Test Coverage Analysis

Skill Purpose: Analyze test coverage, enforce thresholds, and report coverage gaps for code quality gates.

Core Skill Pattern

Objective: Maintain measurable test coverage and prevent regressions in critical areas.

Universal Pattern:

1. •Define coverage thresholds by scope
2. •Collect coverage on CI and locally
3. •Generate HTML/JSON reports
4. •Identify hot spots and low coverage areas
5. •Track coverage changes over time

Key Decisions (Project-Specific):

• •Global vs per-package thresholds
• •Branch vs line coverage weighting
• •Exclusions for generated or vendor code
• •Coverage artifacts retention

Project-Specific Implementation Notes

Customize per project:

• •Decide minimum coverage by module criticality
• •Align coverage gates with quality gates
• •Store coverage reports as CI artifacts

Example Implementation (Jest)

// jest.config.js
module.exports = {
  collectCoverage: true,
  collectCoverageFrom: [
    'app/**/*.{ts,tsx}',
    'lib/**/*.{ts,tsx}',
    '!**/*.d.ts',
    '!**/node_modules/**'
  ],
  coverageThreshold: {
    global: {
      branches: 80,
      functions: 80,
      lines: 80,
      statements: 80
    }
  },
  coverageReporters: ['text', 'json', 'html']
};

Best Practices

1. •Gate merges on coverage thresholds
2. •Track coverage deltas per PR
3. •Prioritize coverage in high-risk areas
4. •Avoid gaming coverage with low-value tests
5. •Keep exclusions explicit and minimal

Stop Conditions

STOP and escalate if:

• •Coverage thresholds are undefined
• •Reports are missing on CI
• •Coverage excludes critical modules

Skill Version: 1.0.0