Removal of Design Problems through Refactorings: Are We Looking at the Right Symptoms?

A design problem is the result of design decisions that negatively impact quality attributes. For example, a stakeholder introduces a design problem when he decides to addresses multiple unrelated responsibilities in a single class, impacting the modifiability and reusability of the system. Given their negative consequences, design problems should be identified and refactored. The literature still lacks evidence on which symptoms' characteristics can be used as strong indicators of design problems. For example, it is unknown if the density and diversity of certain symptoms (e.g., violations of object-oriented principles) are correlated with the occurrence of design problems. Thus, in this paper, we report a case study involving two C# systems. We evaluated the impact of refactoring, focused on removing design problems, on the density and diversity of symptoms. Results indicate that refactored classes usually present higher density and diversity of symptoms. However, the density and diversity of some symptoms, such as the violation of object-oriented principles, was not predominantly higher in refactored classes. Moreover, contrary to our expectations, refactorings caused almost no positive impact on the density and diversity of symptoms.