Unit Test Windows Phone 7 Project

In the windows phone 7 course I recently followed, there was an issue in unit testing a windows phone 7 project (you can find my recent post on this course here). The fact is, you can't create a Visual Studio unit test project for your phone project. Does this mean you cannot unit test your project? Of course it doesn't! Here's a solution to this problem.

First of all, I am using the MVVM pattern in my windows phone 7 project. This means my views, viewmodels and models are separated from each other, so I can place them in different projects. I created a normal windows phone 7 project for my views and a different windows phone 7 class library project for my viewmodels and models. Next thing you can now do is create a third project, also of the windows phone class library kind, which will contain your unit tests. You can see this basic setup in the following picture.

The fact that you take a windows phone 7 class library project for your unit tests is important. This solution will not work if you choose to use for instance a Silverlight class library project.
To this test project I now added the NUnit and Rhinomock dll's using Nuget and with this I can test all I want. One thing I still encountered was an error in my Unit Tests telling me the System.Windows dll could not be found.

This is quite a weird error, especially since the System.Windows.dll is present as reference in the test project. I tried adding different versions of this dll (all in my C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\Silverlight\v4.0\Profile\WindowsPhone folder), but no luck. Eventually I found that the dll was present in the project, but it just didn't get copied to the bin/Debug folder. Changing its Copy Local setting to True did the trick (and I kicked myself for losing quite some time on this stupid error).
So, there you go, a quick and easy way to unit test windows phone 7 projects. Soon I hope to give you some posts about my first Silverlight game and after that my first XNA game.