title: Transform App.Config in unit test
body: <p>I am using slowcheetah transformation and the transformation works fine.</p>
  
  <p>On TeamCity I want my unittest to build my code in release mode and use the app.config from the debug build. In other words how can I</p>
  
  <ol>
  <li>Build my app in release mode.</li>
  <li>Build debug config file</li>
  <li>overwrite app.release.config with app.debug.config.</li>
  </ol>
  
  <p>It's all boils down to trigger the transformation in code.</p>