Test Smell: A Parasitic Energy Consumer in Software Testing

TL;DR

This study is the first to quantify how test smells affect energy consumption during software testing. By combining large-scale data mining on 12 Apache Java projects with a practitioner survey, the authors show that smelly portions of test code consume more energy, quantify the impact across smell types, and demonstrate energy reductions after refactoring. They also reveal a gap in developer awareness and organizational guidance regarding energy-aware testing practices. The findings underscore the need for energy-focused testing guidelines and tooling to reduce waste in large-scale CI pipelines and daily development workflows.

Abstract

Traditionally, energy efficiency research has focused on reducing energy consumption at the hardware level and, more recently, in the design and coding phases of the software development life cycle. However, software testing's impact on energy consumption did not receive attention from the research community. Specifically, how test code design quality and test smell (e.g., sub-optimal design and bad practices in test code) impact energy consumption has not been investigated yet. This study examined 12 Apache projects to analyze the association between test smell and its effects on energy consumption in software testing. We conducted a mixed-method empirical analysis from two dimensions; software (data mining in Apache projects) and developers' views (a survey of 62 software practitioners). Our findings show that: 1) test smell is associated with energy consumption in software testing. Specifically smelly part of a test case consumes 10.92\% more energy compared to the non-smelly part. 2) certain test smells are more energy-hungry than others, 3) refactored test cases tend to consume less energy than their smelly counterparts, and 4) most developers lack knowledge about test smells' impact on energy consumption. We conclude the paper with several observations that can direct future research and developments.

Figures (7)

• Figure 1: An Example of Smelly Test from org.apache.commons.lang3.IntegerRangeTest class in Apache Commons-Lang.
• Figure 2: Overview of The Study Design with Experimental Phases
• Figure 3: Overview of Manual Refactoring of Test Smells and Energy Difference Computation
• Figure 4: Test smells refactoring in testSingleQuoteMatcher() from org.apache.commons.lang3.text.StrMatcherTest.
• Figure 5: Mean ($E_{LOC_{smell}}$) and Median ($E_{LOC_{smell}}$) energy consumption with Test Smells Count ($SC$) in Group size 5. Energy Unit Measured in Joules.