N/A, as of now. There is no staging environment with a public URL so not sure how to test these changes yet.
Once there is, though:
- The [[ https://cards-dev.twitter.com/validator | Twitter Card Validator ]] tests how URLs look on Twitter Cards when Tweeted.
- Facebook has its own [[ https://developers.facebook.com/tools/debug/ | Markup Tester ]] to see how URLs look on Facebook posts when shared. I'm not sure if this works for Messenger as well, but that can be tested by sending a message to someone.