ethereum-waffle

Library for writing and testing smart contracts.

Sweeter and simpler than truffle.

Works with ethers-js. Tastes best with ES6.

Philosophy

• Simpler: minimalistic, a couple of helpers, matchers and tasks rather than a framework, few dependencies.
• Sweeter: Nice syntax, fast, easy to extend.

Versions and ethers compatibility

• Use version 0.2.3+ with ethers 3.* and solidity 4.*
• Use version 1.0.0+ with ethers 4.* and solidity 4.*
• Use version 2.0.5-beta with ethers 4.*; solidity 4, 5 and to use experimental native solc and dockerized solc.

Install:

To start using with npm, type:

npm i ethereum-waffle

or with Yarn:

yarn add ethereum-waffle

Step by step guide

Example contract

Below is example contract written in Solidity. Place it in contracts directory of your project:

pragma solidity ^0.5.1;

import "../BasicToken.sol";

contract BasicTokenMock is BasicToken {

  constructor(address initialAccount, uint256 initialBalance) public {
    balances[initialAccount] = initialBalance;
    totalSupply_ = initialBalance;
  }

}

Example test

Belows is example test written for the contract above written with Waffle. Place it in test directory of your project:

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

chai.use(solidity);

const {expect} = chai;

describe('Example', () => {
  let provider;
  let token;
  let wallet;
  let walletTo;

  beforeEach(async () => {
    provider = createMockProvider();
    [wallet, walletTo] = await getWallets(provider);
    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(wallet.address)).to.eq(993);
    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 from empty account', async () => {
    const tokenFromOtherWallet = contractWithWallet(token, walletTo);
    await expect(tokenFromOtherWallet.transfer(wallet.address, 1))
      .to.be.revertedWith('Not enough balance on sender account');
  });
});

Compile

To compile contracts simply type:

npx waffle

To compile using custom configuration file:

npx waffle config.json

Example configuration file looks like this:

{
  "sourcesPath": "./custom_contracts",
  "targetPath": "./custom_build",
  "npmPath": "./custom_node_modules"
}

Run tests

To run test type in the console:

mocha

Adding a task

For convince, you can add a task to your package.json. In the sections scripts, add following line:

  "test": "waffle && test"

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

npm test

Features walkthrough

Import contracts from npms

Import solidity files from solidity files form npm modules that you added to your project, e.g:

import "openzeppelin-solidity/contracts/math/SafeMath.sol";

Create a mock provider

Create a mock provider (no need to run any tests!) and test your contracts against it, e.g.:

provider = createMockProvider();

Get example wallets

Get wallets you can use to sign transactions:

[wallet, walletTo] = await getWallets(provider);

Deploy contract

Deploy a contract:

token = await deployContract(wallet, BasicTokenMock, [wallet.address, 1000]);

Link a library:

myLibrary = await deployContract(wallet, MyLibrary, []);
link(LibraryConsumer, 'path/to/file:MyLibrary.sol:MyLibrary', myLibrary.address);
libraryConsumer = await deployContract(wallet, LibraryConsumer, []);

Chai matchers

A set of sweet chai matchers, makes your test easy to write and read. Below couple of examples.

• Testing big numbers:

expect(await token.balanceOf(wallet.address)).to.eq(993);

Available matchers for BigNumbers are: equal, eq, above, below, least, most.

• Testing what events where emitted with what arguments:

await expect(token.transfer(walletTo.address, 7))
  .to.emit(token, 'Transfer')
  .withArgs(wallet.address, walletTo.address, 7);

• Testing if transaction was reverted:

await expect(token.transfer(walletTo.address, 1007)).to.be.reverted;

• Testing if transaction was reverted with certain message:

await expect(token.transfer(walletTo.address, 1007)).to.be.revertedWith('Insufficient funds');

• Testing if string is a proper address:

expect('0x28FAA621c3348823D6c6548981a19716bcDc740e').to.be.properAddress;

• Testing if string is a proper secret:

expect('0x706618637b8ca922f6290ce1ecd4c31247e9ab75cf0530a0ac95c0332173d7c5').to.be.properPrivateKey;

• Testing if string is a proper hex value of given length:

expect('0x70').to.be.properHex(2);

• Testing whether the transaction changes balance

await expect(() => myContract.transferWei(receiverWallet.address, 2)).to.changeBalance(receiverWallet, 2);

Note: transaction call should be passed to the expect as a callback (we need to check the balance before the call). The matcher can accept numbers, strings and BigNumbers as a balance change, while the address should be specified as a wallet.

changeBalance calls should not be chained. If you need to chain it, you probably want to use changeBalances matcher.

• Testing whether the transaction changes balance for multiple accounts

await expect(() => myContract.transferWei(receiverWallet.address, 2)).to.changeBalances([senderWallet, receiverWallet], [-2, 2]);

Fast compilation

By default, Waffle uses solcjs. Solcjs is solidity complier cross-complied to javascript. It is slow, but easy to install. As an alternative, you can use the original Solidity compiler, which is faster. There are two options:

1. Dockerized solc
2. Native solc

Dockerized solc (experimental)

This options is pretty easy to install especially if you have docker installed. This is recommended option. If you don't have docker follow instructions.

Pull solc docker container tagged with version you are interested in, for example for version 0.4.24 it will be:

docker pull ethereum/solc:0.4.24

Than setup compiler in your waffle configuration file:

{
  ...
  "compiler": "dockerized-solc",
  "docker-tag": "0.4.24"
}

Default docker tag is latest.

You can now run tests in docker.

Native solc

This option is by far the fastest but requires you to install native solidity. If you need a legacy version that might be somewhat complicated and require you to build solidity from sources.

You can find detailed installation instructions for native solc in (documentation)[https://solidity.readthedocs.io/en/latest/installing-solidity.html#binary-packages].

You need to install version compatible with your sources. If you need latest version that is pretty straight forward. See Installation instructions below.

Installation instructions for latest version of solidity

MacOS

To install lastest versions on MacOS:

brew install solidity

To install other versions, it seems that currently it easiest to build from source:

1. Download sources from (release list on github)[https://github.com/ethereum/solidity/releases]
2. Follow installation instructions in the (documentation)[https://solidity.readthedocs.io/en/develop/installing-solidity.html#building-from-source]

Ubuntu

To install lastest versions on Ubuntu:

sudo add-apt-repository ppa:ethereum/ethereum
sudo apt-get update
sudo apt-get install solc

Project setup

Setup compiler in your waffle configuration file:

{
  ...
  "compiler": "native"
}

To do some detective work and figure out command for particular version go here:

You can now run tests with native solc, eg:

npx waffle

Solcjs and version management

You can setup version which solidity compiler version you would like to use with solcjs in waffle configuration file, e.g.:

{
  ...
  "solcVersion": "v0.4.24+commit.e67f0147"
}

Version naming is somewhat unintuitive. You can deduce version name from [list available here] (https://ethereum.github.io/solc-bin/bin/list.json).

Testing

Note: To make end to end test pass, you need to have docker installed, up and running.

To run test type:

yarn test

Roadmap

• New matcher: changeBalance (see #9)
• Faster testing with native geth (aside from ganache)
• Faster compilation with native and dockerized solc (aside from solcjs)
• Documentation
• Debugging and profiling