diff --git a/editor/AsyncSpellCheckTestHelper.sys.mjs b/editor/AsyncSpellCheckTestHelper.sys.mjs
index 6ceb2a86b205..748e54df6603 100644
--- a/editor/AsyncSpellCheckTestHelper.sys.mjs
+++ b/editor/AsyncSpellCheckTestHelper.sys.mjs
@@ -50,7 +50,7 @@ export function maybeOnSpellCheck(editableElement, callback) {
   let waitingForEnded = isc && isc.spellCheckPending;
   let count = 0;
 
-  function observe(subj, topic, data) {
+  function observe(subj, topic) {
     if (subj != editor) {
       return;
     }
diff --git a/editor/composer/test/test_bug1266815.html b/editor/composer/test/test_bug1266815.html
index 1c565fb2c107..1c0a6d87e182 100644
--- a/editor/composer/test/test_bug1266815.html
+++ b/editor/composer/test/test_bug1266815.html
@@ -41,7 +41,7 @@ var helperAppDlgPromise = new Promise(function(resolve) {
   }
 
   HelperAppLauncherDialog.prototype = {
-    show(aLauncher, aWindowContext, aReason) {
+    show() {
       ok(true, "Whether showing Dialog");
       resolve();
       registrar.unregisterFactory(MOCK_HELPERAPP_DIALOG_CID,
diff --git a/editor/composer/test/test_bug434998.xhtml b/editor/composer/test/test_bug434998.xhtml
index db2261e3a570..0aad78f1981a 100644
--- a/editor/composer/test/test_bug434998.xhtml
+++ b/editor/composer/test/test_bug434998.xhtml
@@ -44,7 +44,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=434998
     QueryInterface: ChromeUtils.generateQI(["nsIWebProgressListener",
                                             "nsISupportsWeakReference"]),
 
-    onStateChange(aWebProgress, aRequest, aStateFlags, aStatus)
+    onStateChange(aWebProgress, aRequest, aStateFlags)
     {
       if (aStateFlags & Ci.nsIWebProgressListener.STATE_STOP)
       {
@@ -65,25 +65,23 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=434998
     },
 
 
-    onProgressChange(aWebProgress, aRequest,
-                                aCurSelfProgress, aMaxSelfProgress,
-                                aCurTotalProgress, aMaxTotalProgress)
+    onProgressChange()
     {
   },
 
-  onLocationChange(aWebProgress, aRequest, aLocation, aFlags)
+  onLocationChange()
     {
     },
 
-    onStatusChange(aWebProgress, aRequest, aStatus, aMessage)
+    onStatusChange()
     {
     },
 
-    onSecurityChange(aWebProgress, aRequest, aState)
+    onSecurityChange()
     {
     },
 
-    onContentBlockingEvent(aWebProgress, aRequest, aEvent)
+    onContentBlockingEvent()
     {
     },
 
diff --git a/editor/libeditor/tests/browserscope/test_richtext.html b/editor/libeditor/tests/browserscope/test_richtext.html
index c07f0a366ad0..332252292901 100644
--- a/editor/libeditor/tests/browserscope/test_richtext.html
+++ b/editor/libeditor/tests/browserscope/test_richtext.html
@@ -23,7 +23,7 @@ SimpleTest.waitForExplicitFinish();
 // Running all of the tests can take a long time, try to account for it
 SimpleTest.requestLongerTimeout(5);
 
