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    3.4.4 • Public • Published


    Ethereum Waffle

    The most advanced framework for testing smart contracts.

    Sweeter, simpler and faster.



    • Simpler: Minimalistic, few dependencies.
    • Sweeter: Nice syntax, easy to extend.
    • Faster: Strong focus on the speed of test execution.


    • Sweet set of chai matchers, e.g.:
      • expect(...)'Error message')
      • expect(...).to.emit(contract, 'EventName').withArgs(...))
    • Importing contracts from npm modules working out of the box, e.g.:
      • import "openzeppelin-solidity/contracts/token/ERC20/ERC20.sol";
    • Fixtures that help write fast and maintainable test suites, e.g.:
      • const {token} = await loadFixture(standardTokenWithBalance);
    • Customizable compilation options with native solc, dockerized solc and any version of solc-js loaded remotely at compiled time
    • Mocking smart contracts, e.g.:
      • const mockToken = await deployMockContract(wallet, IERC20.abi);
    • Support for promise-based configuration, e.g.:
      • use native solc binary for fast compilation in CI environment
      • use solc-js based on contract versions detected (async)
    • Support for TypeScript
    • Type-safe contract deployment and interactions with TypeChain
    • Documentation


    Documentation is available here.


    To get started install ethereum-waffle with yarn:

    yarn add --dev ethereum-waffle

    Or if you prefer using npm:

    npm install --save-dev ethereum-waffle

    Step by step guide

    Add external dependency:

    To add an external library install it using npm:

    npm install @openzeppelin/contracts -D

    or with yarn:

    yarn add @openzeppelin/contracts -D


    Find this example in examples/basic and use it.

    Example contract

    Below is an example contract written in Solidity. Place it in contracts/BasicToken.sol file of your project:

    pragma solidity ^0.6.0;
    import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
    // Example class - a mock class using delivering from ERC20
    contract BasicToken is ERC20 {
        constructor(uint256 initialBalance) ERC20("Basic", "BSC") public {
            _mint(msg.sender, initialBalance);

    Example test

    Below is an example test written for the contract above compiled with Waffle. Place it under test/BasicToken.test.ts file in your project directory:

    import {expect, use} from 'chai';
    import {Contract} from 'ethers';
    import {deployContract, MockProvider, solidity} from 'ethereum-waffle';
    import BasicToken from '../build/BasicToken.json';
    describe('BasicToken', () => {
      const [wallet, walletTo] = new MockProvider().getWallets();
      let token: Contract;
      beforeEach(async () => {
        token = await deployContract(wallet, BasicToken, [1000]);
      it('Assigns initial balance', async () => {
        expect(await token.balanceOf(wallet.address)).to.equal(1000);
      it('Transfer adds amount to destination account', async () => {
        await token.transfer(walletTo.address, 7);
        expect(await token.balanceOf(walletTo.address)).to.equal(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));
      it('Can not transfer from empty account', async () => {
        const tokenFromOtherWallet = token.connect(walletTo);
        await expect(tokenFromOtherWallet.transfer(wallet.address, 1))
      it('Calls totalSupply on BasicToken contract', async () => {
        await token.totalSupply();
      it('Calls balanceOf with sender address on BasicToken contract', async () => {
        await token.balanceOf(wallet.address);
        expect('balanceOf'), [wallet.address]);

    Note: You will also need to install following dependencies with to run the example above:

    yarn add mocha -D
    yarn add chai -D

    Or with npm:

    npm i chai -D
    npm i mocha -D


    To compile your smart contracts run:

    npx waffle

    To compile using a custom configuration file run:

    npx waffle config.json

    Example configuration file looks like this (all fields optional):

      "sourceDirectory": "./custom_contracts",
      "outputDirectory": "./custom_build",
      "nodeModulesDirectory": "./custom_node_modules"

    To enable generation of typechain artifacts:

      "typechainEnabled": true


    To flat your smart contracts run:

    npx waffle flatten

    In configuration file you can add optional field with path to flatten files:

      "flattenOutputDirectory": "./custom_flatten"

    Running tests

    To run the tests run the following command:

    npx mocha

    Adding an npm script

    For convinience, you can add the following to your package.json:

      "scripts": {
        "test": "waffle && mocha"

    Now you can build and test your contracts with one command:

    npm test


    For detailed feature walkthrough checkout documentation.


    Contributions are always welcome, no matter how large or small. Before contributing, please read the code of conduct and contribution policy.

    Before you issue pull request:

    Make sure all tests and linters pass. Make sure you have test coverage for any new features.

    Running tests

    Note: To make end-to-end test pass, you need to:

    • have Docker installed, up and running
    • have Ethereum stable docker image pulled, if not run docker pull ethereum/solc:stable
    • have native solidity 0.5.* installed

    To run tests type:

    yarn test

    To run linter type:

    yarn lint

    Building documentation

    Install Sphinx to build documentation:

    cd docs
    make html

    Before building documentation for the first time you may have to install required python packages:

    pip3 install -r docs/requirements.txt




    Waffle is released under the MIT License.


    npm i ethereum-waffle

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