title: Adding XCTest unit tests to existing app doesn't work
body: <p>I've added tests (XCTests) to an existing C++ command line app in Xcode 5 </p>
  
  <ul>
  <li>via <strong>Test Navigator > (+)</strong>, </li>
  <li>changed the extension of the test class to <code>.mm</code>,</li>
  <li>added the <strong>XCTest framework</strong> to the project.</li>
  </ul>
  
  <p>All compiles fine. Now running the tests just gives me a 'Test failed' message, nothing in the console and neither green nor red lights in the Navigator (i.e. no tests executed).</p>
  
  <p>Starting with a fresh Xcode 5 project and changing the extension of the test class to <code>.mm</code> just works fine so I'd assume it's not just about lacking support for Objective-C++ in XCTest.</p>
  
  <p>Even with a plain, vanilla test target added to the existing C++ project the tests fail before ever running.</p>
  
  <p>Any more gotchas to watch out for when adding XCTests to existing (Objective-)C++ targets?  </p>
  
  <p><strong>Update #1</strong></p>
  
  <p>With Xcode 5.0.2 (on 10.8.5) xctest now crashes in the same scenario with an</p>
  
  <pre><code>*** NSTask: Task create for path '/Users/XXX/Library/Developer/Xcode/DerivedData/RM_Next_Gen-gpihzjouhxvifqcslmywktktizer/Build/Products/Debug/YYY Tests.xctest/Contents/MacOS/YYY Tests' failed: 22, "Invalid argument".  Terminating temporary process.
  objc[3478]: GC: forcing GC OFF because OBJC_DISABLE_GC is set
  *** multi-threaded process forked ***
  </code></pre>