Analyzing the Effects of Refactorings on Bad Smells

This webpage containing the data of the Empirical Study and Systematic Literature Review (SLR) conduct.

Abstract

Refactoring aims to remove bad smells and increase software systems' maintainability by improving their structure without changing their behavior. Even with tools to assist refactoring, many developers do not trust their solutions, claiming that some studies show that refactoring can introduce new bad smells into the source code. However, we have not found a complete catalog that states when this may occur. To investigate this subject deeply, the goal of this dissertation is to evaluate the effects of refactoring on bad smells. Specifically, we want to know if and what refactoring removes bad smells or introduces them. To achieve this goal, we conducted a Systematic Literature Review (SLR) to identify the relationship between refactorings and Fowler's bad smells. We also conducted an Empirical Study with five refactorings to analyze their effects on ten bad smells with five tools. As a result of the empirical study, we present, through the data studied, which bad smells tend to be removed or introduced by the automated refactoring process. In SLR, we found 20 different papers showing the direct relationship between 31 refactorings and 16 bad smells. We produced a catalog showing these relationships, and we also showed a contrast with Fowler's relationships. We identified that the most discussed relationship in the literature is between Move Method and Feature Envy. SLR also revealed different refactoring strategies than those discussed by Fowler for dealing with bad smells. In the empirical study, we observed refactoring generated decrease, increase, and neutral variations in the number of bad smells. Unlike Fowler's definition, we surprisingly found that the decrease cases was the lowest compared to cases of increase and neutral variations. As one of the additional analyzes, we contrast the results found in both studies carried out.

Keywords Refactoring, Bad Smell, Refactoring Impacts, Refactoring Effects

Systemac Literature Review

Filtering Databases

Steps

Database Step 1 Step 2 Step 3 Step 4 Step 5 Step 6
ACM Digital Library 97 68 33 25 12 03
Engineering Village 20 13 06 04 03 03
IEEE Xplore 28 18 12 05 02 00
Science Direct 02 02 01 01 01 00
Scopus 17 11 06 04 03 01
Springer 2,016 210 95 95 43 08
Web of Science 02 02 01 01 01 00
  • Step 1 - Remove Duplicates
  • Step 2 - Reading Title
  • Step 3 - Reading Abstract
  • Step 4 - Inclusion and Exclusion Criteria
  • Step 5 - Reading Introduction and Conclusion
  • Step 6 - Complete Reading of Paper

Files

Places of Publication

Place Total
Book Chapter 01
Conference 08
Journal 09
Symposium 02

Events

Event Total
Frontiers of Computer Science 01
IEEE Transactions on Software Engineering 03
Innovations Syst Softw Eng 01
International Conference on Agile Software Development (XP) 02
International Conference on Enterprise Information Systems (ICEIS) 01
International Conference on Product Focused Software Process Improvement (PROFES) 01
International Conference on Software Analysis, Evolution, and Reengineering 01
International Conference on Software Quality (SWQD) 01
International Journal of System Assurance Engineering and Management 01
International Symposium on Empirical Software Engineering 01
Joint Meeting on Foundations of Software Engineering 01
Journal of Software: Practice and Experience 01
Journal of Systems and Software 01
Recommendation Systems in Software Engineering 01
Requirements Eng 01
Simpósio Brasileiro de Engenharia de Software (SBES) 01
Working Conference on Reverse Engineering (WCRE) 01

Tools found in the Literature

Tool Refactoring Tool Used Bad Smell Tool Used Reference
DCRA Integrated NiCad [1]
RESYS OSORE OCEAN [2]
  Ref-Finder Own Metric Developed [3]
  JDeodorant JDeodorant and DECOR [4]
  JDeodorant JDeodorant [6]
Extract Method Detector Integrated Integrated [9]
Methodbook Integrated Integrated [10]
MMRUC3 Integrated Integrated [11]
  ARIES and JDeodorant JDeodorant [12]
CCShaper Integrated CCFinder [13]
  Refactoring Miner Own Metric Developed [15]
  Ref-Detector Metrics to Detect Smell [16]
Liu’s Approach Integrated Integrated [17]
Tsantalis’s Methodology Integrated Integrated [18]
HIST   Integrated [19]
JMove Integrated Integrated [20]

