We need to build a set of tests that exercise the 'elements' target for scroll-snap-points. Right now, this code is only rarely exercised and could easily be broken as we do more development.
While working on https://bugs.webkit.org/show_bug.cgi?id=142523, I just discovered that scroll snapping with elements in the mainframe for OSX seems to be broken on the current tip. I've added a test case that exhibits this issue.
Created attachment 255692 [details] 3x3 grid of large elements in the mainframe with scroll snap coordinates. Scrolling in the mainframe of this page should trigger scroll snapping.
I did some digging through the history of the specification and I think that all captured snap points exercise the "elements" path. I have also recently imported all of the WPT scroll-snap tests, so I think we have some decent test coverage now. I'm going to resolve bug, but feel free to reopen.