How to Perform Unit Tests on Smart Contracts?
Unit Testing is the most crucial testing method to be carried out of every other testing method; There are many frameworks, tools, and libraries that help you in testing your application one of which is Hardhat. Hardhat helps in compiling and testing smart contracts at the very core. And also has its own built-in Hardhat Network (Local Ethereum Network design for development purposes). It also allows you to deploy contracts, run tests, and debugging of code.
Installing Hardhat
1. To install hardhat to the current project directory, run the following commands in your terminal.
npm init
npm install --save-dev hardhat
2. Next you need to set up your project in the current working directory in order to connect with the Hardhat development environment. For projects set up in the current directory, paste the below command in the command prompt by changing the directory to the current directory you want to set up your project.
npx hardhat
Select Create an empty hardhat.config.js with your keyboard and hit enter, once you’ve run the above command. hardhat.config.js file is important for a hardhat project.
Fig 1.1. Create Hardhat Project
3. Create three important folders in the working directory.
- contracts: To create a smart contract.
- scripts: To run deployment scripts.
- tests: To run and test smart contracts using hardhat on the local blockchain, using JavaScript Framework ‘Mocha’.
Below is the expected folder structure:
Fig 1.2. Folder Structure
4. Other necessary installations (plugins) required, which help in developing a smart contract, testing, and creating an environment. To install it run this in your project working directory. Recommended for npm 7+ versions.
npm install --save-dev @nomicfoundation/hardhat-toolbox
For the npm 6 version or less, it might require installing a few more dependencies,
npm install --save-dev @nomicfoundation/hardhat-toolbox @nomicfoundation/hardhat-network-helpers @nomicfoundation/hardhat-chai-matchers @nomiclabs/hardhat-ethers @nomiclabs/hardhat-etherscan chai ethers hardhat-gas-reporter solidity-coverage @typechain/hardhat typechain @typechain/ethers-v5 @ethersproject/abi @ethersproject/providers
5. In case the above installation fails or shows errors like peer dependency conflict in the dependency tree, is most likely because of the npm version you have installed the error is most probably shown in the npm version above 7. Because npm version 7 and above treats peer dependency conflicts as errors. To tackle such a situation, install the npm version under 7.
OR
`npm install --leagacy-peer-deps`
`npm config set legacy-peer-deps true` to permanently resolve the error
6. Add the installed libraries/modules to hardhat.config.js file, add the ‘ require(“@nomicfoundation/hardhat-toolbox”); ‘ statement as shown below:
Javascript
require("@nomicfoundation/hardhat-toolbox");module.exports = { solidity: "0.8.17", }; |
Contract Creation and Compile using Hardhat
Create any basic solidity smart contract under the contracts folder. For example:
Solidity
// SPDX-License-Identifier: UnLicensedpragma solidity >=0.5.0 <0.9.0;import "hardhat/console.sol";contract Token{ string public name = "Hardhat Token"; string public symbol = "HHT"; uint256 public totalSupply = 10000; address public owner; mapping (address => uint256) balances; constructor(){ /* i.e the deployer will be the owner at first he can then transfer tokens to any other account addresses and he will have all the tokens in his wallet at first.*/ balances[msg.sender] = totalSupply; owner = msg.sender; } function transfer(address to, uint256 amount) external { require(balances[msg.sender]>=amount, "Not enough tokens"); console.log( "Transferring from %s to %s %s tokens",msg.sender,to,amount); balances[msg.sender] -= amount; balances[to] += amount; } function balanceOf(address account) external view returns (uint256) { return balances[account]; } } |
Compile the smart contract to check if there are any errors or anomalies, using the hardhat compiler, use the following command,
npx hardhat compile
How to Test a Smart Contract for Ethereum?
Public Blockchains like Ethereum are immutable, it is difficult to update the code of a smart contract once it has been deployed. To guarantee security, smart contracts must be tested before they are deployed to Mainnet. There are several strategies for testing contracts, but a test suite comprised of various tools and approaches is suitable for detecting both minor and significant security issues in contract code.