QA Metrics
Key performance indicators for software quality—measuring testing effectiveness and code reliability.
Definition
QA Metrics (Quality Assurance Metrics) are quantitative measurements used to evaluate the effectiveness of software testing and the overall quality of code. They help teams understand defect rates, test coverage, and how quickly issues are detected and resolved.
Core QA Metrics
Defect Density
Number of bugs per 1,000 lines of code
Escape Rate
Percentage of bugs found in production
Test Coverage
Percentage of code covered by tests
MTTD (Mean Time to Detect)
How quickly bugs are found
MTTR (Mean Time to Repair)
How quickly bugs are fixed
Categories of QA Metrics
Process Metrics
Measure testing efficiency and workflow
Coverage Metrics
Measure what code is being tested
Defect Metrics
Measure bugs found and fixed
Speed Metrics
Measure testing and fixing velocity
Why QA Metrics Matter
- Release confidence: Know when code is ready for production
- Resource allocation: Understand where to focus testing efforts
- Process improvement: Identify bottlenecks and inefficiencies
- Risk management: Predict where bugs are likely to occur
- Stakeholder communication: Provide data-backed quality reports
Shift-Left Quality Metrics
"Shift-left" means catching bugs earlier in the development cycle, when they're cheaper to fix:
Source: IBM Systems Sciences Institute
QA Metrics Anti-Patterns
Avoid These
- • Targeting 100% test coverage blindly
- • Counting bugs found as a QA "win"
- • Measuring QA by hours spent testing
- • Ignoring escaped defects
Do This Instead
- • Cover critical paths thoroughly
- • Measure bugs prevented, not just found
- • Track quality outcomes, not effort
- • Analyze production incidents
Connecting QA and Dev Metrics
QA metrics are most valuable when connected to development metrics:
- High churn + high defects: Rework creating bugs—slow down and clarify requirements
- Fast cycle time + low escape rate: Healthy process—keep optimizing
- Long lead time + low coverage: Testing bottleneck—invest in automation
- High velocity + high escape rate: Shipping too fast—add quality gates
Frequently Asked Questions
What are the most important QA metrics?
The most important QA metrics are: Defect Density (bugs per KLOC), Escape Rate (bugs found in production vs total bugs), Test Coverage, Mean Time to Detect (MTTD), and Mean Time to Repair (MTTR). Together, these indicate testing effectiveness and quality.
What is defect density?
Defect density measures the number of defects per unit of code, usually per 1,000 lines of code (KLOC). Lower defect density indicates higher code quality. Industry average is 1-25 defects per KLOC.
What is a good test coverage percentage?
While 100% coverage sounds ideal, 70-80% is often considered good for most projects. Coverage above 80% has diminishing returns. Focus on covering critical paths and business logic rather than chasing 100%.
What is escape rate in QA?
Escape rate (or defect leakage) is the percentage of bugs that "escape" to production versus total bugs found. A lower escape rate means your testing catches more bugs before release. Elite teams achieve <5% escape rates.
How do QA metrics relate to developer productivity?
Quality and productivity are interconnected. High defect rates slow development (fixing bugs instead of features). Good QA metrics enable faster iteration by catching issues early and building confidence in releases.
Related Terms
Connect Quality with Activity
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