Issue 6391 - Allow running the browser unit tests with Firefox

test/runners/webdriver.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/>.
  */
 
-/* eslint-env node */
-/* eslint no-console: "off" */
-
 "use strict";
 
 function executeScript(driver, name, script, scriptName, scriptArgs)
 {
   let realScript = `let f = ${script}
-                    return f(...arguments);`;
+                    let callback = arguments[arguments.length - 1];
+                    return Promise.resolve()
+                      .then(() => f(...arguments))
+                      .then(() => callback());`;
   return driver.executeScript(`window.consoleLogs = [];
                                let oldLog = console.log;
                                console.log = msg => {
                                  window.consoleLogs.push(msg);
                                  oldLog.call(this, msg);
                                };`)
-    .then(() => driver.executeScript(realScript, scriptArgs))
+    .then(() => driver.executeAsyncScript(realScript, scriptArgs))
     .then(() => driver.executeScript("return window.consoleLogs;"))
     .then(result =>
     {
-      console.log(`\nTests in ${name}\n`);
+      console.log(`\nBrowser tests in ${name}\n`);
       result.forEach(item => console.log(item));
     })
     .then(() => driver.quit())
   ;
 }
 
 module.exports.executeScript = executeScript;