Sweeter smart contracts testing

Waffle is a library for writing and testing smart contracts. Sweeter, simpler and faster than Truffle.



  • bitten waffle


    Minimalistic, fewer dependencies.

  • waffle with chocolate


    Nicer syntax, easy to learn, and easy to extend.

  • waffle in motion


    Faster contract compilation and tests execution.

Example code

Below is an example contract, that delivers from standard ERC20 token:

pragma solidity ^0.5.1;

import "openzeppelin-solidity/contracts/token/ERC20/ERC20.sol";

contract BasicTokenMock is ERC20 {
  constructor(address initialAccount, uint256 initialBalance) public {
    super._mint(initialAccount, initialBalance);

And an example tests for the contract:

import chai from 'chai';
import {createMockProvider, deployContract, getWallets, solidity} from 'ethereum-waffle';
import BasicTokenMock from './build/BasicTokenMock';
import MyLibrary from './build/MyLibrary';
import LibraryConsumer from './build/LibraryConsumer';

const {expect} = chai;

describe('INTEGRATION: Example', () => {
  let provider = createMockProvider();
  let [wallet, walletTo] = getWallets(provider);
  let token;

  beforeEach(async () => {
    token = await deployContract(wallet, BasicTokenMock, [wallet.address, 1000]);

  it('Assigns initial balance', async () => {
    expect(await token.balanceOf(wallet.address)).to.eq(1000);

  it('Transfer adds amount to destination account', async () => {
    await token.transfer(walletTo.address, 7);
    expect(await token.balanceOf(walletTo.address)).to.eq(7);

  it('Transfer emits event', async () => {
    await expect(token.transfer(walletTo.address, 7))
      .to.emit(token, 'Transfer')
      .withArgs(wallet.address, walletTo.address, 7);

  it('Can not transfer above the amount', async () => {
    await expect(token.transfer(walletTo.address, 1007)).to.be.reverted;

  it('Can not transfer from empty account', async () => {
    const tokenFromOtherWallet = token.connect(walletTo);
    await expect(tokenFromOtherWallet.transfer(wallet.address, 1))

Projects that use Waffle

How to install

To start using with npm, type:

npm i ethereum-waffle

or with Yarn:

yarn add ethereum-waffle