There are two common ways to handle scope discussions. You can handle it in the "theoretical space", that is, by noting the kind of question on Meta in advance and having a discussion ahead of time. Or, there is the "practical space", in which you run into the question on the main site and it segues into a Meta discussion due to opposition. Over the course of the site growth, you will generally encounter both rather equally, but usually you only intentionally run into the former.
During the beta phases, it's an acceptable thing, as Benjol notes, to test the waters by posting such a question. However, it's highly recommended that you never ask a question for the sake of asking. That is, if you want to test if a particular question type or scope is appropriate for the site, ask if it's something you're actually interested in knowing the answer for and believe belongs on the site. When making a point, make a point with something you care for.
If you are not vested in the question, it is probably more useful to just discuss a theoretical example question on the Meta (basically post a sample question body along with your summary of what the question type is). Otherwise, even if the resolution of the Meta discussion is in the question's favor, you'll be left with a question that you don't care for, and that's not often a useful expenditure of people's time. On the flipside, if it's something you don't think belongs, or to which the conclusion is that it doesn't belong, having to clean up and delete the "sample question" is just extra work that isn't necessary.
Beta is where it is important to hit the most kinds of question types so you can concretely shape your scope, especially before you launch into public beta. Asking good questions, if being constructive, is very conducive to helping shape scope. Once you exit beta into a graduated site, generally these questions that inspire revisiting your scope will come over the natural course of the site and will not need forceful evocation. And if you do have concerns about a potential problem, at that stage it is usually more productive to discuss it on the Meta site directly.