<p style="margin-left:0px;">In this article, we will learn how to build a basic Multisig wallet of our own. We will get to learn about hardhat and testing a smart contract using hardhat.</p><p style="margin-left:0px;">This is going to be a longer post so it is recommended that you take your time and follow along with this tutorial to gain the most out of it. In case of any query feel free to contact me.</p><h1 style="margin-left:0px;"><strong>What is a Multisig wallet?</strong></h1><p style="margin-left:0px;">You can think of Multisig wallet as a joint bank account, where signatures of multiple parties are required to initiate the transaction from the account. Similarly, multisig wallet is a smart contract-based wallet that is maintained by multiple different accounts. These accounts are known as owners or admins of the multisig wallet.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*ZvKttxEZGsUnlTG0jffJlQ.png" alt="" loading="eager"></figure><h2 style="margin-left:0px;"><strong>Transaction Life Cycle</strong></h2><ul><li>Every transaction of the Multisig wallet goes through a particular life cycle, i.e. it goes through certain stages.</li><li>To begin the cycle one of the admins will <code>Submit</code> that transaction to the wallet's transactions pool.</li><li>After that other admins <code>Approve</code> that transaction if they agree with the transaction.</li><li>Admins can also <code>Revoke</code> their approval before the transaction gets executed.</li><li>Once a transaction gets the minimum required approvals from the admins any of the admins can then <code>Execute</code> that transaction.</li></ul><p style="margin-left:0px;">Enough with the theory now let’s dive deep into building our own implementation of such a Multisig wallet. We will use hardhat and typescript in this process. First, we will setup a basic starter project with hardhat and typescript, fortunately, a large part of this step is automated with hardhat starter script. Next, we will write <code>IMultisigCore</code> and <code>MultisigCore</code> smart contracts, These contracts will have the core functionalities of the multisig wallet as mentioned above in the article. Other contracts will inherit <code>MultisigCore</code> to add core functionalities to their multisig wallet implementation. We will also inherit this contract in our <code>Multisig</code> contract in order to follow the same pattern.</p><h1 style="margin-left:0px;"><strong>Hardhat Setup</strong></h1><p style="margin-left:0px;">Let’s begin with the hardhat starter project setup. Navigate to the folder where you want to create this project. Then type the following command <code>yarn init</code> and follow the instructions press enter to keep the defaults. This will create a <code>package.json</code> file,i.e. it will create a node project in this directory. Now to install hardhat as one of the dev dependencies run the command <code>yarn add --dev hardhat</code>. We use <code>--dev</code> flag because hardhat is a development dependency. After successful execution of the above command, you can see hardhat added as one of the devDependencies in <code>package.json</code>. Now to run the hardhat command run <code>yarn hardhat</code> when you run this command for the first time you will be prompted with the welcome prompt. Choose <code>Create a TypeScript project</code> with your arrow keys and press enter to keep the defaults. It will install some other dependencies to make it easier to work with types in typescript, etc. Once done you can see that the script has created a boilerplate code with typescript. You will have <code>Lock.sol</code>, <code>Lock.ts</code> in contracts and test directories, and <code>deploy.ts</code> in the scripts directory. You can safely delete those files as in the next section we will be writing our own contract files.</p><h1 style="margin-left:0px;"><code><strong>IMultisigCore</strong></code><strong> interface</strong></h1><p style="margin-left:0px;">Now that we are done with the basic environment setup let’s start building our Multisig wallet library from scratch. In the <code>contracts</code> folder of our project create a sub-folder named <code>MultisigLib</code>. All the code for this project is available on the repository linked at the end. Now we will create an interface <code>IMultisigCore</code> for our Multisig core library contract. This interface file will have declarations for the errors and events emitted from our Multisig contract. You can see from the below code snippet that our contract will emit 5 events <code>Deposit</code>, <code>Submit</code>,<code>Approve</code>,<code>Revoke</code>, and <code>Execute</code>. Read through the comments in the code to understand more about these events.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*RiGMjAuy8Qb__W-V5bXP0g.png" alt="" loading="eager"></figure><p style="margin-left:0px;">Solidity supports custom errors since v0.8.4. Below is a code snippet containing the custom errors thrown by the Multisig core at different points. You can read through the comments to understand when we revert with a particular error.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*rfp0nNNoozTNsb1L211yYg.png" alt="" loading="lazy"></figure><p style="margin-left:0px;">This concludes the <code>IMultisigCore</code> interface which describes the events emitted and the errors thrown by the <code>MultisigCore</code> contract.</p><h1 style="margin-left:0px;"><code><strong>MultisigCore</strong></code><strong> contract</strong></h1><p style="margin-left:0px;">Now let’s take a look at <code>MultisigCore</code> contract where all the multisig magic happens. We will start with the transaction struct and other state variable declarations.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*W8QLHTqF2PvQepL0feEv7Q.png" alt="" loading="eager"></figure><p style="margin-left:0px;">As you can see in the code snippet above that transaction has four attributes <code>to</code> address, <code>value</code>, <code>data</code>, and <code>isExecuted</code> bool. Other than this we have an <code>admins</code> array of addresses, one <code>isAdmin</code> mapping to quickly check if the given address is admin or not, We have similar mapping <code>isApprover</code> to check if, for a given transaction, a given admin is approved or not. We also have <code>minApprovals</code> which is the minimum required approvals to execute any transactions. <code>availableBalance</code> is the balance of the Multisig available to spend in transactions. Next, Let's look at some function modifiers in the contract.