Sandbox credentials?

Developing a new integration via the javascript API to my shiprush/shiprush web.

I can get to the Web Shipping Javascript SDK by ShipRush page with the Demo option to test it out. It has a checkbox for Sandbox. If I check that box, my regular shiprush credentials do not work. Do I need to get sandbox credentials for testing? If I uncheck the Sandbox option, my production credentials do work.