As has been mentioned already a Wine regression test would be ideal here. In this case it's slightly tricky as you're testing a graphical component however it's still achievable. I'd suggest you add a test to gdi/tests/pen.c that creates a 1bpp dibsection, selects that into a dc, draws lines on it with a selection of pens in different graphics modes. After each line get the bits from the dibsection and compare them to what you've found out Windows gives you and then clear the dibsection before drawing with the next pen/graphics mode. If you need any help with this then please let me know.
Huw.