Emulate

# Service Emulation with emulate

Local drop-in replacement services for CI and no-network sandboxes. Fully stateful, production-fidelity API emulation, not mocks.

## Quick Start

```bash
npx emulate
```

All services start with sensible defaults:

| Service   | Default Port |
|-----------|-------------|
| Vercel    | 4000        |
| GitHub    | 4001        |
| Google    | 4002        |
| Slack     | 4003        |
| Apple     | 4004        |
| Microsoft | 4005        |
| AWS       | 4006        |

## CLI

```bash
# Start all services (zero-config)
npx emulate

# Start specific services
npx emulate --service vercel,github

# Custom base port (auto-increments per service)
npx emulate --port 3000

# Use a seed config file
npx emulate --seed config.yaml

# Generate a starter config
npx emulate init

# Generate config for a specific service
npx emulate init --service vercel

# List available services
npx emulate list
```

### Options

| Flag | Default | Description |
|------|---------|-------------|
| `-p, --port` | `4000` | Base port (auto-increments per service) |
| `-s, --service` | all | Comma-separated services to enable |
| `--seed` | auto-detect | Path to seed config (YAML or JSON) |
| `--base-url` | none | Override advertised base URL (supports `{service}` template) |
| `--portless` | off | Serve over HTTPS via portless (auto-registers aliases) |

The port can also be set via `EMULATE_PORT` or `PORT` environment variables.

The advertised base URL (used in OAuth redirects, webhook URLs, etc.) can be overridden via `--base-url`, the `EMULATE_BASE_URL` env var (supports `{service}` template), or per-service `baseUrl` in the seed config. When running under portless, the `PORTLESS_URL` env var is also detected automatically.

## Programmatic API

```bash
npm install emulate
```

Each call to `createEmulator` starts a single service:

```typescript
import { createEmulator } from 'emulate'

const github = await createEmulator({ service: 'github', port: 4001 })
const vercel = await createEmulator({ service: 'vercel', port: 4002 })

github.url   // 'http://localhost:4001'
vercel.url   // 'http://localhost:4002'

await github.close()
await vercel.close()
```

### Options

| Option | Default | Description |
|--------|---------|-------------|
| `service` | *(required)* | `'vercel'`, `'github'`, `'google'`, `'slack'`, `'apple'`, `'microsoft'`, or `'aws'` |
| `port` | `4000` | Port for the HTTP server |
| `seed` | none | Inline seed data (same shape as YAML config) |
| `baseUrl` | none | Override advertised base URL. Per-service `baseUrl` in seed config takes highest priority, then this option, then `EMULATE_BASE_URL` env var (supports `{service}`), then `PORTLESS_URL` (supports `{service}`, automatically set by the `portless` CLI wrapper), then `http://localhost:<port>`. |

### Instance Methods

| Method | Description |
|--------|-------------|
| `url` | Base URL of the running server |
| `reset()` | Wipe the store and replay seed data |
| `close()` | Shut down the HTTP server, returns a Promise |

## Vitest / Jest Setup

```typescript
import { createEmulator, type Emulator } from 'emulate'

let github: Emulator
let vercel: Emulator

beforeAll(async () => {
  ;[github, vercel] = await Promise.all([
    createEmulator({ service: 'github', port: 4001 }),
    createEmulator({ service: 'vercel', port: 4002 }),
  ])
  process.env.GITHUB_EMULATOR_URL = github.url
  process.env.VERCEL_EMULATOR