title: XUnit tests no longer discovered in .Net Core 2
body: <p>After moving project from .Net Core 1.1 to .Net Core 2 I just noticed that my xUnit tests are not discovered in VS 2017 anymore... </p>
  
  <p>any ideas how to get them back? :)</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>After some deeper research I found out that my problem related to this error in my test project: "Could not load file or assembly 'System.Runtime, Version=4.1.1.0"</p>
  
  <p>more details here: 
  <a href="https://developercommunity.visualstudio.com/content/problem/95070/could-not-load-file-or-assembly-systemruntime-vers.html" rel="nofollow noreferrer">https://developercommunity.visualstudio.com/content/problem/95070/could-not-load-file-or-assembly-systemruntime-vers.html</a></p>