From 36d22d82aa202bb199967e9512281e9a53db42c9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 7 Apr 2024 21:33:14 +0200
Subject: Adding upstream version 115.7.0esr.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 editor/spellchecker/tests/bug1200533_subframe.html |  15 ++
 editor/spellchecker/tests/bug1204147_subframe.html |  11 ++
 .../spellchecker/tests/bug1204147_subframe2.html   |   9 +
 editor/spellchecker/tests/bug678842_subframe.html  |   8 +
 editor/spellchecker/tests/bug717433_subframe.html  |   8 +
 editor/spellchecker/tests/chrome.ini               |   9 +
 editor/spellchecker/tests/de-DE/de_DE.aff          |   2 +
 editor/spellchecker/tests/de-DE/de_DE.dic          |   6 +
 editor/spellchecker/tests/en-AU/en_AU.aff          |   2 +
 editor/spellchecker/tests/en-AU/en_AU.dic          |   4 +
 editor/spellchecker/tests/en-GB/en_GB.aff          |   2 +
 editor/spellchecker/tests/en-GB/en_GB.dic          |   4 +
 editor/spellchecker/tests/mochitest.ini            |  68 +++++++
 .../tests/multiple_content_languages_subframe.html |  13 ++
 editor/spellchecker/tests/ru-RU/ru_RU.aff          |   1 +
 editor/spellchecker/tests/ru-RU/ru_RU.dic          |   2 +
 editor/spellchecker/tests/spellcheck.js            |  36 ++++
 .../tests/test_async_UpdateCurrentDictionary.html  |  60 ++++++
 editor/spellchecker/tests/test_bug1100966.html     |  74 ++++++++
 editor/spellchecker/tests/test_bug1154791.html     |  74 ++++++++
 editor/spellchecker/tests/test_bug1200533.html     | 163 ++++++++++++++++
 editor/spellchecker/tests/test_bug1204147.html     | 115 +++++++++++
 editor/spellchecker/tests/test_bug1205983.html     | 134 +++++++++++++
 editor/spellchecker/tests/test_bug1209414.html     | 144 ++++++++++++++
 editor/spellchecker/tests/test_bug1219928.html     |  69 +++++++
 editor/spellchecker/tests/test_bug1365383.html     |  46 +++++
 editor/spellchecker/tests/test_bug1368544.html     |  91 +++++++++
 editor/spellchecker/tests/test_bug1402822.html     | 114 +++++++++++
 editor/spellchecker/tests/test_bug1418629.html     | 210 +++++++++++++++++++++
 editor/spellchecker/tests/test_bug1497480.html     |  94 +++++++++
 editor/spellchecker/tests/test_bug1602526.html     |  57 ++++++
 editor/spellchecker/tests/test_bug1761273.html     |  96 ++++++++++
 editor/spellchecker/tests/test_bug1773802.html     |  96 ++++++++++
 editor/spellchecker/tests/test_bug1837268.html     |  79 ++++++++
 editor/spellchecker/tests/test_bug338427.html      |  61 ++++++
 editor/spellchecker/tests/test_bug366682.html      |  65 +++++++
 editor/spellchecker/tests/test_bug432225.html      |  72 +++++++
 editor/spellchecker/tests/test_bug484181.html      |  73 +++++++
 editor/spellchecker/tests/test_bug596333.html      | 135 +++++++++++++
 editor/spellchecker/tests/test_bug636465.html      |  54 ++++++
 editor/spellchecker/tests/test_bug678842.html      | 106 +++++++++++
 editor/spellchecker/tests/test_bug697981.html      | 137 ++++++++++++++
 editor/spellchecker/tests/test_bug717433.html      | 111 +++++++++++
 .../tests/test_multiple_content_languages.html     | 176 +++++++++++++++++
 .../test_nsIEditorSpellCheck_ReplaceWord.html      |  64 +++++++
 .../tests/test_spellcheck_after_edit.html          | 198 +++++++++++++++++++
 ...t_spellcheck_after_pressing_navigation_key.html |  77 ++++++++
 .../tests/test_spellcheck_selection.html           |  36 ++++
 editor/spellchecker/tests/test_suggest.html        |  42 +++++
 49 files changed, 3323 insertions(+)
 create mode 100644 editor/spellchecker/tests/bug1200533_subframe.html
 create mode 100644 editor/spellchecker/tests/bug1204147_subframe.html
 create mode 100644 editor/spellchecker/tests/bug1204147_subframe2.html
 create mode 100644 editor/spellchecker/tests/bug678842_subframe.html
 create mode 100644 editor/spellchecker/tests/bug717433_subframe.html
 create mode 100644 editor/spellchecker/tests/chrome.ini
 create mode 100644 editor/spellchecker/tests/de-DE/de_DE.aff
 create mode 100644 editor/spellchecker/tests/de-DE/de_DE.dic
 create mode 100644 editor/spellchecker/tests/en-AU/en_AU.aff
 create mode 100644 editor/spellchecker/tests/en-AU/en_AU.dic
 create mode 100644 editor/spellchecker/tests/en-GB/en_GB.aff
 create mode 100644 editor/spellchecker/tests/en-GB/en_GB.dic
 create mode 100644 editor/spellchecker/tests/mochitest.ini
 create mode 100644 editor/spellchecker/tests/multiple_content_languages_subframe.html
 create mode 100644 editor/spellchecker/tests/ru-RU/ru_RU.aff
 create mode 100644 editor/spellchecker/tests/ru-RU/ru_RU.dic
 create mode 100644 editor/spellchecker/tests/spellcheck.js
 create mode 100644 editor/spellchecker/tests/test_async_UpdateCurrentDictionary.html
 create mode 100644 editor/spellchecker/tests/test_bug1100966.html
 create mode 100644 editor/spellchecker/tests/test_bug1154791.html
 create mode 100644 editor/spellchecker/tests/test_bug1200533.html
 create mode 100644 editor/spellchecker/tests/test_bug1204147.html
 create mode 100644 editor/spellchecker/tests/test_bug1205983.html
 create mode 100644 editor/spellchecker/tests/test_bug1209414.html
 create mode 100644 editor/spellchecker/tests/test_bug1219928.html
 create mode 100644 editor/spellchecker/tests/test_bug1365383.html
 create mode 100644 editor/spellchecker/tests/test_bug1368544.html
 create mode 100644 editor/spellchecker/tests/test_bug1402822.html
 create mode 100644 editor/spellchecker/tests/test_bug1418629.html
 create mode 100644 editor/spellchecker/tests/test_bug1497480.html
 create mode 100644 editor/spellchecker/tests/test_bug1602526.html
 create mode 100644 editor/spellchecker/tests/test_bug1761273.html
 create mode 100644 editor/spellchecker/tests/test_bug1773802.html
 create mode 100644 editor/spellchecker/tests/test_bug1837268.html
 create mode 100644 editor/spellchecker/tests/test_bug338427.html
 create mode 100644 editor/spellchecker/tests/test_bug366682.html
 create mode 100644 editor/spellchecker/tests/test_bug432225.html
 create mode 100644 editor/spellchecker/tests/test_bug484181.html
 create mode 100644 editor/spellchecker/tests/test_bug596333.html
 create mode 100644 editor/spellchecker/tests/test_bug636465.html
 create mode 100644 editor/spellchecker/tests/test_bug678842.html
 create mode 100644 editor/spellchecker/tests/test_bug697981.html
 create mode 100644 editor/spellchecker/tests/test_bug717433.html
 create mode 100644 editor/spellchecker/tests/test_multiple_content_languages.html
 create mode 100644 editor/spellchecker/tests/test_nsIEditorSpellCheck_ReplaceWord.html
 create mode 100644 editor/spellchecker/tests/test_spellcheck_after_edit.html
 create mode 100644 editor/spellchecker/tests/test_spellcheck_after_pressing_navigation_key.html
 create mode 100644 editor/spellchecker/tests/test_spellcheck_selection.html
 create mode 100644 editor/spellchecker/tests/test_suggest.html

(limited to 'editor/spellchecker/tests')

diff --git a/editor/spellchecker/tests/bug1200533_subframe.html b/editor/spellchecker/tests/bug1200533_subframe.html
new file mode 100644
index 0000000000..f095c0601f
--- /dev/null
+++ b/editor/spellchecker/tests/bug1200533_subframe.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta http-equiv="Content-Language" content="en-US">
+</head>
+<body>
+<textarea id="none">root en-US</textarea>
+<textarea id="en-GB" lang="en-GB">root en-US, but element en-GB</textarea>
+<textarea id="en-gb" lang="en-gb">root en-US, but element en-gb (lower case)</textarea>
+<textarea id="en-ZA-not-avail" lang="en-ZA">root en-US, but element en-ZA (which is not installed)</textarea>
+<textarea id="en-generic" lang="en">root en-US, but element en</textarea>
+<textarea id="en" lang="en">root en-US, but element en</textarea>
+<textarea id="ko-not-avail" lang="ko">root en-US, but element ko (which is not installed)</textarea>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/bug1204147_subframe.html b/editor/spellchecker/tests/bug1204147_subframe.html
new file mode 100644
index 0000000000..a9b1225cd9
--- /dev/null
+++ b/editor/spellchecker/tests/bug1204147_subframe.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html>
+<head>
+</head>
+<body>
+<textarea id="en-GB" lang="en-GB">element en-GB</textarea>
+<textarea id="en-US" lang="testing-XX">element should default to en-US</textarea>
+
+<div id="trouble-maker" contenteditable>the presence of this div triggers the faulty code path</div>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/bug1204147_subframe2.html b/editor/spellchecker/tests/bug1204147_subframe2.html
new file mode 100644
index 0000000000..935777bd99
--- /dev/null
+++ b/editor/spellchecker/tests/bug1204147_subframe2.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html>
+<head>
+</head>
+<body>
+<textarea id="en-GB" lang="en-GB">element en-GB</textarea>
+<textarea id="en-US" lang="testing-XX">element should default to en-US</textarea>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/bug678842_subframe.html b/editor/spellchecker/tests/bug678842_subframe.html
new file mode 100644
index 0000000000..39d578ee41
--- /dev/null
+++ b/editor/spellchecker/tests/bug678842_subframe.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html>
+<head>
+</head>
+<body>
+<textarea id="textarea" lang="testing-XXX"></textarea>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/bug717433_subframe.html b/editor/spellchecker/tests/bug717433_subframe.html
new file mode 100644
index 0000000000..3c2927e88f
--- /dev/null
+++ b/editor/spellchecker/tests/bug717433_subframe.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html>
+<head>
+</head>
+<body>
+<textarea id="textarea" lang="en"></textarea>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/chrome.ini b/editor/spellchecker/tests/chrome.ini
new file mode 100644
index 0000000000..76faf04121
--- /dev/null
+++ b/editor/spellchecker/tests/chrome.ini
@@ -0,0 +1,9 @@
+[DEFAULT]
+prefs =
+  gfx.font_loader.delay=0
+
+skip-if = os == 'android'
+
+[test_nsIEditorSpellCheck_ReplaceWord.html]
+support-files =
+  spellcheck.js
diff --git a/editor/spellchecker/tests/de-DE/de_DE.aff b/editor/spellchecker/tests/de-DE/de_DE.aff
new file mode 100644
index 0000000000..5dc6896b6d
--- /dev/null
+++ b/editor/spellchecker/tests/de-DE/de_DE.aff
@@ -0,0 +1,2 @@
+# Affix file for German English dictionary
+# Fake file, nothing here.
diff --git a/editor/spellchecker/tests/de-DE/de_DE.dic b/editor/spellchecker/tests/de-DE/de_DE.dic
new file mode 100644
index 0000000000..415c216861
--- /dev/null
+++ b/editor/spellchecker/tests/de-DE/de_DE.dic
@@ -0,0 +1,6 @@
+5
+ein
+guter
+heute
+ist
+Tag
diff --git a/editor/spellchecker/tests/en-AU/en_AU.aff b/editor/spellchecker/tests/en-AU/en_AU.aff
new file mode 100644
index 0000000000..e0c467248d
--- /dev/null
+++ b/editor/spellchecker/tests/en-AU/en_AU.aff
@@ -0,0 +1,2 @@
+# Affix file for British English dictionary
+# Fake file, nothing here.
diff --git a/editor/spellchecker/tests/en-AU/en_AU.dic b/editor/spellchecker/tests/en-AU/en_AU.dic
new file mode 100644
index 0000000000..0a1be725d4
--- /dev/null
+++ b/editor/spellchecker/tests/en-AU/en_AU.dic
@@ -0,0 +1,4 @@
+3
+Mary
+Paul
+Peter
diff --git a/editor/spellchecker/tests/en-GB/en_GB.aff b/editor/spellchecker/tests/en-GB/en_GB.aff
new file mode 100644
index 0000000000..e0c467248d
--- /dev/null
+++ b/editor/spellchecker/tests/en-GB/en_GB.aff
@@ -0,0 +1,2 @@
+# Affix file for British English dictionary
+# Fake file, nothing here.
