improve tests (#2923)

use es6 syntax in all tests, split weather tests, remove callbacks

tests/unit/functions/cmp_versions_spec.js

@@ -1,31 +1,31 @@
 const path = require("path");
 const { JSDOM } = require("jsdom");
 
-describe("Test function cmpVersions in js/module.js", function () {
+describe("Test function cmpVersions in js/module.js", () => {
 	let cmp;
 
-	beforeAll(function (done) {
+	beforeAll((done) => {
 		const dom = new JSDOM(
-			`<script>var Class = {extend: function() { return {}; }};</script>\
+			`<script>var Class = {extend: () => { return {}; }};</script>\
 				<script src="file://${path.join(__dirname, "..", "..", "..", "js", "module.js")}">`,
 			{ runScripts: "dangerously", resources: "usable" }
 		);
-		dom.window.onload = function () {
+		dom.window.onload = () => {
 			const { cmpVersions } = dom.window;
 			cmp = cmpVersions;
 			done();
 		};
 	});
 
-	it("should return -1 when comparing 2.1 to 2.2", function () {
+	it("should return -1 when comparing 2.1 to 2.2", () => {
 		expect(cmp("2.1", "2.2")).toBe(-1);
 	});
 
-	it("should be return 0 when comparing 2.2 to 2.2", function () {
+	it("should be return 0 when comparing 2.2 to 2.2", () => {
 		expect(cmp("2.2", "2.2")).toBe(0);
 	});
 
-	it("should be return 1 when comparing 1.1 to 1.0", function () {
+	it("should be return 1 when comparing 1.1 to 1.0", () => {
 		expect(cmp("1.1", "1.0")).toBe(1);
 	});
 });