IMO if your implementation is that unstable (you mentioned the UI/workflow changes fast) it isn't worth writing a test for it, but also, I don't think it shoud be released to end-users because (and this is making a big assumption, granted), it sounds like the product is trying to figure out what it wants to be.

I am a proponent of having the UI/UX design of a feature be done before development gets started on it. In an ideal XP/agile environment the designers and developers work closely together and constantly iterate, but in practice there are so many variables involved in UX design and so many parties that have an opinion, that it'll be a moving target in that case, which makes development work (and automated tests) an exercise in rework.