title: Azure DevOps VsTest task failing without errors
body: <p>I have a build definition in an on-premise Azure Dev Ops team project. This build definition has a VsTest task that runs unit tests compiled earlier in the build definition.</p>
  
  <p>The issue we're having is the task fails even if all tests pass. The selector we're using to find the test assemblies initially tried to run tests in an assembly that used NUnit. We've filtered those out but that hasn't resolved the issue.</p>
  
  <p>I've turned on the diagnostic logging for the test task but we're not finding any exceptions or error messages.</p>
  
  <pre><code>2020-04-06T20:11:39.0722884Z Test Run Failed.
  2020-04-06T20:11:39.0724468Z Total tests: 5470
  2020-04-06T20:11:39.0725088Z      Passed: 5470
  2020-04-06T20:11:39.0743719Z  Total time: 8.9587 Minutes
  2020-04-06T20:11:39.0908399Z ##[warning]Vstest failed with error. Check logs for failures. There might be failed tests.
  2020-04-06T20:11:39.1165840Z ##[error]Error: C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\Common7\IDE\Extensions\TestPlatform\vstest.console.exe failed with return code: 1
  2020-04-06T20:11:39.5322019Z ##[error]VsTest task failed.
  </code></pre>
  
  <p>I previously had NUnit tests being used but those have been filtered. I've tried updating the NuGet references to the mstest adapters, as well.</p>
  
  <p>Any ideas would be appreciated.</p>