My worst technology experience of all time was maintaining support for a Zebra label printer in VB6. I can assure you that the users of these printers had maybe 1% the cortisol response I did when something went wrong.
Designing software for a printer means being a very aggressive user of a printer. There's no way to unit test this stuff. You just have to print the damn thing and then inspect the physical artifact.
A million years ago I worked on some code which needed to interface with a DICOM radiology printer (the kind that prints on transparency film). Each time I had to test it I felt like I was burning money.