diff --git a/editor/spellchecker/tests/en-GB/en_GB.dic b/editor/spellchecker/tests/en-GB/en_GB.dic
new file mode 100644
index 0000000000..0a1be725d4
--- /dev/null
+++ b/editor/spellchecker/tests/en-GB/en_GB.dic
@@ -0,0 +1,4 @@
+3
+Mary
+Paul
+Peter
diff --git a/editor/spellchecker/tests/mochitest.ini b/editor/spellchecker/tests/mochitest.ini
new file mode 100644
index 0000000000..6d3c53d71b
--- /dev/null
+++ b/editor/spellchecker/tests/mochitest.ini
@@ -0,0 +1,68 @@
+[DEFAULT]
+prefs =
+  gfx.font_loader.delay=0
+
+skip-if = os == 'android'
+support-files =
+  en-GB/en_GB.dic
+  en-GB/en_GB.aff
+  en-AU/en_AU.dic
+  en-AU/en_AU.aff
+  de-DE/de_DE.dic
+  de-DE/de_DE.aff
+  ru-RU/ru_RU.dic
+  ru-RU/ru_RU.aff
+  spellcheck.js
+
+[test_async_UpdateCurrentDictionary.html]
+[test_bug1100966.html]
+[test_bug1154791.html]
+[test_bug1200533.html]
+skip-if =
+  http3
+support-files =
+  bug1200533_subframe.html
+[test_bug1204147.html]
+skip-if =
+  http3
+support-files =
+  bug1204147_subframe.html
+  bug1204147_subframe2.html
+[test_bug1205983.html]
+[test_bug1209414.html]
+[test_bug1219928.html]
+skip-if = true
+[test_bug1365383.html]
+[test_bug1368544.html]
+[test_bug1402822.html]
+[test_bug1418629.html]
+[test_bug1497480.html]
+[test_bug1602526.html]
+[test_bug1761273.html]
+[test_bug1773802.html]
+[test_bug1837268.html]
+[test_bug366682.html]
+[test_bug432225.html]
+[test_bug484181.html]
+[test_bug596333.html]
+[test_bug636465.html]
+[test_bug678842.html]
+skip-if =
+  http3
+support-files =
+  bug678842_subframe.html
+[test_bug697981.html]
+[test_bug717433.html]
+skip-if =
+  http3
+support-files =
+  bug717433_subframe.html
+[test_multiple_content_languages.html]
+skip-if =
+  http3
+support-files =
+  multiple_content_languages_subframe.html
+[test_spellcheck_after_edit.html]
+[test_spellcheck_after_pressing_navigation_key.html]
+[test_spellcheck_selection.html]
+[test_suggest.html]
diff --git a/editor/spellchecker/tests/multiple_content_languages_subframe.html b/editor/spellchecker/tests/multiple_content_languages_subframe.html
new file mode 100644
index 0000000000..da6a4ed664
--- /dev/null
+++ b/editor/spellchecker/tests/multiple_content_languages_subframe.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta http-equiv="Content-Language" content="en-US, en-GB, ko, en-CA">
+</head>
+<body>
+<textarea id="none">root en-US and en-GB</textarea>
+<textarea id="en-GB" lang="en-GB">root multiple, but element only en-GB</textarea>
+<textarea id="en-ZA-not-avail" lang="en-ZA">root multiple en, but element en-ZA (which is not installed)</textarea>
+<textarea id="en" lang="en">root multiple en, but element en</textarea>
+<textarea id="ko-not-avail" lang="ko">root multiple en, but element ko (which is not installed)</textarea>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/ru-RU/ru_RU.aff b/editor/spellchecker/tests/ru-RU/ru_RU.aff
new file mode 100644
index 0000000000..c6cf721484
--- /dev/null
+++ b/editor/spellchecker/tests/ru-RU/ru_RU.aff
@@ -0,0 +1 @@
+SET KOI8-R
diff --git a/editor/spellchecker/tests/ru-RU/ru_RU.dic b/editor/spellchecker/tests/ru-RU/ru_RU.dic
new file mode 100644
index 0000000000..dbfe3a9f23
--- /dev/null
+++ b/editor/spellchecker/tests/ru-RU/ru_RU.dic
@@ -0,0 +1,2 @@
+1
+ÐÒÁ×ÉÌØÎÙÊ
diff --git a/editor/spellchecker/tests/spellcheck.js b/editor/spellchecker/tests/spellcheck.js
new file mode 100644
index 0000000000..b6a1586628
--- /dev/null
+++ b/editor/spellchecker/tests/spellcheck.js
@@ -0,0 +1,36 @@
+function isSpellingCheckOk(aEditor, aMisspelledWords, aTodo = false) {
+  var selcon = aEditor.selectionController;
+  var sel = selcon.getSelection(selcon.SELECTION_SPELLCHECK);
+  var numWords = sel.rangeCount;
+
+  if (aTodo) {
+    todo_is(
+      numWords,
+      aMisspelledWords.length,
+      "Correct number of misspellings and words."
+    );
+  } else {
+    is(
+      numWords,
+      aMisspelledWords.length,
+      "Correct number of misspellings and words."
+    );
+  }
+
+  if (numWords !== aMisspelledWords.length) {
+    return false;
+  }
+
+  for (var i = 0; i < numWords; ++i) {
+    var word = String(sel.getRangeAt(i));
+    if (aTodo) {
+      todo_is(word, aMisspelledWords[i], "Misspelling is what we think it is.");
+    } else {
+      is(word, aMisspelledWords[i], "Misspelling is what we think it is.");
+    }
+    if (word !== aMisspelledWords[i]) {
+      return false;
+    }
+  }
+  return true;
+}
diff --git a/editor/spellchecker/tests/test_async_UpdateCurrentDictionary.html b/editor/spellchecker/tests/test_async_UpdateCurrentDictionary.html
new file mode 100644
index 0000000000..6f8371d2cd
--- /dev/null
+++ b/editor/spellchecker/tests/test_async_UpdateCurrentDictionary.html
@@ -0,0 +1,60 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=856270
+-->
+<head>
+  <title>Test for Bug 856270 - Async UpdateCurrentDictionary</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=856270">Mozilla Bug 856270</a>
+<p id="display"></p>
+<div id="content">
+<textarea id="editor" spellcheck="true"></textarea>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(start);
+
+function start() {
+  var textarea = document.getElementById("editor");
+  textarea.focus();
+
+  const { onSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  )
+  onSpellCheck(textarea, function() {
+    var isc = SpecialPowers.wrap(textarea).editor.getInlineSpellChecker(false);
+    ok(isc, "Inline spell checker should exist after focus and spell check");
+    var sc = isc.spellChecker;
+
+    sc.setCurrentDictionaries(["testing-XX"]).then(() => {
+      is(true, false, "Setting a non-existent dictionary should fail");
+    }, () => {
+      let currentDictionaries = sc.getCurrentDictionaries();
+
+      is(currentDictionaries.length, 0, "expected no dictionaries");
+      // First, set the lang attribute on the textarea, call Update, and make
+      // sure the spell checker's language was updated appropriately.
+      var lang = "en-US";
+      textarea.setAttribute("lang", lang);
+      sc.UpdateCurrentDictionary(function() {
+        currentDictionaries = sc.getCurrentDictionaries();
+        is(currentDictionaries.length, 1, "expected one dictionary");
+        is(sc.getCurrentDictionaries()[0], lang,
+          "UpdateCurrentDictionary should set the current dictionary.");
+        sc.setCurrentDictionaries([]).then(() => {
+          SimpleTest.finish();
+        });
+      });
+    });
+  });
+}
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1100966.html b/editor/spellchecker/tests/test_bug1100966.html
new file mode 100644
index 0000000000..4ed52968a0
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1100966.html
@@ -0,0 +1,74 @@
+<!DOCTYPE>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1100966
+-->
+<head>
+  <title>Test for Bug 1100966</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+</head>
+<body>
+<div id="display">
+</div>
+<div id="content" contenteditable>
+=====<br>
+correct<br>
+fivee sixx<br>
+====
+</div>
+<pre id="test">
+</pre>
+
+<script class="testbody" type="application/javascript">
+
+let { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+/** Test for Bug 1100966 **/
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(function() {
+  var div = document.getElementById("content");
+  div.focus();
+  synthesizeMouseAtCenter(div, {});
+
+  getSpellChecker().UpdateCurrentDictionary(() => {
+    sendString(" ");
+    SimpleTest.executeSoon(function() {
+      sendString("a");
+      SimpleTest.executeSoon(function() {
+        synthesizeKey("KEY_Backspace");
+
+        maybeOnSpellCheck(div, function() {
+          var sel = getSpellCheckSelection();
+          is(sel.rangeCount, 2, "We should have two misspelled words");
+          is(String(sel.getRangeAt(0)), "fivee", "Correct misspelled word");
+          is(String(sel.getRangeAt(1)), "sixx", "Correct misspelled word");
+
+          SimpleTest.finish();
+        });
+      });
+    });
+  });
+});
+
+function getEditor() {
+  var editingSession = SpecialPowers.wrap(window).docShell.editingSession;
+  return editingSession.getEditorForWindow(window);
+}
+
+function getSpellChecker() {
+  return getEditor().getInlineSpellChecker(false).spellChecker;
+}
+
+function getSpellCheckSelection() {
+  var selcon = getEditor().selectionController;
+  return selcon.getSelection(selcon.SELECTION_SPELLCHECK);
+}
+
+</script>
+</body>
+
+</html>
diff --git a/editor/spellchecker/tests/test_bug1154791.html b/editor/spellchecker/tests/test_bug1154791.html
new file mode 100644
index 0000000000..7ed6c53e35
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1154791.html
@@ -0,0 +1,74 @@
+<!DOCTYPE>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1154791
+-->
+<head>
+  <title>Test for Bug 1154791</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+</head>
+<body>
+<div id="display">
+</div>
+
+<div id="content" contenteditable>
+<tt>thiss onee is stilll a</tt>
+</div>
+
+<pre id="test">
+</pre>
+
+<script class="testbody" type="application/javascript">
+
+let { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+/** Test for Bug 1154791 **/
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(function() {
+  var div = document.getElementById("content");
+  div.focus();
+  getSpellChecker().UpdateCurrentDictionary(() => {
+    synthesizeMouseAtCenter(div, {});
+    synthesizeKey("KEY_ArrowLeft");
+    synthesizeKey("KEY_ArrowLeft");
+
+    SimpleTest.executeSoon(function() {
+      synthesizeKey("KEY_Backspace");
+      SimpleTest.executeSoon(function() {
+        sendString(" ");
+
+        maybeOnSpellCheck(div, function() {
+          var sel = getSpellCheckSelection();
+          is(sel.rangeCount, 2, "We should have two misspelled words");
+          is(String(sel.getRangeAt(0)), "thiss", "Correct misspelled word");
+          is(String(sel.getRangeAt(1)), "onee", "Correct misspelled word");
+
+          SimpleTest.finish();
+        });
+      });
+    });
+  });
+});
+
+function getEditor() {
+  var editingSession = SpecialPowers.wrap(window).docShell.editingSession;
+  return editingSession.getEditorForWindow(window);
+}
+
+function getSpellChecker() {
+  return getEditor().getInlineSpellChecker(false).spellChecker;
+}
+
+function getSpellCheckSelection() {
+  var selcon = getEditor().selectionController;
+  return selcon.getSelection(selcon.SELECTION_SPELLCHECK);
+}
+
+</script>
+</body>
+
+</html>
diff --git a/editor/spellchecker/tests/test_bug1200533.html b/editor/spellchecker/tests/test_bug1200533.html
new file mode 100644
index 0000000000..d97dea8ccd
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1200533.html
@@ -0,0 +1,163 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1200533
+-->
+<head>
+  <title>Test for Bug 1200533</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1200533">Mozilla Bug 1200533</a>
+<p id="display"></p>
+<iframe id="content"></iframe>
+
+</div>
+<pre id="test">
+<script class="testbody" ttype="application/javascript">
+
+/** Test for Bug 1200533 **/
+/** Visit the elements defined above and check the dictionary we got **/
+SimpleTest.waitForExplicitFinish();
+var content = document.getElementById("content");
+
+var tests = [
+    // text area, value of spellchecker.dictionary, result.
+    // Result: Document language.
+    [ "none",  "", "en-US" ],
+    // Result: Element language.
+    [ "en-GB", "", "en-GB" ],
+    [ "en-gb", "", "en-GB" ],
+    // Result: Random en-* or en-US (if application locale is en-US).
+    [ "en-ZA-not-avail", "", "*" ],
+    [ "en-generic",      "", "*" ],
+    [ "en",              "", "*" ],
+    // Result: Locale.
+    [ "ko-not-avail",    "", "en-US" ],
+
+    // Result: Preference value in all cases.
+    [ "en-ZA-not-avail", "en-AU", "en-AU" ],
+    [ "en-generic",      "en-AU", "en-AU" ],
+    [ "ko-not-avail",    "en-AU", "en-AU" ],
+
+    // Result: Random en-*.
+    [ "en-ZA-not-avail", "de-DE", "*" ],
+    [ "en-generic",      "de-DE", "*" ],
+    // Result: Preference value.
+    [ "ko-not-avail",    "de-DE", "de-DE" ],
+  ];
+
+var loadCount = 0;
+var retrying = false;
+var script;
+
+var loadListener = async function(evt) {
+  if (loadCount == 0) {
+    script = SpecialPowers.loadChromeScript(function() {
+      /* eslint-env mozilla/chrome-script */
+      // eslint-disable-next-line mozilla/use-services
+      var dir = Cc["@mozilla.org/file/directory_service;1"]
+                  .getService(Ci.nsIProperties)
+                  .get("CurWorkD", Ci.nsIFile);
+      dir.append("tests");
+      dir.append("editor");
+      dir.append("spellchecker");
+      dir.append("tests");
+
+      var hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                       .getService(Ci.mozISpellCheckingEngine);
+
+      // Install en-GB, en-AU and de-DE dictionaries.
+      var en_GB = dir.clone();
+      var en_AU = dir.clone();
+      var de_DE = dir.clone();
+      en_GB.append("en-GB");
+      en_AU.append("en-AU");
+      de_DE.append("de-DE");
+      hunspell.addDirectory(en_GB);
+      hunspell.addDirectory(en_AU);
+      hunspell.addDirectory(de_DE);
+
+      addMessageListener("check-existence",
+                         () => [en_GB.exists(), en_AU.exists(),
+                                de_DE.exists()]);
+      addMessageListener("destroy", () => {
+        hunspell.removeDirectory(en_GB);
+        hunspell.removeDirectory(en_AU);
+        hunspell.removeDirectory(de_DE);
+      });
+    });
+    var existenceChecks = await script.sendQuery("check-existence");
+    is(existenceChecks[0], true, "true expected (en-GB directory should exist)");
+    is(existenceChecks[1], true, "true expected (en-AU directory should exist)");
+    is(existenceChecks[2], true, "true expected (de-DE directory should exist)");
+  }
+
+  SpecialPowers.pushPrefEnv({set: [["spellchecker.dictionary", tests[loadCount][1]]]},
+                            function() { continueTest(evt); });
+};
+
+function continueTest(evt) {
+  var doc = evt.target.contentDocument;
+  var elem = doc.getElementById(tests[loadCount][0]);
+  var editor = SpecialPowers.wrap(elem).editor;
+  editor.setSpellcheckUserOverride(true);
+  var inlineSpellChecker = editor.getInlineSpellChecker(true);
+  const is_en_US = SpecialPowers.Services.locale.appLocaleAsBCP47 == "en-US";
+
+  const { onSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  onSpellCheck(elem, async function() {
+    var spellchecker = inlineSpellChecker.spellChecker;
+    let currentDictionaries;
+    try {
+      currentDictionaries = spellchecker.getCurrentDictionaries();
+    } catch (e) {}
+
+    if (!currentDictionaries && !retrying) {
+      // It's possible for an asynchronous font-list update to cause a reflow
+      // that disrupts the async spell-check and results in not getting a
+      // current dictionary here; if that happens, we retry the same testcase
+      // by reloading the iframe without bumping loadCount.
+      info(`No current dictionary: retrying testcase ${loadCount}`);
+      retrying = true;
+    } else {
+      is(currentDictionaries.length, 1, "expected one dictionary");
+      let dict = currentDictionaries[0];
+      if (tests[loadCount][2] != "*") {
+        is(dict, tests[loadCount][2], "expected " + tests[loadCount][2]);
+      } else if (is_en_US && tests[loadCount][0].startsWith("en")) {
+        // Current application locale is en-US and content lang is en or
+        // en-unknown, so we should use en-US dictionary as default.
+        is(dict, "en-US", "expected en-US that is application locale");
+      } else {
+        var gotEn = (dict == "en-GB" || dict == "en-AU" || dict == "en-US");
+        is(gotEn, true, "expected en-AU or en-GB or en-US");
+      }
+
+      loadCount++;
+      retrying = false;
+    }
+
+    if (loadCount < tests.length) {
+      // Load the iframe again.
+      content.src = "http://mochi.test:8888/tests/editor/spellchecker/tests/bug1200533_subframe.html?firstload=false";
+    } else {
+      // Remove the fake  dictionaries again, since it's otherwise picked up by later tests.
