mocha_test.js - update to modern syntax (#697)

This is a companion change to mdn/content#31050

tools-testing/cross-browser-testing/selenium/mocha_test.js

@@ -1,25 +1,26 @@
-'use strict';
+"use strict";
 
-const assert = require('assert');
+const assert = require("assert");
 
-let webdriver = require('selenium-webdriver'),
-    By = webdriver.By,
-    until = webdriver.until;
+const { Builder, Capabilities, By } = require("selenium-webdriver");
 
-describe('Alert', () => {
-  it('should have the correct text content - this is from the first button', done => {
-    let driver = new webdriver.Builder()
-        .withCapabilities(webdriver.Capabilities.firefox())
-        .build();
+describe("Alert", () => {
+  it("should have the correct text content - this is from the first button", (done) => {
+    let driver = new Builder()
+      .withCapabilities(Capabilities.firefox())
+      .build();
 
-    driver.get('http://mdn.github.io/learning-area/tools-testing/cross-browser-testing/accessibility/native-keyboard-accessibility.html')
-        .then(() => driver.findElement(By.css('button:nth-of-type(1)')))
-        .then(button => button.click())
-        .then(() => driver.switchTo().alert())
-        .then(alert => alert.getText())
-        .then(text => assert.equal(text, 'This is from the first button'))
-        .then(() => driver.quit())
-        .then(done)
-        .catch(err => done(err));
+    driver
+      .get(
+        "http://mdn.github.io/learning-area/tools-testing/cross-browser-testing/accessibility/native-keyboard-accessibility.html"
+      )
+      .then(() => driver.findElement(By.css("button:nth-of-type(1)")))
+      .then((button) => button.click())
+      .then(() => driver.switchTo().alert())
+      .then((alert) => alert.getText())
+      .then((text) => assert.equal(text, "This is from the first button"))
+      .then(() => driver.quit())
+      .then(done)
+      .catch((err) => done(err));
   });
 });