NUnit: “The process cannot access the file … because it is being used by another process.”

Question

I\'m using the NUnit GUI version, and it started to get upset at me when I have a test project loaded in there trying to test things. If I make a change in Visual Studio, an

Answer 1

I had this problem, and after a lot of reading around and experimentation, I realized the culprit was not actually anything in NUnit or my code. It was another library I was using, FakeItEasy, a mock object framework, which was failing to properly release all it's resources.

If you're using FakeItEasy with NUnit and encounter this problem, consider switching to another mock object framework. If you're not using FakeItEasy, or if removing it from your project doesn't fix this, take an inventory of all the 3rd party libraries you are utilizing from the test code, and consider if any of them might be doing something similar.

Alternately, pester the creator of NUnit to explicitly release any resources held by any of the test assemblies it loads, or if you're much more proactive than I, take advantage of the fact that it's an open source project and contribute a solution that does this.