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Deploying a smart contract with Foundry

In this guide, we discuss the basics of the Foundry development toolchain and will describe how to create and deploy a smart contract with Foundry to the Lisk Sepolia testnet.

note

You can deploy a contract on Lisk mainnet by adopting the same process. For deploying to mainnet, ensure that your wallet has enough ETH.

The subsequent text contains commands for both Lisk and Lisk Sepolia for your ease. For more information, see the available Lisk networks and how to connect a wallet with them.

Foundry is a powerful suite of tools to develop, test, and debug your smart contracts. It comprises several individual tools such as:

  • forge: is a command-line tool that is shipped with Foundry. Forge tests, builds, and deploys your smart contracts.
  • cast: is a command-line tool for performing RPC calls e.g., interacting with contracts, sending transactions, and getting onchain data.
  • anvil: is a local testnet node, designed for testing contract behavior from a frontend or over RPC in a local development environment.
  • chisel: is a Solidity REPL, for trying out Solidity snippets on a local or forked network.

Prerequisites​

To build with Foundry, you need:

  • A basic understanding of Solidity.
  • Have Foundry installed on your system. To do that, perform the following steps:
    • From the command line, run: 
      curl -L https://foundry.paradigm.xyz | bash
    • After that, to install the latest (nightly) build of Foundry, run: 
      foundryup
  • For more information, see the Foundry Book's Installation guide.

Wallet funds​

Deploying contracts to the blockchain requires a gas fee. Therefore, you will need to fund your wallet with ETH to cover such gas fees.

For this guide, you will be deploying a contract to the Lisk Sepolia Testnet.

You can deposit the required tokens by using the Lisk Sepolia Bridge.

In case your wallet doesn't hold enough SepoliaETH, use one of the available faucets for the Ethereum Sepolia Testnet like https://sepoliafaucet.com to receive free Testnet ETH. Then, use the aforementioned Lisk Bridge to send tokens from the Ethereum Sepolia Testnet to the Lisk Sepolia Testnet.

Creating a project​

The first step of deploying smart contracts to Lisk is to set up your development environment by creating a Foundry project.

You can separately create a new directory and then initialize a Foundry project, or you can let Foundry create a directory and initiate a Foundry project by running the following command:

forge init foundry_app && cd foundry_app

This command will create a foundry_app and will change the terminal's working directory to the aforementioned folder as well.

Execution logs of the forge init command
Initializing /XYZ/L2/25/foundry_app/foundry_app...
Installing forge-std in /XYZ/L2/25/foundry_app/foundry_app/lib/forge-std (url: Some("https://github.com/foundry-rs/forge-std"), tag: None)
Cloning into '/XYZ/L2/25/foundry_app/foundry_app/lib/forge-std'...
remote: Enumerating objects: 2181, done.
remote: Counting objects: 100% (2177/2177), done.
remote: Compressing objects: 100% (737/737), done.
remote: Total 2181 (delta 1446), reused 2066 (delta 1373), pack-reused 4
Receiving objects: 100% (2181/2181), 614.11 KiB | 766.00 KiB/s, done.
Resolving deltas: 100% (1446/1446), done.
Submodule 'lib/ds-test' (https://github.com/dapphub/ds-test) registered for path 'lib/ds-test'
Cloning into '/XYZ/L2/25/foundry_app/foundry_app/lib/forge-std/lib/ds-test'...
remote: Enumerating objects: 313, done.        
remote: Counting objects: 100% (171/171), done.        
remote: Compressing objects: 100% (79/79), done.        
remote: Total 313 (delta 91), reused 132 (delta 83), pack-reused 142        
Receiving objects: 100% (313/313), 71.35 KiB | 521.00 KiB/s, done.
Resolving deltas: 100% (130/130), done.
    Installed forge-std v1.7.6
    Initialized forge project

By default, any application built with Foundry will have a similar directory structure to the following:

.
├── .github
├── lib
├── script
│   └── Counter.s.sol
├── src
│   └── Counter.sol
├── test
│   └── Counter.t.sol
├── .gitignore
├── .gitmodules
├── foundry.toml
└── README.md

For now, delete the files present in the script/Counter.s.sol, src/Counter.sol, and test/Counter.t.sol as we will be creating a contract, and relevant test code ourselves in the following guide.