-function sendScore(results, continueParams) {
+function sendScore(results) {
   ok(results.length > 1, "At least one test should have been run");
   for (var i = 1; i < results.length; ++i) {
     var result = results[i];
diff --git a/editor/libeditor/tests/test_bug1053048.html b/editor/libeditor/tests/test_bug1053048.html
index 4f9df5e60227..416d6442d66d 100644
--- a/editor/libeditor/tests/test_bug1053048.html
+++ b/editor/libeditor/tests/test_bug1053048.html
@@ -37,7 +37,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1053048
     // synthesizing the key press.  So, we don't need to check whether a
     // notification actually comes here.
     let selectionListener = {
-      notifySelectionChanged(aDocument, aSelection, aReason, aAmount) {
+      notifySelectionChanged() {
         ok(true, "selectionStart: " + textarea.selectionStart);
         ok(true, "selectionEnd: " + textarea.selectionEnd);
       },
diff --git a/editor/libeditor/tests/test_bug1649005.html b/editor/libeditor/tests/test_bug1649005.html
index fbd8e16ef82c..5e08e16493ea 100644
--- a/editor/libeditor/tests/test_bug1649005.html
+++ b/editor/libeditor/tests/test_bug1649005.html
@@ -11,7 +11,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1649005
   <script src="/tests/SimpleTest/EventUtils.js"></script>
   <script>
   /** Test for bug 1649005, bug 1779343 **/
-  window.addEventListener("DOMContentLoaded", (event) => {
+  window.addEventListener("DOMContentLoaded", () => {
     SimpleTest.waitForExplicitFinish();
     SimpleTest.waitForFocus(function() {
       document.body.textContent = ""; // It would be \n\n otherwise...
diff --git a/editor/libeditor/tests/test_bug1659276.html b/editor/libeditor/tests/test_bug1659276.html
index 6789db2e7744..6286e58327f6 100644
--- a/editor/libeditor/tests/test_bug1659276.html
+++ b/editor/libeditor/tests/test_bug1659276.html
@@ -63,7 +63,7 @@ SimpleTest.waitForExplicitFinish();
 SimpleTest.waitForFocus(async () => {
   function waitForTickOfRefeshDriver() {
     function awaitOneRefresh() {
-      return new Promise(function(aResolve, aReject) {
+      return new Promise(function(aResolve) {
         requestAnimationFrame(aResolve);
       });
     }
diff --git a/editor/libeditor/tests/test_bug502673.html b/editor/libeditor/tests/test_bug502673.html
index 0850cf3de0d2..fcfb1f329e05 100644
--- a/editor/libeditor/tests/test_bug502673.html
+++ b/editor/libeditor/tests/test_bug502673.html
@@ -37,7 +37,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=502673
           editor.removeDocumentStateListener(this);
         },
 
-        NotifyDocumentStateChanged(aNowDirty) {
+        NotifyDocumentStateChanged() {
           var editor = SpecialPowers.wrap(this.input).editor;
           editor.removeDocumentStateListener(this);
         },
diff --git a/editor/libeditor/tests/test_bug525389.html b/editor/libeditor/tests/test_bug525389.html
index 500720d92a93..25c6e2b8e3cc 100644
--- a/editor/libeditor/tests/test_bug525389.html
+++ b/editor/libeditor/tests/test_bug525389.html
@@ -17,7 +17,7 @@ function getLoadContext() {
 
 async function runTest() {
   var pasteCount = 0;
-  var pasteFunc = function(event) { pasteCount++; };
+  var pasteFunc = function() { pasteCount++; };
 
   function verifyContent(s) {
     var e = document.getElementById("i1");
diff --git a/editor/libeditor/tests/test_bug569988.html b/editor/libeditor/tests/test_bug569988.html
index c4d4b040babf..6133d383c9c1 100644
--- a/editor/libeditor/tests/test_bug569988.html
+++ b/editor/libeditor/tests/test_bug569988.html
@@ -33,7 +33,7 @@ function runTest() {
     os.addObserver(onPromptLoad, "common-dialog-loaded");
     os.addObserver(onPromptLoad, "tabmodal-dialog-loaded");
 
-    function onPromptLoad(subject, topic, data) {
+    function onPromptLoad(subject) {
       let ui = subject.Dialog ? subject.Dialog.ui : undefined;
       if (!ui) {
         // subject is an tab prompt, find the elements ourselves
diff --git a/editor/libeditor/tests/test_bug607584.xhtml b/editor/libeditor/tests/test_bug607584.xhtml
index f610de544bd4..37bb3dc5a46d 100644
--- a/editor/libeditor/tests/test_bug607584.xhtml
+++ b/editor/libeditor/tests/test_bug607584.xhtml
@@ -44,7 +44,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=607584
     QueryInterface: ChromeUtils.generateQI(["nsIWebProgressListener",
                                             "nsISupportsWeakReference"]),
 
-    onStateChange(aWebProgress, aRequest, aStateFlags, aStatus)
+    onStateChange(aWebProgress, aRequest, aStateFlags)
     {
         if (aStateFlags & Ci.nsIWebProgressListener.STATE_STOP)
         {
@@ -71,25 +71,23 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=607584
     },
 
 
-    onProgressChange(aWebProgress, aRequest,
-                                aCurSelfProgress, aMaxSelfProgress,
-                                aCurTotalProgress, aMaxTotalProgress)
+    onProgressChange()
       {
       },
 
-    onLocationChange(aWebProgress, aRequest, aLocation, aFlags)
+    onLocationChange()
       {
       },
 
-    onStatusChange(aWebProgress, aRequest, aStatus, aMessage)
+    onStatusChange()
       {
       },
 
-    onSecurityChange(aWebProgress, aRequest, aState)
+    onSecurityChange()
       {
       },
 
