Waffle say hello world tutorial with hardhat and ethers
In this Waffle(opens in a new tab) tutorial, we will learn how to set up a simple "Hello world" smart contract project, using hardhat(opens in a new tab) and ethers.js(opens in a new tab). Then we will learn how to add a new functionality to our smart contract and how to test it with Waffle.
Let's start by creating a new project:
yarn init
or
npm init
and installing required packages:
yarn add -D hardhat @nomiclabs/hardhat-ethers ethers @nomiclabs/hardhat-waffle ethereum-waffle chai
or
npm install -D hardhat @nomiclabs/hardhat-ethers ethers @nomiclabs/hardhat-waffle ethereum-waffle chai
Next step is creating a sample hardhat project by running npx hardhat
.
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Select Create a sample project
Our project's structure should look like this:
1MyWaffleProject2├── contracts3│ └── Greeter.sol4├── node_modules5├── scripts6│ └── sample-script.js7├── test8│ └── sample-test.js9├── .gitattributes10├── .gitignore11├── hardhat.config.js12└── package.jsonሁሉንም አሳይ
Now let's talk about some of these files:
- Greeter.sol - our smart contract written in solidity;
1contract Greeter {2string greeting;34constructor(string memory _greeting) public {5console.log("Deploying a Greeter with greeting:", _greeting);6greeting = _greeting;7}89function greet() public view returns (string memory) {10return greeting;11}1213function setGreeting(string memory _greeting) public {14console.log("Changing greeting from '%s' to '%s'", greeting, _greeting);15greeting = _greeting;16}17}ሁሉንም አሳይመገልበጥ
Our smart contract can be divided into three parts:
- constructor - where we declare a string type variable called
greeting
, - function greet - a function that will return the
greeting
when called, - function setGreeting - a function that allows us to change the
greeting
value.
- sample-test.js - our tests file
1describe("Greeter", function () {2 it("Should return the new greeting once it's changed", async function () {3 const Greeter = await ethers.getContractFactory("Greeter")4 const greeter = await Greeter.deploy("Hello, world!")56 await greeter.deployed()7 expect(await greeter.greet()).to.equal("Hello, world!")89 await greeter.setGreeting("Hola, mundo!")10 expect(await greeter.greet()).to.equal("Hola, mundo!")11 })12})ሁሉንም አሳይመገልበጥ
Next step consists of compiling our contract and running tests:
Waffle tests use Mocha (a test framework) with Chai (an assertion library). All you have to do is run npx hardhat test
and wait for the following message to appear.
✓ Should return the new greeting once it's changed
Everything looks great so far, let's add some more complexity to our project
Imagine a situation where someone adds an empty string as a greeting. It wouldn't be a warm greeting, right?
Let's make sure that doesn't happen:
We want to use solidity's revert
when someone passes an empty string. A good thing is that we can easily test this functionality with Waffle's chai matcher to.be.revertedWith()
.
1it("Should revert when passing an empty string", async () => {2 const Greeter = await ethers.getContractFactory("Greeter")3 const greeter = await Greeter.deploy("Hello, world!")45 await greeter.deployed()6 await expect(greeter.setGreeting("")).to.be.revertedWith(7 "Greeting should not be empty"8 )9})ሁሉንም አሳይመገልበጥ
Looks like our new test didn't pass:
Deploying a Greeter with greeting: Hello, world!Changing greeting from 'Hello, world!' to 'Hola, mundo!'✓ Should return the new greeting once it's changed (1514ms)Deploying a Greeter with greeting: Hello, world!Changing greeting from 'Hello, world!' to ''1) Should revert when passing an empty string1 passing (2s)1 failingሁሉንም አሳይ
Let's implement this functionality into our smart contract:
1require(bytes(_greeting).length > 0, "Greeting should not be empty");መገልበጥ
Now, our setGreeting function looks like this:
1function setGreeting(string memory _greeting) public {2require(bytes(_greeting).length > 0, "Greeting should not be empty");3console.log("Changing greeting from '%s' to '%s'", greeting, _greeting);4greeting = _greeting;5}መገልበጥ
Let's run tests again:
✓ Should return the new greeting once it's changed (1467ms)✓ Should revert when passing an empty string (276ms)2 passing (2s)
Congrats! You made it :)
Conclusion
We made a simple project with Waffle, Hardhat and ethers.js. We learned how to set up a project, add a test and implement new functionality.
For more great chai matchers to test your smart contracts, check official Waffle's docs(opens in a new tab).
መጨረሻ የተስተካከለው: @pettinarip(opens in a new tab), 8 ዲሴምበር 2023