Creating the smart contract​

For ease and security, we’ll use the ERC721 contract provided by the OpenZeppelin Contracts library to create a simple ERC-721 smart contract. With OpenZeppelin, we don’t need to write the entire ERC-721 contract. Instead, we can import the library contract and use its functions from the get-go.

To install the OpenZeppelin Contracts library to your project, run:

forge install openzeppelin/openzeppelin-contracts

Inside the src folder, create a smart contract called NFT.sol and add the code below to the newly created file.

src/NFT.sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.23;

import "openzeppelin-contracts/contracts/token/ERC721/ERC721.sol";

contract NFT is ERC721 {
    uint256 public currentTokenId;
    
    // The following will create an ERC721 Token called Lisk.
    constructor() ERC721("Lisk", "LSK") {}

    // For simplicity, we will only implement the mint function of the Lisk token.
    function mint(address recipient) public payable returns (uint256) {
        uint256 newItemId = ++currentTokenId;
        _safeMint(recipient, newItemId);
        return newItemId;
    }
}

Compiling the smart contract​

Once the smart contract's code is ready, it must be compiled using Foundry, to do that, simply run:

forge build

If the smart contract doesn't have any errors, you will see the following output on the terminal:

[⠢] Compiling...
[⠰] Compiling 1 files with 0.8.24
[⠔] Solc 0.8.24 finished in 40.36ms
Compiler run successful!

Testing the smart contract​

By testing the smart contract, you can verify that the smart contract behaves as expected and that it is free of bugs, before deploying it to Lisk.

Foundry provides a rich testing framework to support you in writing tests for smart contracts. See Tests - Foundry Book for examples and references regarding the testing framework.

To test the NFT smart contract, create a new file NFT.t.sol under the test/ directory, and add the following content:

foundry_app/test/NFT.t.sol
// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.20;

import {Test, console} from "forge-std/Test.sol";
import {NFT} from "../src/NFT.sol";

contract NFTTest is Test {

    NFT public lsk;

    // Create dummy addresses for alice and bob
    address alice = makeAddr("alice");
    address bob = makeAddr("bob");

    // Initialize the NFT contract's object
    function setUp() public{
        lsk = new NFT();
    }

    // Pass the address of alice and bob to see whether the mint function successfully passes
    function testMintPass() public {
        lsk.mint(alice);
        lsk.mint(bob);
    }

    // To intentionally create a failing test, let's compare the addresses of alice and bob
    function testMintFail() public {
        assertEq(alice, bob);
    }
}

To run the tests, execute the following command. The -vv flag will output detailed information about the tests run using the following command.

forge test -vv

The output should look like this:

[⠢] Compiling...
No files changed, compilation skipped

Ran 2 tests for test/NFT.t.sol:NFTTest
[FAIL. Reason: assertion failed] testMintFail() (gas: 147160)
Logs:
  Error: a == b not satisfied [address]
        Left: 0x328809Bc894f92807417D2dAD6b7C998c1aFdac6
       Right: 0x1D96F2f6BeF1202E4Ce1Ff6Dad0c2CB002861d3e

[PASS] testMintPass() (gas: 132327)
Test result: FAILED. 1 passed; 1 failed; 0 skipped; finished in 1.13ms

Ran 1 test suite in 1.13ms: 1 tests passed, 1 failed, 0 skipped (2 total tests)

Failing tests:
Encountered 1 failing test in test/NFT.t.sol:NFTTest
[FAIL. Reason: assertion failed] testMintFail() (gas: 147160)

Encountered a total of 1 failing tests, 1 tests succeeded

The first test: testMintPass passed successfully as the criteria for the mint() function were met. We passed the recipient address to the mint() function as required, hence the success.

The second test: testMintFail failed since we asserted that the addresses of alice and bob were the same. The highlighted log output elaborates on how the assertion was false.

Deploying the smart contract​

After successfully building the smart contract, you can now deploy it to the Lisk network. For this example, we will use the Lisk Sepolia network to deploy the NFT contract.

