An attempt to use Debug Window while debugging test code results in FileNotFoundException:

Exception thrown calling IDebugWindowPlugin plugin: System.IO.FileNotFoundException: Could not load file or assembly 'System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. The system cannot find the file specified.
File name: 'System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'