HelloWorld tutorial
A basic tutorial on how to setup the development environment and deploy to Acala EVM+.

Table of contents

About

This is a basic example on how to setup your Truffle development environment as well as testing and deployment configuration to be compatible with Acala EVM+. It contains a rudimentary HelloWorld smart contract and the required configurations and migrations in order to test and deploy it.
NOTE: You can refer to the complete code of this tutorial at https://github.com/AcalaNetwork/truffle-tutorials/tree/master/hello-world​

Setup an empty Truffle project

Assuming you have Truffle and yarn installed, we can jump right into creating a new Truffle project.
You can install Truffle using the following command:
Open a terminal window in a directory where you want your hello-world example to reside and create a directory for it and then initialize a yarn project within it, as well as add Truffle as a dependency, with the following commands:
mkdir hello-world
cd hello-world
yarn init --yes
yarn add truffle
truffle init
In addition to initiating a Truffle project, Truffle has already created contracts, migrations and test directories that we require for this tutorial.

Configure Truffle

As we will be using Truffle to compile, test and deploy the smart contract, we need to configure it. Uncomment the following line in the truffle-config.js:
HINT: For me this is line 21, so even if there is any discrepancy between Truffle versions, this should narrow down the search.
const HDWalletProvider = require('@truffle/hdwallet-provider');
As you may have noticed, we are importing @truffle/hdwallet-provider, so we need to add it to the project. Let's add it as a development dependency:
yarn add --dev @truffle/hdwallet-provider
We will be enabling a classic local development network (like Ganache) as well as Mandala local development network. Both need to be added to the configuration. Let's first enable the classic local development network by ucommenting the section in truffle-config.js (just like HDWalletProvider, this section is from line 44 to line 48 in my file):
development: {
host: "127.0.0.1", // Localhost (default: none)
port: 8545, // Standard Ethereum port (default: none)
network_id: "*", // Any network (default: none)
},
Now that the classic development network is enabled, let's add the Mandala configuration. As the public test network has the same configuration as the local development network, let's add a helper function to the config. Make sure to add this helper method above the module.exports (you can place it below as well, just not within). We will call it mandalaConfig and expect one argument to be passed to it. The argument passed to it is called the endpointUrl and specifies the RPC endpoint, to which the Truffle connects to. Copy the method into your truffle-config.js:
const mandalaConfig = (endpointUrl) => ({
provider: () =>
new HDWalletProvider(mnemonicPhrase, endpointUrl),
network_id: 595,
gasPrice: 0x2f03a803ea, // storage_limit = 64001, validUntil = 360001, gasLimit = 10000000
gas: 0x329b140,
timeoutBlocks: 25,
confirmations: 0
});
Let's break down this configuration:
  • provider uses the HDWalletProvided that we imported. We pass the mnemonic phrase, from which the accounts are derived, as well as the URL for the RPC endpoint of the desired network. You might have noticed that we haven't specified mnemonicPhrase anywhere just yet. Let's do it. Above the mandalaConfig add the following mnemonic:
const mnemonicPhrase = 'fox sight canyon orphan hotel grow hedgehog build bless august weather swarm';
NOTE: This mnemonic phrase is used in all of the examples and represents the default development accounts of Acala EVM+. These accounts are not safe to use and you should use your own, following the secret management guidelines of HDWalletProvider.
Now that we analyzed the provider, let's move on to the other arguments:
  • network_id is the default network ID of the development Mandala network.
  • gasPrice is the default gas price for the local development Mandala network. Commented out section represents additional parameters of Acala EVM+.
  • gas is the current gas limit for transactions.
  • timeoutBlocks and confirmations are set to our discretion and we opted for the values above in this tutorial.
The gas limit and gas price of the example might get out of sync as new blocks are mined on Mandala test network. If you encounter OutOfStorage error, or any other for that matter, while trying to deploy your smart contract using the Remix IDE, we suggest verifying these values following these instructions.
To be able to use the local development network and public test network within the project, we have to add them to the networks section of the config using the mandalaConfig helper. We do this by pasting the following two lines of code into it:
mandala: mandalaConfig("http://127.0.0.1:8545"),
mandalaPublicDev: mandalaConfig("https://acala-mandala-adapter.api.onfinality.io/public"),
Now that Mandala local development network is added to our project, let's take care of the remaining configuration. Mocha timeout should be active, to make sure that we don't get stuck in a loop if something goes wrong during tests. For this line 92 (this is after the modifications) in truffle-config.js should be uncommented:
timeout: 100000
Lastly, let's set the compiler version to 0.8.9 as this is the Solidity version we will be using in our example smart contract. To do this, line 98 needs to be uncommented and modified to:
version: "0.8.9", // Fetch exact version from solc-bin (default: truffle's version)

Add a smart contract

In this tutorial we will be adding a simple smart contract that only stores one value that we can query: Hello World!. To do that, we can use the Truffle built-in utility create:
truffle create contract HelloWorld
This command created a HelloWorld.sol file with a skeleton smart contract within contracts directory. First line of this smart contract should specify the exact version of Solidity we will be using, which is 0.8.9:
pragma solidity =0.8.9;
Now let's add a public helloWorld variable and assign a Hello World! value to it in the beginnging of the smart contract. We should also remove public visibility setting of the constructor() as the compiler ignores it anyway. Replace the body of the smart contract with the following code:
string public helloWorld = 'Hello World!';
​
constructor() {}
NOTE: Make sure that the helloWorld variable visibility is set to public, as this will cause the compiler to create a helloWorld() getter, which we will use to validate the successful deployment of our smart contract.`
Your smart contract in HelloWorld.sol should look like this:
Now that we have the smart contract ready, we have to compile it. For this, we will add the build script to the package.json. To do this, we have to add scripts section to it. We will be using Truffle's compile functionality, so the scripts section should look like this:
"scripts": {
"build": "truffle compile"
}
When you run the build command using yarn build, the build directory is created and it contains the compiled smart contract.

