Unit testing and deploying smart contracts with Forge

In December 2021, the world’s largest crypto-native funding agency, Paradigm Lab’s CTO Georgios launched a weblog relating to the discharge of a brand new framework for (evm-based) sensible contract growth, referred to as Foundry.

It took the Crypto group by storm, and shortly turned the business customary for growth and testing of sensible contracts, owing a lot to its effectivity compared to different frameworks.

As a way to perceive the importance of Foundry, we have to first look into the issues it tries to resolve.

The primary downside that lies with frameworks like Hardhat and Truffle is that they require the builders to know a scripting language like JavaScript/TypeScript so as to work with the framework.

As these scripting languages are internet development-heavy, the solidity developer needn’t know such languages for the sensible contract growth as it’s thought of extra backend oriented.

One other situation is that hardhat itself is applied utilizing TypeScript, so it’s slower than Foundry because the latter is applied utilizing Rust.

(Be aware: If you’re enthusiastic about checking the benchmarks, please take a look at this simulation)

Foundry has loads of cool options except for this like:

• Name stack traces
• Interactive debugger
• Inbuilt-fuzzing
• Solidity scripting

Now, I hope you will have an summary of Foundry and the need of testing sensible contracts utilizing Solidity. Foundry ships with two superb CLI instruments out-of-the-box:

• Forge: Used for testing and deployment of sensible contracts
• Forged: Used to work together with deployed sensible contracts

On this article we’re going to cowl the next:

Let’s get began.

Putting in Foundry

Putting in Foundry is easy and easy.

Open up your terminal and run:

curl -L https://foundry.paradigm.xyz | bash && foundryup

As soon as Foundry is put in, you can begin utilizing Forge and Forged straightaway.

For some OS, you would possibly need to install rust earlier than putting in Foundry.

Establishing a Foundry mission

You may immediately setup a Foundry mission by immediately by working

forge init <PROJECT_NAME>

To make your life simpler, I’ve created a template repository, with which you will get began extra simply. It comprises the required libraries, scripts and listing setup. So, all you might want to do is simply run the next command in your terminal:

The above command creates a brand new listing referred to as foundry-faucet and initializes a brand new Foundry mission utilizing my template. This is able to be the listing construction. The essential directories and information that we need to concentrate on are:

• lib: This comprises all of the dependencies/libraries that we’re going to use. For instance, if we wanna use Solmate, it would reside as a git submodule inside this folder
• scripts: This folder has all of the scripts, like deploying and verifying contracts
• src: This folder has all of the contracts and the assessments related to the contracts
• foundry.toml: This file comprises the configuration choices for the present Foundry mission

We must also replace and set up the libraries used; for that run the next instructions:

git submodule replace --init --recursive
forge set up

Making a easy Faucet contract

Now, we’re going to implement a faucet contract for our ERC20 token which might drip tokens when requested. We are able to additionally limit the quantity of tokens per request by setting a restrict which might be 100 by default in our contract.

Open up the src/Faucet.sol file and add the next code:

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.13;

import {Ownable} from "openzeppelin-contracts/entry/Ownable.sol";
import {IERC20} from "openzeppelin-contracts/token/ERC20/IERC20.sol";

contract Faucet is Ownable {
   /// Tackle of the token that this faucet drips
   IERC20 public token;

   /// For charge limiting
   mapping(tackle => uint256) public nextRequestAt;
   /// Max token restrict per request
   uint256 public restrict = 100;

   /// @param _token The tackle of the tap's token
   constructor(IERC20 _token) {
       token = _token;
   }

