4. Testing Smart Contracts

Write Tests (test/Lock.js)

const { expect } = require("chai");
const { ethers } = require("hardhat");

describe("Lock", function () {
  let lock;
  let owner;
  let otherAccount;
  const unlockTime = Math.floor(Date.now() / 1000) + 3600; // 1 hour from now

  beforeEach(async function () {
    [owner, otherAccount] = await ethers.getSigners();

    const Lock = await ethers.getContractFactory("Lock");
    lock = await Lock.deploy(unlockTime, { value: ethers.parseEther("1") });
  });

  describe("Deployment", function () {
    it("Should set the right unlockTime", async function () {
      expect(await lock.unlockTime()).to.equal(unlockTime);
    });

    it("Should set the right owner", async function () {
      expect(await lock.owner()).to.equal(owner.address);
    });

    it("Should receive and store the funds to lock", async function () {
      expect(await ethers.provider.getBalance(lock.target)).to.equal(
        ethers.parseEther("1")
      );
    });
  });

  describe("Withdrawals", function () {
    it("Should revert with the right error if called too soon", async function () {
      await expect(lock.withdraw()).to.be.revertedWith(
        "You can't withdraw yet"
      );
    });

    it("Should revert with the right error if called from another account", async function () {
      await expect(lock.connect(otherAccount).withdraw()).to.be.revertedWith(
        "You aren't the owner"
      );
    });
  });
});

Run Tests

# Test on local Hardhat network
npx hardhat test

# Test with gas reporting
npx hardhat test --reporter gas

# Test specific file
npx hardhat test test/Lock.js