We often get asked what is the best way to test your site when you have everything setup to ensure payments are working and the processes are working.
In order to effectively test your site membership once it is all setup, you need to make a test purchase. This would require you to go through the process as a real customer - and test using a credit card or test using another Paypal account if you're using Paypal standard as they do not allow you to send funds to yourself
It's important to test the "live" process because this may differ from any sandbox (testing) setup. What we usually recommend doing is just modifying your order buttons or forms to set the price to $0.01c so that you can ask a friend or colleague to test without the risk of high charges if it is a higher priced item. You can of course instantly refund any order inside your paypal once you have completed the order - and the funds and any Paypal charges are refunded anyway
Unfortunately there isn't a more elegant solution to this but this is simply a limitation of Paypal and most payment systems that do not provide a test credit card (Stripe is the only provider that gives a test credit card number for testing and then you can switch to Live mode once you have tested).