What Is a Heisenbug?

Heisenbugs are elusive software bugs that change behavior or disappear when observed, presenting unique challenges for developers and testers. Unlike the more predictable Bohrbugs, Heisenbugs are non-deterministic and often occur in concurrent, multithreading, or timing-sensitive code, making them difficult to reproduce and fix. Traditional debugging methods fall short as they can alter the system's execution timing or behavior, effectively hiding the bug. Modern test automation tools and AI-driven approaches, such as testRigor, offer solutions by focusing on behavior rather than implementation details, reducing test-induced variance, and adapting to changes in the interface without extensive code rewriting. These tools help identify Heisenbugs by stabilizing tests and ensuring they reflect real-world scenarios, allowing teams to focus on genuine issues rather than false alarms. As software systems grow in complexity and scale, Heisenbugs become more prevalent, necessitating the adoption of adaptive and efficient testing methodologies to mitigate their impact.