We have info.magnolia.imaging.AbstractImagingTest#KEEP_GENERATED_FILES_FOR_INSPECTION, but some test methods bypass it: AbstractImagingTest#write() method use it, but tests using AbstractImagingTest#newOutputFile() directly do not.
We should probably:

• ensure consistency (although some generated images are probably never meant to be manually inspected, so maybe we need a flag of sorts)
• simplify output methods (there are too many for test developers to choose from)
• make that flag changeable without modifying code (perhaps a profile in the build)