How do I know the system is working?

A few weeks ago, I received a bug report for Artemis that indicated a user’s reader was not being updated as expected. This error was caused by a feed that caused the polling code to error out and stop. My code assumed a value was present and, if it wasn’t, the program would stop running.To understand this bug, you need to know how Artemis retrieves feeds. Artemis polls feeds once per hour. A feed is only polled if there is at least one user for whom it is midnight in their time zone. This works because Artemis is scheduled to update user feeds once per day. Assuming the hourly job runs, every user’s feed will update (roughly) once per day, at midnight in their time zone.The broken feed had a subscriber in a time zone that was not my own. This meant that I didn’t observe the bug because the polling code didn’t retrieve the feed in my time zone. But others in the time zone in which there was at least one user subscribing to the feed may notice their feed did not contain all the posts…