Reorganize grab_next_visits tests to better check sorting behavior
- factor out test setup and results checking
- properly exercize corner cases of the oldest_scheduled_first policy
Depends on !191 (closed)
Migrated from D4897 (view on Phabricator)
Staging instance, all changes can be removed at any time
Depends on !191 (closed)
Migrated from D4897 (view on Phabricator)