Issue 6985 - Running npm test fails on Windows for adblockpluschrome

test/browsers/firefox.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 "use strict";
 
 const webdriver = require("selenium-webdriver");
 const firefox = require("selenium-webdriver/firefox");
 const {Command} = require("selenium-webdriver/lib/command");
 const {ensureFirefox} = require("../../adblockpluscore/test/runners/" +
                                 "firefox_download");
 
+// We need to require the geckodriver,
+// otherwise on Windows the geckodriver path is not added to process.env.PATH.
+require("geckodriver");
+
 exports.platform = "gecko";
 exports.oldestCompatibleVersion = "57.0";
 exports.ensureBrowser = ensureFirefox;
 
 exports.getDriver = function(browserBinary, devenvPath)
 {
   let options = new firefox.Options();
   options.setBinary(browserBinary);
   options.headless();
 
   let driver = new webdriver.Builder()
     .forBrowser("firefox")
     .setFirefoxOptions(options)
     .build();
 
   let cmd = new Command("moz-install-web-ext")
     .setParameter("path", devenvPath)
     .setParameter("temporary", true);
 
   driver.getExecutor().defineCommand(
     cmd.getName(), "POST",
     "/session/:sessionId/moz/addon/install"
   );
   driver.schedule(cmd, `installWebExt(${devenvPath})`);
 
   return driver;
 };