+      await script.sendQuery("destroy");
+
+      SimpleTest.finish();
+    }
+  });
+}
+
+content.addEventListener("load", loadListener);
+
+content.src = "http://mochi.test:8888/tests/editor/spellchecker/tests/bug1200533_subframe.html?firstload=true";
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1204147.html b/editor/spellchecker/tests/test_bug1204147.html
new file mode 100644
index 0000000000..3d5f0e120f
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1204147.html
@@ -0,0 +1,115 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1204147
+-->
+<head>
+  <title>Test for Bug 1204147</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1204147">Mozilla Bug 1204147</a>
+<p id="display"></p>
+<iframe id="content"></iframe>
+</div>
+
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 1204147 **/
+SimpleTest.waitForExplicitFinish();
+var content = document.getElementById("content");
+// Load a subframe containing an editor with using "en-GB". At first
+// load, it will set the dictionary to "en-GB". The bug was that a content preference
+// was also created. At second load, we check the dictionary for another element,
+// one that should use "en-US". With the bug corrected, we get "en-US", before
+// we got "en-GB" from the content preference.
+
+var firstLoad = true;
+var script;
+
+var loadListener = async function(evt) {
+  if (firstLoad) {
+    script = SpecialPowers.loadChromeScript(function() {
+      /* eslint-env mozilla/chrome-script */
+      // eslint-disable-next-line mozilla/use-services
+      var dir = Cc["@mozilla.org/file/directory_service;1"]
+                  .getService(Ci.nsIProperties)
+                  .get("CurWorkD", Ci.nsIFile);
+      dir.append("tests");
+      dir.append("editor");
+      dir.append("spellchecker");
+      dir.append("tests");
+
+      var hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                       .getService(Ci.mozISpellCheckingEngine);
+
+      // Install en-GB dictionary.
+      let en_GB = dir.clone();
+      en_GB.append("en-GB");
+      hunspell.addDirectory(en_GB);
+
+      addMessageListener("en_GB-exists", () => en_GB.exists());
+      addMessageListener("destroy", () => hunspell.removeDirectory(en_GB));
+    });
+    is(await script.sendQuery("en_GB-exists"), true,
+       "true expected (en-GB directory should exist)");
+  }
+
+  var doc = evt.target.contentDocument;
+  var elem;
+  if (firstLoad) {
+    elem = doc.getElementById("en-GB");
+  } else {
+    elem = doc.getElementById("en-US");
+  }
+
+  var editor = SpecialPowers.wrap(elem).editor;
+  editor.setSpellcheckUserOverride(true);
+  var inlineSpellChecker = editor.getInlineSpellChecker(true);
+
+  const { onSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  onSpellCheck(elem, async function() {
+    let spellchecker = inlineSpellChecker.spellChecker;
+    let currentDictionaries = spellchecker.getCurrentDictionaries();
+    is(currentDictionaries.length, 1, "expected one dictionary");
+    let currentDictionary = currentDictionaries[0];
+    if (firstLoad) {
+      firstLoad = false;
+
+       // First time around, the element's language should be used.
+      is(currentDictionary, "en-GB", "unexpected lang " + currentDictionary + " instead of en-GB");
+
+      // Note that on second load, we load a different page, which does NOT have the trouble-causing
+      // contenteditable in it. Sadly, loading the same page with the trouble-maker in it
+      // doesn't allow the retrieval of the spell check dictionary used for the element,
+      // because the trouble-maker causes the 'global' spell check dictionary to be set to "en-GB"
+      // (since it picks the first one from the list) before we have the chance to retrieve
+      // the dictionary for the element (which happens asynchonously after the spell check has completed).
+      content.src = "http://mochi.test:8888/tests/editor/spellchecker/tests/bug1204147_subframe2.html?firstload=false";
+    } else {
+      // Second time around, the element should default to en-US.
+      // Without the fix, the first run sets the content preference to en-GB for the whole site.
+      is(currentDictionary, "en-US", "unexpected lang " + currentDictionary + " instead of en-US");
+      content.removeEventListener("load", loadListener);
+
+      // Remove the fake en-GB dictionary again, since it's otherwise picked up by later tests.
+      await script.sendQuery("destroy");
+
+      // Reset the preference, so the last value we set doesn't collide with the next test.
+      SimpleTest.finish();
+    }
+  });
+};
+
+content.addEventListener("load", loadListener);
+
+content.src = "http://mochi.test:8888/tests/editor/spellchecker/tests/bug1204147_subframe.html?firstload=true";
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1205983.html b/editor/spellchecker/tests/test_bug1205983.html
new file mode 100644
index 0000000000..3de5e196bf
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1205983.html
@@ -0,0 +1,134 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1205983
+-->
+<head>
+  <title>Test for Bug 1205983</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1205983">Mozilla Bug 1205983</a>
+<p id="display"></p>
+</div>
+
+<div contenteditable id="de-DE" lang="de-DE" onfocus="deFocus()">German heute ist ein guter Tag</div>
+<textarea id="en-US" lang="en-US" onfocus="enFocus()">Nogoodword today is a nice day</textarea>
+
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+function getMisspelledWords(editor) {
+  return editor.selectionController.getSelection(SpecialPowers.Ci.nsISelectionController.SELECTION_SPELLCHECK).toString();
+}
+
+var elem_de;
+var editor_de;
+var selcon_de;
+var script;
+
+var { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+/** Test for Bug 1205983 **/
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(async function() {
+  script = SpecialPowers.loadChromeScript(function() {
+    /* eslint-env mozilla/chrome-script */
+    // eslint-disable-next-line mozilla/use-services
+    var dir = Cc["@mozilla.org/file/directory_service;1"]
+                .getService(Ci.nsIProperties)
+                .get("CurWorkD", Ci.nsIFile);
+    dir.append("tests");
+    dir.append("editor");
+    dir.append("spellchecker");
+    dir.append("tests");
+
+    var hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                     .getService(Ci.mozISpellCheckingEngine);
+
+    // Install de-DE dictionary.
+    var de_DE = dir.clone();
+    de_DE.append("de-DE");
+    hunspell.addDirectory(de_DE);
+
+    addMessageListener("de_DE-exists", () => de_DE.exists());
+    addMessageListener("destroy", () => hunspell.removeDirectory(de_DE));
+  });
+  is(await script.sendQuery("de_DE-exists"), true,
+     "true expected (de_DE directory should exist)");
+
+  document.getElementById("de-DE").focus();
+});
+
+function deFocus() {
+  elem_de = document.getElementById("de-DE");
+
+  maybeOnSpellCheck(elem_de, function() {
+    var editingSession = SpecialPowers.wrap(window).docShell.editingSession;
+    editor_de = editingSession.getEditorForWindow(window);
+    selcon_de = editor_de.selectionController;
+    var sel = selcon_de.getSelection(selcon_de.SELECTION_SPELLCHECK);
+
+    // Check that we spelled in German, so there is only one misspelled word.
+    is(sel.toString(), "German", "one misspelled word expected: German");
+
+    // Now focus the textarea, which requires English spelling.
+    document.getElementById("en-US").focus();
+  });
+}
+
+function enFocus() {
+  var elem_en = document.getElementById("en-US");
+  var editor_en =
+    SpecialPowers.wrap(elem_en)
+                 .editor;
+  editor_en.setSpellcheckUserOverride(true);
+  var inlineSpellChecker = editor_en.getInlineSpellChecker(true);
+
+  maybeOnSpellCheck(elem_en, async function() {
+    var spellchecker = inlineSpellChecker.spellChecker;
+    let currentDictionaries = spellchecker.getCurrentDictionaries();
+    is(currentDictionaries.length, 1, "expected one dictionary");
+    let currentDictionary = currentDictionaries[0];
+
+    // Check that the English dictionary is loaded and that the spell check has worked.
+    is(currentDictionary, "en-US", "expected en-US");
+    is(getMisspelledWords(editor_en), "Nogoodword", "one misspelled word expected: Nogoodword");
+
+    // So far all was boring. The important thing is whether the spell check result
+    // in the de-DE editor is still the same. After losing focus, no spell check
+    // updates should take place there.
+    var sel = selcon_de.getSelection(selcon_de.SELECTION_SPELLCHECK);
+    is(sel.toString(), "German", "one misspelled word expected: German");
+
+    // Remove the fake de_DE dictionary again.
+    await script.sendQuery("destroy");
+
+    // Focus again, so the spelling gets updated, but before we need to kill the focus handler.
+    elem_de.onfocus = null;
+    elem_de.blur();
+    elem_de.focus();
+
+    // After removal, the de_DE editor should refresh the spelling with en-US.
+    maybeOnSpellCheck(elem_de, function() {
+      var endSel = selcon_de.getSelection(selcon_de.SELECTION_SPELLCHECK);
+      // eslint-disable-next-line no-useless-concat
+      is(endSel.toString(), "heute" + "ist" + "ein" + "guter",
+         "some misspelled words expected: heute ist ein guter");
+
+      // If we don't reset this, we cause massive leaks.
+      selcon_de = null;
+      editor_de = null;
+
+      SimpleTest.finish();
+    });
+  });
+}
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1209414.html b/editor/spellchecker/tests/test_bug1209414.html
new file mode 100644
index 0000000000..b4b0cae947
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1209414.html
@@ -0,0 +1,144 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1209414
+-->
+<head>
+  <title>Test for Bug 1209414</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1209414">Mozilla Bug 1209414</a>
+<p id="display"></p>
+</div>
+
+<textarea id="de-DE" lang="de-DE">heute ist ein guter Tag - today is a good day</textarea>
+
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+const Ci = SpecialPowers.Ci;
+
+function getMisspelledWords(editor) {
+  return editor.selectionController.getSelection(Ci.nsISelectionController.SELECTION_SPELLCHECK).toString();
+}
+
+var elem_de;
+var editor_de;
+var script;
+
+/** Test for Bug 1209414 **/
+/*
+ * All we want to do in this test is change the spelling using a right-click and selection from the menu.
+ * This is necessary since all the other tests use setCurrentDictionaries() which doesn't reflect
+ * user behaviour.
+ */
+
+let { maybeOnSpellCheck, onSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(async function() {
+  script = SpecialPowers.loadChromeScript(function() {
+    /* eslint-env mozilla/chrome-script */
+    var chromeWin = actorParent.rootFrameLoader
+                    .ownerElement.ownerGlobal.browsingContext.topChromeWindow;
+    var contextMenu = chromeWin.document.getElementById("contentAreaContextMenu");
+    contextMenu.addEventListener("popupshown",
+                                 () => sendAsyncMessage("popupshown"));
+
+    // eslint-disable-next-line mozilla/use-services
+    var dir = Cc["@mozilla.org/file/directory_service;1"]
+                .getService(Ci.nsIProperties)
+                .get("CurWorkD", Ci.nsIFile);
+    dir.append("tests");
+    dir.append("editor");
+    dir.append("spellchecker");
+    dir.append("tests");
+
+    var hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                     .getService(Ci.mozISpellCheckingEngine);
+
+    // Install de-DE dictionary.
+    let de_DE = dir.clone();
+    de_DE.append("de-DE");
+    hunspell.addDirectory(de_DE);
+
+    addMessageListener("hidepopup", function() {
+      var state = contextMenu.state;
+
+      // Select Language from the menu.  Take a look at
+      // toolkit/modules/InlineSpellChecker.sys.mjs to see how the menu works.
+      contextMenu.ownerDocument.getElementById("spell-check-dictionary-en-US")
+                 .doCommand();
+      contextMenu.hidePopup();
+      return state;
+    });
+    addMessageListener("destroy", () => hunspell.removeDirectory(de_DE));
+    addMessageListener("contextMenu-not-null", () => contextMenu != null);
+    addMessageListener("de_DE-exists", () => de_DE.exists());
+  });
+  is(await script.sendQuery("contextMenu-not-null"), true,
+     "Got context menu XUL");
+  is(await script.sendQuery("de_DE-exists"), true,
+     "true expected (de_DE directory should exist)");
+  script.addMessageListener("popupshown", handlePopup);
+
+  elem_de = document.getElementById("de-DE");
+  editor_de = SpecialPowers.wrap(elem_de).editor;
+  editor_de.setSpellcheckUserOverride(true);
+
+  maybeOnSpellCheck(elem_de, function() {
+    var inlineSpellChecker = editor_de.getInlineSpellChecker(true);
+    var spellchecker = inlineSpellChecker.spellChecker;
+    let currentDictionaries = spellchecker.getCurrentDictionaries();
+
+    // Check that the German dictionary is loaded and that the spell check has worked.
+    is(currentDictionaries.length, 1, "expected one dictionary");
+    is(currentDictionaries[0], "de-DE", "expected de-DE");
+    // eslint-disable-next-line no-useless-concat
+    is(getMisspelledWords(editor_de), "today" + "is" + "a" + "good" + "day", "some misspelled words expected: today is a good day");
+
+    // Focus again, just to be sure that the context-click won't trigger another spell check.
+    elem_de.focus();
+
+    // Make sure all spell checking action is done before right-click to select the en-US dictionary.
+    maybeOnSpellCheck(elem_de, function() {
+      synthesizeMouse(elem_de, 2, 2, { type: "contextmenu", button: 2 }, window);
+    });
+  });
+});
+
+async function handlePopup() {
+  var state = await script.sendQuery("hidepopup");
+  is(state, "open", "checking if popup is open");
+
+  onSpellCheck(elem_de, async function() {
+    var inlineSpellChecker = editor_de.getInlineSpellChecker(true);
+    var spellchecker = inlineSpellChecker.spellChecker;
+    let currentDictionaries = spellchecker.getCurrentDictionaries();
+
+    // Check that the English dictionary is loaded and that the spell check has worked.
+    is(currentDictionaries.length, 2, "expected two dictionaries");
+    let dictionaryArray = Array.from(currentDictionaries);
+    ok(dictionaryArray.includes("de-DE"), "expected de-DE");
+    ok(dictionaryArray.includes("en-US"), "expected en-US");
+    is(getMisspelledWords(editor_de), "", "No misspelled words expected");
+
+    // Remove the fake de_DE dictionary again.
+    await script.sendQuery("destroy");
+
+    // This will clear the content preferences and reset "spellchecker.dictionary".
+    spellchecker.setCurrentDictionaries([]).then(() => {
+      SimpleTest.finish();
+    });
+  });
+}
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1219928.html b/editor/spellchecker/tests/test_bug1219928.html
new file mode 100644
index 0000000000..83ae8de908
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1219928.html
@@ -0,0 +1,69 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1219928
+-->
+<head>
+  <title>Test for Bug 1219928</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1219928">Mozilla Bug 1219928</a>
+<p id="display"></p>
+
+<div contenteditable id="en-US" lang="en-US">
+<p>And here a missspelled word</p>
+<style>
+<!-- and here another onnee in a style comment -->
+</style>
+</div>
+
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 1219928 **/
+/* Very simple test to check that <style> blocks are skipped in the spell check */
+
+var spellchecker;
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(function() {
+  var { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+
+  var elem = document.getElementById("en-US");
+  elem.focus();
+
+  maybeOnSpellCheck(elem, function() {
+    var editingSession = SpecialPowers.wrap(window).docShell.editingSession;
+    var editor = editingSession.getEditorForWindow(window);
+    var selcon = editor.selectionController;
+    var sel = selcon.getSelection(selcon.SELECTION_SPELLCHECK);
+
+    is(sel.toString(), "missspelled", "one misspelled word expected: missspelled");
+
+    spellchecker = SpecialPowers.Cu.createSpellChecker();
+    spellchecker.setFilterType(spellchecker.FILTERTYPE_NORMAL);
+    spellchecker.InitSpellChecker(editor, false, spellCheckStarted);
+  });
+});
+
+function spellCheckStarted() {
+  var misspelledWord = spellchecker.GetNextMisspelledWord();
+  is(misspelledWord, "missspelled", "first misspelled word expected: missspelled");
+
+  // Without the fix, the next misspelled word was 'onnee', so we check that we don't get it.
