Don't forget to test all use cases
Automation fubars are all too fun.
Back in the early days of Powershell I had the bright idea that any user moved to a "Staff Leavers" OU to have their our of office set to a "I have now left the company" script, which I created and was tested, or so I thought.
All was going well, until a day when there were no users in the folder, and I found a feature of Powershell 1.1 where if no results were found all mailboxes were selected, setting every out of office from the MD down.
Oh how we laughed in the forthcoming meetings....