   /// Used to ship the tokens
   /// @param _recipient The tackle of the tokens recipient
   /// @param _amount The quantity of tokens required from the tap
   perform drip(tackle _recipient, uint256 _amount) exterior {
       require(_recipient != tackle(0), "INVALID_RECIPIENT");

       require(_amount <= restrict, "EXCEEDS_LIMIT");

       require(nextRequestAt[_recipient] <= block.timestamp, "TRY_LATER");
       nextRequestAt[_recipient] = block.timestamp + (5 minutes);

       token.switch(_recipient, _amount);
   }

   /// Used to set the max restrict per request
   /// @dev This methodology is restricted and ought to be referred to as solely by the proprietor
   /// @param _limit The brand new restrict for the tokens per request
   perform setLimit(uint256 _limit) exterior onlyOwner {
       restrict = _limit;
   }
}

Our faucet contract has been added. Now we will go forward and compile the contracts by working:

forge construct

If every little thing goes effectively, you need to see an analogous output:

[⠒] Compiling...
[⠒] Compiling 14 information with 0.8.13
Compiler run profitable

Candy! We’ve efficiently arrange our Foundry mission and compiled our contract with none errors! Good job, anon 🎉

Now, we will go forward and begin testing our Faucet contract.

Unit testing utilizing Forge

As , not like Hardhat, Forge helps us write unit assessments utilizing Solidity.

If you happen to open the src/check/Faucet.t.sol file you’ll already see some imports of utils and a BaseSetup contract.

It has some preliminary setup that initializes just a few variables that we will use in our assessments. As well as, the setUp() perform is just like beforeEach in hardhat and it runs earlier than each check.

The setUp() perform creates two addresses and labels them Alice and Bob. It’s useful once you attempt to debug by way of name traces because the label seems within the traces together with the tackle.

(Be aware: vm.label known as a cheatcode and it’s particular to Forge; It helps us to do some particular operations by interacting with the digital machine within the check env. We’ll be seeing extra cheatcodes throughout the course of the article. For the total record of cheatcodes, you possibly can refer to this link)

Substitute the Faucet.t.sol with the next code to get began with the unit assessments;

// SPDX-License-Identifier: MIT
pragma solidity >=0.8;

import {console} from "forge-std/console.sol";
import {stdStorage, StdStorage, Check} from "forge-std/Check.sol";
import {IERC20} from "openzeppelin-contracts/token/ERC20/IERC20.sol";

import {Utils} from "./utils/Utils.sol";
import {Faucet} from "../Faucet.sol";
import {MockERC20} from "../MockERC20.sol";

contract BaseSetup is Check {
   Utils inside utils;
   Faucet inside faucet;
   MockERC20 inside token;

   tackle payable[] inside customers;
   tackle inside proprietor;
   tackle inside dev;
   uint256 inside faucetBal = 1000;

   perform setUp() public digital {
       utils = new Utils();
       customers = utils.createUsers(2);
       proprietor = customers[0];
       vm.label(proprietor, "Proprietor");
       dev = customers[1];
       vm.label(dev, "Developer");

       token = new MockERC20();
       faucet = new Faucet(IERC20(token));
       token.mint(tackle(faucet), faucetBal);
   }
}

You may see that we’ve got now created new state variables like faucet, token and in addition we’ve renamed alice and bob to proprietor and dev for simple interpretation. On this context, dev is somebody who requests tokens from the tap whereas the proprietor is the proprietor of the tap itself.

Within the final three strains of the setUp() methodology, we deploy a mock token for the tap, go its tackle within the constructor of the new Faucet() (faucet deployment), after which name and mint some tokens to the deployed faucet contract.

Now, we’ll inherit the BaseSetup contract to write down unit assessments for our Faucet contract.

Beneath the BaseSetup contract, add the next code:

contract FaucetTest is BaseSetup {
   uint256 amountToDrip = 1;

   perform setUp() public override {
       tremendous.setUp();
   }

As talked about earlier, the setUp() methodology runs earlier than all of the testcases and right here we’re calling the setUp() methodology of the bottom contract which is the BaseSetup contract by way of tremendous.setUp().

