Cypress Hardhat

cypress-hardhat

[](https://www.npmjs.com/package/cypress-hardhat) [](https://github.com/Uniswap/cypress-hardhat/actions/workflows/test.yaml)

A jest environment with hardhat built in.

`cypress-hardhat` is a hardhat plugin for running a hardhat fork for your tests. Instead of running a separate `hardhat node`, this environment runs a node and communicates the url and test accounts to cypress - with some test utilities to boot.

Installation

First, install `cypress-hardhat` and its dependencies (using `yarn` or `npm`).

The environment needs `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 ethers hardhat
yarn add -D cypress-hardhat

Then, set up your `hardhat.config.js` file. You'll need to [configure mainnet forking](https://hardhat.org/hardhat-network/guides/mainnet-forking#forking-from-mainnet) to set the initial state of the hardhat network within jest.

NOTE: You should set the [`accounts` field](https://hardhat.org/hardhat-network/reference#accounts) to include as few accounts as possible to reduce startup time for your tests' hardhat network.

`cypress-hardhat` may be configured to respond to `wallet_switchEthereumChain` requests to help test EIP-3326 interactions. To configure this behavior, add a `forks` field to your `hardhat.config.js` with the chains you are going to switch to:

const forks = {
  [1]: {
    url: `${process.env.JSON_RPC_PROVIDER}`,
    blockNumber: 17023328,
    httpHeaders: {},
  },
  [137]: {
    url: `${process.env.POLYGON_JSON_RPC_PROVIDER}`,
    blockNumber: 43600000,
    httpHeaders: {},
  },
}

module.exports = {
  forks,
  networks: {...},
  ...
}

Finally, install the plugin in your cypress configuration (see the [cypress docum