This article explains the advantages of the Presentation Model pattern over the Model-View-Controller and Model-View-Presenter. This will improve your decisions about GUI implementations for desktop.

One of the major challenges in the development of desktop software is the effective use of unit tests that cover the GUI functionalities and its interactions with the remainder of the software. The complexity of this implementation lies in the control of selected items in lists and tables, modal dialogs, clicks and events. In fact, it is extremely difficult to develop good tests on the GUI when the application logic is tightly-coupled to UI components.

You probably have already heard about design patterns that could help in this case, especially those that separate the application logic from UI components. Perhaps the most famous is the Model-View-Controller (MVC), which has been widely used not only for desktop applications but also for web development.

There is a relevant question that we should ask ourselves at this point: Is this separation between logic and UI components enough to reduce the complexity of writing GUI unit tests?

Figure 1 presents the three most important presentation patterns for desktop development. Besides the MVC, there is one called Model-View-Presenter (MVP) that consists of a small variation of the first one (see Martin Fowler’s description of them for more details).

Figure 1: Patterns for desktop application development.

The important thing to notice in this picture is that both MVC and MVP describe the controller/presenter with a reference to the view. So, to create an instance of the controller inside the test code, we need the view as well. This still makes the development of unit tests difficult.

There is a turnaround to this problem, which is basically to add an interface between the controller and the view to break this dependency and abstract the view’s components. But the idea behind this solution increases the amount of code and does not imply in less complexity and clean organization. In most of the cases, this resolution is not worth the effort when there is a third option such as the Presentation Model pattern.