Alright, now allow us to begin including unit assessments for our contract. Proper beneath the setUp() methodology of the FaucetTest contract, add the next piece of code:

   perform test_drip_transferToDev() public {
       console.log(
           "Ought to switch tokens to recipient when `drip()` known as"
       );
       uint256 _inititalDevBal = token.balanceOf(dev);

       /// Ensure that preliminary dev steadiness is Zero
       assertEq(_inititalDevBal, 0);

       /// Request some tokens to the dev pockets from the pockets
       faucet.drip(dev, amountToDrip);

       uint256 _devBalAfterDrip = token.balanceOf(dev);

      /// The distinction ought to be equal to the quantity requested from the tap
       assertEq(_devBalAfterDrip - _inititalDevBal, amountToDrip);
   }

The above code helps us to check the drip() methodology. The workflow is easy.

1. First, retailer the preliminary steadiness of the dev in a variable (_inititalDevBal)
2. Ensure it’s 0, as we didn’t mint any tokens to the dev. That is what the road assertEq(_inititalDevBal, 0); does
3. Then name the drip() methodology from the faucet contract occasion
4. Fetch the steadiness of dev after the drip() known as
5. The distinction between the steadiness of the dev account earlier than and after the drip() ought to be equal to amountToDrip, which is saved as a state variable within the FaucetTest contract

Now, allow us to save the file and run the check: forge check.

You must see the output in your terminal one thing just like this:

Cool! Let’s add some extra assessments.

The above check verifies that the drip() methodology transfers the tokens to the dev. So, we must also verify that the switch is a sound one, which suggests the token steadiness of the tap ought to be lowered.

Add the next check beneath — the test_drip_transferToDev() methodology.

 perform test_drip_reduceFaucetBalance() public {
       console.log("The tap steadiness ought to be lowered");
       faucet.drip(dev, amountToDrip);
       assertEq(token.balanceOf(tackle(faucet)), faucetBal - amountToDrip);
   }

This makes positive that the tokens that the dev acquired are literally despatched from the tap — if that’s the case, the steadiness of the tap ought to be lowered.

We are able to be certain by working the check suite once more : forge check

If every little thing goes effectively, then your output ought to be just like this:

Candy! If in case you have observed, we’ve got console.log statements in our check instances, however they don’t seem to be exhibiting up within the console. The reason being that Forge doesn’t show logs by default. To get the logs displayed, we have to run the command with verbosity 2 : forge check -vv will show the logs.

Additionally if there are any occasions which can be emitted by your contract, you possibly can view them within the assessments with verbosity three (-vvv). You will get an in depth name hint in your assessments as excessive as verbosity stage 5, which helps in higher debugging.

Alright, let’s preserve including extra assessments. Now we’re going to check our charge restrict mechanism. There ought to be at the very least a five-minute interval earlier than calling drip() with the identical recipient tackle.

   perform test_drip_revertIfThrottled() public {
       console.log("Ought to revert if tried to throttle");
       faucet.drip(dev, amountToDrip);

       vm.expectRevert(abi.encodePacked("TRY_LATER"));
       faucet.drip(dev, amountToDrip);
   }

vm.expectRevert(bytes32) is one other cheat code that checks if the subsequent name reverts with the given error message. On this case, the error message is TRY_LATER. It accepts the error message as bytes not as a string, therefore we’re utilizing abi.encodePacked.

If you happen to bear in mind, I discussed that Forge ships with a fuzzer out-the-box. Let’s give it a attempt.

We mix the assessments test_drip_transferToDev and test_drip_reduceFaucetBalance, and as an alternative of passing the inputs manually, we’d enable the fuzzer to enter the values in order that we will ensure that our contract handles totally different inputs.

   perform test_drip_withFuzzing(tackle _recipient, uint256 _amount) public {
       console.log("Ought to deal with fuzzing");
       /// inform the constraints to the fuzzer, in order that the assessments do not revert on dangerous inputs.
       vm.assume(_amount <= 100);
       vm.assume(_recipient != tackle(0));
       uint256 _inititalBal = token.balanceOf(_recipient);
       faucet.drip(_recipient, _amount);
       uint256 _balAfterDrip = token.balanceOf(_recipient);
       assertEq(_balAfterDrip - _inititalBal, _amount);
       assertEq(token.balanceOf(tackle(faucet)), faucetBal - _amount);
   }

Fuzzing is property-based testing. Forge will apply fuzzing to any check that takes at the very least one parameter.

