title: How to fix Could not load file or assembly 'nunit.engine, Version=3.7.0.0
body: <p>I have a webappliction with a separate test-project using NUnit to run unittests. When my test-project is trying to discover tests I run into the following exception:</p>
  
  <pre><code>An exception occurred while test discoverer 'NUnit3TestDiscoverer' was loading tests. Exception: Could not load file or assembly 'nunit.engine, Version=3.7.0.0, Culture=neutral, PublicKeyToken=2638cd05610744eb' or one of its dependencies. The system cannot find the file specified.
  </code></pre>
  
  <p>This is of course a very common error, but I can't find a reference to this particular assembly anywhere or what other dependency is actually causing the issue. Another thing is that I currently have <code>3.9.0</code> installed of NUnit instead of the mentioned <code>3.7.0</code>.
  I have already tried cleaning and rebuilding the solution and restored all Nuget packages and clearing the <code>obj</code> directory didn't help either.</p>