gecko-dev/toolkit/components/reader/test/browser_readerMode_hidden_nodes.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/**
 * Test that the reader mode button appears and works properly on
 * reader-able content.
 */
const TEST_PREFS = [
  ["reader.parse-on-load.enabled", true],
];

const TEST_PATH = getRootDirectory(gTestPath).replace("chrome://mochitests/content", "http://example.com");

var readerButton = document.getElementById("reader-mode-button");

add_task(async function test_reader_button() {
  registerCleanupFunction(function() {
    // Reset test prefs.
    TEST_PREFS.forEach(([name, value]) => {
      Services.prefs.clearUserPref(name);
    });
    while (gBrowser.tabs.length > 1) {
      gBrowser.removeCurrentTab();
    }
  });

  // Set required test prefs.
  TEST_PREFS.forEach(([name, value]) => {
    Services.prefs.setBoolPref(name, value);
  });

  let tab = gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser);
  is_element_hidden(readerButton, "Reader mode button is not present on a new tab");
  // Point tab to a test page that is not reader-able due to hidden nodes.
  let url = TEST_PATH + "readerModeArticleHiddenNodes.html";
  let paintPromise = ContentTask.spawn(tab.linkedBrowser, "", function() {
    return new Promise(resolve => {
      addEventListener("DOMContentLoaded", function onDCL() {
        removeEventListener("DOMContentLoaded", onDCL);
        addEventListener("MozAfterPaint", function onPaint() {
          removeEventListener("MozAfterPaint", onPaint);
          resolve();
        });
      });
    });
  });
  BrowserTestUtils.loadURI(tab.linkedBrowser, url);
  await paintPromise;

  is_element_hidden(readerButton, "Reader mode button is still not present on tab with unreadable content.");
});