Test URLs
Firewall
How to configure firewalls - Do you have a strictly configured environment? Take a look here to get proper settings for your firewall/web services. Link to faq
Payment Management in Resurs Merchant Portal
You can see the generated invoice for payment method INVOICE in Merchant Portal, since the invoice is not sent by mail in the test-environment.
MAPI / Merchant API
See MAPI documentation here for more information.