title: Importing NSubstitute into Unity project
body: <p>I'm trying to use NSubstitute in my Unity project (Unity version 2019.2.2f1). No matter how to import it, my IDE, both Visual Studio and JetBrains Rider, would give an error when I try <code>using NSubstitute</code> saying NSubstitute is undefined.</p>
  
  <p>I have tried many options and versions of NSubstitute packages (4.2.1 and 2.0.3). I also import the dll file from net35 folder of the package into a Plugins folder in my Unity project. I also tried to install the same version of NSubstitute using Nuget in the IDE.</p>