Issue 6717 - Part 2: run qunit in headless firefox

test/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 FIREFOX_VERSION = "57.0";
 
 const path = require("path");
-
 const webdriver = require("selenium-webdriver");
 const {By, until} = webdriver;
 const firefox = require("selenium-webdriver/firefox");
 const {Command} = require("selenium-webdriver/lib/command");
-
 const {ensureFirefox} = require("../adblockpluscore/test/runners/" +
                                 "firefox_download");
+
+function reportElements(test, driver, success)
+{
+  return driver.findElements(
+    By.css(`#qunit-tests ${success ? ".pass" : ".fail"} .test-name`)
+  ).then(elements => Promise.all(elements.map(elem =>
+    elem.getAttribute("innerHTML").then(data => test.ok(success, data))
+  )));
+}
 
 exports.runFirefox = function(test)
 {
   // https://stackoverflow.com/a/45045036
   function installWebExt(driver, extension)
   {
     let cmd = new Command("moz-install-web-ext")
       .setParameter("path", path.resolve(extension))
       .setParameter("temporary", true);
 
@@ skipping 35 matching lines @@
       // Navigate to the qunit index
       driver.executeScript("location.href = \"qunit/index.html\";")
     ).then(() =>
       // Wait for qunit-results to be present
       driver.wait(until.elementLocated(By.id("qunit-testresult")))
     ).then(() =>
       // Wait for tests to finish
       driver.wait(() =>
         driver.findElement(By.id("qunit-testresult"))
           .getAttribute("innerHTML").then(data =>
-             data.search("Tests completed") >= 0))
-    ).then(() =>
-    {
-      // Find passed tests
-      driver.findElements(By.css("#qunit-tests .pass .test-name"))
-        .then(elements =>
-        {
-          for (let elem of elements)
-          {
-            elem.getAttribute("innerHTML").then(data =>
-              test.ok(true, data));
-          }
-        });
-      // Find failed tests
-      driver.findElements(By.css("#qunit-tests .fail .test-name"))
-        .then(elements =>
-        {
-          for (let elem of elements)
-          {
-            elem.getAttribute("innerHTML").then(data =>
-              test.ok(false, `Undefined error in ${data}`));
-          }
-        });
-    }).then(() =>
+             data.includes("Tests completed")))
+    ).then(() => Promise.all([
+      reportElements(test, driver, true),
+      reportElements(test, driver, false)
+    ])).then(() =>
     {
       driver.quit();

[Sebastian Noack, 2018/08/23 21:54:20]

This looks like a potential race condition. You want to call driver.quit()
and test.done() once the above actions completed (asynchronously), don't you?
So it seems what you want to do is something like this:

  .then(() => Promise.all([
    driver.findElements(...).then(elements =>
      Promise.all(elements.map(...))
    ),
    driver.findElements(...).then(elements =>
      Promise.all(elements.map(...))
    )
  ])).then(() =>
  {
    driver.quit();
    test.done();
  });

[tlucas, 2018/08/24 10:25:09]

Done + made it dry

       test.done();
-    });
+    }, err =>
+      driver.quit().then(() =>
+      {
+        throw err;
+      })
+    );
   });
 };