Impact of refactoring on external code quality improvement: An empirical evaluation

Refactoring is the process of improving the design of the existing code by changing its internal structure without affecting its external behaviour, with the main aims of improving the quality of software product. Therefore, there is belief that refactoring improves quality factors such as understandability, flexibility, and reusability. Moreover, there are also claims that refactoring yields higher development productivity. However, there is limited empirical evidence to support such assumptions. The objective of this study is to validate/invalidate the claims that refactoring improves software quality. Experimental research approach was used to achieve the objective and ten selected refactoring techniques were used for the analysis. The impact of each refactoring technique was assessed based on external measures namely; analysability, changeability, time behaviour and resource utilization. After analysing the experimental results, among the tested ten refactoring techniques, “Replace Conditional with Polymorphism” ranked in the highest as having high percentage of improvement in code quality. “Introduce Null Object” was ranked as worst which is having highest percentage of deteriorate of code quality.