Real-Time Defect Scenarios (Manual Testing)
Real-world defect scenarios help testers communicate observations, classify issues, and report impact clearly. Use these examples to structure your bug reports and interview answers.
1. Login Works but Session Expires Immediately
Observation: User logs in successfully but gets logged out on next click.
Likely Cause: Session timeout or cookie configuration issue.
Type: Functional / Configuration defect
Severity: High
How to Report: Include browser, environment, session timeout value.
2. Data Saved but Not Displayed After Refresh
Observation: Form submission succeeds, but data disappears on page reload.
Likely Cause: Backend commit or API response issue.
Type: Functional defect
Severity: High
Tester Action: Verify DB/API logs if accessible; attach screenshots.
3. Error Message Not Displayed for Invalid Input
Observation: System blocks action but shows no message.
Likely Cause: Missing validation handling.
Type: Usability + Functional defect
Severity: Medium
Expected: Clear, user-friendly error message.
4. Feature Works in QA but Fails in UAT
Observation: Same steps, different result.
Likely Cause: Environment/config mismatch.
Type: Environment / Configuration defect
Severity: High
Tester Action: Compare endpoints, feature flags, roles.
5. Calculation Correct Individually, Wrong in Summary
Observation: Line item totals correct; grand total incorrect.
Likely Cause: Rounding or aggregation logic error.
Type: Functional defect
Severity: Critical (financial impact)
Evidence: Provide calculation breakdown.
6. Approved User Cannot Access Authorized Page
Observation: User with correct role gets access denied.
Likely Cause: Role-permission mapping issue.
Type: Security / Authorization defect
Severity: High
Tester Action: Verify role config and access matrix.
7. Dropdown Values Missing After Recent Change
Observation: Dropdown previously populated is now empty.
Likely Cause: Regression due to recent code change.
Type: Regression defect
Severity: Medium
Tester Action: Link defect to recent CR/build.
8. Application Hangs on Double Click
Observation: Double-clicking submit freezes the page.
Likely Cause: Missing duplicate request handling.
Type: Functional / Performance defect
Severity: High
Expected: Disable button after first click.
9. Wrong Error Message Displayed
Observation: “Invalid password” shown when username is empty.
Likely Cause: Incorrect validation sequence.
Type: Functional + Usability defect
Severity: Low–Medium
Impact: User confusion.
10. Search Works for Exact Match Only
Observation: Partial keyword returns no results.
Likely Cause: Search logic limitation.
Type: Functional / Requirement gap
Severity: Medium
Tester Action: Confirm requirement vs enhancement.
11. Uploaded File Accepted but Not Processed
Observation: Upload success message, but file not reflected anywhere.
Likely Cause: Async job failure or integration issue.
Type: Functional / Integration defect
Severity: High
Evidence: File name, timestamp, user.
12. Data Visible to Unauthorized User
Observation: User sees another user’s data.
Likely Cause: Access control failure.
Type: Security defect
Severity: Critical
Action: Immediate escalation.
13. Browser-Specific UI Break
Observation: UI aligned in Chrome, broken in Edge.
Likely Cause: CSS compatibility issue.
Type: Compatibility defect
Severity: Medium
Attach: Browser versions and screenshots.
14. Feature Flag OFF but Feature Visible
Observation: Feature appears despite being disabled.
Likely Cause: Flag not wired correctly.
Type: Configuration defect
Severity: High
Tester Action: Validate flag state and cache.
15. Report Data Mismatch with Screen Data
Observation: Report totals don’t match UI totals.
Likely Cause: Different data source or filter.
Type: Data integrity defect
Severity: High
Evidence: Date range, filters, user role.
16. Email Triggered Multiple Times
Observation: Single action sends multiple emails.
Likely Cause: Duplicate event handling.
Type: Functional defect
Severity: Medium
Impact: User trust issue.
17. Mandatory Field Not Enforced
Observation: Form submits with empty mandatory field.
Likely Cause: Missing validation.
Type: Functional defect
Severity: Medium
18. Performance Degrades After Data Growth
Observation: Feature was fast earlier, now slow.
Likely Cause: No pagination/indexing (conceptual).
Type: Performance defect (conceptual)
Severity: High
Tester Action: Provide data volume context.
19. Fix Breaks Another Feature
Observation: After defect fix, unrelated feature fails.
Likely Cause: Incomplete regression coverage.
Type: Regression defect
Severity: High
Lesson: Expand regression scope.
20. Production-Only Defect
Observation: Issue not reproducible in QA/UAT.
Likely Cause: Prod config/data difference.
Type: Environment / Configuration defect
Severity: Critical
Tester Action: Support RCA and rollback validation.
Interview Tip (Very Important)
When explaining a defect scenario:
- State the observation
- Identify type & severity
- Explain impact
- Mention how you reported it
- Show collaboration mindset