A data processing system replicates the operation of a target graphics processor using a graphics processor of the data processing system. A driver for the target graphics processor converts higher level commands and program expressions intended for the target graphics processor into lower level control data and instructions suitable for use by the target graphics processor. The lower level control data and instructions suitable for use by the target graphics processor are then converted into lower level control data and instructions for the graphics processor of the data processing system. The graphics processor of the data processing system then generates an output using the lower level control data and instructions for the graphics processor of the data processing system. The data processing system provides an efficient and comprehensive testing environment when replicating the operation of the target graphics processor.