Test smell: A parasitic energy consumer in software testing

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 aims to examine open-source software 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 perspectives; software (data mining in 12 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, the smelly part of a test case consumes 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 (45 % of the survey respondents) lack knowledge about test smells’ impact on energy consumption. Based on the results, we emphasize raising developers awareness regarding the impact of test smells on energy consumption. Additionally we present several observations that can direct future research and developments.