Here's a little taste of what BitmapCompare can do for you. No only can it do slightly fuzzy comparisons that filter out the noise introduced by, say, a lossy compression algorithm. It can also tell you what is wrong with an image.
Expected:
Actual:
Actual marked up with errors (different kinds of mark up):
So when you are using it in a test, you assert on whether or not the images are equal and you report the marked up actual to cue you in on what's wrong.
