I fixed it in a new PR that has correct attribution to you as a Co-Author:
https://github.com/discourse/discourse/pull/19335
To make our test suite not depend on a working internet connection (and working Youtube), we stub all internet requests by making those call return with a cached response. the onebox_response function will call the file with a matching name as the parameter passed from the folder discourse/spec/fixtures/onebox at main · discourse/discourse · GitHub.
I added a new .response file for a shorts so we have a good test, but that was all that was necessary for this. Thanks for the PR!