To What Extent Cognitive-Driven Development Improves Code Readability?

Background: Cognitive-Driven Development (CDD) is a coding design technique that aims to reduce developers' cognitive effort in understanding a given code unit (e.g., a class). By following CDD design practices, it is expected that the coding units to be smaller and, thus, easier to maintain and evolve. However, it is so unknown whether these smaller code units coded using CDD standards are easier to understand. Aims: This work aims to assess how much CDD improves code readability. Method: To achieve this goal, we conducted a two-phase study. We start by inviting professional software developers to vote (and justify their rationale) on the most readable pair of code snippets (from a set of 10 pairs); one of the pairs was coded using CDD practices. We received 133 answers. In the second phase, we applied the state-of-the-art readability model to the 10-pairs of CDD-driven refactorings. Results: We observed some conflicting results. On the one hand, developers perceived that seven (out of 10) CDD-driven refactorings were more readable than their counterparts; for two other CDD-driven refactorings, developers were undecided, while only in one of the CDD-driven refactorings, developers preferred the original code snippet. On the other hand, we noticed that only one CDD-driven refactorings has better performance readability, assessed by state-of-the-art readability models. Conclusions: Our results provide initial evidence that CDD could be an exciting approach for software design.