jest-environment-hardhat

A jest environment with hardhat built in.

jest-environment-hardhat is a drop-in jest environment for running hardhat inline with your tests. Instead of running a separate hardhat node, this environment runs a node and exposes a global Hardhat interface - with some helper utilities - to interact with it.

Installation

First, install jest-environment-hardhat and its dependencies (using yarn or npm).

The environment needs @nomiclabs/hardhat-ethers, ethers, and hardhat installed as well. These are installed as peer dependencies to ensure that you retain control over versioning, so you'll need to install them explicitly:

yarn add -D @nomiclabs/hardhat-ethers ethers hardhat
yarn add -D jest-environment-hardhat

Then, set up your hardhat.config.js file. You'll need to require @nomiclabs/hardhat-ethers from your hardhat.config.js file in order to install it as a hardhat plugin. You'll also need to configure mainnet forking to set the initial state of the hardhat network within jest.

NOTE: You should set the accounts field to include as few accounts as possible to reduce startup time for your tests' hardhat network.

Then, use the runner either using a doc-comment, or using jest configuration (see the jest documentation for details):

/**
 * @jest-environment hardhat
 */

test('use hardhat in this test file', () => {
  expect(hardhat).toBeDefined()
})

jest-environment-hardhat extends a node environment by default. A jsdom environment is also available, using hardhat/jsdom.

/**
 * @jest-environment hardhat/jsdom
 */

test('use hardhat and jsdom in this test file', () => {
  expect(hardhat).toBeDefined()
  const element = document.createElement('div')
  expect(element).not.toBeNull()
})

Subclassing your own runner

jest-environment-hardhat subclasses a node environment by default, and exports a jsdom environment under hardhat/jsdom.

If you'd like to extend your own environment, you can use the setup function exported by jest-environment-hardhat/setup. See src/node.ts for an example.

Documentation

Using the environment will expose hardhat on the global scope, which you can use to interact with the hardhat network in your tests.

For documentation on the hardhat global, see the type declarations.

For examples of how to interact with the hardhat network, see the tests.

Typescript

If you are using Typescript, import types by importing the library in your test or setup file:

/**
 * @jest-environment hardhat
 */

import 'jest-environment-hardat'

test('use hardhat in this test file', () => {
  expect(hardhat).toBeDefined()
})

Made with 🦄 by Uniswap Labs