title: Why am I getting "_OBJC_CLASS_$..., referenced from:" linker error when I have correctly linked frameworks?
body: <p><strong>My Problem</strong></p>
  
  <p>I getting "_OBJC_CLASS_$..., referenced from:" linker error when compiling some Xcode projects (it happens in both iOS and Mac projects) I have correctly linked frameworks and imports.</p>
  
  <p><strong>Setup</strong></p>
  
  <ul>
  <li>One application target</li>
  <li>One test target</li>
  <li>All frameworks linked correctly</li>
  </ul>
  
  <p>On compile I get the following linker errors:
  "_OBJC_CLASS_$_JGCountdownTimer", referenced from:
        objc-class-ref in JGCountdownTimerTestCase.o</p>
  
  <p>for many classes that are used in tests.</p>
  
  <p><strong>What I've Tried</strong></p>
  
  <ul>
  <li>Checked that imports are all present</li>
  <li>Removed all non standard frameworks</li>
  <li>If I compile a class for both the test target and the app target it fixes the issue. But then I get other warnings from the compiler.</li>
  </ul>