At PlanetScale, our backend API is built with Ruby on Rails. It’s a pretty standard Rails application. We use minitest for our test suite and FactoryBot for creating test data. Our team has invested time into keeping our test suite fast as our app has grown. When working locally, we run individual tests or just one test at a time to keep it efficient. We've also improved the parallelization of tests on CI with 64 core machines, which significantly reduced our test suite running time from around 12 minutes to 3-4 minutes. By auditing and optimizing our factories using FactoryBot, we were able to create fewer objects, reducing our test run time further to around 1 minute. Our approach has improved team productivity by providing quick feedback cycles for feature development.