This diploma thesis deals with the design and implementation of a computer-controlled device for testing gas boiler control units, especially in the development phase. The reason for creating a test facility is the inadequacy of older test systems and the automation of existing testing. The test device in development consists of individual different cards. Each of the cards inserted into the motherboard performs its function in the system. Each of the cards has a special functionality which simulates the real conditions of the developed product. The basis of most cards is a microcontroller with a Cortex-M core, which communicates with the connected computer using the MODBUS protocol on the RS-485 communication interface. All cards on the bu...