Add broken alert validation check

Just a note to add a check that makes sure that broken kafka notices actually fail the validation test. I've been doing this by hand whenever I touch the unit test, explicitly changing the author field to None and confirming the unit test gives me a validation error, because an early version of the unit test would pass but then not fail when the validation failed.

It seems weird to me to have a unit test that tests another unit test, but I worry that not adding this could result in the unit test silently breaking.