# Setup

Attest is a testing library that makes your TypeScript types available at runtime, giving you access to precise type-level assertions and performance benchmarks.

Assertions are framework agnostic and can be seamlessly integrated with your existing Vitest, Jest, or Mocha tests.

Benchmarks can run from anywhere and will deterministically report the number of type instantiations contributed by the contents of the `bench` call.

If you've ever wondered how ArkType can guarantee identical behavior between its runtime and static parser implementations and highly optimized editor performance, Attest is your answer⚡

## Installation

```bash
npm install -D @ark/attest
```

> **Note**
>
> This package is still in alpha! Your feedback will help us iterate toward a
> stable 1.0.

## Global setup

To use attest's type assertions, you'll need to call its setup and cleanup methods before your first test and after your last test, respectively. This usually involves some kind of globalSetup/globalTeardown config.

> **Warning**
>
> If you run your tests in watch mode or otherwise iteratively during dev, you
> will want to enable [`skipTypes`](https://arktype.io/docs/attest/options#skiptypes).

### Vitest

```ts title="vitest.config.ts"
import { defineConfig } from "vitest/config"

export default defineConfig({
	test: {
		globalSetup: ["setupVitest.ts"]
	}
})
```

```ts title="setupVitest.ts"
import { setup } from "@ark/attest"

// config options can be passed here
export default () => setup({})
```

### Mocha

```json title="package.json"
"mocha": {
	"require": "./setupMocha.ts"
}
```

```ts title="setupMocha.ts"
import { setup, teardown } from "@ark/attest"

// config options can be passed here
export const mochaGlobalSetup = () => setup({})

export const mochaGlobalTeardown = teardown
```

You should also add `.attest` to your repository's `.gitignore` file.

Bun support is currently pending [them supporting @prettier/sync for type formatting](https://github.com/oven-sh/bun/issues/10768). If this is a problem for you, please 👍 that issue so they prioritize it!