The title of this thesis is a PWB Testing System. The testing system is done primarily for Xemec LTD's service, but will be given for the use of circuit boards assembler in future. The testing system is intended to expedite and facilitate functional testing of PWBs as well as finding and locating faults. Thesis was carried out as a project work in the spring of 2010. The project included a system requirements definition, software and electronics design, implementation and testing. The testing system includes a microcontroller downloadable test program, required additional electronics and user interface application for PC. The system has been designed so that it uses PWBs own electronics as much as possible to make the additional electronics as simple and reliable as possible. The test software have been made as simple as possible and fast, when a small computational power of its own microcontroller action does not slow down the test. Most of the activities of the software has tried to implement to the user interface application. Software is written in C and Python programming languages. Testing electronics contains mostly discrete passive-components. Testing electronics prototype has been built by hand-solder components, but will be designed and manufactured for surface-mount components in future to get the PWB integrated in a smallest possible space. The result of this project is a working testing system, that tests PWBs I/O-connections, locates faults and saves test results to a text file. The interface application is ported for Linux, and Windows operating systems.