Quite new to unit testing. I am writing unit tests for my code using Chai+Mocha and Sinon and I am stuck at a point because I am not able to decide whether I should use a Sinon stub or a fake. I have two functions processHash and processBatch. processHash internally calls processBatch, since I have already written a test case for processBatch I don’t think it makes sense to test it again when I test processHash