title: Error getting to Test Window in VS 2012 RC
body: <p>I have been using the customer preview of Visual Studio 2012 up until day before yesterday when the Release Candidate became available.  After I installed the Release Candidate, I can't get to the Test Window (Test / Windows / Test Explorer).</p>
  
  <p>I get the following lengthy error which I've copied manually here.  (Since this is my first question, I couldn't post the picture, and the screen would not allow me to copy the text to the clipboard.  Hopefully there are no typos.)</p>
  
  <pre><code>The composition produced a single composition error. The root cause is provided below.  Review the CompositionException.Errors property for more detailed information.
  
  1) Value cannot be null.
  Parameter name: testPlatform
  
  Resulting in: An exception occurred while trying to create an instance of type 'Microsoft.VisualStudio.TestWindow.Model.ReqeustConfigurationFactory'.
  
  Resulting in: Cannot activate part
  'Microsoft.VisualStudio.TestWindow.Model.ReqeustConfigurationFactory'.
  Element: Microsoft.VisualStudio.TestWindow.Model.ReqeustConfigurationFactory --&gt;
  Microsoft.VisualStudio.TestWindow.Model.ReqeustConfigurationFactory --&gt; CachedAssemblyCatalog
  
  Resulting in: Cannot get export
  Microsoft.VisualStudio.TestWindow.Model.ReqeustConfigurationFactory
  (ContractName="Microsoft.VisualStudio.TestWindow.Model.RequestConfigurationFactory")' from part
  'Microsoft.VisualStudio.TestWindow.Model.ReqeustConfigurationFactory'.
  Element:
  Microsoft.VisualStudio.TestWindow.Model.ReqeustConfigurationFactory
  (ContractName="Microsoft.VisualStudio.TestWindow.Model.RequestConfigurationFactory") --&gt; CachedAssemblyCatalog
  </code></pre>
  
  <p>The error occurs regardless of whether I have opened a solution or not.  A second attempt to open the window yields "Cannot create the tool window."  After restarting Visual Studio, and attempting to get to the Test Window, I get the long message again.</p>
  
  <p>At the time I upgraded Visual Studio to the Release Candidate, I had installed:</p>
  
  <ul>
  <li>NUnit</li>
  <li>SpecFlow</li>
  <li>ReSharper (Beta)</li>
  <li>Code Contracts -- the last thing I had installed before upgrading Visual Studio.  I cannot guarantee that the test window was working after I installed this.</li>
  </ul>
  
  <p>I have searched the web for key phrases out of the error message, but found no help.</p>
  
  <p>I have also:</p>
  
  <ul>
  <li>Repaired Visual Studio (which solved a problem I was having getting to the Extension Manager, but not the Test Window problem)</li>
  <li>Uninstalled Visual Studio and reinstalled it </li>
  <li>Uninstalled each of the Extensions/packages listed above (NUnit, SpecFlow, ReSharper, Code Contracts). Uninstalling didn't seem to help, so I have re-installed all of them,
  one at a time.  I've also confirmed that I can run tests in the ReSharper test window.</li>
  <li>Deleted the currentsettings.vssettings file from C:\Users\\Documents\Visual Studio 11\Settings, hoping it contained the problem and would be recreated correctly.  I got a message that "The IDE will use your most recent settings for this session".  I don't know where to find those...</li>
  <li>Reset settings from the Import and Export Settings option.</li>
  </ul>
  
  <p>None of these actions has helped.</p>
  
  <p>It looks to me like a config file somewhere is missing an element for testPlatform, but I have no idea where that would be (or in what format, or what Options page entry would set it.)</p>
  
  <p>Any help would GREATLY be appreciated.</p>