[DEPRECATED] This repository is now deprecated in favour of the new development monorepo.
Hi there! Welcome to our Optimistic Ethereum ERC20 Waffle example!
If your preferred smart contract testing framework is Truffle, see our Optimistic Ethereum ERC20 Truffle tutorial here.
If you're interested in writing your first L2-compatible smart contract using Waffle as your smart contract testing framework, then you've come to the right place! This repo serves as an example for how go through and compile & test your contracts on both Ethereum and Optimistic Ethereum.
Let's begin!
Please make sure you've installed the following before continuing:
To start, clone this Waffle-ERC20-Example repo, enter it, and install all of its dependencies:
git clone https://github.com/ethereum-optimism/Waffle-ERC20-Example.git
cd Waffle-ERC20-Example
yarn installCompiling a contract for Optimistic Ethereum is pretty easy!
First we'll need to install the @eth-optimism/solc and solc packages.
Since we currently only support solc versions 0.5.16, 0.6.12, and 0.7.6 for Optimistic Ethereum contracts, we'll be using version 0.7.6 in this example.
Let's add these two packages:
yarn add @eth-optimism/solc@0.7.6-alpha.1
yarn add solc@0.7.6Next we just need to add a new Waffle config to compile our contracts.
Create waffle-ovm.json and add this to it:
{
"compilerVersion": "./node_modules/@eth-optimism/solc",
"sourceDirectory": "./contracts",
"outputDirectory": "./build-ovm"
}Here, we specify the new custom Optimistic Ethereum compiler we just installed and the new build path for our compiled contracts.
And we're ready to compile! All you have to do is specify the waffle-ovm.json config in your waffle command:
yarn waffle waffle-ovm.jsonOur waffle-ovm.json config file tells Waffle that we want to use the Optimistic Ethereum solidity compiler.
Yep, it's that easy. You can verify that everything went well by looking for the build-ovm directory.
Here, build-ovm signifies that the contracts contained in this directory have been compiled for the OVM, the Optimistic Virtual Machine, as opposed to the Ethereum Virtual Machine. Now let's move on to testing!
Testing with Waffle is easy. We've included a simple set of ERC20 tests inside Waffle-ERC20-Example/test/erc20.spec.js. Let's run these tests with waffle:
yarn mocha 'test/*.spec.js' --timeout 10000If everything went well, you should see a bunch of green checkmarks.
Woot! It's finally time to test our contract on top of Optimistic Ethereum. But first we'll need to get a local version of an Optimistic Ethereum node running...
Fortunately, we have some handy dandy tools that make it easy to spin up a local Optimistic Ethereum node!
Since we're going to be using Docker, make sure that Docker is installed on your machine prior to moving on (info on how to do that here). We recommend opening up a second terminal for this part. This way you'll be able to keep the Optimistic Ethereum node running so you can execute some contract tests.
Now we just need to download, build, and install our Optimistic Ethereum node by running the following commands.
Please note that docker-compose build will take a while.
We're working on improving this (sorry)!
git clone git@github.com:ethereum-optimism/optimism.git
cd optimism
yarn install
yarn build
cd ops
docker-compose build
docker-compose upYou now have your very own locally deployed instance of Optimistic Ethereum! 🙌
With your local instance of Optimistic Ethereum up and running, let's test your contracts! Since the two JSON RPC provider URLs (one for your local instance Ethereum and Optimistic Ethereum) have already been specified in your .env file, all we need to do next is run the test command.
To do that, run:
yarn TARGET=OVM mocha 'test/*.spec.js' --timeout 50000Notice that we use the TARGET=OVM flag to let mocha know that we want to use the build-ovm folder as our path to our JSON files.
(Remember that these JSON files were compiled using the Optimistic Ethereum solidity compiler!)
You should see a set of passing tests for your ERC20 contract. If so, congrats! You're ready to deploy an application to Optimistic Ethereum. It really is that easy.
And uh... yeah. That's pretty much it.
Tutorial complete.
Hopefully now you know the basics of working with Optimistic Ethereum!
Our goal is to bring the OVM as close to 100% compatibility with all existing Ethereum projects, but our software is still in an early stage. Our community hub docs will maintain the most up to date list of known incompatibilities between the OVM and EVM, along with our plans to fix them.
The OVM provides a fresh new take on layer 2 development: it's mostly identical to layer 1 development. However, there are a few differences that are worth noting, which you can read more about in our EVM comparison documentation. No hoops, no tricks--the Ethereum you know and love, ready to scale up with L2. For more info on our progress and what's going on behind the scenes, you can follow us on Twitter.
Want to try deploying contracts to the Optimistic Ethereum testnet next? Check out the full integration guide on the Optimism community hub.
Example project not working? Create a Github Issue, or hop in our Discord channel and ask away.