In a dye transfer printer, a donor web having successive dye transfer areas and opposite longitudinal edge areas alongside each one of the dye transfer areas is subjected to a longitudinal tension when the donor web is advanced in the printer. A read light travels while spreading in the core and scatters and interferes by the data image, and data is reproduced from a data reproduction light generated by this scattering and interference. The system is able to automatically generate test code to exercise components of the middleware using information about these components that would otherwise be available to the application under test.