Test Coverage Analysis

Test Coverage Analysis

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

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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

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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

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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']
};

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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

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Stop Conditions

STOP and escalate if:

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

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Skill Version: 1.0.0