A bug slips past your eye: What did you do?

Recently one of hour developers found a bug in a backend service. The bug was related to a certain module going down but not performing some expected tasks as it should have.
Not that I didn’t test this, but the issue seemed to be based on a scenario that didn’t cross my mind. I did went through 36 other bugs in the related user story, some of which were quite deep.

But this recent bug got me thinking, could I have spotted this?
Could I have kept testing this feature back when I thought I had completed the testing?
Share your stories about what you went through when a production bug miss past your eye.


we are all doing our best to ensure product quality and we are all human. it’s already a good achievement that you found 36. I know your feeling, why didn’t I have seen that bug. All members in the team are responsible for product quality. You also could have raised the question, why didn’t development had a unit test for this. Each test level find specific bugs and are easier to find it there. Although I’m a system tester, I also keep an eye on CT tests and even back-end bugs.


Was the bug critical? If it is something minor, I always tell myself that “exhaustive testing is impossible”. If it is something critical (and this happened to me last year), I think it is good to think if I could have done something differently, but not to blame myself (although I sometimes do :slight_smile: ), but to learn from it and find a way to do it differently next time.
The bug I missed last year was very hard for me to find and nothing I had experienced before. So I could blame myself (or the devs :slight_smile: ) but that wouldn’t help anyone. So I’d rather prepare myself for it and others like it and not let it pass me by next time. And yes, next time a completely different critical bug might pass, so it might be time to think about risk analysis and my test prioritisation :slight_smile:


I learn from it:

  • How early did that mistake happen and how many people missed considering it? Could I have been involved earlier to see it coming?
  • What have I done at the various times when I was close to potentially checking the product for an issue like that?
  • Did I waste my time with other less valuable tasks?
  • Did I waste my time chasing low-impact, low-risk issues?
  • Is there some knowledge about the backend or architecture of the product that I’m missing?
  • Could I take some time to do developer reviews or be part of development solution discussions?
  • Can I maybe pair with some developers to support them in brainstorming potential failures?
  • Was it a one-off thing or recurring due to process, due to people, due to pressure, or?

Was it 36 unique bugs, or part of a trend with the same root cause ? Make sure you are testing the important things. Although… it sounds like the code quality was poor to begin with. Write some automated API tests to cover this and make sure you understand why you missed this bug. Also, be thankful that a developer found the bug instead of a customer.

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I tested everything from not so important to really important. Sadly no API automation in this since they’re not used.