In my recent article Eco Worriers: Saving the Planet, One Unoptimized Website at a Time for the fantastic annual Perf Planet advent calendar, I mentioned how I created a Private WebPageTest setup to use my own custom test agents, which were configured to use an extra Lighthouse plugin (The Green Web Foundation’s "greenhouse").
In this article I’ll show how to create custom WebPageTest agents, and how to configure your Private WebPageTest instance to use these instead of the default test agents.