"Designing Embedded Systems for Testability: Building Hardware and Firmware That Can Be Verified, Diagnosed, and Maintained" Embedded systems are often designed with functionality as the primary goal. The processor must run the application, sensors must deliver meaningful data, communication interfaces must exchange messages, and actuators must respond within required timing limits. However, a system that works is not automatically a system that can be tested, diagnosed, manufactured, or maintained effectively. As embedded products become more complex, testability becomes a core engineering requirement. Modern embedded systems may include microcontrollers, external memories, analog front ends, wireless radios, power electronics, secure bootloaders, RTOS-based firmware, safety mechanisms, and multiple communication buses. When a failure occurs, engineers need more than the observation that "the product does not work." They need evidence that identifies which subsystem failed and why. Designing for testability means building hardware and firmware so that important internal behavior can be observed, controlled, stimulated, measured, and verified. A testable embedded system is easier to bring up, easier to debug, easier to manufacture, easier to validate, and easier to support in the field. Most importantly, testability must influence the architecture from the beginning. It is difficult and expensive to add meaningful visibility after the schematic is complete, the PCB is routed, and the firmware architecture is already tightly coupled to hardware.