On the Influence of Human Factors for Identifying Code Smells: A Multi-Trial Empirical Study

Context: Code smells are symptoms in the source code that represent poor design choices. Professional developers often perceive several types of code smells as indicators of actual design problems. However, the identification of code smells involves multiple steps that are subjective in nature, requiring the engagement of humans. Human factors are likely to play a key role in the precise identification of code smells in industrial settings. Unfortunately, there is limited knowledge about the influence of human factors on smell identification. Goal: We aim at investigating whether the precision of smell identification is influenced by three key human factors, namely reviewer's professional background, reviewer's module knowledge and collaboration of reviewers during the task. We also aim at deriving recommendations for allocating human resources to smell identification tasks. Method: We performed 19 comparisons among different subsamples from two trials of a controlled experiment conducted in the context of an empirical study on code smell identification. One trial was conducted in industrial settings while the other had involved graduate students. The diversity of the samples allowed us to analyze the influence of the three factors in isolation and in conjunction. Results: We found that (i) reviewers' collaboration significantly increases the precision of smell identification, but (ii) some professional background is required from the reviewers to reach high precision. Surprisingly, we also found that: (iii) having previous knowledge of the reviewed module does not affect the precision of reviewers with higher professional background. However, this factor was influential on successful identification of more complex smells. Conclusion: We expect that our findings are helpful to support researchers in conducting proper experimental procedures in the future. Besides, they may also be useful for supporting project managers in allocating resources for smell identification tasks.