usually set up PInvoke calls. I showed how to hide the calls themselves from consuming code so they don't have to duplicate the pre and postprocessing that's often needed. And I briefly showed how you could make the wrapper-calls non-static so you can mock the class they're in and that way test the consuming code. In this post I'll show exactly how to do this using the new Rhino Mocks 3.5 AAA model.

Unit testing and PInvoking

I'm big on unit testing, I like to test everything and I feel uncomfortable when I'm unable to write tests for some of my code. So even though some parts of your application are hard to test I'm willing to take some extra time to make them testable. In this post I want to show you some tricks I use to unit-test code that uses platform invoked functions.

Marshalling strings with StringBuilder

The dotNet framework is pretty smart when it comes to marshalling managed to unmanaged datatypes for PInvoke calls. When you want to pass a Guid from the managed to the unmanaged world the framework knows how to transform the .Net Guid structure to a Windows GUID without you even asking for it.

PInvoke, managed and unmanaged datatypes

I'm doing a lot of PInvoking lately. One of the hard parts is mapping the unmanaged datatypes found in c++ include files to managed datatypes.

I found a nice article on codeproject with a list of the most common mappings. I'll repeat the list here so I can find it easilly, maybe other people can benefit from it too. I'll keep the list up-to-date with my own mappings and some remarks.