rjest-install

A blazing-fast, drop-in replacement for Jest. Install via npm and run your tests in ~14ms on warm runs — 100x faster than standard Jest.

rjest-install is the official npm distribution of rjest, a Rust-based test runner that keeps a background daemon (jestd) alive across invocations. It reads your existing jest.config.* files with zero configuration changes and supports the same CLI flags you already use (--watch, --coverage, --runInBand, --testNamePattern, --json, --machine).

Why rjest?

• 100x faster warm runs — 14ms vs 1.4s on typical TypeScript projects
• Zero config — reads jest.config.js, jest.config.ts, or package.json Jest settings automatically
• Drop-in replacement — same CLI flags, test syntax, matchers, and snapshot format
• Built for AI agents — structured JSON and --machine output for fast feedback loops
• Persistent caching — SWC transforms cached on disk via sled; survive restarts

Installation

npm install -D rjest-install

Requires Node.js 16+ and a Rust binary (downloaded automatically on first run).

Quick Start

# Run all tests (daemon starts automatically)
npx rjest

# Watch mode
npx rjest --watch

# Coverage
npx rjest --coverage

# Filter by test name
npx rjest --testNamePattern="add"

# Structured JSON output for CI / AI agents
npx rjest --json
npx rjest --machine

How It Works

1. Daemon (jestd) — a Rust process that runs in the background, parsing Jest config once, building a dependency graph, and pre-warming Node.js workers.
2. SWC Transforms — TypeScript/JSX is compiled natively in Rust and cached by content hash (blake3). No Babel or ts-jest needed.
3. Worker Pool — persistent Node.js processes execute tests in a VM context, avoiding repeated V8 cold-start overhead.
4. CLI Shim — forwards commands to the daemon over low-latency IPC (nng), then renders Jest-style output.

Architecture

┌─────────────┐     IPC (nng)      ┌──────────────┐
│   jest CLI  │  ◄──────────────►  │    jestd     │
│  (rjest)    │                    │   (Rust)     │
└─────────────┘                    └──────┬───────┘
                                        │
                     ┌──────────────────┼──────────────────┐
                     │                  │                  │
                ┌────▼────┐      ┌────▼────┐      ┌────▼────┐
                │ Worker 1│      │ Worker 2│      │ Worker N│
                │ (Node)  │      │ (Node)  │      │ (Node)  │
                └─────────┘      └─────────┘      └─────────┘

Daemon Management

# Check if the daemon is running
npx rjest --daemon-status

# Stop the daemon (caches persist on disk)
npx rjest --daemon-stop

# Force a cold restart
npx rjest --daemon-restart

Compatibility

• Node.js: 16+
• Platforms: macOS (Intel & Apple Silicon), Linux (x86_64 & aarch64), Windows (x86_64)
• Config files: jest.config.js, jest.config.ts, jest.config.mjs, package.json
• Matchers: toBe, toEqual, toThrow, toHaveBeenCalled, resolves, rejects, etc.
• Features: snapshots, fake timers, jest.fn(), jest.mock(), coverage (Istanbul), watch mode

See the compatibility matrix for full details.

Performance

| Metric | rjest | Jest | Speedup | | --- | --- | --- | --- | | Cold start | 1.9s | 1.4s | 0.7x | | Warm run | 14ms | 1.4s | 100x |

AI Agent Usage

# Fast, structured output for automated workflows
npx rjest --onlyChanged --machine

# Filter by test name pattern
npx rjest --testNamePattern="authentication" --json

Documentation

• Full Documentation
• Architecture
• Compatibility
• Performance
• Changelog

Contributing

Contributions are welcome! Please open an issue or PR on the main repository.

License

MIT