Update Your NUnit Config Files!

If you’ve moved up to the live version of VS2005 and/or the .NET Framework, you’ll need to update your NUnit config files — you’ll notice this when you try and load your previously working NUnit test projects and you get the dreaded BadImageFormatException.

Add this line as the top-most in the <startup> section of your nunit-gui.exe.config and nunit-console.exe.config files:

      <supportedRuntime version="v2.0.50727" />

Voila!