-    onContentBlockingEvent(aWebProgress, aRequest, aEvent)
+    onContentBlockingEvent()
       {
       },
 
diff --git a/editor/libeditor/tests/test_bug611182.html b/editor/libeditor/tests/test_bug611182.html
index 7843156fda27..125dcacb625e 100644
--- a/editor/libeditor/tests/test_bug611182.html
+++ b/editor/libeditor/tests/test_bug611182.html
@@ -92,7 +92,7 @@ SimpleTest.waitForFocus(function() {
   // start running all tests.
   var myXHR = new XMLHttpRequest();
   myXHR.open("GET", "file_bug611182.sjs?queryTotalTests");
-  myXHR.onload = function(e) {
+  myXHR.onload = function() {
     totalTests = myXHR.responseText;
     runAllTests();
   };
diff --git a/editor/libeditor/tests/test_bug616590.xhtml b/editor/libeditor/tests/test_bug616590.xhtml
index 1f6cb3d0f88d..4a4bad7224c8 100644
--- a/editor/libeditor/tests/test_bug616590.xhtml
+++ b/editor/libeditor/tests/test_bug616590.xhtml
@@ -43,7 +43,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=616590
     QueryInterface: ChromeUtils.generateQI(["nsIWebProgressListener",
                                             "nsISupportsWeakReference"]),
 
-    onStateChange(aWebProgress, aRequest, aStateFlags, aStatus)
+    onStateChange(aWebProgress, aRequest, aStateFlags)
     {
       if (aStateFlags & Ci.nsIWebProgressListener.STATE_STOP)
       {
@@ -60,25 +60,23 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=616590
     },
 
 
-    onProgressChange(aWebProgress, aRequest,
-                                aCurSelfProgress, aMaxSelfProgress,
-                                aCurTotalProgress, aMaxTotalProgress)
+    onProgressChange()
     {
     },
 
-    onLocationChange(aWebProgress, aRequest, aLocation, aFlags)
+    onLocationChange()
     {
     },
 
-    onStatusChange(aWebProgress, aRequest, aStatus, aMessage)
+    onStatusChange()
     {
     },
 
-    onSecurityChange(aWebProgress, aRequest, aState)
+    onSecurityChange()
     {
     },
 
-    onContentBlockingEvent(aWebProgress, aRequest, aEvent)
+    onContentBlockingEvent()
     {
     },
 
diff --git a/editor/libeditor/tests/test_bug674770-2.html b/editor/libeditor/tests/test_bug674770-2.html
index 9b052770520a..ab2fbca68b30 100644
--- a/editor/libeditor/tests/test_bug674770-2.html
+++ b/editor/libeditor/tests/test_bug674770-2.html
@@ -320,7 +320,7 @@ function initForBodyEditableDocumentTests() {
   frameDocument.getElementById("editor2").removeEventListener("click", clickEventHandler);
 
   iframe.onload =
-    function(aEvent) { SimpleTest.executeSoon(runBodyEditableDocumentTests1); };
+    function() { SimpleTest.executeSoon(runBodyEditableDocumentTests1); };
   iframe.srcdoc = "<body contenteditable>body:</body>";
 }
 
diff --git a/editor/libeditor/tests/test_bug780908.xhtml b/editor/libeditor/tests/test_bug780908.xhtml
index 590316ef4623..6bfa306a714e 100644
--- a/editor/libeditor/tests/test_bug780908.xhtml
+++ b/editor/libeditor/tests/test_bug780908.xhtml
@@ -46,7 +46,7 @@ adapted from test_bug607584.xhtml by Kent James <kent@caspia.com>
     QueryInterface: ChromeUtils.generateQI(["nsIWebProgressListener",
                                             "nsISupportsWeakReference"]),
 
-    onStateChange(aWebProgress, aRequest, aStateFlags, aStatus)
+    onStateChange(aWebProgress, aRequest, aStateFlags)
     {
         if (aStateFlags & Ci.nsIWebProgressListener.STATE_STOP)
         {
@@ -69,25 +69,23 @@ adapted from test_bug607584.xhtml by Kent James <kent@caspia.com>
     },
   
   
-    onProgressChange(aWebProgress, aRequest,
-                                aCurSelfProgress, aMaxSelfProgress,
-                                aCurTotalProgress, aMaxTotalProgress)
+    onProgressChange()
       {
       },
   
-    onLocationChange(aWebProgress, aRequest, aLocation, aFlags)
+    onLocationChange()
       {
       },
   
-    onStatusChange(aWebProgress, aRequest, aStatus, aMessage)
+    onStatusChange()
       {
       },
   
