Test Coverage Report Skill

Generate and analyze test coverage reports.

When to Use

• After running tests
• Before creating PR
• Identifying untested code
• Improving test coverage

Quick Reference

# Python coverage
pytest --cov=src --cov-report=html tests/

# View report
open htmlcov/index.html

# Terminal report
pytest --cov=src --cov-report=term-missing tests/

Coverage Metrics

Line Coverage

Percentage of code lines executed by tests:

src/module.mojo
  Lines: 45/50 (90%)
  Missing: 12, 18, 23, 35, 41

Branch Coverage

Percentage of decision branches taken:

Branches: 8/10 (80%)
Missing branches: line 12->15, line 18->20

Coverage Goals

| Category | Minimum | Target | Critical | |----------|---------|--------|----------| | Line coverage | 80% | 90% | 100% | | Branch coverage | 70% | 85% | 95% | | Critical paths | - | - | 100% |

Coverage Report

Coverage Report
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
File                Lines    Missing    Coverage
────────────────────────────────────────────────
src/tensor.mojo       150         5      96.7%
src/nn.mojo          200        30      85.0%
src/utils.mojo        50        10      80.0%
────────────────────────────────────────────────
TOTAL                400        45      88.8%

Minimum coverage: 80% ✅
Target coverage: 90% ❌
Critical paths: 100% ✅

Improving Coverage

1. Identify gaps - Find uncovered lines in report
2. Write tests - Add tests for untested code
3. Re-run - Generate new report
4. Verify - Check coverage improved
5. Repeat - Until targets met

Coverage Workflow

# 1. Run tests with coverage
pytest --cov=src --cov-report=html --cov-report=term-missing tests/

# 2. Identify missing coverage
# Review "Missing" column in output

# 3. Write tests for gaps
# ... create test files ...

# 4. Re-run
pytest --cov=src --cov-report=html tests/

# 5. Check improvement
# Compare htmlcov/index.html

CI Integration

- name: Test Coverage
  run: |
    pytest --cov=src --cov-report=xml
    codecov -f coverage.xml

Error Handling

| Error | Fix | |-------|-----| | "No module named pytest" | Install: pip install pytest-cov | | "Cannot find tests/" | Verify test directory exists | | No coverage report | Ensure tests ran successfully |

References

• Related skill: phase-test-tdd for test generation
• Related skill: quality-run-linters for complete quality check
• Pytest docs: https://docs.pytest.org/en/stable/