Test Coverage Skill

Purpose

Measure, report, and enforce test coverage thresholds.

Activation

• User says "check coverage" or "what's the coverage?"
• Before creating a PR
• When coverage drops below threshold

How It Works

1. Detect Test Framework

JavaScript/TypeScript:
  jest.config.* → npx jest --coverage
  vitest.config.* → npx vitest --coverage
  .nycrc → npx nyc report

Python:
  pytest.ini → pytest --cov
  pyproject.toml [tool.pytest] → pytest --cov

.NET:
  *.Tests.csproj → dotnet test /p:CollectCoverage=true

2. Run Coverage

# JavaScript/TypeScript
npx jest --coverage --coverageReporters=text-summary

# Python
pytest --cov=src --cov-report=term-missing

# .NET
dotnet test /p:CollectCoverage=true /p:CoverletOutputFormat=lcov

3. Report

Coverage Report
═══════════════
Lines:    85% (120/141)
Branches: 78% (45/58)
Functions: 92% (33/36)

Below 80% threshold:
  src/auth.ts: 65% (missing edge cases)
  src/utils.ts: 72% (missing error paths)

Threshold

• Minimum: 80% line coverage
• Target: 90% line coverage
• Branches: 75% minimum

Anti-Patterns

1. Do NOT skip coverage on "simple" files
2. Do NOT mock everything — integration tests need real calls
3. Do NOT ignore coverage drops — investigate and fix