Unit testing and deploying good contracts with Forge

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

It took the Crypto group by storm, and shortly turned the business commonplace for growth and testing of good 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 as a way to work with the framework.

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

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

(Notice: If you’re eager about checking the benchmarks, please take a look at this simulation)

Foundry has lots of cool options other than this like:

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

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

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

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

Let’s get began.

Putting in Foundry

Putting in Foundry is straightforward and simple.

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 may need to install rust earlier than putting in Foundry.

Organising a Foundry venture

You’ll be able to immediately setup a Foundry venture by straight away by operating

forge init <PROJECT_NAME>

To make your life simpler, I’ve created a template repository, with which you may get began extra simply. It comprises the required libraries, scripts and listing setup. So, all it is advisable 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 venture utilizing my template. This could be the listing construction. The vital 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 is going to 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 checks related to the contracts
• foundry.toml: This file comprises the configuration choices for the present Foundry venture

We also needs to 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 may drip tokens when requested. We are able to additionally limit the quantity of tokens per request by setting a restrict which will likely 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 {
   /// Deal with of the token that this faucet drips
   IERC20 public token;

   /// For price 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
   operate 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 technique is restricted and needs to be referred to as solely by the proprietor
   /// @param _limit The brand new restrict for the tokens per request
   operate setLimit(uint256 _limit) exterior onlyOwner {
       restrict = _limit;
   }
}

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

forge construct

If the whole lot goes effectively, it’s best to see the same output:

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

Candy! We’ve efficiently arrange our Foundry venture 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 you already know, in contrast to Hardhat, Forge helps us write unit checks utilizing Solidity.

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

It has some preliminary setup that initializes a number of variables that we will use in our checks. As well as, the setUp() operate is much like beforeEach in hardhat and it runs earlier than each take a look at.

The setUp() operate creates two addresses and labels them Alice and Bob. It’s useful while you attempt to debug through name traces because the label seems within the traces together with the tackle.

(Notice: 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 take a look at env. We’ll be seeing extra cheatcodes through the course of the article. For the total listing of cheatcodes, you may refer to this link)

Change the Faucet.t.sol with the next code to get began with the unit checks;

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

import {console} from "forge-std/console.sol";
import {stdStorage, StdStorage, Take a look at} from "forge-std/Take a look at.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 Take a look at {
   Utils inner utils;
   Faucet inner faucet;
   MockERC20 inner token;

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

   operate 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’ll be able to see that now we have now created new state variables like faucet, token and likewise 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 traces of the setUp() technique, we deploy a mock token for the tap, cross 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 put in writing unit checks for our Faucet contract.

Beneath the BaseSetup contract, add the next code:

contract FaucetTest is BaseSetup {
   uint256 amountToDrip = 1;

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

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

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

   operate 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 stability 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 needs to be equal to the quantity requested from the tap
       assertEq(_devBalAfterDrip - _inititalDevBal, amountToDrip);
   }

The above code helps us to check the drip() technique. The workflow is straightforward.

1. First, retailer the preliminary stability of the dev in a variable (_inititalDevBal)
2. Ensure that 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() technique from the faucet contract occasion
4. Fetch the stability of dev after the drip() known as
5. The distinction between the stability of the dev account earlier than and after the drip() needs 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 take a look at: forge take a look at.

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

Cool! Let’s add some extra checks.

The above take a look at verifies that the drip() technique transfers the tokens to the dev. So, we also needs to test that the switch is a legitimate one, which suggests the token stability of the tap needs to be decreased.

Add the next take a look at beneath — the test_drip_transferToDev() technique.

 operate test_drip_reduceFaucetBalance() public {
       console.log("The tap stability needs to be decreased");
       faucet.drip(dev, amountToDrip);
       assertEq(token.balanceOf(tackle(faucet)), faucetBal - amountToDrip);
   }

This makes certain that the tokens that the dev acquired are literally despatched from the tap — in that case, the stability of the tap needs to be decreased.

We are able to be sure that by operating the take a look at suite once more : forge take a look at

If the whole lot goes effectively, then your output needs to be much like this:

Candy! If in case you have observed, now we have console.log statements in our take a look at circumstances, 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 take a look at -vv will show the logs.

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

Alright, let’s hold including extra checks. Now we’re going to take a look at our price restrict mechanism. There needs to be a minimum of a five-minute interval earlier than calling drip() with the identical recipient tackle.

   operate 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 following 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 strive.

We mix the checks test_drip_transferToDev and test_drip_reduceFaucetBalance, and as a substitute of passing the inputs manually, we might permit the fuzzer to enter the values in order that we will ensure that our contract handles totally different inputs.

   operate 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 checks do not revert on unhealthy 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 take a look at that takes a minimum of one parameter.

While you execute the take a look at suite, you will discover 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() technique 256 instances with random inputs. Nonetheless, we will override this quantity utilizing the FOUNDRY_FUZZ_RUNS atmosphere variable.

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

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

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

Within the test_setLimit_revertIfNotOwner() technique, 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 shouldn't be the proprietor message as our Faucet contract inherits the Ownable contract.

Okay allow us to ensure that no checks fail by operating forge take a look at once more.

Candy 🥳 Now it’s time for deployment.

Contract deployment to Kovan testnet

Create a brand new file from .env.instance file and identify 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 could 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 really went by, you may 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 may execute the ./scripts/deploy_faucet_kovan.shscript.

It’s going to 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 must confirm the contract on Etherscan and likewise mint some MockERC20 tokens to the Faucet (you should use forged for this!) for it to work as meant. I’ll go away this to you guys as an train to strive it yourselves!

As at all times, you will discover the GitHub repository for this text here.

Conclusion

On this article we solely lined a number of items of Forge. Foundry is a really highly effective framework for good contracts and it’s quickly creating as effectively.

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