I'm working in image processing (mainly OCR) and I wonder how I should integrate unit tests in my development.
I'm already using unit tests for more "common" type of code but when dealing with image processing code I'm not sure how to deal with it. This kind of code always need some image data input/output and mocking this is not obvious. For now I'm mostly doing integration tests but they take a while to run and I would like some ideas on how to break down this kind of code into unit tests so that I can run them more quickly.
Edit: Analyzing a character can go through many steps involving multiple rotation, scaling and morphological operations. These steps change often as the algorithm is being developed. Thus the input and expected output can evolve a lot while testing. Each character can be 100x100 pixels so hardcoding them in the code or working with generated data is out of question.