In the past year at SoundCloud, we've improved our CI from a single machine running our limited unit test suite to several machines running a linter, unit tests, acceptance tests and building several versions of our app including the AppStore version for every commit. This enabled us to move away from pull-requests and code reviews and use trunk based development and pairing, as well as scale the team from 3 to 7 developers.
We've stopped relying on Xcode Schemes for builds, we're using instead command line tools and compile-time parameters to automatically build internal versions of our app and distribute it internally.
In order to make our release process more reliable, the AppStore version of the app is created by re-signing an AdHoc build. This enables us to test the exact same binary that will be submitted to the AppStore.
This talk will focus on 3 areas of our continuous integration: testing, building with user defined build settings and signing apps.