List of Papers

Filtering Steps

[1] A Duplicated Code Refactoring Advisor

[2] An Approach for Semantically-Enriched Recommendation of Refactorings Based on the Incidence of Code Smells

[3] An Experimental Investigation on the Innate Relationship Between Quality and Refactoring

[4] Analysis of Code Smell to Quantify the Refactoring

[5] Common Refactorings, a Dependency Graph and some Code Smells: An Empirical Study of Java OSS

[6] Investigating the Evolution of Code Smells in Object-Oriented Systems

[7] Learning to Rank Extract Method Refactoring Suggestions for Long Methods

[8] Leveraging Code Smell Detection with Inter-smell Relations

[9] Major Motivations for Extract Method Refactorings: Analysis Based on Interviews and Change Histories

[10] Methodbook: Recommending Move Method Refactorings via Relational Topic Models

[11] MMRUC3: A Recommendation Approach of Move Method Refactoring Using Coupling, Cohesion, and Contextual Similarity to Enhance Software Design

[12] Recommending Refactoring Operations in Large Software Systems

[13] Refactoring Support Based on Code Clone Analysis

[14] Supporting Requirements to Code Traceability Through Refactoring

[15] Understanding the Impact of Refactoring on Smells: A Longitudinal Study of 23 Software Projects

Snowballing

[16] Does Refactoring Improve Software Structural Quality? A Longitudinal Study of 25 Projects

[17] Domino Effect: Move More Methods Once a Method is Moved

[18] Identification of Move Method Refactoring Opportunities

[19] Mining Version Histories for Detecting Code Smells

[20] Recommending Move Method Refactorings Using Dependency Sets

Empirical Study

Research Phases

Phases

Refactorings Applied

System Extract Class Extract Method Move Method Replace Refactoring Total
Checkstyle-5.6 56 149 18 5 228
Commons-codec 10 77 15   102
Commons-io 5 45 3 2 55
Commons-lang 31 *     31
Commons-logging 4 44 * 1 49
JHotDraw-7.5.1 58 * 13 * 71
Quartz-1.8.3 26 * 6 11 43
Squirrel_sql-3.1.2 18 65 6 * 89
Total 208 380 61 19 668
  • Replace Refactoring - Replace Type Code with State/Strategy and Replace Conditional with Polymorphism

Bad Smells Detected by Tools

Abbreviation Bad Smell T1 T2 T3 T4 T5
DC Data Class       * *
FE Feature Envy     * *  
LC Large Class *        
ZC Lazy Class *       *
LM Long Method * * *    
LP Long Parameter List * *      
MC Message Chains *        
RB Refused Bequest *     * *
SS Shotgun Surgery       *  
SG Speculative Generality *       *
  Total 7 2 2 4 4
  • T1: Decor, T2: Designite, T3: JDeodorant, T4: JSpIRIT, and T5: Organic

Impacts Assessment

Steps

Files

  • Selected Systems and Detected Bad Smells - This link contain the original version and all refactored versions of the systems; and the Bad Smells detected by the five tools in the original and refactored version

  • Applied Refactorings and Comparative Analysis - This link contain all refactorings applied with the annotations in some ajusts make by Eclipse IDE and a summarization of the refactorings applied; and also the comparative analysis between original and refactored versions

Bad Smells Introduced and Removed by Refactoring

Steps

Result Contrast Empirical Study and SLR

Steps

Publications

  • Silva, Cleiton; Santana, A.; Figueiredo, Eduardo ; Bigonha, Mariza A. S., Revisiting the Bad Smell and Refactoring Relationship: A Systematic Literature Review. 23rd Iberoamerican Conference on Software Engineering (CIbSE), Experimental Software Engineering (ESELAW). Curitiba (online), Brazil, 2020. Page Link

  • Tavares, Cleiton; Bigonha, Mariza; Figueiredo, Eduardo, Analyzing the Impact of Refactoring on Bad Smells (short paper). Proceedings of the 34th Brazilian Symposium on Software Engineering (SBES), pages 97-101. Natal (online), Brazil, 2020. https://doi.org/10.1145/3422392.3422408. Page Link

  • Tavares, Cleiton; Bigonha, Mariza A. S.; Figueiredo, Eduardo, Quantifying the Effects of Refactorings on Bad Smells. 10th Workshop on Theses and Dissertations - Master Students (WTDSOFT). Natal (online), Brazil, 2020.

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