Intro

Ethereum contracts are often developed in the same repository as the web app interfaces that call them. This allows developers to fall into the trap of testing their smart contracts by interacting with them in the web user interface.

Because of the sensitive nature of contract development, it’s important that every line of contract code is represented in the tests. It is paramount that the development process discourages workflows other than test driven development.

I describe how I set up travis to automatically deploy contracts to test networks on every tagged commit, and publish the resulting build artifacts to npm for usage as an npm dependency of the UI package.

The resulting contract development workflow is as follows:

  1. Write unit tests
  2. Make changes to contracts to satisfy tests
  3. Create a tagged release commit
    • Travis runs truffle migrate on your desired networks
    • Travis runs npm publish with the contract build artifacts
  4. Update my UI package to point at the latest contract package version
    • Use your contract artifacts via require('contract-package/build/contracts/Contract.json')

Get an infura API key

Go here to register an infura token.

Copy my truffle.js

This truffle.js file sets up infura providers. We’ll fill in the MNEMONIC and INFURA_API_KEY variables in the Travis UI later.

const INFURA_API_KEY = process.env.INFURA_API_KEY;
const MNEMONIC = process.env.MNEMONIC;
const HDWalletProvider = require('truffle-hdwallet-provider');

const NETWORK_IDS = {
  // mainnet: 1,
  ropsten: 2,
  rinkeby: 4,
  kovan: 42
};

module.exports = {
  networks: {}
};

for (let networkName in NETWORK_IDS) {
  module.exports.networks[ networkName ] = {
    provider: new HDWalletProvider(MNEMONIC, 'https://' + networkName + '.infura.io/' + INFURA_API_KEY),
    network_id: NETWORK_IDS[ networkName ]
  };
}

Generate a BIP39 mnemonic

Generate a BIP39 mnemonic to use for deploying your contracts. You can go here to do so.

Acquire Testnet Ether

This depends on the network you want to deploy to, but for Kovan you can use a faucet described here.

Go to myetherwallet to get the public key for your BIP39. Use this public key when requesting ether from the faucets.

Create a script to deploy to the testnet in package.json

We will use this script to tell truffle to deploy to the testnet we defined in our truffle.js above.

{
  "scripts": {
    "migrate:kovan": "truffle migrate --network kovan"
  },
  "files": [
    "build/"
  ]
}

Set up your travis.yml

Now you need Travis to know how to deploy your artifacts. To do so, first set up the Travis npm deployment provider using travis setup npm. Then, insert the additional script deployment provider from the snippet below-it should come before the npm provider since you want the build artifacts deployed to npm to include information about to which networks it was deployed. Note script may only take one command. If you wish to deploy to multiple testnets, you will have to use a script to call npm several times.

deploy:
  - provider: script
    skip_cleanup: true
    script: npm run migrate:kovan
    on:
      all_branches: true
      tags: true
  - provider: npm....

Give Travis your MNEMONIC and INFURA_API_KEY environment variables

Go to your project at the Travis website to add the environment variables MNEMONIC and INFURA_API_KEY. These should be your BIP39 mnemonic generated earlier and your API key that you got from infura.

Make sure to surround your MNEMONIC in QUOTES! Because the mnemonic has spaces in it, and travis inserts those variables exactly as typed, your deployments will not work unless your mnemonic is entered with quotes.

Example: discuss-eth

I’m using this workflow in my project to build a decentralized forum. Give me a hollar if you want to help!

Next Steps

It would be great for Travis to implement a deployment provider that supports this workflow for Truffle.

This can also be used to deploy to the mainnet, but I would discourage it since you’d have to send ether to a wallet to which the Travis team has access-though it should be a relatively small amount of ether depending on the size of your contract.