All align.m programs were tested on the following synthetic image pairs:
 
 

		Image with itself. Shift is (0,0)
		Shift is exactly 3 pixels horizontally, 5 pixels vertically.
		Shift is exactly 3.5 pixels horizontally, 5.5 pixels vertically.

Excluding the first image pair (the identical images), each image pair was aligned twice - once with each image as the reference image.

The images posted for the exercise were also tested, using each image, in each image pair as the reference image.