-    onSecurityChange(aWebProgress, aRequest, aState)
+    onSecurityChange()
       {
       },
 
-    onContentBlockingEvent(aWebProgress, aRequest, aEvent)
+    onContentBlockingEvent()
       {
       },
 
diff --git a/editor/libeditor/tests/test_composition_with_highlight_in_texteditor.html b/editor/libeditor/tests/test_composition_with_highlight_in_texteditor.html
index d6bb703231c4..0990d87adb5f 100644
--- a/editor/libeditor/tests/test_composition_with_highlight_in_texteditor.html
+++ b/editor/libeditor/tests/test_composition_with_highlight_in_texteditor.html
@@ -23,9 +23,9 @@ SimpleTest.waitForFocus(() => {
   );
   const editActionListener = {
     QueryInterface: SpecialPowers.ChromeUtils.generateQI(["nsIEditActionListener"]),
-    WillDeleteText: (textNode, offset, length) => {},
-    DidInsertText: (textNode, offset, aString) => {},
-    WillDeleteRanges: (rangesToDelete) => {},
+    WillDeleteText: () => {},
+    DidInsertText: () => {},
+    WillDeleteRanges: () => {},
   };
   // Highlight "a"
   findSelection.setBaseAndExtent(
diff --git a/editor/libeditor/tests/test_dragdrop.html b/editor/libeditor/tests/test_dragdrop.html
index 6295661faa7a..5c7d9409281c 100644
--- a/editor/libeditor/tests/test_dragdrop.html
+++ b/editor/libeditor/tests/test_dragdrop.html
@@ -3101,7 +3101,7 @@ async function doTest() {
     beforeinputEvents = [];
     inputEvents = [];
     dragEvents = [];
-    const onDragStart = aEvent => {
+    const onDragStart = () => {
       input.style.display = "none";
       document.documentElement.scrollTop;
       input.style.display = "";
@@ -3147,7 +3147,7 @@ async function doTest() {
     beforeinputEvents = [];
     inputEvents = [];
     dragEvents = [];
-    const onDragStart = aEvent => {
+    const onDragStart = () => {
       textarea.style.display = "none";
       document.documentElement.scrollTop;
       textarea.style.display = "";
@@ -3193,13 +3193,13 @@ async function doTest() {
     beforeinputEvents = [];
     inputEvents = [];
     dragEvents = [];
-    const onMouseMove = aEvent => {
+    const onMouseMove = () => {
       input.style.display = "none";
       document.documentElement.scrollTop;
       input.style.display = "";
       document.documentElement.scrollTop;
     };
-    const onMouseDown = aEvent => {
+    const onMouseDown = () => {
       document.addEventListener("mousemove", onMouseMove, {once: true});
     }
     const onDrop = aEvent => {
@@ -3243,13 +3243,13 @@ async function doTest() {
     beforeinputEvents = [];
     inputEvents = [];
     dragEvents = [];
-    const onMouseMove = aEvent => {
+    const onMouseMove = () => {
       textarea.style.display = "none";
       document.documentElement.scrollTop;
       textarea.style.display = "";
       document.documentElement.scrollTop;
     };
-    const onMouseDown = aEvent => {
+    const onMouseDown = () => {
       document.addEventListener("mousemove", onMouseMove, {once: true});
     }
     const onDrop = aEvent => {
diff --git a/editor/libeditor/tests/test_execCommandPaste_noTarget.html b/editor/libeditor/tests/test_execCommandPaste_noTarget.html
index 6586ca768d74..70de112a781b 100644
--- a/editor/libeditor/tests/test_execCommandPaste_noTarget.html
+++ b/editor/libeditor/tests/test_execCommandPaste_noTarget.html
@@ -32,7 +32,7 @@
 
     // Check that reading text from the clipboard in non-privileged contexts
     // still doesn't work.
-    function onpstfail(e) {
+    function onpstfail() {
       ok(false, "Should not see paste event triggered by non-privileged call");
     }
     document.addEventListener("paste", onpstfail);
diff --git a/editor/libeditor/tests/test_middle_click_paste.html b/editor/libeditor/tests/test_middle_click_paste.html
index eaa918c19433..d34411e54b03 100644
--- a/editor/libeditor/tests/test_middle_click_paste.html
+++ b/editor/libeditor/tests/test_middle_click_paste.html
@@ -224,7 +224,7 @@ async function doTextareaTests(aTextarea) {
   aTextarea.value = "";
 
