Test pre-authorization of credit card using pay pal.

Knowing what pre-authorization is the key. So, understand what is it if it's new word.
1. Login to pay-pal sand box account > click on "Test Account" and make a note of the total balance amount.
2. Login to the site and place an order. Check pay-pal > Initial amount must be retained. And confirm the amount on hold(Under review status).
3. On site, place enough quantity of items to trigger the release of pre-authorization.
Then check paypal > all of the order amount must be summed up to the initial balance.

For now, this is it.
Will describe in depth when I find sufficient time.