test.js

import { execFile } from 'child_process';
import { JSDOM } from 'jsdom';

const { Promise } = global;

const options = { resources: 'usable', runScripts: 'dangerously' };
const server = execFile('node', [ './dist/server/index.js' ], { cwd: process.cwd() });
const browser = { };

beforeAll(async () => {
	await new Promise(resolve => setTimeout(resolve, 2000));

	const dom = await JSDOM.fromURL('http://localhost:8080', options);

	await new Promise(resolve => dom.window.addEventListener('load', resolve));

	Object.assign(browser, { window: dom.window });
});

afterAll(() => {
	server.kill();
});

describe('...', () => {

	test('...', () => {
		const { document } = browser.window;
		const draggable = document.querySelectorAll('[draggable]');

		expect(draggable.length).toBe(12);
	});
});