The More Confident You Are About Your Testing, The Bigger the Bug You Missed

As software professionals, we’ve all experienced that sinking feeling: confidently shipping a release only to have a major issue surface soon after. It’s almost a cliché in the testing world — confidence in testing often precedes the discovery of a significant bug. But why does this happen? And how can we guard against overconfidence while striving for excellence in testing?

Photo by Domino Studio on Unsplash

This article explores the psychology behind this phenomenon, provides real-world examples, and provides actionable steps to balance confidence and vigilance in software testing.

Human nature leans toward optimism, especially when deadlines are tight, and pressure mounts to deliver. Overconfidence bias — our tendency to overestimate our abilities — plays a major role in testing.

Here’s how it typically unfolds:

Trust in Familiarity: “This module has been stable for months. It’s unlikely to break.”Reliance on Automation: “Our automated tests have 95% coverage. What could go wrong?”Experience-Driven Assumptions: “I’ve tested similar features before. I’m confident this will hold.”