Im getting myself into smartcontract development using solidity, I wrote the below smart contract and I have some issues with the Chai and Mocha test for the first function addCandidate()

//SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.5.0 <0.9.0;

contract VotingContract{
    address public moderator;
    struct Candidate {
        uint256 id;
        string  name;
        uint256 voteCount;
    struct Voter {
        string name;
        mapping(address => bool)  hasVoted;
    mapping(address => Voter) public votes;
    mapping(uint256 => Candidate) public candidateLookup; //candidates will be identified with an unique ID
    uint256 public candidateCount; //Will be used to track the number of candidates
    enum State {beforeStart, running, halted} 
    State public electionState;
    event AddedCandidate(string _name);
    event Voted( uint256 id, string _name);

    constructor () {
        moderator = msg.sender;
        electionState = State.beforeStart;
        candidateCount = 0; //Not really necesary to initalize to zero as per solidity documentation -> A variable which is declared will have an initial default value whose byte-representation is all zeros. The “default values” of variables are the typical “zero-state” of whatever the type is. For example, the default value for a bool is false. The default value for the uint or int types is 0
    modifier onlyModerator{
        require(msg.sender == moderator, 'Only the moderator of the election can use this function');
    modifier votingInProcess {
        require(electionState == State.running, 'The election is not active at this moment');
    function addCandidate(string memory _name) public onlyModerator returns(bool){
        Candidate storage newCandidate = candidateLookup[candidateCount];
        newCandidate.id = candidateCount;
        newCandidate.name = _name;
        newCandidate.voteCount = 0;
        emit AddedCandidate(_name);
        return true;
    function getCandidate(uint256 _id) public view returns(uint256, string memory){
       string memory name = candidateLookup[_id].name;
       uint256 voteCount = candidateLookup[_id].voteCount;
       return (voteCount, name);
    function getCandidates() external view returns(string[] memory, uint256[] memory){
        string [] memory names = new string[](candidateCount);
        uint256[] memory voteCounts = new uint[](candidateCount);
        for (uint256 i = 0; i < candidateCount; i++) {
            names[i] = candidateLookup[i].name;
            voteCounts[i] = candidateLookup[i].voteCount;
        return (names, voteCounts);

    function startVoting() external onlyModerator {
        electionState = State.running;
    function haltVoting() external onlyModerator {
        electionState = State.halted;
    function vote(uint256 _id, string memory _name) public votingInProcess returns (bool){
        Voter storage newVoter = votes[msg.sender];
        require(_id >= 0 && _id <= candidateCount, 'There is no candidate with the specified ID');
        require(newVoter.hasVoted[msg.sender] == false, 'You can only vote one time!');
        newVoter.name = _name;
        newVoter.hasVoted[msg.sender] = true;
        emit Voted(_id, _name);
        return true;

This is the test I have done so far

//getting the contract json representation
const VotingContract = artifacts.require('./VotingContract');
const BN = web3.utils.BN;

let instance;
let accounts;
let owner;

contract('VotingContract', async(accs) => {
    accounts = accs;
    moderator = accounts[0];

it('Can add a candidate', async() => {
    let instance = await VotingContract.deployed();
    let id = 0;
    let newCandidateName = 'Candidate1'
    await instance.addCandidate(newCandidateName, {from: moderator});
    let request = await instance.candidateLookup.call(id)
    assert.equal(request, newCandidateName)

But it fails, this is what I receive

  1) Can add a candidate

  0 passing (489ms)
  1 failing

  1) Can add a candidate:
     AssertionError: expected { Object (0, 1, ...) } to equal 'Candidate1'
      at Context.<anonymous> (test\VotingContract.test.js:21:12)
      at processTicksAndRejections (internal/process/task_queues.js:93:5)

I dont understand from where does the { Object (0, 1, ...) } comes from,

Can any one point me in the right direction? What is this? What documentation should I read? Any additional feedback about the smartcontract I developed will be appreciated!

1 Answer 1


The candidateLookup is mapping of a uint to Candidate (a struct) and not to string (candidateName). So accessing candidateLookup will always returns a struct.

You can try

assert.equal(request[1], newCandidateName)

because a per your struct definition;

request[0]: id,
request[1]: name,
request[2]: voteCount
  • Ohhhh, you are right! Thanks Prashant! yup, the test is passing now :) Commented May 12, 2021 at 18:15

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