One of the issues of maintaining a CI pipeline is how to know if the various components: (a) source repository (b) build farm (c) artifacts repository (d) test farm – are working at any point in time since when developers want a build, they do not want to have to be blocked by problems with the pipeline.
One way to check this is to have regularly scheduled build/test runs on very simple apps with no major external dependencies.
I had created just this a while back called the Canary App (see https://github.com/foohm71/Canary-iOS and https://github.com/foohm71/Canary-Android) just for this. The contain some simple tests that do not utilize any network so test should always pass. Currently UI tests are only in UI Automation (iOS) and Robotium (Android).
The nice thing about having regularly scheduled runs is that if the build/test run fails, you can check to see which part of your CI pipeline is having issues and immediately address them before a critical build kicks off.