You don't need to do a test post. Any previous post you've made will update with your new siggie. You can just go back to one of those and see how things look. And you don't need to repost. The original post will update with each picture change you make.
Re: test
Allergic to soy, oat, egg, peanuts, and tree nuts
Allergic to soy, oat, egg, peanuts, and tree nuts
Allergic to soy, oat, egg, peanuts, and tree nuts