Due Dates Lines Test horizontal and vertical lines, positive and negative slopes, and slopes of absolute value greater than and less than one. Curves For all conic sections, including ellipses, you may require that the major axis be horizontal or vertical. I.e. you get full credit even if you can't display them at arbitrary angles.
Areas Make sure boundary fill can replace multiple colors stopping at the boundary color.
Test scan fill routines with areas that include horizontal and vertical line segments.