How to test Membership while Wordpress site is offline?

I should mention again that my site is currently offline for development using Mamp.

Is there a way I can 'pretend' to be a visitor and sign up to a subscription on my site?

Right now, if I tell Wordpress to view my website as a visitor, all I can do is 'buy' and 'pay' for a subscription but I can't see any kind of form to fill in with details.

Is this the experience the user will get, literally just a payment? Or do you know where exactly I can find and how I test filling in a form with information such as username, email address etc?