Add the --verify, --verifier, --verifier-url, and the sender account's --private-key flag to the forge create command to directly verify the smart contract on BlockScout.

forge create --rpc-url https://rpc.sepolia-api.lisk.com \
--etherscan-api-key 123 \
--verify \
--verifier blockscout \
--verifier-url https://sepolia-blockscout.lisk.com/api \
--private-key <PRIVATE_KEY> \
src/NFT.sol:NFT

If the deployment is successful, the output should look like the following:

# The aforementioned command will first deploy the contract and display the following output:

[⠒] Compiling...
No files changed, compilation skipped
Deployer: 0x5e1A92F84cA1CE280B3Cb29d79C3368f45b41EBB
Deployed to: 0x108872F713A27bc22ca1db8CEefCAC8CbeDdF9E5
Transaction hash: 0xf465528f43e5cbc9b5206e46048feba0b920179813c3eb8c3bdbccbfd13d731e

# Once the contract is deployed successfully, the above-mentioned command will then verify the contract as well!

Starting contract verification...
Waiting for blockscout to detect contract deployment...
Start verifying contract `0x108872F713A27bc22ca1db8CEefCAC8CbeDdF9E5` deployed on 4202

Submitting verification for [src/NFT.sol:NFT] 0x108872F713A27bc22ca1db8CEefCAC8CbeDdF9E5.
Submitted contract for verification:
        Response: `OK`
        GUID: `108872f713a27bc22ca1db8ceefcac8cbeddf9e565e71790`
        URL: https://sepolia-blockscout.lisk.com/address/0x108872f713a27bc22ca1db8ceefcac8cbeddf9e5
Contract verification status:
Response: `OK`
Details: `Pending in queue`
Contract verification status:
Response: `OK`
Details: `Pass - Verified`
Contract successfully verified

After the smart contract is deployed and verified, you can interact with it by calling its public functions.

Verifying the smart contract​

Each deployed contract should be verified so that users and other developers can inspect the source code, and be sure that it matches the deployed bytecode on the blockchain.

Further, if you want to allow others to interact with your contract using the block explorer such as Blockscout's Read contract and Write Contract interfaces, it first needs to be verified.

The above contract has already been verified, so you should be able to view your version on a block explorer already, but we'll still walk through how to verify a contract on the Lisk Sepolia testnet.

info

You can't re-verify a contract identical to one that has already been verified. If you attempt to do so, such as verifying the above contract, you'll get an error similar to:

Start verifying contract `0x108872F713A27bc22ca1db8CEefCAC8CbeDdF9E5` deployed on 4202

Contract [src/NFT.sol:NFT] "0x108872F713A27bc22ca1db8CEefCAC8CbeDdF9E5" is already verified. Skipping verification.

In case your smart contract isn't verified, grab the deployed address and run:

forge verify-contract <CONTRACT_ADDRESS> \
./src/<CONTRACT_FILE>.sol:<CONTRACT_NAME> \
--chain 4202 \
--watch \
--verifier blockscout \
--verifier-url https://sepolia-blockscout.lisk.com/api

You should see an output similar to the following:

Starting contract verification...
Waiting for blockscout to detect contract deployment...
Start verifying contract `0xcCaA1C3eb8FEb5b09a5Eac1359BC4c70E18e29d9` deployed on 4202

Submitting verification for [src/NFT.sol:NFT] 0xcCaA1C3eb8FEb5b09a5Eac1359BC4c70E18e29d9.
Submitted contract for verification:
       Response: `OK`
       GUID: `ccaa1c3eb8feb5b09a5eac1359bc4c70e18e29d965e5c95a`
       URL: https://sepolia-blockscout.lisk.com/address/0xccaa1c3eb8feb5b09a5eac1359bc4c70e18e29d9
Contract verification status:
Response: `OK`
Details: `Pending in queue`
Contract verification status:
Response: `OK`
Details: `Pass - Verified`
Contract successfully verified

Use the contract's address e.g., 0xcCaA1C3eb8FEb5b09a5Eac1359BC4c70E18e29d9 to search for your contract on Blockscout to confirm that it is verified.

Interacting with the Smart Contract​

As mentioned earlier, if you verified the smart contract on Blocksout, you can use the Read contract and Write contract sections under the Contract tab to interact with the deployed contract.

The Read contract tab can be used without connecting a wallet, however, to use the Write contract tab, you'll need to connect your wallet first. You can do that by clicking the Connect wallet button.

