NetTuts.com has posted part seven in their "Refactoring Legacy Code" series today, continuing on with the refactor of their example application to improve maintainability and testability. In this latest article they focus in on the presentation layer.

In this seventh chapter of our refactoring tutorials, we will do a different type of refactoring. We observed in the past lessons that there is presentation related code scattered all over our legacy code. We will try to identify all the presentation related code that we can and we will then take the necessary steps to separate it from business logic.

The tutorial starts with a look at the Single Responsibility Principle (part of the SOLID design principles) and how it relates to the idea of clean architecture. They continue down the path of separating out the business logic and isolating it from the presentation layer (the display* handling). They create an "Extract" class that combines the logic and presentation though combination functionality. They walk you through the code, showing the changes you'll need to make and the tests to match.