Empirical Quantitive Investigation of the Effect of GoF Design Patterns on the Quality of Software Systems

Design patterns are universal, reusable fixes for common issues in software design. They are supposed to encourage better design choices by rep-urposing already-established successful solutions, saving cost and time. The purpose of the current study is to present quantitive evidence about the expected implications on software quality by employing GoF design patterns; 10 commonly applied patterns have been empirically assessed for their impact on software quality. The evaluated patterns are: Factory Method, Prototype, Singleton, Adapter, Composite, Decorator, Observer, State, Template Method, and Proxy. The study considers software quality attributes that match the intents of the subject design patterns; these attributes are: software maintainability, testability, reusability, simple design, sensitivity to change, and error-proneness. The empirical evaluation of patterns is performed by computing 10 software quality metrics for pattern classes that have been detected in 10 real open-source projects implemented with Java. The findings reveal that the evaluated patterns promote software quality, except for the classes of Prototype, Composite, and Singleton, which were often found not cohesive.