Idea: Test distribution of ATOM content instead of HTML

[Alkarex]

Hello,
At the moment, it looks like to the content distributed by a distribution test is only HTML:
https://websub.rocks/subscriber/300

However, there are clients supporting only ATOM (which also seems to be a relatively more common scenario), for which the proposed test does not work.
What do you think about proposing a distribution test of ATOM content?

If there is interest, I could try to submit a PR.
Let me know :-)