When developing operating systems and other hardware-related functionality, many critical behaviors can only be properly tested on real hardware. Drivers, firmware interactions, and peripherals are difficult, sometimes even impossible, to test reliably in a virtualized environment. At the same time, the NixOS integration test framework provides a developer experience that is invaluable for reproducible integration testing, but is limited to virtual machines.

In this talk, we present an extension to the Nixpkgs integration test framework that allows the familiar test driver running inside its QEMU VM to control a real machine over the network. This is enabled by a REST-based backend that manages provisioning, booting, and interaction with physical devices.

We will discuss the overall architecture, the integration with the test framework, and what it takes to enable reproducible Hardware-in-the-Loop test automation.