title: Unit Tests show in Test Explorer but won't run in Visual Studio (2013 & 2015)
body: <p>I have several ms unit test projects in my solution, when I go to Test Explorer all the unit test projects show up in the list:</p>
  
  <p><a href="https://i.stack.imgur.com/ErOPH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ErOPH.png" alt="Test Explorer with Test Projects and their counts"></a></p>
  
  <p>When I hit "Run All" there is only one project that is discovered and run.</p>
  
  <p><a href="https://i.stack.imgur.com/WzW9N.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WzW9N.png" alt="Output window from selecting &quot;Run All&quot;"></a></p>
  
  <p>I can execute the other projects by selecting them individually and hitting "Run Selected Tests" but the Test Projects will not execute together automatically. </p>
  
  <p>These tests use to run fine in the solution but have stopped within the last month or so running when "Run All" is used.</p>
  
  <p>Thanks for any help!</p>