Having lots of tests is great, but it also takes a long time to run them on every change. While this gives us confidence, it also slows down feedback loops, sometimes dramatically. But what if we could fail faster? Instead of blindly executing the entire test suite, we identify which tests actually exercise the modified classes, using bytecode instrumentation. These tests are executed first, giving you relevant feedback as quickly as possible. We’ll introduce an experimental open-source tool that integrates with Maven and JUnit that brings this idea to life. Along the way, we’ll also look at how this works under the hood, using instrumentation techniques to track which classes are actually used during tests. If you care about developer productivity, fast feedback, and smarter CI pipelines, this talk is for you. Johannes Bechberger Johannes Bechberger is a JVM developer working on profilers and their underlying technology in the SapMachine team at SAP. This includes improvements to async-profiler and its ecosystem, a website to view the different JFR event types, and improvements to the FirefoxProfiler, making it usable in the Java world. He started at SAP in 2022 after two years of research studies at the KIT in the field of Java security analyses. His work today is comprised of many open-source contributions and his blog, where he writes regularly on in-depth profiling and debugging topics, and of working on his JEP Candidate 435 to add a new profiling API to the OpenJDK.
Java User Group Karlsruhe