This plugin adds Ethereum-specific capabilities to the Chai assertion library, making your smart contract tests easy to write and read.
Check its documentation to learn more.
We recommend using npm 7 or later. If you do that, then you just need to install the plugin itself:
npm install --save-dev @nomicfoundation/hardhat-chai-matchers
If you are using an older version of npm, you'll also need to install all the packages used by the plugin.
npm install --save-dev @nomicfoundation/hardhat-chai-matchers chai @nomiclabs/hardhat-ethers ethers
That's also the case if you are using yarn:
yarn add --dev @nomicfoundation/hardhat-chai-matchers chai @nomiclabs/hardhat-ethers ethers
After installing it, add the plugin to your Hardhat config:
Then you'll be able to use the matchers in your tests:
expect(await token.totalSupply()).to.equal(1_000_000); await expect(token.transfer(token, 1000)).to.be.revertedWith( "Cannot transfer to the contract itself" ); await expect(token.transfer(recipient, 1000)) .to.emit(token, "Transfer") .withArgs(owner, recipient, 1000);