+  misspelledWord = spellchecker.GetNextMisspelledWord();
+  isnot(misspelledWord, "onnee", "second misspelled word should not be: onnee");
+
+  spellchecker = "";
+
+  SimpleTest.finish();
+}
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1365383.html b/editor/spellchecker/tests/test_bug1365383.html
new file mode 100644
index 0000000000..d4333b4eb0
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1365383.html
@@ -0,0 +1,46 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1365383
+-->
+<head>
+  <title>Test for Bug 1365383</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1365383">Mozilla Bug 1365383</a>
+<p id="display"></p>
+<div id="content">
+<textarea id="editor" spellcheck="true"></textarea>
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(() => {
+  let textarea = document.getElementById("editor");
+  let editor = SpecialPowers.wrap(textarea).editor;
+
+  let spellChecker = SpecialPowers.Cu.createSpellChecker();
+
+  // Callback parameter isn't set
+  spellChecker.InitSpellChecker(editor, false);
+
+  textarea.focus();
+
+  const { onSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  onSpellCheck(textarea, () => {
+    // Callback parameter isn't set
+    spellChecker.UpdateCurrentDictionary();
+
+    var canSpellCheck = spellChecker.canSpellCheck();
+    ok(canSpellCheck, "spellCheck is enabled");
+    SimpleTest.finish();
+  });
+});
+</script>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1368544.html b/editor/spellchecker/tests/test_bug1368544.html
new file mode 100644
index 0000000000..4a182615a8
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1368544.html
@@ -0,0 +1,91 @@
+<!DOCTYPE html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi=id=1368544
+-->
+<html>
+<head>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1368544">Mozilla Bug 1368544</a>
+<div id="display"></div>
+<textarea id=textarea></textarea>
+<pre id="test">
+</pre>
+
+<script class="testbody">
+function hasEmptyTextNode(div) {
+  return div.firstChild.nodeType === Node.TEXT_NODE && div.firstChild.length === 0;
+}
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(() => {
+  let textarea = document.getElementById("textarea");
+  let editor = SpecialPowers.wrap(textarea).editor;
+
+  let spellChecker = SpecialPowers.Cu.createSpellChecker();
+  spellChecker.InitSpellChecker(editor, false);
+
+  textarea.focus();
+
+  const { onSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  onSpellCheck(textarea, () => {
+    spellChecker.UpdateCurrentDictionary(() => {
+      textarea.value = "ABC";
+      ok(editor.rootElement.hasChildNodes(),
+         "editor of textarea has child nodes");
+      sendString("D");
+      is(textarea.value, "ABCD", "D is last character");
+      ok(editor.rootElement.hasChildNodes(),
+         "editor of textarea has child nodes");
+      textarea.value = "";
+      ok(editor.rootElement.hasChildNodes(),
+         "editor of textarea has child node even if value is empty");
+
+      sendString("AAA");
+      synthesizeKey("KEY_Backspace", {repeat: 3});
+      is(textarea.value, "", "value is empty");
+      ok(editor.rootElement.hasChildNodes(),
+         "editor of textarea has child node even if value is empty");
+
+      textarea.value = "ABC";
+      SpecialPowers.wrap(textarea).setUserInput("");
+      is(textarea.value, "",
+         "textarea should become empty when setUserInput() is called with empty string");
+      ok(hasEmptyTextNode(editor.rootElement),
+            "editor of textarea should only have an empty text node when user input emulation set the value to empty");
+      todo(editor.rootElement.childNodes.length === 1, "editor of textarea should only have a single child");
+      if (editor.rootElement.childNodes.length > 1) {
+        is(editor.rootElement.childNodes.length, 2, "There should be only one additional <br> node");
+        is(editor.rootElement.lastChild.tagName.toLowerCase(), "br", "The node should be a <br> element node");
+        ok(!SpecialPowers.wrap(editor.rootElement.lastChild).isPaddingForEmptyEditor,
+            "The <br> should not be a padding <br> element");
+      }
+      textarea.value = "ABC";
+      synthesizeKey("KEY_Enter", {repeat: 2});
+      textarea.value = "";
+      ok(editor.rootElement.hasChildNodes(),
+         "editor of textarea has child node even if value is empty");
+
+      sendString("AAA");
+      is(textarea.value, "AAA", "value is AAA");
+      textarea.addEventListener("keyup", (e) => {
+        if (e.key == "Enter") {
+          textarea.value = "";
+          ok(editor.rootElement.hasChildNodes(),
+             "editor of textarea has child node even if value is empty");
+          SimpleTest.finish();
+        }
+      });
+
+      synthesizeKey("KEY_Enter");
+    });
+ });
+});
+</script>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1402822.html b/editor/spellchecker/tests/test_bug1402822.html
new file mode 100644
index 0000000000..6380060001
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1402822.html
@@ -0,0 +1,114 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1402822
+-->
+<head>
+  <title>Test for Bug 1402822</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1402822">Mozilla Bug 1402822</a>
+<p id="display"></p>
+</div>
+
+<textarea id="editor">heute ist ein guter Tag - today is a good day</textarea>
+
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+const Ci = SpecialPowers.Ci;
+
+let { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+function getMisspelledWords(editor) {
+  return editor.selectionController.getSelection(Ci.nsISelectionController.SELECTION_SPELLCHECK).toString();
+}
+
+/** Test for Bug 1402822 **/
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(start);
+async function start() {
+  let script = SpecialPowers.loadChromeScript(() => {
+    /* eslint-env mozilla/chrome-script */
+    // eslint-disable-next-line mozilla/use-services
+    let dir = Cc["@mozilla.org/file/directory_service;1"]
+                .getService(Ci.nsIProperties)
+                .get("CurWorkD", Ci.nsIFile);
+    dir.append("tests");
+    dir.append("editor");
+    dir.append("spellchecker");
+    dir.append("tests");
+
+    let hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                     .getService(Ci.mozISpellCheckingEngine);
+
+    // Install de-DE dictionary.
+    let de_DE = dir.clone();
+    de_DE.append("de-DE");
+    hunspell.addDirectory(de_DE);
+
+    addMessageListener("destroy", () => hunspell.removeDirectory(de_DE));
+    addMessageListener("de_DE-exists", () => de_DE.exists());
+  });
+  is(await script.sendQuery("de_DE-exists"), true,
+     "true expected (de_DE directory should exist)");
+
+  let textarea = document.getElementById("editor");
+  let editor = SpecialPowers.wrap(textarea).editor;
+  textarea.focus();
+
+  maybeOnSpellCheck(textarea, () => {
+    let isc = SpecialPowers.wrap(textarea).editor.getInlineSpellChecker(false);
+    ok(isc, "Inline spell checker should exist after focus and spell check");
+    let spellchecker = isc.spellChecker;
+
+    spellchecker.setCurrentDictionaries(["en-US"]).then(() => {
+      let currentDictionaries = spellchecker.getCurrentDictionaries();
+
+      is(currentDictionaries.length, 1, "expected one dictionary");
+      is(currentDictionaries[0], "en-US", "expected en-US");
+      is(getMisspelledWords(editor), "heuteisteinguter", "some misspelled words expected: heuteisteinguter");
+      spellchecker.setCurrentDictionaries(["en-US", "de-DE"]).then(() => {
+        textarea.blur();
+        textarea.focus();
+        maybeOnSpellCheck(textarea, () => {
+          currentDictionaries = spellchecker.getCurrentDictionaries();
+
+          is(currentDictionaries.length, 2, "expected two dictionaries");
+          is(currentDictionaries[0], "en-US", "expected en-US");
+          is(currentDictionaries[1], "de-DE", "expected de-DE");
+          is(getMisspelledWords(editor), "", "No misspelled words expected");
+
+          spellchecker.setCurrentDictionaries(["de-DE"]).then(() => {
+            textarea.blur();
+            textarea.focus();
+            maybeOnSpellCheck(textarea, async function() {
+              currentDictionaries = spellchecker.getCurrentDictionaries();
+
+              is(currentDictionaries.length, 1, "expected one dictionary");
+              is(currentDictionaries[0], "de-DE", "expected de-DE");
+              is(getMisspelledWords(editor), "todayisagoodday", "some misspelled words expected: todayisagoodday");
+
+              // Remove the fake de_DE dictionary again.
+              await script.sendQuery("destroy");
+
+              // This will clear the content preferences and reset "spellchecker.dictionary".
+              spellchecker.setCurrentDictionaries([]).then(() => {
+                SimpleTest.finish();
+              });
+            });
+          });
+        });
+      });
+    });
+  });
+}
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1418629.html b/editor/spellchecker/tests/test_bug1418629.html
new file mode 100644
index 0000000000..442663f0c2
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1418629.html
@@ -0,0 +1,210 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Mozilla bug 1418629</title>
+  <link rel=stylesheet href="/tests/SimpleTest/test.css">
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/editor/spellchecker/tests/spellcheck.js"></script>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1418629">Mozilla Bug 1418629</a>
+<p id="display"></p>
+<div id="content" style="display: none;">
+
+</div>
+
+<input id="input1" spellcheck="true">
+<textarea id="textarea1"></textarea>
+<div id="edit1" contenteditable=true></div>
+
+<script>
+const { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+SimpleTest.waitForExplicitFinish();
+
+function getEditor(input) {
+  if (input instanceof HTMLInputElement ||
+      input instanceof HTMLTextAreaElement) {
+    return SpecialPowers.wrap(input).editor;
+  }
+
+  return SpecialPowers.wrap(window).docShell.editor;
+}
+
+function resetEditableContent(input) {
+  if (input instanceof HTMLInputElement ||
+      input instanceof HTMLTextAreaElement) {
+    input.value = "";
+    return;
+  }
+  input.innerHTML = "";
+}
+
+async function test_with_single_quote(input) {
+  let misspeltWords = [];
+
+  input.focus();
+  resetEditableContent(input);
+
+  synthesizeKey("d");
+  synthesizeKey("o");
+  synthesizeKey("e");
+  synthesizeKey("s");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(input, resolve); });
+  let editor = getEditor(input);
+  // isSpellingCheckOk is defined in spellcheck.js
+  ok(isSpellingCheckOk(editor, misspeltWords), "no misspelt words");
+
+  synthesizeKey("n");
+  synthesizeKey("\'");
+  is(input.value || input.textContent, "doesn\'", "");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(input, resolve); });
+  // XXX This won't work since mozInlineSpellWordUtil::SplitDOM removes
+  // last single quote unfortunately that is during inputting.
+  // isSpellingCheckOk is defined in spellcheck.js
+  todo_is(isSpellingCheckOk(editor, misspeltWords, true), true,
+          "don't run spellchecker during inputting word");
+
+  synthesizeKey(" ");
+  is(input.value || input.textContent, "doesn\' ", "");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(input, resolve); });
+  misspeltWords.push("doesn");
+  // isSpellingCheckOk is defined in spellcheck.js
+  ok(isSpellingCheckOk(editor, misspeltWords), "should run spellchecker");
+}
+
+async function test_with_twice_characters(input, ch) {
+  let misspeltWords = [];
+
+  input.focus();
+  resetEditableContent(input);
+
+  synthesizeKey("d");
+  synthesizeKey("o");
+  synthesizeKey("e");
+  synthesizeKey("s");
+  synthesizeKey("n");
+  synthesizeKey(ch);
+  synthesizeKey(ch);
+  is(input.value || input.textContent, "doesn" + ch + ch, "");
+
+  // trigger spellchecker
+  synthesizeKey(" ");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(input, resolve); });
+  misspeltWords.push("doesn");
+  let editor = getEditor(input);
+  // isSpellingCheckOk is defined in spellcheck.js
+  ok(isSpellingCheckOk(editor, misspeltWords), "should run spellchecker");
+}
+
+async function test_between_single_quote(input) {
+  let misspeltWords = [];
+
+  input.focus();
+  resetEditableContent(input);
+
+  synthesizeKey("\'");
+  synthesizeKey("t");
+  synthesizeKey("e");
+  synthesizeKey("s");
+  synthesizeKey("t");
+  synthesizeKey("\'");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(input, resolve); });
+  let editor = getEditor(input);
+  ok(isSpellingCheckOk(editor, misspeltWords),
+     "don't run spellchecker between single qoute");
+}
+
+async function test_with_email(input) {
+  let misspeltWords = [];
+
+  input.focus();
+  resetEditableContent(input);
+
+  synthesizeKey("t");
+  synthesizeKey("t");
+  synthesizeKey("t");
+  synthesizeKey("t");
+  synthesizeKey("@");
+  synthesizeKey("t");
+  synthesizeKey("t");
+  synthesizeKey("t");
+  synthesizeKey("t");
+  synthesizeKey(".");
+  synthesizeKey("c");
+  synthesizeKey("o");
+  synthesizeKey("m");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(input, resolve); });
+  let editor = getEditor(input);
+  ok(isSpellingCheckOk(editor, misspeltWords),
+     "don't run spellchecker for email address");
+
+  synthesizeKey(" ");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(input, resolve); });
+  ok(isSpellingCheckOk(editor, misspeltWords),
+     "no misspelt words due to email address");
+}
+
+async function test_with_url(input) {
+  let misspeltWords = [];
+
+  input.focus();
+  resetEditableContent(input);
+
+  synthesizeKey("h");
+  synthesizeKey("t");
+  synthesizeKey("t");
+  synthesizeKey("p");
+  synthesizeKey(":");
+  synthesizeKey("/");
+  synthesizeKey("/");
+  synthesizeKey("t");
+  synthesizeKey("t");
+  synthesizeKey("t");
+  synthesizeKey("t");
+  synthesizeKey(".");
+  synthesizeKey("c");
+  synthesizeKey("o");
+  synthesizeKey("m");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(input, resolve); });
+  let editor = getEditor(input);
+  ok(isSpellingCheckOk(editor, misspeltWords),
+     "don't run spellchecker for URL");
+
+  synthesizeKey(" ");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(input, resolve); });
+  ok(isSpellingCheckOk(editor, misspeltWords),
+     "no misspelt words due to URL");
+}
+
+SimpleTest.waitForFocus(() => {
+  for (let n of ["input1", "textarea1", "edit1"])  {
+    add_task(test_with_single_quote.bind(null,
+                                         document.getElementById(n)));
+    add_task(test_with_twice_characters.bind(null,
+                                             document.getElementById(n),
+                                             "\'"));
+    add_task(test_with_twice_characters.bind(null,
+                                             document.getElementById(n),
+                                             String.fromCharCode(0x2019)));
+    add_task(test_between_single_quote.bind(null,
+                                            document.getElementById(n)));
+    add_task(test_with_email.bind(null, document.getElementById(n)));
+    add_task(test_with_url.bind(null, document.getElementById(n)));
+  }
+});
+</script>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1497480.html b/editor/spellchecker/tests/test_bug1497480.html
new file mode 100644
index 0000000000..a7063271f4
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1497480.html
@@ -0,0 +1,94 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1497480
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 1497480</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="spellcheck.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1497480">Mozilla Bug 1497480</a>
+<p id="display"></p>
+
+<div id="outOfTarget" contenteditable>Bug 1497480</div>
+<div id="light"></div>
+
+<script>
+
+/** Test for Bug 1497480 **/
+let gMisspeltWords = [];
+let { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+const template = document.createElement("template");
+template.innerHTML = `<div id="target" contenteditable>Test</div>`;
+
+let shadow = document.getElementById("light").attachShadow({mode: "closed"});
+shadow.appendChild(template.content.cloneNode(true));
+
+let target = shadow.getElementById("target");
+let outOfTarget = document.getElementById("outOfTarget");
+
+function getEditor() {
+  var win = window;
+  var editingSession = SpecialPowers.wrap(win).docShell.editingSession;
+  return editingSession.getEditorForWindow(win);
+}
+
+// Wait for the page to be ready for testing
+add_task(async function() {
+  await new Promise((resolve) => {
+    SimpleTest.waitForFocus(() => {
+      SimpleTest.executeSoon(resolve);
+    }, window);
+  });
+
+  // Wait for first full spell-checking.
