In this paper, we present a boundary scan based system test approach for large and complex electronic systems. Using the multi-drop architecture, a test bus is extended through the backplane and the boundary scan chain of every board is connected to this test bus through a gateway device. We present a comprehensive system test method using this test architecture to achieve high quality, reliability and efficient diagnosis of structural defects and some functional errors. This test architecture enables many advanced test methods like, embedded test application for periodic system maintenance, high quality backplane test for efficient diagnosis of structural defects on the backplane, in-system remote programming of programmable devices in the field. Finally, we present a novel fault injection method to detect and diagnose various functional errors in the system software of an electronic system. These methods were implemented in various systems and we present some implementation data to show the effectiveness of these advanced test methods.