Add a test

To add a test for the smart contract, we can again use the Truffle built-in create utility:
truffle create test HelloWorld
This creates a hello_world.js file in test directory and we can start writing the tests. If you open the file, you can see that Truffle has already imported our smart contract in the first line of the file, so we can jump right into writing the tests. First we will create a before action. We require one globally available variable, called instance, that will hold the information about the deployed smart contract. The before action in itself will just make sure that the smart contract is deployed. To add it, replace the current it block with the following code:
let instance;
​
before("setup development environment", async function () {
instance = await HelloWorld.deployed();
return assert.isTrue(true);
});
Now that we have everything set up, let's add a new it block, in which we will test that the right value is assigned to the helloWorld variable:
it("returns the right value after the contract is deployed", async function() {
});
The last step in building our example test is to get the value of the helloWorld variable from the smart contract and assert that is is equal to Hello World!. To do this, place the following two lines into the it block:
const hello_world = await instance.helloWorld();
​
expect(hello_world).to.equal("Hello World!");
Your test/hello_world.js should look like this:
To be able to run the tests, we will add two additional scripts to the package.json. One script will be used to test on a traditional local development network and one will be used to test on a Mandala local development network. We already added both into the network section of truffle-config.js. Add these lines to the scripts section of your package.json:
"test": "truffle test",
"test-mandala": "truffle test --network mandala"
This script can be run using yarn test or yarn test-mandala, depending on which network we want to use to run the tests.
NOTE: To be able to run the tests in Truffle, we need to add a migration for the smart contracts that we are testing. We will do this in the next section of this tutorial.
When you run the test with yarn test, your tests should pass with the following output:
yarn test
​
​
yarn run v1.22.15
warning ../../../../../package.json: No license field
$ truffle test
Using network 'development'.
​
​
Compiling your contracts...
===========================
> Everything is up to date, there is nothing to compile.
​
Deploying HelloWorld
HelloWorld deployed at: 0xC1a9a4fAed294383EC9918078417FA348090964b
​
​
Contract: HelloWorld
βœ“ returns the right value after the contract is deployed (40ms)
​
​
1 passing (134ms)
​
✨ Done in 18.41s.

Add a deploy script

Finally let's add a script that deploys the example smart contract. We can again use Truffle built-in utility create to create a migration file:
truffle create migration HelloWorld
The utility created a bare-bones migration file in the migrations folder. First thing we need to do is import our smart contract into it. We do this with the following line of code at the top of the file:
const HelloWorld = artifacts.require("HelloWorld");
To make sure that our migration will successfully deploy our smart contract, we have to make sure that our deployer is ready. To do that, we need to modify the deployment function to be asynchronous. Replace the 3rd line of the migration with:
module.exports = async function (deployer) {
Now that we have the smart contract imported within the migration, we can deploy the smart contract. We do this by invoking deployer, which is defined in the definition of the function. Additionally we will output the address of the deployed smart contract:
console.log("Deploying HelloWorld");
​
await deployer.deploy(HelloWorld);
​
console.log("HelloWorld deployed at:", HelloWorld.address);
This completes our migration and allows us to deploy the example smart contract as well as run tests for it.
Your HelloWorld migration should look like this:
All that is left to do is update the scripts section in the package.json with the deploy and deploy-mandala scripts. To add these scripts to your project, place the following lines within scripts section of the package.json:
"deploy": "truffle migrate",
"deploy-mandala": "truffle migrate --network mandala"
Running the yarn deploy script should return the following output:
yarn deploy
​
​
yarn run v1.22.15
warning ../../../../../package.json: No license field
$ truffle migrate
​
Compiling your contracts...
===========================
> Everything is up to date, there is nothing to compile.
​
​
​
Starting migrations...
======================
> Network name: 'development'
> Network id: 1637493978695
> Block gas limit: 6721975 (0x6691b7)
​
​
1637495010_hello_world.js
=========================
Deploying HelloWorld
​
Deploying 'HelloWorld'
----------------------
> transaction hash: 0xfc4edba5e6266a8504a8cd49298600e2cb46f4a336b05100a078ab9e0be1c3a9
> Blocks: 0 Seconds: 0
> contract address: 0x3493cD3C0F5B5EE72733F302f460dAD06f81b29e
> block number: 23
> block timestamp: 1637503061
> account: 0x9fc75A752a8672b570819Ad8f29277A8E27F33CB
> balance: 99.93235234
> gas used: 199289 (0x30a79)
> gas price: 20 gwei
> value sent: 0 ETH
> total cost: 0.00398578 ETH
​
HelloWorld deployed at: 0x3493cD3C0F5B5EE72733F302f460dAD06f81b29e
​
> Saving migration to chain.
> Saving artifacts
-------------------------------------
> Total cost: 0.00398578 ETH
​
​
Summary
=======
> Total deployments: 1
> Final cost: 0.00398578 ETH
​
​
✨ Done in 22.81s.

Summary

We have initiated an empty Truffle project and configured it to work with Acala EVM+. We added HelloWorld.sol smart contract, that can be compiled using yarn build, and wrote a test for it, which can be run using yarn test or yarn test-mandala. Additionally we added the deploy script that can be run using yarn deploy or yarn deploy-mandala.
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Outline
Table of contents
About
Setup an empty Truffle project
Configure Truffle
Add a smart contract
Add a test
Add a deploy script
Summary