Ability to integrate with Paypals' Sandbox site
To do complete end to end testing of Paypal integration it would be very helpful if an option under "Payment Settings" was available to indicate whether to use production paypal (paypal.com) or test paypal (sandbox.paypal.com). This option would require that two sets of API credentials be kept - one for paypal.com and one for sandbox.paypal.com.
One large benefit of using sandbox.paypal.com is that NO money is actually involved in the testing transactions. The paypal sandbox is setup exactly like the production paypal site except for the use of test accounts that automatically generate credit card numbers, expiration dates, bank accounts with routing numbers, etc. The dollar values that have been placed in your wild apricot hosted website do not need to be changed. All that changes is where to point the system for transaction processing.
Dmitry Buterin commented
Frankly, I am not that impressed with PayPal sandbox myself - I find it flaky - some technical things work differently in the sandbox and live environment. Testing PayPal integration can be done with 1 dollar donation using the live account - and it can be easily refunded too.