@jklymak Is an image test really necessary (I think that we are currently trying to avoid as much as possible these kinds of test, that are bloating a bit the git historic)? Couldn't one simply test that after init the z-order of the Shadow instance indeed smaller than the z-order of the parent patch?

@afvincent I guess I was also worried about the transform issue in #9426 but maybe both can be finessed without an actual image test? But sure, just checking that the zorders are ordered properly is great!

I think that the best way is (as mentioned in a few other places) to have an "as if" test: generate figure 1 with the shadow created before the rectangle is added (the previously failing case) and figure 2 with two manually positioned rectangles with the correct zorder and correct positions. It's a bit tricky to write though and I'm fine with taking care of it in #9426 (after this PR gets merged).

Thanks a lot @clintval!