How GitHub reduced testing time for iOS apps with new runner features

The GitHub iOS team reduced their CI testing time by 60% (from 38 minutes to 15 minutes) by switching to M1 macOS runners and splitting their test suite into separate jobs for each of the app's ~60 modules. This modular approach allows for faster feedback loops, with some small modules completing tests in 2-3 minutes. They also analyzed CI performance by dividing build and test steps and noted that the use of Apple silicon aligns CI environments with local development machines, enabling more confident local fixes.