What kind of test account do I need to open with Paypal and Authorize.net to perform some tests without using a live credit card?
In order to test the credit card processing in the cart or registration modules without actually submitting real CC data, you can create a PayPal Sandbox account. This requires that you go to an entirely separate PayPal site and create a new and separate account from your main PayPal business or WPS account. Here's the site: http://developer.paypal.com.
For Authorize.net you can apply for a test account here http://developer.authorize.net/testac.... When you have your authorize.net test account enter it under gateway section in the module settings and check the test mode checkbox.