Defect
A defect is any deviation of actual behavior from expected behavior, where the software does not meet requirements, design specifications, or user expectations.
A defect answers: “What is wrong compared to what was expected?”
1. Definition
A defect is any deviation of actual behavior from expected behavior, where the software does not meet requirements, design specifications, or user expectations.
A defect answers: “What is wrong compared to what was expected?”
2. Synonyms
- Bug
- Issue
- Fault
- Error (context-dependent)
(In testing practice, these are often used interchangeably.)
3. Sources of Defects
- Incorrect or ambiguous requirements
- Design flaws
- Coding mistakes
- Integration issues
- Environment/configuration problems
- Data issues
4. Types of Defects
4.1 Functional Defects
- Feature does not work as expected
- Business rule violations
4.2 UI Defects
- Alignment, layout, or visual issues
- Broken links or buttons
4.3 Performance Defects
- Slow response
- Timeouts or freezes
4.4 Security Defects
- Unauthorized access
- Sensitive data exposure
4.5 Compatibility Defects
- Browser/OS/device-specific failures
4.6 Usability Defects
- Confusing workflows
- Unclear messages
5. Severity Levels (Impact)
- Critical – System crash, data loss
- High – Major functionality broken
- Medium – Partial functionality issue
- Low – Minor UI or cosmetic issue
6. Priority Levels (Urgency)
- P1 (Immediate)
- P2 (High)
- P3 (Medium)
- P4 (Low)
(Severity = impact; Priority = urgency.)
7. Defect Lifecycle (High-Level)
- New
- Assigned
- Open
- Fixed
- Re-Tested
- Closed / Reopened
(Detailed lifecycle is typically covered as a separate topic.)
8. Manual Tester’s Responsibilities
- Identify and confirm defects
- Report defects clearly and accurately
- Assign correct severity
- Re-test fixes
- Close or reopen defects
9. Common Defect Attributes
- ID
- Summary
- Steps to reproduce
- Expected vs actual result
- Severity & priority
- Status
- Environment & build
10. Real-Time Example
Defect: Password field accepts fewer characters than specified
- Requirement: Minimum 8 characters
- Actual: Accepts only 6
This is a functional defect with high severity.
11. Common Mistakes
- Reporting non-defects (misunderstood requirements)
- Duplicate defect reporting
- Incorrect severity assignment
- Poor reproduction steps
12. Interview-Ready Answers
Short answer:
A defect is a deviation between expected and actual behavior of a software application.
Detailed answer:
A defect is any flaw in software where it fails to meet specified requirements, design expectations, or user needs.
13. Key Takeaway
Defects are not just bugs—they are risks to quality, business, and user trust.