Sandbox Environment Usage for Testing Shipping callback

Hello,

I am trying to integrate the Web Shipping Javascript SDK in our platform, and I'd like to test the shipping callback, I already have a sandbox account but I cannot test the shipping because I don't have a carrier setup, so my questions are:

-Are there any test shipping carrier data that I could use to setup a fake shipping carrier account?
-If I setup a valid shipping carrier that is used in live shiprush account will that cause any charges?
-Is it possible to use the sandbox to simulate shipments and get the OnShipmentCompleted Callback called without having the shipping carrier setup?
-If not do you have a sample data structure of the information returned in the OnShipmentCompleted callback?

Thanks for your help.