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*8DBuqwMI52xpffvGpOoUig.png" alt="" loading="lazy"></figure><p style="margin-left:0px;"><code>onlyAdmin</code> allows only admins to call the function. <code>notExecuted</code> checks and allows the function call if the given transaction is not executed yet, Simillarly <code>notApproved</code> checks and allows the function call only if the given transaction is not yet approved by the caller, i.e. reverts if already approved by the caller. <code>isApproved</code> is the inverse of the <code>notApproved</code> modifier. Now we will look into the constructor and other functions of the contract where these modifiers are used.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*ri1Ik2jEXlEGrQQKmKnY-g.png" alt="" loading="lazy"></figure><p style="margin-left:0px;">In the constructor of this contract, we set the <code>admins</code> and <code>minApprovals</code>, and update the <code>isAdmin</code> mapping for all the given admins. In <code>_submit</code> function we push new transactions to the <code>transactions</code> array, update <code>availableBalance</code> and emit <code>Submit</code> event. In <code>_approve</code> and <code>_revoke</code> functions we update <code>isApprover</code> mapping and emit <code>Approve</code> or <code>Revoke</code> event accordingly. In <code>_execute</code> function we check for the approval count for the transaction and then if we have the minimum required approvals we updated the transaction in the storage and execute the transaction with the following lines of code.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*SYNoGOJHYFrQx62dmYZidA.png" alt="" loading="lazy"></figure><p style="margin-left:0px;">With <code>txn.to.call{value: txn.value}(txn.data)</code> we are passing the value and data of the transaction in the call to the address in <code>txn.to</code>. This is it for the <code>MultisigCore</code> contract, this is all it takes to create a multi-sig wallet.</p><h1 style="margin-left:0px;"><code><strong>Multisig</strong></code><strong> Wallet contract</strong></h1><p style="margin-left:0px;">In the last section, we wrote the <code>MultisigLib</code> contracts, i.e. <code>MultisigLib/IMultisigCore</code>, and <code>MultisigLib/MultisigCore</code>. In this section, we will use that contract to build our multisig wallet. In the contracts folder, i.e. outside the <code>MultisigLib</code> folder create a new file <code>Multisig.sol</code></p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*9A5QTZc8VqvCa5ZMMBDQeg.png" alt="" loading="eager"></figure><p style="margin-left:0px;">As you can see above <code>submit</code>, <code>approve</code>, <code>revoke</code>, <code>execute</code> functions, and the contructor of this contract are fairly straightforward. The only new thing in this contract is the <code>receive</code> and <code>fallback</code> functions, these are the functions that allow this contract to receive funds even without calling any function call.</p><h1 style="margin-left:0px;"><strong>Deployment script</strong></h1><p style="margin-left:0px;">Next, we will write the deployment script to deploy this Multisig contract. This script is similar to the default script from the hardhat starter. Below are the contents of the <code>deploy.ts</code> script.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*O28-Y1GDiuaS3FUxJ4ZCDg.png" alt="" loading="eager"></figure><h1 style="margin-left:0px;"><strong>Testing Multisig wallet contract</strong></h1><p style="margin-left:0px;">We now have a Multisig wallet contract, now we will test the functionalities of this contract. Hardhat uses mocha and chai for testing smart contracts. All these tests follow the describe-it format of writing tests.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*oKeAQZdPdfbw4i1hhwpB8w.png" alt="" loading="eager"></figure><p style="margin-left:0px;">One such describe block can also have other nested descriptions inside it. This allows us to describe our contract with such describes and nested describes that test different parts of the contract.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*zDUghzHL_e2lxLNAR-XHIQ.png" alt="" loading="lazy"></figure><h1 style="margin-left:0px;"><strong>Fixtures and loadFixture</strong></h1><p style="margin-left:0px;">Hardhat allows for fixtures which is a way to have multiple tests have the same initial conditions. The fixture is basically a way to restore the network back to a certain state. First time when <code>loadFixture</code> is called with a function it runs the function and every time it is called next hardhat resets the network to the state it was in at the first run of the function. This allows us to have the same initial conditions for our tests. For our tests, we will mainly use three fixtures <code>deployMultisigFixture</code>, <code>depositFixture</code>, and <code>submitFixture</code> each of these fixture build on top of each other. You can see the below code snippet.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*3DZWM6cme9HUJ1cTB-L30A.png" alt="" loading="eager"></figure><p style="margin-left:0px;"><code>deployMultisigFixture</code> as the name suggests is the deployment fixture, it provides the deployed contract, contract factory, and other deployment parameters. <code>depositFixture</code> builds on top of <code>deployMultisigFixture</code> where all three admins transfer one ether to the Multisig contract. <code>submitFixture</code> builds on top of <code>depositFixture</code> where all three admins submit one transaction each.</p><figure class="image image_resized" style="width:679.994px;"><img src="https://miro.medium.com/v2/resize:fit:784/1*GCcrIYIwzGze--yFfhZKoA.png" alt="" loading="lazy"></figure><p style="margin-left:0px;">Above is the code snippet of the tests for execute functionality, all other tests are written in a similar way. You can find and read through all the tests in <code>Multisig.test.ts</code> file in the test directory in the repo associated with this post. This concludes the post thank you for reading till the end, hope you have learned something from this.</p><p style="margin-left:0px;">Repo: <code>ts-multisig</code> <a href="https://github.com/BuildBearLabs/Tutorials"><u>https://github.com/BuildBearLabs/Tutorials</u></a></p><p style="margin-left:0px;">Author: Nisarg Chaudhari (<a href="https://twitter.com/nisargsc"><u>@nisargsc</u></a>)</p>

Learn how to build a Multisig wallet with hardhat and typescript

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