My friend Rachel Kibler asked me the other day "do you have a blog post about why we test software?" and I was surprised to find that, despite having touched on the topic many times, I haven't. So then I thought I'd write one. And then I thought it might be fun to crowdsource so I asked in the Association for Software Testing member's Slack, on LinkedIn , and on Twitter for reasons, one sentence each. And it was fun! Here are the varied answers, a couple lightly edited, with thanks to everyone who contributed. Edit: I did a bit of analysis of the responses in Reasons to be Cheerful, Part 2 . --00-- Software is complicated, and the people that use it are even worse. — Andy Hird Because there is what software does, what people say it does, and what other people want it to do, and those are often not the same. — Andy Hird Because someone asked/told us to — Lee Hawkins To learn, and identify risks — Louise Perold sometimes: reducing the risk of harming people — ...