You just need to test the filter itself. Just create an instance and call the OnActionExecuted() method with test data then check the result. It helps to pull the code apart as much as possible.
Here's an example I've written. Most of the heavy lifting is done inside the CsvResult class which can be tested individually. You don't need to test the filter on an actual controller.
Making that work is the MVC framework's responsibility.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.