Cronos Testnet Deployment

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Photo by Billy Huynh on Unsplash

In this article, we will explore how to deploy a Simple storgage contract from Truffle to the Cronos testnet.

About

Truffle is a development environment for writing smart contracts on the Ethereum blockchain. It allows developers to:

  • Compile contracts
  • Test contracts
  • Deploy contracts
  • Debug contracts

Cronos Chain is a EVM that runs parallel on to Crypto.org’s blockchain

It provides many usability including:

  • EVM Compatibility
  • Fast and efficient scalability
  • Easy to port Dapps from Etheruem and other EVM compatible chains

You can learn more about each here:

TruffleSuite

Cronos Chain

Project Setup

The first step we need to do is set up a project with Truffle before we start writing our smart contract.

  • Go to the folder where you want the project to live
mkdir <project name>
  • Then move into that folder you just created
cd <project name>

Now we will install Truffle into out project with the following command:

truffle init

You should get a similar output

Starting init...
================
> Copying project files to /Users/Desktop/cronos-truffle-example
Init successful, sweet!
Try our scaffold commands to get started:
$ truffle create contract YourContractName # scaffold a contract
$ truffle create test YourTestName         # scaffold a test
http://trufflesuite.com/docs

Next install npm so that we can add a couple of dependencies.

Use the following command to install npm.

npm i -y
You can use npm i, I chose to use -y to bypass each setup step questions during the install

Once we installed npm, we will import two dependencies we will use for our project.

Run the following command to install them both

npm i dotenv @truffle/hdwallet-provider

Writing the smart contract

Inside the contracts directory, create a new file and name it SimpleStorage.sol

Then put the following code into the file

We won’t get into too much of the code since this tutorial is more about deploying a contract using Truffle to the Cronos Testnet. Here is information on writing smart contracts using Solidity

Next, we will have to write a migration script.

Inside the migrations directory, add another file and name it 2_deploy_SimpleStorage.js

Now inside the file, write the following code:

To learn more on how migrations in Truffle works here

Cronos Testnet Configuration

Now that we have a smart contract, we first have to configure the network before we are able to deploy it to the testnet.

Let’s set up the Cronos testnet configuration by going into the truffle-config.js file

There are a lot of information about how to use this file, but we will simplify it.

Right above the module.exports = { , we will add the following:

require("dotenv").config();
const HDWalletProvider = require('@truffle/hdwallet-provider');

Here we are getting the dotenv package to hide our private key later on and also getting the HDWalletProvider as a Web3 provider

Next, we will setup the Cronos testnet configuration.

Inside the networks: { find the rospten network and replace it with the following code:

cronosTestnet: {
provider: () => new HDWalletProvider(process.env.PRIVATE_KEY, "https://cronos-testnet-3.crypto.org:8545"),
network_id: "*",       // Cronos's testnet id
skipDryRun: true
},

This code added the Cronos testnet address https://cronos-testnet-3.crypto.org:8545 to the config file and uses the HDWalletProvider to connect to with by using a given private key from an account.

Let’s simply the whole file and the code should look like the following:

Setting Up Test Account

Before we can deploy our contract, we first have to connect our wallet to the testnet. In order to do so, we will configure it using Metamask.

You can find out more about Metamask

  • Log into Metamask
  • Under the network menu at the top, click on the button to Add Network
  • Input the following information to add a new network:
Network Name: <Name to call Cronos Testnet>
- RPC Url : https://cronos-testnet-3.crypto.org:8545/
- ChainId: 338
- Symbol: tCro
- Block Explorer URL: https://cronos.crypto.org/explorer/testnet3/

Once the testnet is added to Metamask, we fill fund it with some test Cronos.

Go to the faucet and fund the account you will be testing with.

Now that we have setup our test network and have tCro, the last thing we need to do before deploying our contract is to pass in our account’s private key in our truffle-config file.

In order to do this more securely, we will store the private key in a .env file.

In the root directory of the project, type in the following command:

touch .env

This will create a file called .env in the root directory.

Inside this directory, we will assign a the variable PRIVATE_KEY= our private key

To get the private key, go to the Metamask account you are using for the test and when you click the 3 dots next to it, select the Account details

Select the Export Private Key button. Metamask will ask for your account password and once you type that in, you should be given the private key. Now copy this key into the .env file.

It should look similar to the following.

PRIVATE_KEY=e902eef0dd0a0c03845b9b743c7834839
Note that this is not a real private and is used for demonstration purpose

Since we already declared this variable in our truffle-config file in the HDWallet-Provder method, we do not have to do anything else.

provider: () => new HDWalletProvider(process.env.PRIVATE_KEY, `https://cronos-testnet-3.crypto.org:8545`),

Deploy smart contract

Now that we have:

✔️ A smart contract

✔️ Network configuration setup

✔️ Connected Metamask account to the testnet

✔️ Fund the account with test tokens

We are able to deploy our contract to the testnet:

In the root directory of the project, we can run the following truffle command to deploy our contract:

truffle deploy --network cronosTestnet

You should get similar output in the terminal

Compiling your contracts...
===========================
> Everything is up to date, there is nothing to compile.
Starting migrations...
======================
> Network name:    'cronosTestnet'
> Network id:      338
> Block gas limit: 81500000 (0x4db9760)
1_initial_migration.js
======================
Deploying 'Migrations'
----------------------
> transaction hash:    0x5be6f16117df6f65b170af759df881be8afc8f6b144790cec2fe26dc2ee8eeb7
> Blocks: 0            Seconds: 4
> contract address:    0xAAEc9B476c0897d7A4b80Cdd61314446A402237e
> block number:        1301726
> block timestamp:     1641843771
> account:             0x2880627569ffA41965536CE20B0596009eDfA744
> balance:             98.74523
> gas used:            250954 (0x3d44a)
> gas price:           5000 gwei
> value sent:          0 ETH
> total cost:          1.25477 ETH
> Saving migration to chain.
> Saving artifacts
-------------------------------------
> Total cost:             1.25477 ETH
2_deploy_SimpleStorage.js
=========================
Deploying 'SimpleStorage'
-------------------------
> transaction hash:    0x4feb1d3bd554d44a12e115646448224d36be69d8d9626f4d83e181c6bd97b50a
> Blocks: 1            Seconds: 5
> contract address:    0x68118E9543a5CBded1d7255844b0FA40177C9641
> block number:        1301730
> block timestamp:     1641843795
> account:             0x2880627569ffA41965536CE20B0596009eDfA744
> balance:             96.97724
> gas used:            308985 (0x4b6f9)
> gas price:           5000 gwei
> value sent:          0 ETH
> total cost:          1.544925 ETH
⠋ Saving migration to chain.

You should also notice that the amount of your test tokens has reduced.

Finally, you can check that the contract has been deployed to Cronos’ testnet by getting the contracts address that was created in the output of the terminal when it was deployed and paste it into Cronos’ testnet block explorer Here

The result should look something similar to this:

Screen shot of Cronos testnet transaction

You can see that the contract was created and a transaction has been made to the contract on the Cronos testnet.

Thanks for reading this article and I hope you find it useful.

Stay tuned for more articles on blockchain, smart contracts and much more!

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