Abstract: Fault simulation apparatus 10 that simulates faults in a piece of equipment 12 coupled to a VME bus 11. A computer 30 generates user defined faults that are to be simulated and provides initialization data and control signals to VME fault insertion apparatus 20 coupled between the VME bus 11 and the piece of equipment 12. The VME fault insertion apparatus 20 comprises bus fault logic 15 interposed in request and acknowledgment signal lines and data lines, that intercepts normal bus data transmission, and inserts user-defined data into bus data that is transmitted to the equipment 12 to simulate failures therein in response to fault definition signals 23.