The DRT output that most of the layout tests rely on doesn't include any information about transforms. This makes it hard to use DRT output to test the effects of transforms. I'll attach a test that shows this.
It would be good if layer output included the transform (affine matrix), and a root-relative bounding rect.
Created attachment 22212 [details]
Testcase for which DRT does not reveal the bug
This testcase (from bug 18885) requires visual inspection to see the failure, but DRT could be enhanced to detect the problem.