+  synthesizeMouseAtCenter(outOfTarget, {}, window);
+  await new Promise((resolve) => {
+    maybeOnSpellCheck(outOfTarget, function() {
+      resolve();
+    });
+  });
+});
+
+// Should perform spell-checking when anchor navigates away from ShadowDOM.
+add_task(async function() {
+  synthesizeMouseAtCenter(target, {}, window);
+  sendString(" spellechek");
+  gMisspeltWords.push("spellechek");
+  synthesizeMouseAtCenter(outOfTarget, {}, window);
+  await new Promise((resolve) => {
+    maybeOnSpellCheck(target, function() {
+      ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+         "Spell-checking should be performed when anchor navigates away from ShadowDOM");
+      SimpleTest.executeSoon(resolve);
+    });
+  });
+});
+
+// Should perform spell-checking when pressing enter in contenteditable in ShadowDOM.
+add_task(async function() {
+  synthesizeMouseAtCenter(target, {}, window);
+  sendString(" spellechck");
+  gMisspeltWords.push("spellechck");
+  synthesizeKey("KEY_Enter", {}, window);
+  await new Promise((resolve) => {
+    maybeOnSpellCheck(target, function() {
+      ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+         "Spell-checking should be performed when pressing enter in contenteditable in ShadowDOM");
+      SimpleTest.executeSoon(resolve);
+    });
+  });
+});
+
+</script>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1602526.html b/editor/spellchecker/tests/test_bug1602526.html
new file mode 100644
index 0000000000..e8c2886d9d
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1602526.html
@@ -0,0 +1,57 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Mozilla bug 1602526</title>
+  <link rel=stylesheet href="/tests/SimpleTest/test.css">
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/editor/spellchecker/tests/spellcheck.js"></script>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1602526">Mozilla Bug 1602526</a>
+<p id="display"></p>
+<div id="content" style="display: none;">
+
+</div>
+
+<div id="contenteditable" contenteditable=true>kkkk&#xf6;kkkk</div>
+
+<script>
+const { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+SimpleTest.waitForExplicitFinish();
+
+function getEditor() {
+  return SpecialPowers.wrap(window).docShell.editor;
+}
+
+SimpleTest.waitForFocus(async () => {
+  let contenteditable = document.getElementById("contenteditable");
+  let misspeltWords = [];
+  misspeltWords.push("kkkk\u00f6kkkk");
+
+  contenteditable.focus();
+  window.getSelection().collapse(contenteditable.firstChild, contenteditable.firstChild.length);
+
+  synthesizeKey(" ");
+
+  // Run spell checker
+  await new Promise((resolve) => { maybeOnSpellCheck(contenteditable, resolve); });
+
+  synthesizeKey("a");
+  synthesizeKey("a");
+  synthesizeKey("a");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(contenteditable, resolve); });
+  let editor = getEditor();
+  // isSpellingCheckOk is defined in spellcheck.js
+  // eslint-disable-next-line no-undef
+  ok(isSpellingCheckOk(editor, misspeltWords), "correct word is seleced as misspell");
+
+  SimpleTest.finish();
+});
+</script>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1761273.html b/editor/spellchecker/tests/test_bug1761273.html
new file mode 100644
index 0000000000..543e56e810
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1761273.html
@@ -0,0 +1,96 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1761273
+-->
+<head>
+  <title>Test for Bug 1761273</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1761273">Mozilla Bug 1761273</a>
+<p id="display"></p>
+</div>
+
+<textarea id="editor" lang="en-US">heute ist ein guter Tag - today is a good day</textarea>
+
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+const Ci = SpecialPowers.Ci;
+
+let {
+  getDictionaryContentPref,
+  onSpellCheck,
+} = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+/** Test for Bug 1402822 **/
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(start);
+async function start() {
+  let script = SpecialPowers.loadChromeScript(() => {
+    /* eslint-env mozilla/chrome-script */
+    // eslint-disable-next-line mozilla/use-services
+    let dir = Cc["@mozilla.org/file/directory_service;1"]
+                .getService(Ci.nsIProperties)
+                .get("CurWorkD", Ci.nsIFile);
+    dir.append("tests");
+    dir.append("editor");
+    dir.append("spellchecker");
+    dir.append("tests");
+
+    let hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                     .getService(Ci.mozISpellCheckingEngine);
+
+    // Install de-DE dictionary.
+    let de_DE = dir.clone();
+    de_DE.append("de-DE");
+    hunspell.addDirectory(de_DE);
+
+    addMessageListener("destroy", () => hunspell.removeDirectory(de_DE));
+    addMessageListener("de_DE-exists", () => de_DE.exists());
+  });
+  is(await script.sendQuery("de_DE-exists"), true,
+     "true expected (de_DE directory should exist)");
+
+  let textarea = document.getElementById("editor");
+  textarea.focus();
+
+  onSpellCheck(textarea, async () => {
+    let isc = SpecialPowers.wrap(textarea).editor.getInlineSpellChecker(true);
+    ok(isc, "Inline spell checker should exist after focus and spell check");
+    let spellchecker = isc.spellChecker;
+
+    // Setting the language to the language of the texteditor should not set the
+    // content preference.
+    await spellchecker.setCurrentDictionaries(["en-US"]);
+    let dictionaryContentPref = await getDictionaryContentPref();
+    is(dictionaryContentPref, "", "Content pref should be empty");
+
+    await spellchecker.setCurrentDictionaries(["en-US", "de-DE"]);
+    dictionaryContentPref = await getDictionaryContentPref();
+    is(dictionaryContentPref, "en-US,de-DE,", "Content pref should be en-US,de-DE,");
+
+    await spellchecker.setCurrentDictionaries(["de-DE"]);
+    dictionaryContentPref = await getDictionaryContentPref();
+    is(dictionaryContentPref, "de-DE,", "Content pref should be de-DE,");
+
+    // Remove the fake de_DE dictionary again.
+    await script.sendQuery("destroy");
+
+    // This will clear the content preferences and reset "spellchecker.dictionary".
+    await spellchecker.setCurrentDictionaries([]);
+    dictionaryContentPref = await getDictionaryContentPref();
+    is(dictionaryContentPref, "", "Content pref should be empty");
+
+    SimpleTest.finish();
+  });
+}
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1773802.html b/editor/spellchecker/tests/test_bug1773802.html
new file mode 100644
index 0000000000..e31c819761
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1773802.html
@@ -0,0 +1,96 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1773802
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 1773802</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1773802">Mozilla Bug 1773802</a>
+<p id="display"></p>
+</div>
+
+<textarea id="editor">correct правильный, incarrect непровильный</textarea>
+
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+const Ci = SpecialPowers.Ci;
+
+let { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+function getMisspelledWords(editor) {
+  return editor.selectionController.getSelection(Ci.nsISelectionController.SELECTION_SPELLCHECK).toString();
+}
+
+/** Test for Bug 1773802 **/
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(start);
+async function start() {
+  let script = SpecialPowers.loadChromeScript(() => {
+    /* eslint-env mozilla/chrome-script */
+    // eslint-disable-next-line mozilla/use-services
+    let dir = Cc["@mozilla.org/file/directory_service;1"]
+                .getService(Ci.nsIProperties)
+                .get("CurWorkD", Ci.nsIFile);
+    dir.append("tests");
+    dir.append("editor");
+    dir.append("spellchecker");
+    dir.append("tests");
+
+    let hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                     .getService(Ci.mozISpellCheckingEngine);
+
+    // Install ru-RU dictionary.
+    let ru_RU = dir.clone();
+    ru_RU.append("ru-RU");
+    hunspell.addDirectory(ru_RU);
+
+    addMessageListener("destroy", () => hunspell.removeDirectory(ru_RU));
+    addMessageListener("ru_RU-exists", () => ru_RU.exists());
+  });
+  is(await script.sendQuery("ru_RU-exists"), true,
+     "true expected (ru_RU directory should exist)");
+
+  let textarea = document.getElementById("editor");
+  let editor = SpecialPowers.wrap(textarea).editor;
+  textarea.focus();
+
+  maybeOnSpellCheck(textarea, () => {
+    let isc = SpecialPowers.wrap(textarea).editor.getInlineSpellChecker(false);
+    ok(isc, "Inline spell checker should exist after focus and spell check");
+    let spellchecker = isc.spellChecker;
+
+    spellchecker.setCurrentDictionaries(["en-US", "ru-RU"]).then(async () => {
+      textarea.blur();
+      textarea.focus();
+      maybeOnSpellCheck(textarea, async function() {
+        let currentDictionaries = spellchecker.getCurrentDictionaries();
+
+        is(currentDictionaries.length, 2, "expected two dictionaries");
+        is(currentDictionaries[0], "en-US", "expected en-US");
+        is(currentDictionaries[1], "ru-RU", "expected ru-RU");
+        is(getMisspelledWords(editor), "incarrectнепровильный", "some misspelled words expected: incarrect непровильный");
+
+        // Remove the fake ru_RU dictionary again.
+        await script.sendQuery("destroy");
+
+        // This will clear the content preferences and reset "spellchecker.dictionary".
+        spellchecker.setCurrentDictionaries([]).then(() => {
+          SimpleTest.finish();
+        });
+      });
+    });
+  });
+}
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug1837268.html b/editor/spellchecker/tests/test_bug1837268.html
new file mode 100644
index 0000000000..1467a328b5
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug1837268.html
@@ -0,0 +1,79 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Mozilla bug 1837268</title>
+  <link rel=stylesheet href="/tests/SimpleTest/test.css">
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/editor/spellchecker/tests/spellcheck.js"></script>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1837268">Mozilla Bug 1837268</a>
+<p id="display"></p>
+<div id="content" style="display: none;">
+
+</div>
+
+<div id="contenteditable" contenteditable=true>aabbcc</div>
+
+<script>
+const { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.importESModule(
+  "resource://testing-common/AsyncSpellCheckTestHelper.sys.mjs"
+);
+
+SimpleTest.waitForExplicitFinish();
+
+function getEditor() {
+  return SpecialPowers.wrap(window).docShell.editor;
+}
+
+SimpleTest.waitForFocus(async () => {
+  let contenteditable = document.getElementById("contenteditable");
+  contenteditable.addEventListener("beforeinput", (ev) => {
+    ev.preventDefault();
+    let text = contenteditable.textContent;
+    const sel = window.getSelection();
+    let offset = sel.anchorOffset;
+    switch (ev.inputType) {
+      case "insertText":
+        text = text.substring(0, offset) + ev.data + text.substring(offset);
+        offset += 1;
+        break;
+      case "deleteContentBackward":
+        text = text.substring(0, offset - 1) + text.substring(offset);
+        offset -= 1;
+        break;
+      default:
+        return;
+    }
+    if (contenteditable.firstChild) {
+      contenteditable.firstChild.nodeValue = text;
+    } else {
+      contenteditable.textContent = text;
+    }
+    sel.collapse(contenteditable.firstChild ?? contenteditable, offset);
+  });
+
+  let misspelledWords = [];
+  misspelledWords.push("aabbc"); // One c removed.
+
+  contenteditable.focus();
+  window.getSelection().collapse(contenteditable.firstChild, contenteditable.firstChild.length);
+
+  // Run spell checker
+  await new Promise((resolve) => { maybeOnSpellCheck(contenteditable, resolve); });
+
+  synthesizeKey("KEY_Backspace");
+  synthesizeKey(" ");
+
+  await new Promise((resolve) => { maybeOnSpellCheck(contenteditable, resolve); });
+  let editor = getEditor();
+  // isSpellingCheckOk is defined in spellcheck.js
+  // eslint-disable-next-line no-undef
+  ok(isSpellingCheckOk(editor, misspelledWords), "correct word is selected as misspelled");
+
+  SimpleTest.finish();
+});
+</script>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug338427.html b/editor/spellchecker/tests/test_bug338427.html
new file mode 100644
index 0000000000..dd869ffc11
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug338427.html
@@ -0,0 +1,61 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=338427
+-->
+<head>
+  <title>Test for Bug 338427</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=338427">Mozilla Bug 338427</a>
+<p id="display"></p>
+<div id="content">
+<textarea id="editor" lang="testing-XX" spellcheck="true"></textarea>
+
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 338427 **/
+function init() {
+    var { onSpellCheck } = SpecialPowers.ChromeUtils.import(
+      "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+    );
+    var textarea = document.getElementById("editor");
+    var editor = SpecialPowers.wrap(textarea).editor;
+    var spellchecker = editor.getInlineSpellChecker(true);
+    spellchecker.enableRealTimeSpell = true;
+    textarea.focus();
+
+    onSpellCheck(textarea, function() {
+        var list = spellchecker.spellChecker.GetDictionaryList();
+        ok(!!list.length, "At least one dictionary should be present");
+
+        var lang = list[0];
+        spellchecker.spellChecker.setCurrentDictionaries([lang]).then(() => {
+          onSpellCheck(textarea, function() {
+            try {
+                var dictionaries =
+                    spellchecker.spellChecker.getCurrentDictionaries();
+            } catch (e) {}
+            is(dictionaries.length, 1, "Expected one dictionary");
+            is(dictionaries[0], lang, "Unexpected spell check dictionary");
+
+            // This will clear the content preferences and reset "spellchecker.dictionary".
