Everytime I need to provide my test cases with a .config file my brain freezes over and I completely forget how I did it last time. Of course I google for “nunit solution config files” and I get lots of unhelpful answers. In particular the suggestion that …

If you use NUnit’s Visual Studio support to load a Visual Studio project or solution, such as mytests.csproj or mytests.sln, the config file must be named mytests.config.

… which is plain wrong. So I move around the .config file with all possible combinations of paths and assembly names to no avail. Finally I fire up trusty old Process Monitor and of course find out that what NUnit is REALLY looking for is mytests.sln.config . From there it’s a slap on the head and plain sailing.