Modern vehicles use Electronic Control Units (ECU), connected via Controller Area Network (CAN) to perform functions. Many of these functions are distributed across several ECUs. This network interconnection enables the sharing of sensors, calculated information and actuators. As new functionality is added, the number of ECUs and their complexity increase.This paper describes the values and possibilities of a Hardware-In-the-Loop (HIL) based Integration Lab, which enables a wide range of automatic tests to be performed on networked ECUs.The Integration Lab is the complex rebuild of a Scania truck/bus, containing the ECU superset, for connecting and testing networked ECUs. It involves more than 30 ECUs and eleven CAN networks.