They were previously not covered at all, either by integration tests or unit tests.
This PR also fixes a bug where the `num_comments` field was incorrectly set to include all types of comments.
It sets num_closed_issues: 0 as default in milestone unit test fixtures. If they are not set, Incr("num_closed_issues") will be a noop because the field is null.
Aravinth Manivannan