+            spellchecker.spellChecker.setCurrentDictionaries([]).then(() => {
+              SimpleTest.finish();
+            });
+          });
+        });
+    });
+}
+
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(init);
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug366682.html b/editor/spellchecker/tests/test_bug366682.html
new file mode 100644
index 0000000000..ac38bcf9d2
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug366682.html
@@ -0,0 +1,65 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=366682
+-->
+<head>
+  <title>Test for Bug 366682</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="spellcheck.js"></script>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=366682">Mozilla Bug 366682</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+</div>
+<pre id="test">
+<script type="application/javascript">
+
+/** Test for Bug 366682 **/
+
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(runTest);
+
+var gMisspeltWords;
+
+function getEdit() {
+  return document.getElementById("edit");
+}
+
+function editDoc() {
+  return getEdit().contentDocument;
+}
+
+function getEditor() {
+  var win = editDoc().defaultView;
+  var editingSession = SpecialPowers.wrap(win).docShell.editingSession;
+  return editingSession.getEditorForWindow(win);
+}
+
+function runTest() {
+  editDoc().body.innerHTML = "<div>errror and an other errror</div>";
+  gMisspeltWords = ["errror", "errror"];
+  editDoc().designMode = "on";
+  editDoc().defaultView.focus();
+
+  const { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  maybeOnSpellCheck(editDoc().documentElement, evalTest);
+}
+
+function evalTest() {
+  ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+     "All misspellings accounted for.");
+  SimpleTest.finish();
+}
+</script>
+</pre>
+
+<iframe id="edit" width="200" height="100" src="about:blank"></iframe>
+
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug432225.html b/editor/spellchecker/tests/test_bug432225.html
new file mode 100644
index 0000000000..2168429613
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug432225.html
@@ -0,0 +1,72 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=432225
+-->
+<head>
+  <title>Test for Bug 432225</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="spellcheck.js"></script>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=432225">Mozilla Bug 432225</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+<script type="application/javascript">
+
+/** Test for Bug 432225 **/
+
+let { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(runTest);
+
+var gMisspeltWords = [];
+
+function getEdit() {
+  return document.getElementById("edit");
+}
+
+function editDoc() {
+  return getEdit().contentDocument;
+}
+
+function getEditor() {
+  var win = editDoc().defaultView;
+  var editingSession = SpecialPowers.wrap(win).docShell.editingSession;
+  return editingSession.getEditorForWindow(win);
+}
+
+function runTest() {
+  editDoc().designMode = "on";
+  setTimeout(function() { addWords(100); }, 0);
+}
+
+function addWords(aLimit) {
+  if (aLimit == 0) {
+    ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+       "All misspellings accounted for.");
+    SimpleTest.finish();
+    return;
+  }
+  getEdit().focus();
+  sendString("aa OK ");
+  gMisspeltWords.push("aa");
+  maybeOnSpellCheck(editDoc(), function() {
+    addWords(aLimit - 1);
+  });
+}
+</script>
+</pre>
+
+<iframe id="edit" width="200" height="100" src="about:blank"></iframe>
+
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug484181.html b/editor/spellchecker/tests/test_bug484181.html
new file mode 100644
index 0000000000..30f0b359c8
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug484181.html
@@ -0,0 +1,73 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=484181
+-->
+<head>
+  <title>Test for Bug 484181</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="spellcheck.js"></script>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=484181">Mozilla Bug 484181</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+<script type="application/javascript">
+
+/** Test for Bug 484181 **/
+
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(runTest);
+
+var gMisspeltWords;
+
+function getEditor() {
+  var win = window;
+  var editingSession = SpecialPowers.wrap(win).docShell.editingSession;
+  return editingSession.getEditorForWindow(win);
+}
+
+function append(str) {
+  var edit = document.getElementById("edit");
+  var editor = getEditor();
+  var sel = editor.selection;
+  sel.selectAllChildren(edit);
+  sel.collapseToEnd();
+  sendString(str);
+}
+
+function runTest() {
+  gMisspeltWords = ["haz", "cheezburger"];
+  var edit = document.getElementById("edit");
+  edit.focus();
+
+  const { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  maybeOnSpellCheck(edit, function() {
+    ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+       "All misspellings before editing are accounted for.");
+
+    append(" becaz I'm a lulcat!");
+    maybeOnSpellCheck(edit, function() {
+      gMisspeltWords.push("becaz");
+      gMisspeltWords.push("lulcat");
+      ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+         "All misspellings after typing are accounted for.");
+
+      SimpleTest.finish();
+    });
+  });
+}
+</script>
+</pre>
+
+<div><div></div><div id="edit" contenteditable="true">I can haz cheezburger</div></div>
+
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug596333.html b/editor/spellchecker/tests/test_bug596333.html
new file mode 100644
index 0000000000..ce6714565b
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug596333.html
@@ -0,0 +1,135 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=596333
+-->
+<head>
+  <title>Test for Bug 596333</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="spellcheck.js"></script>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=596333">Mozilla Bug 596333</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+<script type="application/javascript">
+
+/** Test for Bug 596333 **/
+const Ci = SpecialPowers.Ci;
+
+SimpleTest.waitForExplicitFinish();
+addLoadEvent(runTest);
+
+var gMisspeltWords;
+var onSpellCheck;
+
+function getEditor() {
+  return SpecialPowers.wrap(document.getElementById("edit")).editor;
+}
+
+function append(str) {
+  var edit = document.getElementById("edit");
+  edit.focus();
+  edit.selectionStart = edit.selectionEnd = edit.value.length;
+  sendString(str);
+}
+
+function getLoadContext() {
+  return SpecialPowers.wrap(window).docShell.QueryInterface(Ci.nsILoadContext);
+}
+
+function paste(str) {
+  var Cc = SpecialPowers.Cc;
+  var trans = Cc["@mozilla.org/widget/transferable;1"].createInstance(Ci.nsITransferable);
+  trans.init(getLoadContext());
+  var s = Cc["@mozilla.org/supports-string;1"].createInstance(Ci.nsISupportsString);
+  s.data = str;
+  trans.setTransferData("text/plain", s);
+
+  let beforeInputEvent = null;
+  let inputEvent = null;
+  window.addEventListener("beforeinput", aEvent => { beforeInputEvent = aEvent; }, {once: true});
+  window.addEventListener("input", aEvent => { inputEvent = aEvent; }, {once: true});
+  getEditor().pasteTransferable(trans);
+  isnot(beforeInputEvent, null, '"beforeinput" event should be fired');
+  if (beforeInputEvent) {
+    is(beforeInputEvent.cancelable, true, '"beforeinput" event for "insertFromPaste" should be cancelable');
+    is(beforeInputEvent.inputType, "insertFromPaste", 'inputType of "beforeinput" event should be "insertFromPaste"');
+    is(beforeInputEvent.data, str, `data of "beforeinput" event should be "${str}"`);
+    is(beforeInputEvent.dataTransfer, null, 'dataTransfer of "beforeinput" event should be null on <textarea>');
+    is(beforeInputEvent.getTargetRanges().length, 0, 'getTargetRanges() of "beforeinput" event should return empty array on <textarea>');
+  }
+  is(inputEvent.type, "input", '"input" event should be fired');
+  is(inputEvent.inputType, "insertFromPaste", '"inputType of "input" event should be "insertFromPaste"');
+  is(inputEvent.data, str, `data of "input" event should be "${str}"`);
+  is(inputEvent.dataTransfer, null, 'dataTransfer of "input" event should be null on <textarea>');
+  is(inputEvent.getTargetRanges().length, 0, 'getTargetRanges() of "input" event should return empty array on <textarea>');
+}
+
+function runOnFocus() {
+  var edit = document.getElementById("edit");
+
+  gMisspeltWords = ["haz", "cheezburger"];
+  ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+     "All misspellings before editing are accounted for.");
+  append(" becaz I'm a lulcat!");
+  onSpellCheck(edit, function() {
+    gMisspeltWords.push("becaz");
+    gMisspeltWords.push("lulcat");
+    ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+       "All misspellings after typing are accounted for.");
+
+    // Now, type an invalid word, and instead of hitting "space" at the end, just blur
+    // the textarea and see if the spell check after the blur event catches it.
+    append(" workd");
+    edit.blur();
+    onSpellCheck(edit, function() {
+      gMisspeltWords.push("workd");
+      ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+         "All misspellings after blur are accounted for.");
+
+      // Also, test the case when we're entering the first word in a textarea
+      gMisspeltWords = ["workd"];
+      edit.value = "";
+      append("workd ");
+      onSpellCheck(edit, function() {
+        ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+           "Misspelling in the first entered word is accounted for.");
+
+        // Make sure that pasting would also trigger spell checking for the previous word
+        gMisspeltWords = ["workd"];
+        edit.value = "";
+        append("workd");
+        paste("           x");
+        onSpellCheck(edit, function() {
+          ok(isSpellingCheckOk(getEditor(), gMisspeltWords),
+             "Misspelling is accounted for after pasting.");
+
+          SimpleTest.finish();
+        });
+      });
+    });
+  });
+}
+
+function runTest() {
+  var edit = document.getElementById("edit");
+  edit.focus();
+
+  onSpellCheck = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  ).onSpellCheck;
+  onSpellCheck(edit, runOnFocus);
+}
+</script>
+</pre>
+
+<textarea id="edit">I can haz cheezburger</textarea>
+
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug636465.html b/editor/spellchecker/tests/test_bug636465.html
new file mode 100644
index 0000000000..97252d92df
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug636465.html
@@ -0,0 +1,54 @@
+<!doctype html>
+<title>Mozilla bug 636465</title>
+<link rel=stylesheet href="/tests/SimpleTest/test.css">
+<script src="/tests/SimpleTest/EventUtils.js"></script>
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<script src="/tests/SimpleTest/WindowSnapshot.js"></script>
+<a href="https://bugzilla.mozilla.org/show_bug.cgi?id=636465"
+   target="_blank">Mozilla Bug 636465</a>
+<input id="x" value="foobarbaz" spellcheck="true" style="background-color: transparent; border: transparent;">
+<script>
+SimpleTest.waitForExplicitFinish();
+
+function runTest() {
+  const { onSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  var x = document.getElementById("x");
+  x.focus();
+  onSpellCheck(x, function() {
+    x.blur();
+    var spellCheckTrue = snapshotWindow(window);
+    x.setAttribute("spellcheck", "false");
+    var spellCheckFalse = snapshotWindow(window);
+    x.setAttribute("spellcheck", "true");
+    x.focus();
+    onSpellCheck(x, function() {
+      x.blur();
+      var spellCheckTrueAgain = snapshotWindow(window);
+      x.removeAttribute("spellcheck");
+      var spellCheckNone = snapshotWindow(window);
+      var ret = compareSnapshots(spellCheckTrue, spellCheckFalse, false)[0];
+      ok(ret,
+         "Setting the spellcheck attribute to false should work");
+      if (!ret) {
+        ok(false, "\nspellCheckTrue: " + spellCheckTrue.toDataURL() + "\nspellCheckFalse: " + spellCheckFalse.toDataURL());
+      }
+      ret = compareSnapshots(spellCheckTrue, spellCheckTrueAgain, true)[0];
+      ok(ret,
+         "Setting the spellcheck attribute back to true should work");
+      if (!ret) {
+        ok(false, "\nspellCheckTrue: " + spellCheckTrue.toDataURL() + "\nspellCheckTrueAgain: " + spellCheckTrueAgain.toDataURL());
+      }
+      ret = compareSnapshots(spellCheckNone, spellCheckFalse, true)[0];
+      ok(ret,
+         "Unsetting the spellcheck attribute should work");
+      if (!ret) {
+        ok(false, "\spellCheckNone: " + spellCheckNone.toDataURL() + "\nspellCheckFalse: " + spellCheckFalse.toDataURL());
+      }
+      SimpleTest.finish();
+    });
+  });
+}
+addLoadEvent(runTest);
+</script>
diff --git a/editor/spellchecker/tests/test_bug678842.html b/editor/spellchecker/tests/test_bug678842.html
new file mode 100644
index 0000000000..f5f190ab0f
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug678842.html
@@ -0,0 +1,106 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=678842
+-->
+<head>
+  <title>Test for Bug 678842</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=678842">Mozilla Bug 678842</a>
+<p id="display"></p>
+<iframe id="content"></iframe>
+
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 678842 **/
+SimpleTest.waitForExplicitFinish();
+var content = document.getElementById("content");
+// load a subframe containing an editor with a defined unknown lang. At first
+// load, it will set dictionary to en-US. At second load, it will return current
+// dictionary. So, we can check, dictionary is correctly remembered between
+// loads.
+
+var firstLoad = true;
+var script;
+
+var loadListener = async function(evt) {
+  if (firstLoad) {
+    script = SpecialPowers.loadChromeScript(function() {
+      /* eslint-env mozilla/chrome-script */
+      // eslint-disable-next-line mozilla/use-services
+      var dir = Cc["@mozilla.org/file/directory_service;1"]
+                  .getService(Ci.nsIProperties)
+                  .get("CurWorkD", Ci.nsIFile);
+      dir.append("tests");
+      dir.append("editor");
+      dir.append("spellchecker");
+      dir.append("tests");
+
+      var hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                       .getService(Ci.mozISpellCheckingEngine);
+
+      // Install en-GB dictionary.
+      let en_GB = dir.clone();
+      en_GB.append("en-GB");
+      hunspell.addDirectory(en_GB);
+
+      addMessageListener("en_GB-exists", () => en_GB.exists());
+      addMessageListener("destroy", () => hunspell.removeDirectory(en_GB));
+    });
+    is(await script.sendQuery("en_GB-exists"), true,
+       "true expected (en-GB directory should exist)");
+  }
+
+  var doc = evt.target.contentDocument;
+  var elem = doc.getElementById("textarea");
+  var editor = SpecialPowers.wrap(elem).editor;
+  editor.setSpellcheckUserOverride(true);
+  var inlineSpellChecker = editor.getInlineSpellChecker(true);
+
+  const { onSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  onSpellCheck(elem, async function() {
+    let spellchecker = inlineSpellChecker.spellChecker;
+    let currentDictionaries = spellchecker.getCurrentDictionaries();
+    is(currentDictionaries.length, 1, "expected one dictionary");
+    let currentDictionary = currentDictionaries[0];
+
+    if (firstLoad) {
+      firstLoad = false;
+
+       // First time around, the dictionary defaults to the locale.
+      is(currentDictionary, "en-US", "unexpected lang " + currentDictionary + " instead of en-US");
+
+      // Select en-GB.
+      spellchecker.setCurrentDictionaries(["en-GB"]).then(() => {
+        content.src = "http://mochi.test:8888/tests/editor/spellchecker/tests/bug678842_subframe.html?firstload=false";
+      });
+    } else {
+      is(currentDictionary, "en-GB", "unexpected lang " + currentDictionary + " instead of en-GB");
+      content.removeEventListener("load", loadListener);
+
+      // Remove the fake en-GB dictionary again, since it's otherwise picked up by later tests.
+      await script.sendQuery("destroy");
+
+      // This will clear the content preferences and reset "spellchecker.dictionary".
