Writing traditional arrange-act-assert tests for performance is difficult: what do you assert on? In this screencast, we'll look at a simple method for doing ongoing performance analysis: running small benchmarks across the commits in version control. With a few lines of shell scripts and RSpec, we can get a visual sense of our system's performance over time, allowing us to catch performance problems before they make it to production. The run-command-on-git-revisions script used here is available on GitHub.