Fixed

let expect = require('chai').expect;
let charLookup = require('./char_lookup.js');

describe("charLookup", function () {
    it(' should return undefined with a non-string as a first parameter', function () {
        expect(lookupChar(13, 0)).to.equal(undefined, "The function did not return correct result");
    });
    it('should return undefined with a non-number as a second parameter', function () {
        expect(lookupChar("test", "wrong")).to.equal(undefined, "The function did not return correct result");
    });
    it('should return undefined with a floating point number as a second parameter', function () {
        expect(lookupChar("test", 3.12)).to.equal(undefined, "The function did not return correct result");
    });
    it(' should return incorrect index with an incorrect index as a value', function () {
        expect(lookupChar("test", 13)).to.equal("Incorrect index", "The function did not return correct result");
    });
    it(' should return incorrect index with a negative index as a value', function () {
        expect(lookupChar("test", -1)).to.equal("Incorrect index", "The function did not return correct result");
    });
    it('with an index value equal to string length, should return incorrect index', function () {
        expect(lookupChar("pesho", 5)).to.equal("Incorrect index", "The function did not return correct result");
    });
    it(' should return incorrect index with an index equal to string length', function () {
        expect(lookupChar("test", 4)).to.equal("Incorrect index", "The function did not return correct result");
    });
    it('should return correct value with correct parameters', function () {
        expect(lookupChar("Rest", 0)).to.equal("R", "The function did not return correct result");
    });
    it('with correct parameters should return correct value', function () {
        expect(lookupChar("testing", 5)).to.equal("n", "The function did not return correct result");
    });
});