Two people died because of a Unicode support error. Another died because of a camera’s inability to distinguish colours from one another, and yet another died because of bad GPS data. Many thousands more deaths could have been prevented by a single variable, if the developers had thought to include it. As software developers, our skills and ideas are increasingly crucial for keeping the world running. We don’t have time to test for, find, and fix all of the bugs. Most bugs are annoying, some bugs allow for sneaky behaviour, but the most innocuous of edge cases can sometimes lead to an actual loss of life. No software ever holds up to contact with reality, but in this talk, Lilly Ryan shows you some of the more extreme consequences of tech debt, and offers guidelines on how your team can more easily identify assumptions and eliminate edge case behaviour when developing software. That boring task hiding in your backlog might just save a life.