Some time ago we decided to expand our pool of Android devices. These are used in our Continuous Integration (CI) pipeline. But running our tests we noticed a peculiar behaviour: Only 3 devices would execute the suite while the rest would wait. Then as soon as a device finished one of the waiting devices would proceed with the test suite.

We are developing Apps for Android and one important aspect of our pipeline is automated device testing using Espresso. My co-worker recently had to debug an Android test that would fail on only one of our various devices.