+      spellchecker.setCurrentDictionaries([]).then( () => {
+        SimpleTest.finish();
+      });
+    }
+  });
+};
+
+content.addEventListener("load", loadListener);
+
+content.src = "http://mochi.test:8888/tests/editor/spellchecker/tests/bug678842_subframe.html?firstload=true";
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug697981.html b/editor/spellchecker/tests/test_bug697981.html
new file mode 100644
index 0000000000..044f82048b
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug697981.html
@@ -0,0 +1,137 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=697981
+-->
+<head>
+  <title>Test for Bug 697981</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=697981">Mozilla Bug 697981</a>
+<p id="display"></p>
+</div>
+
+<textarea id="de-DE" lang="de-DE" onfocus="deFocus()">German heute ist ein guter Tag</textarea>
+<textarea id="en-US" lang="en-US" onfocus="enFocus()">Nogoodword today is a nice day</textarea>
+
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+function getMisspelledWords(editor) {
+  return editor.selectionController.getSelection(SpecialPowers.Ci.nsISelectionController.SELECTION_SPELLCHECK).toString();
+}
+
+var elem_de;
+var editor_de;
+var script;
+
+var { maybeOnSpellCheck, onSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+/** Test for Bug 697981 **/
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(async function() {
+  script = SpecialPowers.loadChromeScript(function() {
+    /* eslint-env mozilla/chrome-script */
+    // eslint-disable-next-line mozilla/use-services
+    var dir = Cc["@mozilla.org/file/directory_service;1"]
+                .getService(Ci.nsIProperties)
+                .get("CurWorkD", Ci.nsIFile);
+    dir.append("tests");
+    dir.append("editor");
+    dir.append("spellchecker");
+    dir.append("tests");
+
+    var hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                     .getService(Ci.mozISpellCheckingEngine);
+
+    // Install de-DE dictionary.
+    var de_DE = dir.clone();
+    de_DE.append("de-DE");
+    hunspell.addDirectory(de_DE);
+
+    addMessageListener("de_DE-exists", () => de_DE.exists());
+    addMessageListener("destroy", () => hunspell.removeDirectory(de_DE));
+  });
+  is(await script.sendQuery("de_DE-exists"), true,
+     "true expected (de_DE directory should exist)");
+
+  document.getElementById("de-DE").focus();
+});
+
+function deFocus() {
+  elem_de = document.getElementById("de-DE");
+  editor_de = SpecialPowers.wrap(elem_de).editor;
+  editor_de.setSpellcheckUserOverride(true);
+  var inlineSpellChecker = editor_de.getInlineSpellChecker(true);
+
+  maybeOnSpellCheck(elem_de, function() {
+    var spellchecker = inlineSpellChecker.spellChecker;
+    try {
+      var currentDictionaries = spellchecker.getCurrentDictionaries();
+    } catch (e) {}
+
+    // Check that the German dictionary is loaded and that the spell check has worked.
+    is(currentDictionaries.length, 1, "expected one dictionary");
+    is(currentDictionaries[0], "de-DE", "expected de-DE");
+    is(getMisspelledWords(editor_de), "German", "one misspelled word expected: German");
+
+    // Now focus the other textarea, which requires English spelling.
+    document.getElementById("en-US").focus();
+  });
+}
+
+function enFocus() {
+  var elem_en = document.getElementById("en-US");
+  var editor_en = SpecialPowers.wrap(elem_en).editor;
+  editor_en.setSpellcheckUserOverride(true);
+  var inlineSpellChecker = editor_en.getInlineSpellChecker(true);
+
+  onSpellCheck(elem_en, async function() {
+    let spellchecker = inlineSpellChecker.spellChecker;
+    let currentDictionaries = spellchecker.getCurrentDictionaries();
+
+    // Check that the English dictionary is loaded and that the spell check has worked.
+    is(currentDictionaries.length, 1, "expected one dictionary");
+    is(currentDictionaries[0], "en-US", "expected en-US");
+    is(getMisspelledWords(editor_en), "Nogoodword", "one misspelled word expected: Nogoodword");
+
+    // So far all was boring. The important thing is whether the spell check result
+    // in the de-DE editor is still the same. After losing focus, no spell check
+    // updates should take place there.
+    is(getMisspelledWords(editor_de), "German", "one misspelled word expected: German");
+
+    // Remove the fake de_DE dictionary again.
+    await script.sendQuery("destroy");
+
+    // Focus again, so the spelling gets updated, but before we need to kill the focus handler.
+    elem_de.onfocus = null;
+    elem_de.blur();
+    elem_de.focus();
+
+    // After removal, the de_DE editor should refresh the spelling with en-US.
+    maybeOnSpellCheck(elem_de, function() {
+      spellchecker = inlineSpellChecker.spellChecker;
+      try {
+        currentDictionaries = spellchecker.getCurrentDictionaries();
+      } catch (e) {}
+
+      // Check that the default English dictionary is loaded and that the spell check has worked.
+      is(currentDictionaries.length, 1, "expected one dictionary");
+      is(currentDictionaries[0], "en-US", "expected en-US");
+      // eslint-disable-next-line no-useless-concat
+      is(getMisspelledWords(editor_de), "heute" + "ist" + "ein" + "guter",
+         "some misspelled words expected: heute ist ein guter");
+
+      SimpleTest.finish();
+    });
+  });
+}
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_bug717433.html b/editor/spellchecker/tests/test_bug717433.html
new file mode 100644
index 0000000000..2f09cb70fd
--- /dev/null
+++ b/editor/spellchecker/tests/test_bug717433.html
@@ -0,0 +1,111 @@
+<!DOCTYPE html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=717433
+-->
+<head>
+  <title>Test for Bug 717433</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=717433">Mozilla Bug 717433</a>
+<p id="display"></p>
+<iframe id="content"></iframe>
+
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 717433 **/
+SimpleTest.waitForExplicitFinish();
+var content = document.getElementById("content");
+// Load a subframe containing an editor with language "en". At first
+// load, it will set the dictionary to en-GB or en-US. We set the other one.
+// At second load, it will return the current dictionary. We can check that the
+// dictionary is correctly remembered between loads.
+
+var firstLoad = true;
+var expected = "";
+var script;
+
+var loadListener = async function(evt) {
+  if (firstLoad) {
+    script = SpecialPowers.loadChromeScript(function() {
+      /* eslint-env mozilla/chrome-script */
+      // eslint-disable-next-line mozilla/use-services
+      var dir = Cc["@mozilla.org/file/directory_service;1"]
+                  .getService(Ci.nsIProperties)
+                  .get("CurWorkD", Ci.nsIFile);
+      dir.append("tests");
+      dir.append("editor");
+      dir.append("spellchecker");
+      dir.append("tests");
+
+      var hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                       .getService(Ci.mozISpellCheckingEngine);
+
+      // Install en-GB dictionary.
+      var en_GB = dir.clone();
+      en_GB.append("en-GB");
+      hunspell.addDirectory(en_GB);
+
+      addMessageListener("en_GB-exists", () => en_GB.exists());
+      addMessageListener("destroy", () => hunspell.removeDirectory(en_GB));
+    });
+    is(await script.sendQuery("en_GB-exists"), true,
+       "true expected (en-GB directory should exist)");
+  }
+
+  var doc = evt.target.contentDocument;
+  var elem = doc.getElementById("textarea");
+  var editor = SpecialPowers.wrap(elem).editor;
+  editor.setSpellcheckUserOverride(true);
+  var inlineSpellChecker = editor.getInlineSpellChecker(true);
+
+  const { onSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  onSpellCheck(elem, async function() {
+    let spellchecker = inlineSpellChecker.spellChecker;
+    let currentDictionaries = spellchecker.getCurrentDictionaries();
+
+    is(currentDictionaries.length, 1, "expected one dictionary");
+    let currentDictionary = currentDictionaries[0];
+
+    if (firstLoad) {
+      firstLoad = false;
+
+      // First time around, we get a random dictionary based on the language "en".
+      if (currentDictionary == "en-GB") {
+        expected = "en-US";
+      } else if (currentDictionary == "en-US") {
+        expected = "en-GB";
+      } else {
+        is(true, false, "Neither en-US nor en-GB are current");
+      }
+      spellchecker.setCurrentDictionaries([expected]).then(() => {
+        content.src = "http://mochi.test:8888/tests/editor/spellchecker/tests/bug717433_subframe.html?firstload=false";});
+    } else {
+      is(currentDictionary, expected, expected + " expected");
+      content.removeEventListener("load", loadListener);
+
+      // Remove the fake en-GB dictionary again, since it's otherwise picked up by later tests.
+      await script.sendQuery("destroy");
+
+      // This will clear the content preferences and reset "spellchecker.dictionary".
+      spellchecker.setCurrentDictionaries([]).then(() => {
+        SimpleTest.finish();
+      });
+    }
+  });
+};
+
+content.addEventListener("load", loadListener);
+
+content.src = "http://mochi.test:8888/tests/editor/spellchecker/tests/bug717433_subframe.html?firstload=true";
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_multiple_content_languages.html b/editor/spellchecker/tests/test_multiple_content_languages.html
new file mode 100644
index 0000000000..c3357dec91
--- /dev/null
+++ b/editor/spellchecker/tests/test_multiple_content_languages.html
@@ -0,0 +1,176 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Test for multiple Content-Language values</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<p id="display"></p>
+<iframe id="content"></iframe>
+
+<pre id="test">
+<script class="testbody">
+
+/** Test for multiple Content-Language values **/
+/** Visit the elements defined above and check the dictionaries we got **/
+SimpleTest.waitForExplicitFinish();
+var content = document.getElementById("content");
+
+var tests = [
+    // text area, value of spellchecker.dictionary, result.
+    // Result: Document language.
+    [ "none",  "", ["en-US", "en-GB"] ],
+
+    // Result: Element language.
+    [ "en-GB", "", ["en-GB"] ],
+    // Result: Random en-* or en-US (if application locale is en-US).
+    [ "en-ZA-not-avail", "", ["*"] ],
+    [ "en",              "", ["*"] ],
+    // Result: Locale.
+    [ "ko-not-avail",    "", ["en-US"] ],
+
+    // Result: Document language, plus preference value in all cases.
+    [ "none",            "en-AU", ["en-US", "en-GB", "en-AU"] ],
+    [ "en-ZA-not-avail", "en-AU", ["en-AU"] ],
+    [ "ko-not-avail",    "en-AU", ["en-AU"] ],
+
+    // Result: Document language, plus first matching preference language.
+    [ "none",            "en-AU,en-US", ["en-US", "en-GB", "en-AU"] ],
+    // Result: First matching preference language.
+    [ "en-ZA-not-avail", "en-AU,en-US", ["en-AU"] ],
+    // Result: Fall back to preference languages.
+    [ "ko-not-avail",    "en-AU,en-US", ["en-AU", "en-US"] ],
+
+    // Result: Random en-*.
+    [ "en-ZA-not-avail", "de-DE", ["*"] ],
+    // Result: Preference value.
+    [ "ko-not-avail",    "de-DE", ["de-DE"] ],
+  ];
+
+var loadCount = 0;
+var retrying = false;
+var script;
+
+var loadListener = async function(evt) {
+  if (loadCount == 0) {
+    script = SpecialPowers.loadChromeScript(function() {
+      /* eslint-env mozilla/chrome-script */
+      // eslint-disable-next-line mozilla/use-services
+      var dir = Cc["@mozilla.org/file/directory_service;1"]
+                  .getService(Ci.nsIProperties)
+                  .get("CurWorkD", Ci.nsIFile);
+      dir.append("tests");
+      dir.append("editor");
+      dir.append("spellchecker");
+      dir.append("tests");
+
+      var hunspell = Cc["@mozilla.org/spellchecker/engine;1"]
+                       .getService(Ci.mozISpellCheckingEngine);
+
+      // Install en-GB, en-AU and de-DE dictionaries.
+      var en_GB = dir.clone();
+      var en_AU = dir.clone();
+      var de_DE = dir.clone();
+      en_GB.append("en-GB");
+      en_AU.append("en-AU");
+      de_DE.append("de-DE");
+      hunspell.addDirectory(en_GB);
+      hunspell.addDirectory(en_AU);
+      hunspell.addDirectory(de_DE);
+
+      addMessageListener("check-existence",
+                         () => [en_GB.exists(), en_AU.exists(),
+                                de_DE.exists()]);
+      addMessageListener("destroy", () => {
+        hunspell.removeDirectory(en_GB);
+        hunspell.removeDirectory(en_AU);
+        hunspell.removeDirectory(de_DE);
+      });
+    });
+    var existenceChecks = await script.sendQuery("check-existence");
+    is(existenceChecks[0], true, "true expected (en-GB directory should exist)");
+    is(existenceChecks[1], true, "true expected (en-AU directory should exist)");
+    is(existenceChecks[2], true, "true expected (de-DE directory should exist)");
+  }
+
+  SpecialPowers.pushPrefEnv({set: [["spellchecker.dictionary", tests[loadCount][1]]]},
+                            function() { continueTest(evt); });
+};
+
+function continueTest(evt) {
+  var doc = evt.target.contentDocument;
+  var elem = doc.getElementById(tests[loadCount][0]);
+  var editor = SpecialPowers.wrap(elem).editor;
+  editor.setSpellcheckUserOverride(true);
+  var inlineSpellChecker = editor.getInlineSpellChecker(true);
+  const is_en_US = SpecialPowers.Services.locale.appLocaleAsBCP47 == "en-US";
+
+  const { onSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  onSpellCheck(elem, async function() {
+    var spellchecker = inlineSpellChecker.spellChecker;
+    let currentDictionaries;
+    try {
+      currentDictionaries = spellchecker.getCurrentDictionaries();
+    } catch (e) {}
+
+    if (!currentDictionaries && !retrying) {
+      // It's possible for an asynchronous font-list update to cause a reflow
+      // that disrupts the async spell-check and results in not getting a
+      // current dictionary here; if that happens, we retry the same testcase
+      // by reloading the iframe without bumping loadCount.
+      info(`No current dictionary: retrying testcase ${loadCount}`);
+      retrying = true;
+    } else {
+      let expectedDictionaries = tests[loadCount][2];
+      let dictionaryArray = Array.from(currentDictionaries);
+      is(
+        dictionaryArray.length,
+        expectedDictionaries.length,
+        "Expected matching dictionary count"
+      );
+      if (expectedDictionaries[0] != "*") {
+        ok(
+          dictionaryArray.every(dict => expectedDictionaries.includes(dict)),
+          "active dictionaries should match expectation"
+        );
+      } else if (is_en_US && tests[loadCount][0].startsWith("en")) {
+        // Current application locale is en-US and content lang is en or
+        // en-unknown, so we should use en-US dictionary as default.
+        is(
+          dictionaryArray[0],
+          "en-US",
+          "expected en-US that is application locale"
+        );
+      } else {
+        let dict = dictionaryArray[0];
+        var gotEn = (dict == "en-GB" || dict == "en-AU" || dict == "en-US");
+        is(gotEn, true, "expected en-AU or en-GB or en-US");
+      }
+
+      loadCount++;
+      retrying = false;
+    }
+
+    if (loadCount < tests.length) {
+      // Load the iframe again.
+      content.src = "http://mochi.test:8888/tests/editor/spellchecker/tests/multiple_content_languages_subframe.html?firstload=false";
+    } else {
+      // Remove the fake  dictionaries again, since it's otherwise picked up by later tests.
