Visual Studio: How to Resolve TestWindowPackage.Initialize Failure

Posted by OmegaMan at May 25, 2015

Category: Errors, Visual Studio


I began to receive the error message box in Visual Studio after a restart from an install of an unrelated to test Visual Studio plugin (which I have used in the past):

The ‘TestWindowPackage’ package did not load correctly.  … examining the file … AppData\Roaming\Microsoft\VisualStudio\12.0\ActivityLog.xml

Looking at that log showed these errors:

TestWindowPackage.Initialize failed with exception … System.InvalidOperationException:

Loading MEF components failed with the following exception:
The composition produced a single composition error. The root cause is provided below. Review the CompositionException.Errors property for more detailed information.

No exports were found that match the constraint:
    ContractName    Microsoft.VisualStudio.TestWindow.VsHost.PackageContainer
    RequiredTypeIdentity    Microsoft.VisualStudio.TestWindow.VsHost.PackageContainer


To resolve the issue I did step 1 and 2 but am showing step 3 in case it helps.

  1. Close all instances of Visual Studio.
  2. Delete all files in AppData\Local\Microsoft\VisualStudio\12.0\ComponentModelCache Note that directory is not found in Roaming as the activity log file, but in Local.
  3. Restart, if that doesn’t work then start over with step 4.
  4. From a Visual Studio Command Line do this operation: devenv /setup /ResetSkipPkgs See (/Setup (devenv.exe)) for more information.


  1. Ron McCormack says


    Step 1 &2 solved my issue

  2. David Allen says

    thanks, steps 1 & 2 fixed my issue as well.
    After deleting the cache, I got a different error on loading. But closed and opened Visual Studio again and it is all better.

  3. Alek says

    Many thanks, step 1 fixed the issue for me!

    Some blogs suggested purging the Visual Studio installation completely. Good thing I continued searching for an answer and found your blog. 🙂

    For the record, my error messages in ActivityLog were different than yours; however, the actual result was similar, test explorer could not open and show any tests.

  4. Anthony says

    Steps 1 and 2 did it!!!! Thank you so much!!!!!!!!!!

  5. Andy says

    Step1 and 2 helped !

  6. SQL Data Dictionary says

    Brilliant! I thought I was done for. Clearing the folder worked for me.

  7. Ben says

    Thank you, I ran into this same issues with Visual Studio 2015 after installing update 2. Steps 1 and 2 fixed it for me.

  8. Michael says

    Thanks, after a small path adjustment it worked for Visual Studio 2015:

  9. Henry says

    Soluciono el problema con el primero
    (First step solved it for me).


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