While you execute the check suite, you’ll find the next line within the output:

[PASS] test_drip_withFuzzing(tackle,uint256) (runs: 256)

From the above output we will infer that the Forge fuzzer referred to as the test_drip_withFuzzing() methodology 256 occasions with random inputs. Nevertheless, we will override this quantity utilizing the FOUNDRY_FUZZ_RUNS surroundings variable.

Now, allow us to add a pair extra assessments for the owner-only methodology setLimit()

perform test_setLimit() public {
       console.log("Ought to set the restrict when referred to as by the proprietor");
       faucet.setLimit(1000);

       /// the restrict ought to be up to date assertEq(faucet.restrict(), 1000); } perform test_setLimit_revertIfNotOwner() public { console.log("Ought to revert if not referred to as by Proprietor"); /// Units the msg.sender as dev for the subsequent tx vm.prank(dev); vm.expectRevert(abi.encodePacked("Ownable: caller will not be the proprietor")); faucet.setLimit(1000); }

Within the test_setLimit_revertIfNotOwner() methodology, a brand new cheatcode vm.prank(tackle) is used. It pranks the vm by overriding the msg.sender with the given tackle; in our case it’s dev. So, the setLimit() ought to revert with the caller will not be the proprietor message as our Faucet contract inherits the Ownable contract.

Okay allow us to ensure that no assessments fail by working forge check once more.

Candy 🥳 Now it’s time for deployment.

Contract deployment to Kovan testnet

Create a brand new file from .env.instance file and title it as .env. Please fill your INFURA_API_KEY and the PRIVATE_KEY (with Kovan testnet funds).

As soon as all of the fields are populated, you’re all set for deployment to Kovan. Earlier than deploying the tap, we have to deploy our ERC20 token.

You’ll find the deployment scripts contained in the scripts listing, and deploy the MockERC20 token to Kovan testnet by executing the ./scripts/deploy_token_kovan.sh bash script.

The output would look one thing like this:

Deployer: (YOUR_DEPLOYMENT_ADDRESS)

Deployed to: 0x1a70d8a2a02c9cf0faa5551304ba770b5496ed80

Transaction hash: 0xa3780d2e3e1d1f9346035144f3c2d62f31918b613a370f416a4fb1a6c2eadc77

To ensure that the transaction truly went via, you possibly can search the transaction hash in https://kovan.etherscan.io

Copy the Deployed to: tackle, as it’s the tackle of the MockERC20 token that we must always use for deploying our Faucet contract. To deploy the tap, you possibly can execute the ./scripts/deploy_faucet_kovan.shscript.

It can immediate you to enter the token tackle; then enter the copied MockERC20 token tackle that was deployed earlier.

The output ought to look one thing like this:

Woohoo 🚀🚀 We’ve efficiently compiled, examined, and deployed our contract to the Kovan testnet utilizing Forge

We nonetheless have to confirm the contract on Etherscan and in addition mint some MockERC20 tokens to the Faucet (you need to use forged for this!) for it to work as supposed. I’ll depart this to you guys as an train to attempt it yourselves!

As at all times, you’ll find the GitHub repository for this text here.

Conclusion

On this article we solely coated just a few items of Forge. Foundry is a really highly effective framework for sensible contracts and it’s quickly growing as effectively.

There are extra cool options like code-coverage, contract verification, fuel snapshots, name traces, and interactive debugging. Be at liberty to mess around with the repo by testing out extra options. Glad coding 🎊