You have been testing WhatsApp Application for the past few months and of lately while executing the test cases, you are not able to identify any issues in the application. What might be the reason and using which Testing principal this could have been handled?

 There can be multiple reasons for it, to consider a few are:

You might not have updated the test cases as per the change in requirements.

Change in OS [ Android -> Lollipop to marshmallow], [iOS 8 ->9], so if we keep running the same set of scenarios and test data over and over again it will turn out to be useless.

This could have been handled effectively under ‘’The Pesticide Paradox” principle which states if you keep running the same set of tests over and over again, chances are no more new defects will be discovered by those test cases.