title: Assembly has reference to non-existent assembly 'Unity.PerformanceTesting'
body: <p>I'm trying to add ECS to the project. I have added a packages: Entities, Jobs and Collections. But Unity keeps throwing me this error all the time. I have not found a solution to this problem anywhere.</p>
  
  <p>Unity 2018.3.3f1</p>
  
  <p>Error:</p>
  
  <pre><code>Assembly has reference to non-existent assembly 'Unity.PerformanceTesting'
  (Packages/com.unity.entities/Unity.Entities.PerformanceTests/Unity.Entities.PerformanceTests.asmdef)
  </code></pre>
  
  <p>Edit:
  I found a solution. I had to add to manifest.json</p>
  
  <pre><code>"com.unity.test-framework.performance": "0.1.49-preview"
  </code></pre>