+      await script.sendQuery("destroy");
+
+      SimpleTest.finish();
+    }
+  });
+}
+
+content.addEventListener("load", loadListener);
+
+content.src = "http://mochi.test:8888/tests/editor/spellchecker/tests/multiple_content_languages_subframe.html?firstload=true";
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_nsIEditorSpellCheck_ReplaceWord.html b/editor/spellchecker/tests/test_nsIEditorSpellCheck_ReplaceWord.html
new file mode 100644
index 0000000000..6088b97e3e
--- /dev/null
+++ b/editor/spellchecker/tests/test_nsIEditorSpellCheck_ReplaceWord.html
@@ -0,0 +1,64 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Test for nsIEditorSpellCheck.ReplaceWord()</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css">
+</head>
+<body>
+<div contenteditable spellcheck="true" lang="en-US"></div>
+<script>
+"use strict";
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(async () => {
+  const { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+  const editor = document.querySelector("div[contenteditable]");
+  async function replaceWord(aMisspelledWord, aCorrectWord, aReplaceAll) {
+    const editorObj = SpecialPowers.wrap(window).docShell.editingSession.getEditorForWindow(window);
+    const inlineSpellChecker = editorObj.getInlineSpellChecker(true);
+    await new Promise(resolve => maybeOnSpellCheck(editor, resolve));
+    const editorSpellCheck = inlineSpellChecker.spellChecker;
+    editorObj.beginTransaction();
+    try {
+      editorSpellCheck.ReplaceWord(aMisspelledWord, aCorrectWord, aReplaceAll);
+    } catch (e) {
+      ok(false, `Unexpected exception: ${e.message}`);
+    }
+    editorObj.endTransaction();
+    editorSpellCheck.GetNextMisspelledWord();
+  }
+
+  async function testReplaceAllMisspelledWords(aCorrectWord) {
+    editor.innerHTML = "<p>def abc def<br>abc def abc</p><p>abc def abc<br>def abc def</p>";
+    editor.focus();
+    editor.getBoundingClientRect();
+    await replaceWord("abc", aCorrectWord, true);
+    is(
+      editor.innerHTML,
+      `<p>def ${aCorrectWord} def<br>${aCorrectWord} def ${aCorrectWord}</p><p>${aCorrectWord} def ${aCorrectWord}<br>def ${aCorrectWord} def</p>`,
+      `nsIEditorSpellCheck.ReplaceWord(..., true) should replace all misspelled words with ${
+        (() => {
+          if (aCorrectWord.length > "abc".length) {
+            return "longer";
+          }
+          return aCorrectWord.length < "abc".length ? "shorter" : "same length"
+        })()
+      } correct word`
+    );
+    editor.blur();
+    editor.getBoundingClientRect();
+  }
+  await testReplaceAllMisspelledWords("ABC");
+  await testReplaceAllMisspelledWords("ABC!");
+  await testReplaceAllMisspelledWords("AB");
+
+  // TODO: Add tests for not all replacing cases.
+
+  SimpleTest.finish();
+});
+</script>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_spellcheck_after_edit.html b/editor/spellchecker/tests/test_spellcheck_after_edit.html
new file mode 100644
index 0000000000..e4fa76d2e4
--- /dev/null
+++ b/editor/spellchecker/tests/test_spellcheck_after_edit.html
@@ -0,0 +1,198 @@
+<!doctype html>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Spellcheck result after edit</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<script>
+let { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+function waitForTick() {
+  return new Promise(resolve =>
+    SimpleTest.executeSoon(
+      () => requestAnimationFrame(
+        () => requestAnimationFrame(resolve)
+      )
+    )
+  );
+}
+
+async function waitForOnSpellCheck(
+  aSpellCheckSelection,
+  aEditingHost,
+  aWaitForNumberOfMisspelledWords,
+  aWhen
+) {
+  info(`Waiting for onSpellCheck (${aWhen})...`);
+  for (let retry = 0; retry < 100; retry++) {
+    await waitForTick();
+    await new Promise(resolve => maybeOnSpellCheck(aEditingHost, resolve));
+    if (aWaitForNumberOfMisspelledWords === 0) {
+      if (aSpellCheckSelection.rangeCount === 0) {
+        break;
+      }
+    } else if (aSpellCheckSelection.rangeCount >= aWaitForNumberOfMisspelledWords) {
+      break;
+    }
+  }
+}
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(async () => {
+  /**
+   * test object should have:
+   *   init function
+   *     @param normalSel       The normal selection for the editing host
+   *     @param editingHost     The editing host of the editor
+   *     @return                Number of misspelled word in the editor
+   *
+   *  run function
+   *     @param editingHost     The editing host of the editor
+   *     @return                Expected number of misspelled word in the editor
+   *
+   *  check function
+   *     @param spellCheckSel   The spellcheck selection for the editing host
+   *     @param editingHost     The editing host of the editor
+   */
+  for (const test of [
+      {
+        init: (normalSel, editingHost) => {
+          info("Staring to test spellcheck of misspelled word after joining paragraphs");
+          // eslint-disable-next-line no-unsanitized/property
+          editingHost.innerHTML = "<p>It is</p><p>what I want</p>";
+          normalSel.collapse(editingHost.querySelector("p + p").firstChild, 0);
+          return 0;
+        },
+        run: (editingHost) => {
+          document.execCommand("delete");
+          return 0;
+        },
+        check: (spellCheckSel, editingHost) => {
+          is(
+            spellCheckSel.rangeCount,
+            0,
+            "The joined misspelled word shouldn't be marked as misspelled word because caret is in the word"
+          );
+        },
+      },
+      {
+        init: (normalSel, editingHost) => {
+          info("Staring to test spellcheck of correct word after joining paragraphs");
+          // eslint-disable-next-line no-unsanitized/property
+          editingHost.innerHTML = "<p>It's beco</p><p>ming nicer</p>";
+          normalSel.collapse(editingHost.querySelector("p + p").firstChild, 0);
+          return 2;
+        },
+        run: (editingHost) => {
+          document.execCommand("delete");
+          return 0;
+        },
+        check: (spellCheckSel, editingHost) => {
+          is(
+            spellCheckSel.rangeCount,
+            0,
+            "There shouldn't be misspelled word after joining separated word anyway"
+          );
+        },
+      },
+      {
+        init: (normalSel, editingHost) => {
+          info("Staring to test spellcheck of correct words after splitting a paragraph");
+          // eslint-disable-next-line no-unsanitized/property
+          editingHost.innerHTML = "<p>It iswhat I want</p>";
+          normalSel.collapse(editingHost.querySelector("p").firstChild, "It is".length);
+          return 1;
+        },
+        run: (editingHost) => {
+          document.execCommand("insertParagraph");
+          return 0;
+        },
+        check: (spellCheckSel, editingHost) => {
+          is(
+            spellCheckSel.rangeCount,
+            0,
+            "No word should be marked as misspelled after split"
+          );
+        },
+      },
+      {
+        init: (normalSel, editingHost) => {
+          info("Staring to test spellcheck of misspelled words after splitting a paragraph");
+          // eslint-disable-next-line no-unsanitized/property
+          editingHost.innerHTML = "<p>It's becoming nicer</p>";
+          normalSel.collapse(editingHost.querySelector("p").firstChild, "It's beco".length);
+          return 0;
+        },
+        run: (editingHost) => {
+          document.execCommand("insertParagraph");
+          return 1;
+        },
+        check: (spellCheckSel, editingHost) => {
+          is(
+            spellCheckSel.rangeCount,
+            1,
+            "The split word in the first paragraph should be marked as misspelled, but the second paragraph's should be so because of caret is in it"
+          );
+          if (!spellCheckSel.rangeCount) {
+            return;
+          }
+          is(
+            SpecialPowers.unwrap(spellCheckSel.getRangeAt(0).startContainer),
+            editingHost.querySelector("p").firstChild,
+            "First misspelled word should start in the first child of the first <p>"
+          );
+          is(
+            SpecialPowers.unwrap(spellCheckSel.getRangeAt(0).endContainer),
+            editingHost.querySelector("p").firstChild,
+            "First misspelled word should end in the first child of the first <p>"
+          );
+          is(
+            spellCheckSel.getRangeAt(0).startOffset,
+            "It's ".length,
+            "First misspelled word should start after 'It '"
+          );
+          is(
+            spellCheckSel.getRangeAt(0).endOffset,
+            "It's beco".length,
+            "First misspelled word should end by after 'bec'"
+          );
+        },
+      },
+    ]) {
+    const editingHost = document.createElement("div");
+    editingHost.setAttribute("contenteditable", "");
+    editingHost.setAttribute("spellcheck", "true");
+    document.body.appendChild(editingHost);
+    editingHost.focus();
+    const editor =
+      SpecialPowers.wrap(window).docShell.editingSession.getEditorForWindow(window);
+    const nsISelectionController = SpecialPowers.Ci.nsISelectionController;
+    const normalSel = editor.selectionController.getSelection(
+        nsISelectionController.SELECTION_NORMAL
+    );
+    const spellCheckSel = editor.selectionController.getSelection(
+      nsISelectionController.SELECTION_SPELLCHECK
+    );
+    const initialMisspelledWords = test.init(normalSel, editingHost);
+    await waitForOnSpellCheck(
+      spellCheckSel, editingHost, initialMisspelledWords, "before edit"
+    );
+    await waitForTick();
+    const expectedMisspelledWords = test.run(editingHost);
+    await waitForOnSpellCheck(
+      spellCheckSel, editingHost, expectedMisspelledWords, "after edit"
+    );
+    test.check(spellCheckSel, editingHost);
+    editingHost.remove();
+    await waitForTick();
+  }
+  SimpleTest.finish();
+});
+</script>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_spellcheck_after_pressing_navigation_key.html b/editor/spellchecker/tests/test_spellcheck_after_pressing_navigation_key.html
new file mode 100644
index 0000000000..2f0c3bed7d
--- /dev/null
+++ b/editor/spellchecker/tests/test_spellcheck_after_pressing_navigation_key.html
@@ -0,0 +1,77 @@
+<!doctype html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1729653
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 1729653</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<textarea rows="20" cols="50">That undfgdfg seems OK.</textarea>
+<script>
+let { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+);
+
+function waitForTick() {
+  return new Promise(resolve => SimpleTest.executeSoon(resolve));
+}
+
+function waitForOnSpellCheck(aTextArea) {
+  info("Waiting for onSpellCheck...");
+  return new Promise(resolve => maybeOnSpellCheck(aTextArea, resolve));
+}
+
+/** Test for Bug 1729653 **/
+SimpleTest.waitForExplicitFinish();
+SimpleTest.waitForFocus(async () => {
+  const textarea = document.querySelector("textarea");
+  textarea.focus();
+  textarea.selectionStart = textarea.selectionEnd = "That undfgdfg".length;
+  const editor = SpecialPowers.wrap(textarea).editor;
+  const nsISelectionController = SpecialPowers.Ci.nsISelectionController;
+  const selection = editor.selectionController.getSelection(nsISelectionController.SELECTION_SPELLCHECK);
+  const spellChecker = SpecialPowers.Cu.createSpellChecker();
+  spellChecker.InitSpellChecker(editor, false);
+  info("Waiting for current dictionary update...");
+  await new Promise(resolve => spellChecker.UpdateCurrentDictionary(resolve));
+  if (selection.rangeCount === 0) {
+    await waitForOnSpellCheck(textarea);
+  }
+  if (selection.rangeCount == 1) {
+    is(
+      selection.getRangeAt(0).toString(),
+      "undfgdfg",
+      "\"undfgdfg\" should be marked as misspelled word at start"
+    );
+  } else {
+    is(selection.rangeCount, 1, "We should have a misspelled word at start");
+  }
+  synthesizeKey(" ");
+  synthesizeKey("KEY_Backspace");
+  textarea.addEventListener("keydown", event => {
+    event.stopImmediatePropagation();  // This shouldn't block spellchecker to handle it.
+  }, {once: true});
+  synthesizeKey("KEY_End");
+  await waitForTick();
+  if (selection.rangeCount === 0) {
+    await waitForOnSpellCheck(textarea);
+  }
+  if (selection.rangeCount == 1) {
+    is(
+      selection.getRangeAt(0).toString(),
+      "undfgdfg",
+      "\"undfgdfg\" should be marked as misspelled word at end"
+    );
+  } else {
+    is(selection.rangeCount, 1, "We should have a misspelled word at end");
+  }
+  SimpleTest.finish();
+});
+</script>
+</body>
+</html>
diff --git a/editor/spellchecker/tests/test_spellcheck_selection.html b/editor/spellchecker/tests/test_spellcheck_selection.html
new file mode 100644
index 0000000000..0d0887a8f3
--- /dev/null
+++ b/editor/spellchecker/tests/test_spellcheck_selection.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Bug 1779846: Test enableSelectionChecking=true on nsIEditorSpellCheck.InitSpellChecker</title>
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<link rel="stylesheet" href="/tests/SimpleTest/test.css" />
+
+<div contenteditable lang="en-US">missspelled</div>
+
+<script>
+add_task(async function() {
+  await new Promise(resolve => SimpleTest.waitForFocus(resolve));
+
+  let { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+
+  let editingHost = document.querySelector("div[contenteditable][lang=en-US]");
+  editingHost.focus();
+
+  await new Promise(resolve => maybeOnSpellCheck(editingHost, resolve));
+
+  let editingSession = SpecialPowers.wrap(window).docShell.editingSession;
+  let editor = editingSession.getEditorForWindow(window);
+  let spellchecker = SpecialPowers.Cu.createSpellChecker();
+  spellchecker.setFilterType(spellchecker.FILTERTYPE_NORMAL);
+
+  /* Select "missspelled" in the <div>. */
+  window.getSelection().selectAllChildren(editingHost);
+
+  /* Pass true to InitSpellChecker to spellcheck the current selection of the editor.*/
+  await new Promise(resolve => spellchecker.InitSpellChecker(editor, true, resolve));
+
+  /* InitSpellChecker with enableSelectionChecking=true shouldn't throw any errors. */
+  ok(spellchecker.canSpellCheck());
+});
+</script>
diff --git a/editor/spellchecker/tests/test_suggest.html b/editor/spellchecker/tests/test_suggest.html
new file mode 100644
index 0000000000..2bdee93c1d
--- /dev/null
+++ b/editor/spellchecker/tests/test_suggest.html
@@ -0,0 +1,42 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Test for nsIEditorSpellChecfker.sugget</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+
+<div contenteditable id="en-US" lang="en-US">missspelled</div>
+
+<pre id="test">
+<script class="testbody" type="text/javascript">
+add_task(async function() {
+  await new Promise(resolve => SimpleTest.waitForFocus(resolve));
+
+  let { maybeOnSpellCheck } = SpecialPowers.ChromeUtils.import(
+    "resource://testing-common/AsyncSpellCheckTestHelper.jsm"
+  );
+
+  let element = document.getElementById("en-US");
+  element.focus();
+
+  await new Promise(resolve => maybeOnSpellCheck(element, resolve));
+
+  let editingSession = SpecialPowers.wrap(window).docShell.editingSession;
+  let editor = editingSession.getEditorForWindow(window);
+  let spellchecker = SpecialPowers.Cu.createSpellChecker();
+  spellchecker.setFilterType(spellchecker.FILTERTYPE_NORMAL);
+  await new Promise(resolve => spellchecker.InitSpellChecker(editor, false, resolve));
+
+  let suggestions = await spellchecker.suggest("misspelled", 5);
+  is(suggestions.length, 0, "\"misspelled\" is correct word");
+
+  suggestions = await spellchecker.suggest("missspelled", 5);
+  is(suggestions.length, 5, "\"missspelled\" isn't correct word");
+});
+</script>
+</pre>
+</body>
+</html>
-- 
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