title: How to xUnit-Test in Rider? I'm getting error CS0246
body: <p>I'm new to C#, and even more to unit testing in C#. Now I wanted to add unit tests to an application, but I can't seem to get it done in JetBrains Rider:</p>
  
  <p>I created a new "Unit Test Project" inside my solution, besides my WPF application project. Rider installs <code>xunit</code>, <code>xunit.abstractions</code>, <code>xunit.assert</code>, <code>xunit.core</code>, <code>xunit.extensibility.core</code> and <code>xunit.extensibility.execution</code>. It also creates a <code>Tests.cs</code> class containing a <code>Test1()</code> method with a <code>[Fact]</code> attribute. Problem is: it immediately says <code>'Fact' is not an attribute</code>.</p>
  
  <p>When building, it yields two [CS0246] Errors:</p>
  
  <pre><code>Tests.cs(8, 10): [CS0246] Der Typ- oder Namespacename "Fact" wurde nicht gefunden (fehlt eine using-Direktive oder ein Assemblyverweise?)
  Tests.cs(8, 10): [CS0246] Der Typ- oder Namespacename "FactAttribute" wurde nicht gefunden (fehlt eine using-Direktive oder ein Assemblyverweise?)
  </code></pre>
  
  <p>I'm not sure what the exact English translation would be, but I guess you get the idea. What references are missing? Is this a bug in Rider?</p>
  
  <p>I tried it with NUnit as well, with similar results.</p>
  
  <p>Besides that: Do I need to follow any file structure or naming conventions for the tests to be autodetected?</p>