Even when the product or some feature is thoroughly tested, it can happen that a bug slips through and ends up in production. This can be really frustrating, but it is a natural part of the software development process. As QAs, we must do our best to minimize cases like this by setting up a process that will improve the quality of the product and minimize the risk of letting bugs slip into production.
Here are some typical causes behind escaped bugs and how you can prevent them from happening again:
Unclear or Evolving Requirements
If the product requirements are not complete, if they are hard to understand, or if they are changing without communication, it is almost impossible to test them correctly. Situations like this are hard for the QAs to test the requirements because we can’t be sure about the scenarios we need to cover, about the expected results, and we also can not plan the testing correctly.
Example: A story says “Users should be able to search for products,” but doesn’t specify criteria, filters, special characters, or whether search should be case-insensitive. It also doesn’t say what should happen if there are no results found.
As QAs, we can write or perform some basic test cases, but a lot of scenarios and edge cases can be missed.
How to prevent it:
- By asking questions early and communicating the requirements with the team. We need to clarify the requirements completely, even before development begins.
- Participate in backlog grooming and refinement sessions.
- If you see that the requirements are not complete, don’t assume the expected behavior. Confirm it with the Product Owner.
Environment Mismatches
Sometimes the product may be tested and work perfectly fine on your Test Environment, but when the version gets to the Production Environment, the users are suddenly complaining about some scenario that you know was tested and worked fine. This can happen due to differences in configuration, data, or integrations that weren’t present in the test environment.
How to prevent it:
- Make test environments as close to production as possible.
- Communicate with the team and learn about any potential differences between the environments.
- Include the integration validations in the test plan.
- Add sanity checks after deployment or in staging environments.
Time Pressure and Rushed Testing
When the deadline is short, the time for testing may be squeezed, and you end up with some time that is not enough to properly test the product. By performing rushed testing, some bugs may slip through and end up in production.
How to prevent it:
- Advocate for realistic testing timelines and include buffer time in sprint planning.
- Implement an automation regression test suite. Automate high-risk areas to speed up regression without sacrificing coverage.
- Set up and maintain a prioritized checklist for what must be tested under pressure.
Over-Reliance on Happy Path Testing
If you test only the happy paths and ideal scenarios, you may miss bugs that happen during unusual inputs or error conditions.
Example: A file upload works fine for valid formats, but crashes with a corrupt file or large size scenarios that no one thought to test.
How to prevent it:
- Think like a curious or even a malicious user who will check all the positive and negative scenarios.
- Add negative and boundary tests alongside positive ones.
- Encourage team members to perform exploratory testing beyond scripted cases.
Incomplete Test Data
Testing with only clean and ideal test data may lead to missing some scenarios that are not working if you are using some real-world or edge-case data.
Example: While you are testing, you are using an account with full permissions for all tests. In production, users with limited roles experience UI failures.
How to prevent it:
- Use a variety of test users and datasets representing real-life scenarios.
- Include roles, permissions, empty states, and unusual input in test planning.
Human Errors
By performing manual testing, it is possible to miss some scenarios, overlook an edge case, or misinterpret requirements. We need to do our best to minimize this, but it’s a normal human error that may happen to everyone.
How to prevent it:
- Communicate with the team, pair testing, or peer review for critical areas.
- Regularly revisit and improve test cases based on missed bugs or changed requirements.
- Use automation tests to reduce repetitive manual errors.
Inadequate Exploratory Testing
Without structured exploratory testing, it’s easy to miss some functional or usability issues.
How to prevent it:
- Allocate dedicated time for exploratory testing in each sprint.
- Make a plan or create a checklist to be sure that all the features are covered.
- Don’t focus just on the functional issues. Focus also on UX, accessibility, and integration flows.
No testing approach can guarantee zero bugs. But we must do our best to understand why bugs escape, to constantly improve the test processes, to improve test coverage, and to advocate for quality across the team.
