how do I fix this error? ReferenceError: totalSupply is not defined - error-handling

Question

Im using a course, and I got this error:
ReferenceError: totalSupply is not defined
and Idk what it means by that, cause I never got this error before.
can somebody help me fix this error? thanks
and this is my code:
const { assert } = require("chai");
const KryptoBird = artifacts.require("KryptoBird");
// check for chai
require('chai')
.use(require('chai-as-promised'))
.should()
contract('KryptoBird', (accounts) => {
let contract
before( async () => {
contract = await KryptoBird.deployed()
})
describe('deployment', async() => {
it("deploys successfully", async () => {
const address = contract.address;
assert.notEqual(address, '')
assert.notEqual(address, null)
assert.notEqual(address, undefined)
assert.notEqual(address, 0x0)
})
it('has a name', async() => {
const name = await contract.name()
assert.equal(name, 'KryptoBird')
})
it('has a symbol', async() => {
const symbol = await contract.symbol()
assert.equal(symbol, 'KBIRDZ')
})
})
describe('minting', async ()=> {
it('creates a new token', async ()=> {
const result = await contract.mint('https...1')
const totalSupply = await contract.totalSupply();
assert.equal(totalSupply, 1)
const event = result.logs[0].args
assert.equal(event._from, '0x0000000000000000000000000000000000000000', 'from is the contract')
assert.equal(event._to, accounts[0], 'to is msg.sender')
await contract.mint('https...1').should.be.rejected
})
})
describe('indexing', async()=> {
it('lists KryptoBirdz', async()=> {
// Mint three new tokens
await contract.mint('https...2')
await contract.mint('https...3')
await contract.mint('https...4')
const totalSupply = await contract.totalSupply()
})
let result = []
let KryptoBird
for(i = 1; i <= totalSupply; i++) {
KryptoBird = await contract.kryptoBirdz(i)
result.push(KryptoBird)
}
let expected = ['https...1','https...2','https...3','https...4']
assert.equal(result.join(','), expected.join(','))
})
})
if u need another contract, just tell me, and if u could help me, thanks so much, because I need to finish this today. I've been trying to fix this for 2 hours, it didnt work. so please, if u could help me, it would mean a LOT to me.
here:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;
import './ERC721Connecter.sol';
contract KryptoBird is ERC721Connecter {
string[] public kryptoBirdz;
mapping(string => bool) _kryptoBirdzExists;
function mint(string memory _kryptoBird) public {
require(!_kryptoBirdzExists[_kryptoBird],
'Error - kryptoBird already exists');
// this is deprecated - uint _id = KryptoBirdz.push(_kryptoBird);
kryptoBirdz.push(_kryptoBird);
uint _id = kryptoBirdz.length - 1;
// .push no logner returns the length but a ref to the added element
_mint(msg.sender, _id);
_kryptoBirdzExists[_kryptoBird]=true;
}
constructor() ERC721Connecter('KryptoBird','KBIRDZ')
{}
}