MSTest cannot find TestAdapter.dll : <p>I'm using the built-in Visual Studio test tools (<code>Test -&gt; Run -&gt; etc</code> in the menu).  I just started having a problem where I get the following error when I try to run tests</p>

<p><code>[3/29/2018 1:39:14 PM Error] System.IO.FileNotFoundException: C:\Users\brubin\AppData\Local\Temp\VisualStudioTestExplorerExtensions\MSTest.TestAdapter.1.1.18/build/_common/Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.dll
   at Microsoft.VisualStudio.TestWindow.Controller.TestPlatformProvider.PerformShadowCopy(IEnumerable'1 testExtensions)</code></p>

<p>That's followed by some errors that say</p>

<p><code>Make sure that test discoverer &amp; executors are registered and platform &amp; framework version settings are appropriate and try again.</code></p>

<p>When I look at the folder <code>C:\Users\brubin\AppData\Local\Temp\VisualStudioTestExplorerExtensions\MSTest.TestAdapter.1.1.18/build/_common/</code>, there are no files in that folder.  However, I haven't knowingly changed anything about my test setup and this was working several days ago, so I don't know why it would have stopped working.</p>

<p>My projects are using the MSTest.TestFramework (MSTest V2) version v1.2 NuGet package.</p>

<p>One thing I noticed that may have caused this problem is that if I go to <code>Tools -&gt; Extensions and Updates</code>, I see that my Microsoft Visual Studio Test Platform was updated a few days ago, on 3/23 (I think that's when I installed a Visual Studio update).  However, if that broke something, I have no idea where to look to see what's broken, or how to fix it.</p>

<p><a href="https://i.stack.imgur.com/Wa25J.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Wa25J.png" alt="enter image description here"></a></p>
