First, you would need to have a QuickBooks Online Test Account. Here is the link that show you how to create the QuickBooks sandbox account to test: https://developer.intuit.com/app/developer/qbo/docs/develop/sandboxes
Click on the first link ‘Create and test with a sandbox company’ and it’ll walk you through the set up. According to QBO, they should have some sample data in there to start off with.
Create an Authorize.Net sandbox account if you don’t already have one. You can create one here: https://developer.authorize.net/hello_world/sandbox.html.. Please be sure to gether the API Login ID and Transaction Key when complete as these will be needed to install EzPay. If you have trouble capturing these, you can find/or recreate them here: https://ezpayhelpdesk.freshdesk.com/support/solutions/articles/33000168691-how-to-obtain-your-authorize-net-api-login-and-transaction-key
Once you get this set up, you’ll need to go to https://sandbox.myezpay.com/ and walk through the wizard connecting the ANet sandbox.
You should now be able to test MyEzPay Online.