As a fairly recent feature in goals, you can verify a goal setup before saving.
This is particularly useful for the Destination URL and Event goal types, since a typo or a small regex error could prevent any goals from being registered.
It’s important to recognize that your goal setup could still be faulty even if verification shows a percentage match, since an incorrect goal setup could be matching some pageview or event data, but if the verification process yields a 0% match, you can be fairly certain that your goal is set up incorrectly (or that you can expect at least week-long gaps in goal completions going forward).
Goal verification goes back seven days. To see how your Destination URL goal would have performed over a longer period, you can apply the URL as a table filter in the Pages report.