index.test.js

const { ethers } = require("ethers");
const Ganache = require("ganache-core");

const MAINNET_NODE_URL = "<insert mainnet node url here>";
const PRIV_KEY = "<insert ANY private key here>";
const GAS_LIMIT = 2000000;

const startChain = async () => {
	const ganache = Ganache.provider({
		fork: MAINNET_NODE_URL,
		network_id: 1,
		accounts: [
			{
				secretKey: PRIV_KEY,
				balance: ethers.utils.hexlify(ethers.utils.parseEther("1000")),
			},
		],
		gasLimit: GAS_LIMIT,
	});

	const provider = new ethers.providers.Web3Provider(ganache);
	const wallet = new ethers.Wallet(PRIV_KEY, provider);

	return wallet;
};

jest.setTimeout(100000);
const uniswap = require("@studydefi/money-legos/uniswap");
const erc20 = require("@studydefi/money-legos/erc20");

describe("do some tests", () => {
	let wallet;

	beforeAll(async () => {
		wallet = await startChain();
	});

	test("initial DAI balance of 0", async () => {
		const daiContract = new ethers.Contract(erc20.dai.address, erc20.dai.abi, wallet);
		const daiBalanceWei = await daiContract.balanceOf(wallet.address);
		const daiBalance = ethers.utils.formatUnits(daiBalanceWei, 18);
		expect(parseFloat(daiBalance)).toBe(0);
	});

	test("initial ETH balance of 1000 ETH", async () => {
		const ethBalanceWei = await wallet.getBalance();
		const ethBalance = ethers.utils.formatEther(ethBalanceWei);
		expect(parseFloat(ethBalance)).toBe(1000);
	});

	test("buy DAI from Uniswap", async () => {
		// 1. instantiate contracts
		const daiContract = new ethers.Contract(erc20.dai.address, erc20.dai.abi, wallet);
		const uniswapFactoryContract = new ethers.Contract(uniswap.factory.address, uniswap.factory.abi, wallet);
		const daiExchangeAddress = await uniswapFactoryContract.getExchange(erc20.dai.address, {
			gasLimit: GAS_LIMIT,
		});
		const daiExchangeContract = new ethers.Contract(daiExchangeAddress, uniswap.exchange.abi, wallet);

		// 2. do the actual swapping
		await daiExchangeContract.ethToTokenSwapInput(
			1, // min amount of token retrieved
			2525644800, // random timestamp in the future (year 2050)
			{
				gasLimit: GAS_LIMIT,
				value: ethers.utils.parseEther("5"),
			}
		);

		// util function
		const fromWei = (x) => ethers.utils.formatUnits(x, 18);

		// 3. check DAI balance
		const daiBalanceWei = await daiContract.balanceOf(wallet.address);
		const daiBalance = parseFloat(fromWei(daiBalanceWei));
		expect(daiBalance).toBeGreaterThan(0);
		console.log("daiBalance", daiBalance);
	});
});