True story:
We release features internally in the company before rolling it to users.
Once, I reversed the check for a certain feature, which broke production for everyone except employees!
Innocent little !:
if (!employee) enableFeature()
It passed staging and regression testing and went into production at night. We patted ourselves on the back and called it a day. Was woken up by angry calls at 5am from users sitting in other time zones 🙈
lesson learned: always test as users, not developers