RailsConf 2024 - From slow to go: Rails test profiling hands-on by Vladimir Dementyev 

Ever wished your Rails test suite to complete faster so you don’t waste your time procrastinating while waiting for the green light (or red, who knows-it’s still running)? Have you ever tried increasing the number of parallel workers on CI to solve the problem and reached the limit so there is no noticeable difference anymore?
If these questions catch your eye, come to my workshop on test profiling and learn how to identify and fix test performance bottlenecks in the most efficient way. And let your CI providers not complain about the lower bills afterward.
I will guide you through the test profiling upside-down pyramid, from trying to apply common Ruby profilers (Stackprof, Vernier) and learn from flamegrpahs to identifying test-specific performance issues via the TestProf toolbox.