mkdir my-smart-contract
cd my-smart-contract
truffle init

pragma solidity ^0.8.0;

contract SimpleStorage {
    uint private storedData;
    
    function set(uint x) public {
        storedData = x;
    }
    
    function get() public view returns (uint) {
        return storedData;
    }
}

pragma solidity ^0.8.0;

contract Voting {
    mapping(address => bool) public voters;
    mapping(string => uint256) public votes;
    string[] public candidates;

    constructor(string[] memory _candidates) {
        candidates = _candidates;
    }

    function vote(string memory _candidate) public {
        require(!voters[msg.sender], "Already voted.");
        require(isValidCandidate(_candidate), "Invalid candidate.");
        
        voters[msg.sender] = true;
        votes[_candidate]++;
    }

    function isValidCandidate(string memory _candidate) private view returns (bool) {
        for (uint i = 0; i < candidates.length; i++) {
            if (keccak256(abi.encodePacked(candidates[i])) == keccak256(abi.encodePacked(_candidate))) {
                return true;
            }
        }
        return false;
    }

    function getVotes(string memory _candidate) public view returns (uint256) {
        require(isValidCandidate(_candidate), "Invalid candidate.");
        return votes[_candidate];
    }
}

const Web3 = require('web3');
const web3 = new Web3('http://localhost:8545');
const votingABI = [...]; // コントラクトのABI
const votingAddress = '...'; // デプロイされたコントラクトのアドレス

const votingContract = new web3.eth.Contract(votingABI, votingAddress);

async function vote(candidate) {
    const accounts = await web3.eth.getAccounts();
    await votingContract.methods.vote(candidate).send({from: accounts[0]});
}

async function getVotes(candidate) {
    const votes = await votingContract.methods.getVotes(candidate).call();
    console.log(`${candidate} has ${votes} votes`);
}

const Voting = artifacts.require("Voting");

contract("Voting", (accounts) => {
    let voting;

    before(async () => {
        voting = await Voting.new(["Candidate1", "Candidate2", "Candidate3"]);
    });

    it("should allow a voter to cast a vote", async () => {
        await voting.vote("Candidate1", {from: accounts[0]});
        const votes = await voting.getVotes("Candidate1");
        assert.equal(votes, 1, "Candidate1 should have 1 vote");
    });

    it("should not allow a voter to vote twice", async () => {
        try {
            await voting.vote("Candidate2", {from: accounts[0]});
            assert.fail("The transaction should have thrown an error");
        } catch (err) {
            assert.include(err.message, "revert", "The error message should contain 'revert'");
        }
    });

    it("should not allow voting for an invalid candidate", async () => {
        try {
            await voting.vote("InvalidCandidate", {from: accounts[1]});
            assert.fail("The transaction should have thrown an error");
        } catch (err) {
            assert.include(err.message, "revert", "The error message should contain 'revert'");
        }
    });
});

truffle test

const Voting = artifacts.require("Voting");

module.exports = function(deployer) {
  deployer.deploy(Voting, ["Candidate1", "Candidate2", "Candidate3"]);
};

truffle migrate --network ropsten