Currently PayPal Express can be implemented as Express Checkout Shortcut (ECS) or Express Checkout Mark (ECM).

It is mandatory to send the shipping address in the “authorization” or “preauthorization” request. Otherwise you don’t have the PayPal sellers-protection. Use shipping address also as billing address. Your customer should have an option to change billing address while checking out. If you want to use multi partial capture, you need to set settleaccount to yes or auto, to be able to send another capture afterwards. Do not use settleaccount=no.

PAYONE platform must be allowed to use your PayPal-account.

Please find here how this is configured within PayPal administration:

How to Configure Your PayPal Account for Processing over the Payone Platform

Test data is created individual in a Sandbox Account which is connected to your PayPal account.

Under https://developer.paypal.com you can login to the dashboard and create your own various Sandbox test accounts with different scenarios (buyer, seller, countries, currencies, account types, payment methods etc. ) 

You can now test payment through your e-commerce application (for example your shop). You will need to mark the "mode" parameter with the value "test" (mode=test). Use the buyer test account that you have just created as the test customer.

If you want to make End-to-End Tests with PayPal, you'll also need a Sandbox Merchant Account. Please contact our Merchant Service so we can store the Sandbox Merchant Account details in your PAYONE Account.