Hardware Simulation and Mock Interfaces Questions

Approaches to building and testing firmware without direct access to physical boards. Cover register and peripheral simulation, emulator and virtual platform usage, creating mock interfaces and test doubles for sensors and actuators, designing hardware abstraction layers to enable host based unit testing, hardware in the loop strategies, fault injection techniques, and continuous integration pipelines that exercise firmware tests. Discuss trade offs between fidelity of simulation and cycle time to maintainable, reliable test suites.