Using cast for interaction​

With Foundry's rich command-line tool: cast it is possible to interact with any deployed contract whether it is reading or writing data on the blockchain. Let's perform a call without publishing a transaction (a read), then sign and publish a transaction (a write) to the deployed contract.

Performing a call​

A key component of the Foundry toolkit, cast enables us to interact with contracts, send transactions, and get onchain data using Ethereum RPC calls. First, we will perform a call from an account, without publishing a transaction.

Fill out the following <PLACEHOLDERS> and then, run the command:

cast call <DEPLOYED_CONTRACT_ADDRESS> --rpc-url https://rpc.sepolia-api.lisk.com "balanceOf(address)" <YOUR_ACCOUNT_ADDRESS_HERE>

You should receive 0x0000000000000000000000000000000000000000000000000000000000000000 in response, which equals 0 in hexadecimal. This makes sense as you've only deployed the NFT contract for now, however, no NFTs have been minted yet, and therefore your account's balance is zero.

Signing and sending a transaction​

Now let's sign and send a transaction, calling the mint(address) function on the NFT contract we just deployed.

Again, fill out the following <PLACEHOLDERS> and then, run the command:

cast send <DEPLOYED_CONTRACT_ADDRESS> --rpc-url https://rpc.sepolia-api.lisk.com "mint(address)" <RECIPIENT_ADDRESS_HERE> --private-key <SENDER_PRIVATE_KEY>
info

As the cast send command writes data on the blockchain, it needs a sender account's private key to be passed to the --private-key flag. The transaction will be sent successfully if the sender account has sufficient funds.

The aforesaid is not required for cast call command, because that only retrieves already published data from the smart contract.

If the transaction execution is successful, Foundry will respond with information about the transaction, including the blockNumber, gasUsed, transactionHash, and much more.

blockHash               0xfa9d32794b0fc9c1a10d39c5289613dfe80b55f8ead06475ca877a389e088e67
blockNumber             2165375
contractAddress         
cumulativeGasUsed       137472
effectiveGasPrice       3000000253
from                    0x5e1A92F84cA1CE280B3Cb29d79C3368f45b41EBB
gasUsed                 93597
logs                    [{"address":"0x108872f713a27bc22ca1db8ceefcac8cbeddf9e5","topics":["0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef","0x0000000000000000000000000000000000000000000000000000000000000000","0x000000000000000000000000488ba3c013020bd1712ed6a1997c4212d9711954","0x0000000000000000000000000000000000000000000000000000000000000001"],"data":"0x","blockHash":"0xfa9d32794b0fc9c1a10d39c5289613dfe80b55f8ead06475ca877a389e088e67","blockNumber":"0x210a7f","transactionHash":"0x76750ee1aaeed89c8f165d6f547002eb3bb833a142f73d63c1c3c9980fce8796","transactionIndex":"0x1","logIndex":"0x0","removed":false}]
logsBloom               0x00000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040000000000000000200000000008000000000000000000040000000000000000000000000000020000000000000000080800000000000000000000000010000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000001000000000000400000000000000000000000000000000060000000000000000000000000000000000000000000000000000000000000000000
root                    
status                  1
transactionHash         0x76750ee1aaeed89c8f165d6f547002eb3bb833a142f73d63c1c3c9980fce8796
transactionIndex        1
type                    2
to                      0x1088…f9e5
l1Fee             "0x30fb62bfb0c"
l1GasPrice             "0x6d49929"
l1GasUsed             "0x8a4"

Finally, you can confirm the minting by performing the call again. We should see that our balance increased from 0 to 1.

cast call <DEPLOYED_CONTRACT_ADDRESS> --rpc-url https://rpc.sepolia-api.lisk.com "balanceOf(address)" <YOUR_ACCOUNT_ADDRESS_HERE>

And the response: 0x0000000000000000000000000000000000000000000000000000000000000001 (1 in hex) — congratulations, you deployed a contract and minted an NFT with Foundry!

See the minted token for this guide on the Blockscout explorer.

That's it! Although this is just the tip of the iceberg, there is a lot more to learn about Foundry. For all things Foundry, check out the Foundry book, or head to the official Telegram dev chat or support chat.