lcov-comparer

A CLI tool to compare code coverage between two lcov.info reports and generate readable diffs across:

• Statements
• Branches
• Functions
• Lines

Supports multiple output formats and thresholds, ideal for CI and review workflows.

🚀 Usage

npx lcov-comparer <coverage-old.info> <coverage-new.info> [options]

🛠 Options

Flag	Description	Default
--formats	Comma-separated list of formats: html, json, csv, md, console	html
--out-dir	Directory to output report files	Current directory
--threshold <n>	Only include files where any metric delta ≥ n%	null (disabled)
--max-coverage-drop <n>	Exit with code 1 if any average delta is below -n%	null (disabled)
--summary	Print total coverage delta summary to stdout	false

📦 Format Support

Works with lcov.info files produced by:

• vitest --coverage
• jest --coverage
• nyc

📁 Output

Output is saved into the specified --out-dir (or current folder by default), one file per format.

For example:

npx lcov-comparer a.info b.info --formats html,json,md --out-dir ./coverage-diff

Will generate:

./coverage-diff/
  ├── coverage-diff.html
  ├── coverage-diff.json
  └── coverage-diff.md

📊 Example table

Files are sorted by the most significant delta across all metrics.

File	Statements	Δ	Branches	Δ	Functions	Δ	Lines	Δ
src/app.ts	70.0% → 90.0%	+20.0%	40.0% → 80.0%	+40.0%	50.0% → 100.0%	+50.0%	70.0% → 90.0%	+20.0%
helpers.ts	90.0% → 70.0%	−20.0%	100.0% → 50.0%	−50.0%	100.0% → 100.0%	+0.0%	95.0% → 70.0%	−25.0%

💡 Tip for CI

Use --summary for console output, and --max-coverage-drop to break pipeline if coverage drops too much.

npx lcov-comparer old.info new.info --summary --max-coverage-drop 5