Today, there is no way to easily test a Subscription Form/Center. You have to publish it and push it through a Journey. I'd like to be able to test the Subscription Form/Center using my own account or specifying an account without having to push it through a Journey. Let me just open the form or page and test it after picking who I am like you do to test emails.

Under Review
Ideas Administrator

Thank you for your feedback. We are going to review this idea for possible implementation. Sincerely, Petr Jantac, Microsoft