uncov

A zero-dependency CLI tool that reports files with low test coverage from Vitest/Istanbul JSON output.

Features

• Zero dependencies - Single binary, instant startup
• Zero config - Just run uncov in any project with coverage output
• Cross-platform - Binaries for macOS (arm64, x64), Linux (x64), Windows (x64)
• CI-friendly - JSON output, exit codes for automation
• Optional setup - Bootstrap coverage scripts with uncov init

Installation

Quick Install (Recommended)

curl -fsSL https://raw.githubusercontent.com/llbbl/uncov/main/install.sh | bash

This automatically detects your platform, downloads the latest binary, verifies the checksum, and installs to your PATH.

npm / pnpm / bun

# npm
npm install -g uncov

# pnpm
pnpm add -g uncov

# bun
bun add -g uncov

Download Binary

Download the latest release for your platform from GitHub Releases.

# macOS (Apple Silicon)
curl -fsSL https://github.com/llbbl/uncov/releases/latest/download/uncov-darwin-arm64 -o uncov
chmod +x uncov
sudo mv uncov /usr/local/bin/

# macOS (Intel)
curl -fsSL https://github.com/llbbl/uncov/releases/latest/download/uncov-darwin-x64 -o uncov
chmod +x uncov
sudo mv uncov /usr/local/bin/

# Linux
curl -fsSL https://github.com/llbbl/uncov/releases/latest/download/uncov-linux-x64 -o uncov
chmod +x uncov
sudo mv uncov /usr/local/bin/

Build from Source

git clone https://github.com/llbbl/uncov.git
cd uncov
bun install
bun run build:local

Quick Start

1. Run your tests with coverage:

   pnpm test:coverage
   # or
   vitest run --coverage

2. Report low coverage files:

   uncov

Output:

Files at or below 10% line coverage: 3

   0.00%  LH    0/LF  120   src/renderer.ts
   5.26%  LH    2/LF   38   src/bootstrap.ts
  10.00%  LH   10/LF  100   src/engine.ts

Commands

uncov (default)

Report files below coverage threshold.

uncov                     # Files at or below 10% coverage (default)
uncov --threshold 50      # Files at or below 50% coverage
uncov --threshold 0       # Only 0% coverage files
uncov --fail              # Exit 1 if any files below threshold
uncov --json              # JSON output for scripting
uncov --verbose           # Show debug information
uncov --no-color          # Disable colorized output

uncov init

Bootstrap coverage configuration in your project.

uncov init                # Interactive setup
uncov init --force        # Overwrite existing config
uncov init --dry-run      # Preview changes without modifying files

This command:

1. Detects your package manager (pnpm, bun, npm, yarn)
2. Adds scripts to package.json:
   • test:coverage - Run tests with coverage
   • coverage:low - Run uncov
3. Creates vitest.config.ts with coverage settings
4. Adds coverage/ to .gitignore

uncov check

Verify coverage setup is correct.

uncov check               # Verify setup
uncov check --verbose     # Show detailed check information

Checks:

• Vitest config exists
• Coverage config is present
• coverage-summary.json exists
• Required scripts are configured

Configuration

uncov.config.json

{
  "threshold": 10,
  "exclude": ["**/*.test.ts", "**/index.ts"],
  "failOnLow": false,
  "coveragePath": "coverage/coverage-summary.json"
}

package.json

{
  "uncov": {
    "threshold": 20,
    "failOnLow": true
  }
}

Configuration Priority

1. CLI flags (highest)
2. uncov.config.json
3. package.json uncov field
4. Defaults (lowest)

Exit Codes

Code	Meaning
0	Success (or low coverage files found but --fail not set)
1	Low coverage files found and --fail set
2	Missing coverage-summary.json or config error

Development

Setup

git clone https://github.com/llbbl/uncov.git
cd uncov
bun install

Commands

Using Just (recommended):

just              # Show available commands
just install      # Install dependencies
just dev          # Run CLI locally
just dev --help   # Run CLI with args
just test         # Run tests
just lint         # Lint with Biome
just lint-fix     # Fix lint issues
just build        # Build local binary
just build-all    # Build all platform binaries
just check        # Run lint + tests
just clean        # Remove build artifacts

Or using bun directly:

bun run dev           # Run CLI locally
bun test              # Run tests
bun run lint          # Lint with Biome
bun run lint:fix      # Fix lint issues
bun run build:local   # Build local binary
bun run build         # Build all platform binaries

Project Structure

uncov/
├── src/
│   ├── cli.ts              # Entry point, arg parsing
│   ├── commands/           # Command implementations
│   ├── lib/                # Core logic
│   └── utils/              # Helpers
├── test/                   # Tests
├── scripts/
│   └── build.ts            # Cross-platform build
└── docs/
    └── spec.md             # Full specification

See docs/spec.md for the full specification.

License

MIT