analyzing-test-coverage

jeremylongshore/claude-code-plugins-plus-skillsDeveloper ToolsReview advisedSnapshot 7222fee82375

Installs: 0

Summary

Analyze code coverage metrics and identify untested code paths.

SKILL.md

Test Coverage Analyzer

Current State

!ls package.json pyproject.toml Cargo.toml go.mod 2>/dev/null || echo 'No project manifest found' !node -v 2>/dev/null || python3 --version 2>/dev/null || echo 'No runtime detected'

Overview

Analyze code coverage metrics to identify untested code paths, dead code, and coverage gaps across line, branch, function, and statement dimensions. Supports Istanbul/nyc (JavaScript/TypeScript), coverage.py (Python), JaCoCo (Java), and Go coverage tools.

Prerequisites

Coverage tool installed and configured (Istanbul/nyc, c8, coverage.py, JaCoCo, or go test -cover)
Test suite that can run with coverage instrumentation enabled
Coverage threshold targets defined (recommended: 80% lines, 70% branches)
Coverage output format set to JSON or LCOV for programmatic analysis
Git history available for coverage trend comparison

Instructions

Run the test suite with coverage instrumentation enabled:
- JavaScript: npx jest --coverage --coverageReporters=json-summary,lcov
- Python: pytest --cov=src --cov-report=json --cov-report=term-missing
- Go: go test -coverprofile=coverage.out ./...
- Java: Configure JaCoCo Maven/Gradle plugin with XML report output.
Parse the coverage report and extract per-file metrics:
- Line coverage percentage per file.
- Branch coverage percentage per file.
- Function coverage percentage per file.
- Uncovered line ranges (specific line numbers).
Identify critical coverage gaps by prioritizing:
- Files with coverage below the threshold (sort ascending by coverage %).
- Files with high complexity but low coverage (use cyclomatic complexity if available).
- Recently modified files with decreasing coverage trends.
- Public API functions and exported modules lacking any tests.

Error	Cause	Solution
Coverage report shows 0%	Tests ran but coverage instrumentation was not enabled	Verify `--coverage` flag is passed; check that source files are not excluded by config
Coverage includes `node_modules`	Coverage collection scope too broad	Add `collectCoverageFrom` in Jest config; set `--cov=src` in pytest; exclude vendor dirs
Branch coverage much lower than line coverage	Conditional logic is only partially tested	Write tests for both truthy and falsy conditions on each branch; focus on edge cases
Coverage drops after refactor	New code added without corresponding tests	Set `coverageThreshold` with `global` minimums; add `--changedSince` for incremental checks
Flaky coverage numbers between runs	Non-deterministic test execution skipping code paths	Sort tests deterministically; run coverage with `--runInBand` for consistent results

{
  "jest": {
    "coverageThreshold": {
      "global": {
        "branches": 70,
        "functions": 80,
        "lines": 80,
        "statements": 80
      },
      "src/utils/": {
        "branches": 90,
        "lines": 95
      }
    },
    "collectCoverageFrom": [
      "src/**/*.{ts,tsx}",
      "!src/**/*.d.ts",
      "!src/**/index.ts"
    ]
  }
}

Coverage Gaps (sorted by impact):
1. src/auth/oauth.ts        Lines: 45%  Branches: 30%  [Lines 42-67, 89-103 uncovered]
   Suggestion: Add tests for token refresh failure and expired session handling
2. src/api/middleware.ts     Lines: 62%  Branches: 41%  [Lines 28-35, 71-80 uncovered]
   Suggestion: Test rate limiting edge cases and malformed header handling
3. src/utils/parser.ts       Lines: 71%  Branches: 55%  [Lines 112-130 uncovered]
   Suggestion: Test malformed input, empty string, and encoding edge cases

analyzing-test-coverage

Summary

SKILL.md

Test Coverage Analyzer

Current State

Overview

Prerequisites

Instructions

Output

Error Handling

Examples

Resources

Related skills