While testing the Polygon() function for my bug report - https://bugs.winehq.org/show_bug.cgi?id=36891, I used a test program that performs a Polygon() operation on a memory device context, and then saves it to a bitmap - i.e. a *.bmp file.
I then compared the bitmaps produced under Windows and Wine using a program I wrote in Qt, that just compares width/height, and then makes a pixel-by-pixel comparison (and the Polygon() function did indeed produce a slightly different bitmap).
Since this process can be easily automated, I'm wondering if such a framework is already being used? If not, I could probably make a sample test program and image comparison tool, if anyone is interested.
It would be fairly easily to spot all kinds of bugs in the drawing functions using such a testing system.