As a good developer, you decide to divide and conquer the user story, so you'll start with the first part, I want to rate an idea. After that, you will face the author should be notified by email. That sounds like a plan.

In terms of business rules, rating an idea is as easy as finding the idea by its identifier in the ideas repository, where all the ideas live, add the rating, recalculate the average and save the idea back. If the idea does not exist or the repository is not available we should throw an exception so we can show an error message, redirect the user or do whatever the business asks us for.

In order to execute this UseCase, we just need the idea identifier and the rating from the user. Two integers that would come from the user request.

Your company web application is dealing with a Zend Framework 1 legacy application. As most of companies, probably some parts of your app may be newer, more SOLID, and others may just be a big ball of mud. However, you know that...