Test fails with unable to find Microsoft.QualityTools.Testing.Fakes

I'm using Visual Studio Premium 2013 and some tests are failing with this message:

Test Name:      My test:      
Test Source:      My test:
Test Outcome:      Failed
Test Duration:      0:00:00.1262976

Result Message:      
Test method MyTest  threw exception:
System.IO.FileLoadException: Could not load file or assembly 'Microsoft.QualityTools.Testing.Fakes, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
Result StackTrace:      
at MyTestMethod()
   at ... etc

The project reference is to version 12, I don't have version 11 installed - I can't find anywhere that is telling it to look for version 11 - any ideas why it would be looking for version 11 and causing this error?
Who is Participating?
Chris MillardConnect With a Mentor Commented:
I'm not familiar with this error, but someone at this thread http://stackoverflow.com/questions/27741115/need-a-work-around-microsoft-qualitytools-testing-fakes suggests:-

Re-referencing the test assembly and recreating the Fakes assembly sorted the issue for me.
All Courses

From novice to tech pro — start learning today.