title: Xcode bot test session exited without completing
body: <p>I've been getting semi random instances of...</p>
  
  <pre><code>Test operation failure: Test session exited(-1) without completing.
  _finishWithError:Error Domain=IDEUnitTestsOperationsObserverErrorDomain Code=3 "Test session exited(-1) without completing." UserInfo=0x7fcd0a83c2c0 {NSLocalizedDescription=Test session exited(-1) without completing.} didCancel: 1
  Finished syncing device diagnostic logs after 0.0s.
  </code></pre>
  
  <p>errors on my Xcode CI bots. I haven't got a clue on how to fix this. These has been attempted without any positive result</p>
  
  <ul>
  <li>Cleaning the <code>DerivedData</code> folder of the Xcode build server – all folder named <code>DerivedData</code> within <code>/Library/Developer/XcodeServer</code></li>
  <li>Restarting the server machine</li>
  </ul>
  
  <p>Any ideas how to fix this?</p>
  
  <p>Some environment:</p>
  
  <ul>
  <li>Xcode 6.3.2</li>
  <li>iOS SDK 8.3</li>
  <li>OS X 10.10.3</li>
  <li>Server 4.0.3</li>
  </ul>