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

1. 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.

1. 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).

1. 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.

1. Analyze uncovered branches specifically:

• Find if/else blocks where only one branch is tested.
• Identify switch/case statements with missing case coverage.
• Locate error handling paths (catch, except) never exercised.
• Check || and && short-circuit conditions.

1. Generate a prioritized action plan:

• List top 10 files needing coverage improvement with specific line ranges.
• Suggest test scenarios for each uncovered branch.
• Estimate effort (small/medium/large) for each coverage improvement.

1. Compare current coverage against the previous commit or baseline:

• Calculate coverage delta per file.
• Flag files where coverage decreased.
• Verify new c