You can test fire the event by using this link: https://pubsubhubbub.appspot.com/publish

1. Publish video to your channel.
2. Check Atom feed: https://www.youtube.com/feeds/videos.xml?channel_id=<CHANNEL_ID_STARTING_WITH_UC>
3. https://pubsubhubbub.appspot.com/publish Publish the event.

Then you can test to see how your callback is receiving data from the YouTube.

Yet, you won't be able to know when the post call was made for the newly uploaded video since this is manually triggered. New upload trigger seems to be flaky: https://issuetracker.google.com/issues/204101548.