What is the difference between test coverage and code quality?

Question

Accepted Answer

**Test Coverage** — percentage of code tested. **Code Quality** — overall code health.

**Test Coverage:**
- Measures tested code percentage.
- Line, branch, function coverage.
- Quantitative metric.
- Not everything needs 100%.

```
Test Coverage:
Lines: 80% (800/1000 lines tested)
Branches: 75% (75/100 branches)
Functions: 90% (90/100 functions)
(Quantitative)
```

**Code Quality:**
- Readability, maintainability.
- Best practices, patterns.
- Qualitative assessment.
- Tools: linters, code review.

```
Code Quality:
- Clear naming
- Small functions
- No duplication
- Following patterns
(Qualitative)
```

**Key differences:**
- **Coverage** — quantitative.
- **Quality** — qualitative.
- **Coverage** — test completeness.
- **Quality** — code health.

Systems Analyst: What is the difference between test coverage and code quality?