title: How to mock a void return method affecting an object
body: <p>I am writing unit tests for my application and I was wondering if it is possible for the Mockito framework to affect an object that is passed into a method that returns void of a mocked class. For instance, calling a mocked validation class that contains a method that returns void but tracks various changes and metadata via an object passed in as an argument. .</p>
  
  <pre><code>public GetCartItemsOutput getCartItems(GetCartItemsInput getCartItemsInput) {
      CartItemsFilter cartItemsFilter = new CartItemsFilter();
      validator.validateCartItemsInput(getCartItemsInput, cartItemsFilter); ...
  </code></pre>
  
  <p>I mocked the validator class for my other tests but for this one I need mock the changes to the cartItemsFilter object which I do not know how to do.</p>