Created attachment 107407 [details]
reduced version of the bug.
I am assigning a transition to run on the hover even to an after pseudoelement, but the transition doesn't work at all. Instead, it instantly moves to the end point.
pseudoelements are special - they do not appear the DOM, DOM Events can't reference them as targets, and they don't expose a computedStyle. It's not clear that transitions *should* work on them.
OK so after discussion with another CSS WG member it turns out that transitions definitely should work on ::before and ::after pseudoelements, so this is a valid bug.
Animations also do not work.
*** Bug 69927 has been marked as a duplicate of this bug. ***
This is duplicate of 23209
*** This bug has been marked as a duplicate of bug 23209 ***