How to fix "$ is not defined" error when unit testing Jquery with Typescript using Mocha?

I am writing Mocha unit tests for Typescript code containing Jquery. I'm using jsdom for getting the document object. When I compile my TS code to JS and run the tests, it throws an error [ReferenceError: $ is not defined].

My Typescript code is here

export function hello(element) : void {
    $(element).toggleClass('abc');
};

My unit test code is as follows:

import {hello} from '../src/dummy';

var expect = require('chai').expect;
var jsdom = require('jsdom');
var document = jsdom.jsdom();
var window = document.defaultView;

var $ = require('jquery')(window);

describe('TEST NAME', () => {

    it('should run', (done) => {
        hello($('div'));
        done();
    });
});

When I run Mocha test it shows

    <failure message="$ is not defined"><![CDATA[ReferenceError: $ is not defined
  at Object.hello (D:\newGadgets\gadgets\base\gadget\DrawPad\out\src\defaultTools\dummy.js:3:5)
  at Context.<anonymous> (D:\newGadgets\gadgets\base\gadget\DrawPad\out\test\dummy.test.js:10:17)
  at callFnAsync (D:\newGadgets\gadgets\build\node_modules\mocha\lib\runnable.js:349:8)
  at Test.Runnable.run (D:\newGadgets\gadgets\build\node_modules\mocha\lib\runnable.js:301:7)
  at Runner.runTest (D:\newGadgets\gadgets\build\node_modules\mocha\lib\runner.js:422:10)
  at D:\newGadgets\gadgets\build\node_modules\mocha\lib\runner.js:528:12
  at next (D:\newGadgets\gadgets\build\node_modules\mocha\lib\runner.js:342:14)
  at D:\newGadgets\gadgets\build\node_modules\mocha\lib\runner.js:352:7
  at next (D:\newGadgets\gadgets\build\node_modules\mocha\lib\runner.js:284:14)
  at Immediate._onImmediate (D:\newGadgets\gadgets\build\node_modules\mocha\lib\runner.js:320:5)
]]></failure>

Also tried using global.$ = require("jquery"); but does not work.