5 Little-Known Bug Types That Often Slip Through

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5 Little-Known Bug Types That Often Slip Through

Even the most rigorously tested software can have hidden flaws. While QA teams often focus on common bugs, there are rare or unexpected bug types that can cause serious issues if overlooked. Understanding these uncommon bugs helps improve software quality, reduces user complaints, and prevents costly fixes after release. In this blog, we’ll explore 5 […]

Jayesh Mistry

ISTQB Certified

Sep 16, 2025

3 min read

Even the most rigorously tested software can have hidden flaws. While QA teams often focus on common bugs, there are rare or unexpected bug types that can cause serious issues if overlooked. Understanding these uncommon bugs helps improve software quality, reduces user complaints, and prevents costly fixes after release. In this blog, we’ll explore 5 Rare Software Bug types, what causes them, and how to detect them.

1. Heisenbugs

Definition: Heisenbugs are bugs that appear sporadically and seem to “disappear” when you try to debug them.Cause: Often caused by timing issues, memory corruption, or race conditions in concurrent programs.Detection Tips:

Use logging instead of interactive debugging.
Run automated regression tests multiple times.
Employ tools for concurrency and memory analysis.

2. Mandelbugs

Definition: Mandelbugs are extremely complex bugs that appear almost random due to the software’s complexity.Cause: Rooted in intricate interactions of code, hardware, or environment, making them hard to reproduce.Detection Tips:

Perform stress testing and scenario simulation.
Use automated testing in diverse environments.
Document edge cases thoroughly.

3. Bohrbugs

Definition: Bohrbugs are consistent and predictable bugs that can be reproduced reliably under specific conditions.Cause: Usually due to coding errors, logic flaws, or incorrect algorithm implementation.Detection Tips:

Regular unit testing and code reviews.
Regression tests to ensure bug fixes don’t reappear.

4. Schroedinbugs

Definition: Bugs that appear only when a certain condition or context is known, often due to incorrect assumptions about code behavior.Cause: Misinterpretation of data, hidden dependencies, or assumptions made by developers.Detection Tips:

Peer code reviews focusing on assumptions.
Incorporate boundary testing and unusual inputs.
Use static analysis tools to identify hidden dependencies.

5. Boomerang Bugs

Definition: Bugs that disappear temporarily after a fix but return under different conditions or updates.Cause: Incomplete fixes, overlooked dependencies, or configuration changes.Detection Tips:

Maintain proper version control and regression testing.
Track bug history to understand recurrence patterns.
Test across multiple environments before release.

Why QA Teams Should Care

Prevent Critical Failures: Rare bugs may cause crashes or data loss in production.
Enhance User Trust: Avoid user complaints and negative reviews by catching hidden issues early.
Reduce Costs: Fixing bugs after release is significantly more expensive than during development.

Best Practices to Detect Rare Bugs

1Automated Regression Testing: Repeatedly run automated tests in different scenarios.
2Stress and Load Testing: Simulate high load and unusual conditions.
3Peer Code Reviews: Catch hidden assumptions and logic errors.
4Use Advanced Debugging Tools: Memory analyzers, concurrency detectors, and static analysis.
5Document Edge Cases: Keep track of unusual situations that may trigger hidden bugs.

FAQs

1. What are rare software bugs?Rare software bugs are uncommon or unexpected errors that often escape standard QA processes but can cause serious issues.

2. Can rare bugs be predicted?Some can be anticipated through stress testing and code analysis, but others only appear under unusual conditions.

3. Are Heisenbugs the same as Bohrbugs?No. Heisenbugs appear sporadically and are hard to reproduce, while Bohrbugs are predictable and consistently reproducible.

4. How can QA teams reduce rare bugs?Through rigorous automated testing, peer code reviews, stress testing, and careful documentation of edge cases.

5. Why are rare bugs important?Even though they are uncommon, rare bugs can significantly impact user experience, product reliability, and company reputation.

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