Currently the only way to test Deauth is in your production environment, or to change the Deauth url to your dev environment and install the production version of your app, then uninstall it.
Check out my post here for more in depth instructions on how to test it deauth:
Does the App needs to be published in the Marketpalce for the Deauthorization Event Webhook ro be triggered?
As of now I’m working on an App which hasn’t been published yet (I plan to send the request of approval soon) (even though it has a shareable URL) but I don’t manage to trigger the webhook (by uninstalling the App from the list of installed apps).
No, you can test by installing the production version of your app as see on the “Submit” page, and then uninstalling it on the installed apps page.