ReSharper Not Executing Your Tests?

Today I ran into a small issue as ReSharper was not willing to execute my tests. Generally it does but today it was different. Let me explain.

I have two assemblies, one that contains the unit tests and one that contains the code under test. In ReSharper’s session window the unit tests were properly listed. I was even able to “execute” them. However it would always show that them as not executed with a gray bullet in front of them. This was the behavior for both “Run Test” and “Debug Test”. The Output window was empty and didn’t show anything that would indicate what was wrong.

I also check my unit tests but all attributes were properly in place and both the class and the methods were public and the methods had the correct signature. So what was going on?

To diagnose the issue I launched the unit test tool as a stand-alone application. When I tried to load the assembly with the unit tests it was immediately clear what was wrong when I saw the word BadImageFormatException displayed in a message box.

It turned out that the assembly with the unit tests was set to build for “Any CPU” while the assembly under test was build for “x86”. Since I am using a 64 bit machine the two assemblies were compiled as per those targets. The unit tests as 64 bit while the assembly under test as 32 bit. No wonder it didn’t work.

This is easy to fix, in my case by setting the target for the assembly with the unit tests to “x86” as well. It would, however, be nice if ReSharper had reported the exception in some form as it would have saved time. Well, maybe in the next version? Maybe this post helps you to save some time.

(Note: I’m using ReSharper version 6.0.2202.688 with Visual Studio 2010 SP1 on a 64 bit Windows 7 Enterprise Edition)