There are many of my customers looking for ways to test their SaaS offerings when receiving notification from the Azure Marketplace. I understand the problem, given that currently, there is no simulated payload on the AMP Partner Center portal (yet).
To help solve the problem, I developed a Command Line Interface (CLI) to help these customers simulate any payload allowed through the Azure Marketplace.
The tool provides ways for the tester to enter a subscription ID, plan ID, action, HTTP status, and other important payload parameters to help verify their SaaS App respond properly to situations like subscription cancellations, plan changes, and others appropriately.
In the future, I am planning enhancements like adding files as inputs and parameterize the commands to help developers run automation tests.
The code is Open Source under the MIT license and can be found here if you are looking to publish an offer to the marketplace.