In software testing, what you don’t know is often your biggest risk. As smart as we think we all are, no reasonable amount of brainstorming and careful test planning can discover all possible tests that should be put in place for a given system. ...

My team discovered a bug recently that had been around in our daily builds a while.  We did a retrospective after the fact and found some interesting facts.  We had a test case covering the scenario, and it had been passing with no problems...