You can create your Reverb Sandbox account here: https://sandbox.reverb.com/signup
The Sandbox is just like Reverb Production but will allow you to experiment with creation and deletion of listings without impacting your production listings. Please ensure your shop settings and profile are setup before getting started.
Our Swagger documentation can be found here: https://reverb.com/swagger#!/
You can default to PayPal/Reverb Bucks for your payment settings found in Shop Settings -> Policies.
You can use 4111 1111 1111 1111 for the credit card number, 10/2020 for expiration, and 737 for the CVC to buy any of your items for testing purposes (can be found in Shop Settings -> My Bill).
Once an item is purchased you can mark the order paid/shipped as necessary through your seller dashboard.