Running unit tests that use Microsoft Fakes on Team Build

As you may know I worked on TFS Branch Tool which is one of the ALM Rangers solutions. As usual we are dogfooding latest technology and at some point our builds started failing. We tried to investigate cause and found that product team deployed latest VS 2013 bits into golden image of the agent. We identified that some of the tests that use Microsoft Fakes are failing on hosted build. Don’t be surprised that everything was fine on developer’s computer. So, business as usual.

As it often happens in developer’s life finding of the root cause usually takes 90% of time that needed for solving an issue. Symptoms were very strange — failing unit tests behaved same way like Fakes aren’t running at all. In our case we tested the code that uses Team Foundation Client OM and we had shims to avoid connection to real Team Foundation Server. So, tests are failing because code under test is…