A detailed case study of building a fully automated hardware-in-the-loop end-to-end test system for laptop OS releases. The system physically controls display connections, laptop lid, docking station, and webcams to verify display resolution and video frame drop detection without modifying the product under test. OpenCV with ArUco codes was used to analyze webcam photos of physical screens to confirm correct display resolution and detect dropped frames in video playback. NixOS was used to manage the complex multi-machine configuration reproducibly. Key learnings include the critical importance of distinguishing infrastructure failures from product failures, robust error handling in hardware-coupled systems, and how testability must be designed in from the start at all integration levels.
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