Mock methods that return void

Previously, I posted Void methods and Mockito in Java that verifies if any of the methods of a object passed as a argument were invoked.

This time we want to alter the behavior of a method that returns void.

Mock to alter a Method Behavior

Consider this code snippet:

How are we to mock this using Mockito? We want to test for a scenario where

Introducing Mockito.doAnswer

doAnswer allows us to change something within a method particularly objects passed as arguments.

When you inject the dog object to some object, it will be dealing with an unfriendly animal.