title: "Message from debugger: unable to attach" when running Tests on OSX app
body: <p>I am unable to run my tests on my OSX app - the project builds fine but when I run Product -> Test in Xcode 8.2. It says : 
  <code>Message from debugger: unable to attach</code></p>
  
  <p>How do I get my tests working again? </p>
  
  <p><a href="https://i.stack.imgur.com/GAiv7.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/GAiv7.jpg" alt="Unable to Attach Xcode"></a></p>