1. A computer-implemented method for generating stochastic PDL test inputs, wherein the method comprises: modifying at least one PDL file, by performing at least one of the steps of: replacing existing text data in the PDL file with randomly generated text data; or replacing values of parameters associated with at least one existing graphics object in the PDL file with randomly generated parameter values, or replacing values of parameters associated with at least one image object in the PDL file with randomly generated parameter values, or replacing values of parameters associated with graphical combining operations for at least one image or graphics object with randomly generated parameter values; and storing the at least one modified PDL file.