Continuous Integration, CI, pipelines are widely used to ensure code quality through automated builds, tests, and static analysis. While prior work has examined the overall energy consumption of CI workflows, the energy consumption of individual phases remains unexplored. This study investigates the energy consumption of static analysis using SpotBugs across 10 open-source Java projects. SpotBugs was selected based on a systematic literature review, its widespread usage, and its configurable effort levels. Energy measurements were conducted for the four SpotBugs effort levels on both Gradle and Maven projects. The results show that energy consumption differs significantly between efforts, with the biggest differences between Min and Less, and Less and More. Performance analysis shows that increased effort improves bug detection in projects, but comes with a higher energy consumption. The most efficient effort is Min, which found the most warnings with regards to energy consumption.

Test Prioritisation (TP) is one among many dif ferent methods to optimise pipelines in Continuos Integration (CI). However very little research has been performed on the energy usage of this process. This paper documents the simulation of TP on mul tiple Java open source projects and presents the en ergy consumption of this part of the pipeline. The results of the experiment show that the costs of per forming this CI technique under realistic conditions outweigh the benefits in terms of energy spending. Other Ci optimisation processes such as Test Selec tion may prove more valuable and combining them with TP might be redundant.

Within the context of Continuous Integration, pipeline checks must run fully and continuously. Some of these checks are done through Static Analysis Security Tools (SAST). However, they are costly, with a significant, non-negligible environmental impact. In this report, one of the most used SAST tools (SpotBugs with the Find Security Bugs plugin) is analyzed, and its average consumption costs are calculated. Additionally, optimizations are explored that would serve to reduce overheads and, thus, environmental impact. It was found that the 3 Spotbugs configurations analyzed (Default, High Effort, Low Threshold) lead to an increase in consumption rates only in specific situations. These are namely either very large projects configured through Gradle with the High Effort Configuration (exhaustive, lead to an increase in cost of over 7%); and small to medium sized projects configured through Maven when running with the Low Threshold configuration (reports low-priority issues, lead to an increase in costs of 1%). This means that for small to large Gradle projects, and large to very large Maven Projects, exhaustive methods are recommended since the tradeoff between energy costs and higher efficiency is negligible. Additionally, it was detected that for similarly sized projects running SpotBugs+FSB, Maven consumes over 100 times as much energy as equivalent Gradle Projects.

Continuous integration pipelines execute auto-mated tests on every commit, consuming substan-tial energy. Batch testing, which groups multiplecommits into a single test run, has been shown toreduce test executions in simulation studies, but noprior work has measured whether these reductionstranslate into actual energy savings.This study measures CPU package energy con-sumption of CI builds under a baseline run-all ap-proach and two batching strategies (BatchStop4and linear-4 lwd) across eight open-source Javaprojects. BatchStop4 achieves energy savings be-tween 57% and 88% (mean: 80.3%), while linear-4 lwd achieves savings between 59% and 94%(mean: 85.2%). Energy savings correlate almostperfectly with time savings (r >0.99), and base-line failure rate strongly predicts achievable sav-ings, while CPU utilisation shows no significant re-lationship. These findings provide empirical evi-dence that batch testing effectively reduces the en-vironmental footprint of continuous integration.