title: Unit testing with Excel workbook
body: <p>I'm starting to get into unit testing more. I have a project where Excel is the "engine" and it can't be taken out (at this time). I need to provide the workbook with various inputs, run a macro in the workbook, and then collect the results. It's a huge nasty workbook so taking anything out of it isn't an option right now.</p>
  
  <p>So given that the main dependency is Excel.Interop objects, how do I setup unit tests where almost all the code is hitting Excel?</p>