   let pasteEventCount = 0;
-  function pasteEventLogger(event) {
+  function pasteEventLogger() {
     pasteEventCount++;
   }
   aTextarea.addEventListener("paste", pasteEventLogger);
@@ -381,7 +381,7 @@ async function doContenteditableTests(aEditableDiv) {
   aEditableDiv.innerHTML = "";
 
   let pasteEventCount = 0;
-  function pasteEventLogger(event) {
+  function pasteEventLogger() {
     pasteEventCount++;
   }
   aEditableDiv.addEventListener("paste", pasteEventLogger);
diff --git a/editor/libeditor/tests/test_paste_redirect_focus_in_paste_event_listener.html b/editor/libeditor/tests/test_paste_redirect_focus_in_paste_event_listener.html
index b82938158e9f..89d7531fa56e 100644
--- a/editor/libeditor/tests/test_paste_redirect_focus_in_paste_event_listener.html
+++ b/editor/libeditor/tests/test_paste_redirect_focus_in_paste_event_listener.html
@@ -57,7 +57,7 @@ SimpleTest.waitForFocus(async () => {
       const editableElementDesc = `<${
         editableElement.tagName.toLocaleLowerCase()
       }${editableElement.hasAttribute("contenteditable") ? " contenteditable" : ""}>`;
-      (test_from_editableElement_to_input => {
+      (() => {
         const input = document.querySelector("#dest > input");
         editableElement.focus();
         editableElement.addEventListener(
@@ -84,7 +84,7 @@ SimpleTest.waitForFocus(async () => {
         input.value = "";
       })();
 
-      (test_from_editableElement_to_contenteditable => {
+      (() => {
         const contentEditable = document.querySelector("#dest > div[contenteditable]");
         editableElement.focus();
         editableElement.addEventListener(
@@ -111,7 +111,7 @@ SimpleTest.waitForFocus(async () => {
         contentEditable.innerHTML = "<br>";
       })();
 
-      (test_from_editableElement_to_non_editable => {
+      (() => {
         const button = document.querySelector("#dest > button");
         editableElement.focus();
         editableElement.addEventListener(
diff --git a/editor/libeditor/tests/test_texteditor_wrapping_long_line.html b/editor/libeditor/tests/test_texteditor_wrapping_long_line.html
index 14a445bbb0bb..013e563a278e 100644
--- a/editor/libeditor/tests/test_texteditor_wrapping_long_line.html
+++ b/editor/libeditor/tests/test_texteditor_wrapping_long_line.html
@@ -11,7 +11,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1733878
   <script src="/tests/SimpleTest/EventUtils.js"></script>
   <script>
   /** Test for bug 1733878 **/
-  window.addEventListener("DOMContentLoaded", (event) => {
+  window.addEventListener("DOMContentLoaded", () => {
     SimpleTest.waitForExplicitFinish();
     SimpleTest.waitForFocus(function() {
       document.body.textContent = ""; // It would be \n\n otherwise...
diff --git a/editor/spellchecker/tests/test_spellcheck_after_edit.html b/editor/spellchecker/tests/test_spellcheck_after_edit.html
index 24806addee2a..7c3f656855e0 100644
--- a/editor/spellchecker/tests/test_spellcheck_after_edit.html
+++ b/editor/spellchecker/tests/test_spellcheck_after_edit.html
@@ -67,11 +67,11 @@ SimpleTest.waitForFocus(async () => {
           normalSel.collapse(editingHost.querySelector("p + p").firstChild, 0);
           return 0;
         },
-        run: (editingHost) => {
+        run: () => {
           document.execCommand("delete");
           return 0;
         },
-        check: (spellCheckSel, editingHost) => {
+        check: (spellCheckSel) => {
           is(
             spellCheckSel.rangeCount,
             0,
@@ -86,11 +86,11 @@ SimpleTest.waitForFocus(async () => {
           normalSel.collapse(editingHost.querySelector("p + p").firstChild, 0);
           return 2;
         },
-        run: (editingHost) => {
+        run: () => {
           document.execCommand("delete");
           return 0;
         },
-        check: (spellCheckSel, editingHost) => {
+        check: (spellCheckSel) => {
           is(
             spellCheckSel.rangeCount,
             0,
@@ -105,11 +105,11 @@ SimpleTest.waitForFocus(async () => {
           normalSel.collapse(editingHost.querySelector("p").firstChild, "It is".length);
           return 1;
         },
-        run: (editingHost) => {
+        run: () => {
           document.execCommand("insertParagraph");
           return 0;
         },
-        check: (spellCheckSel, editingHost) => {
+        check: (spellCheckSel) => {
           is(
             spellCheckSel.rangeCount,
             0,
@@ -124,7 +124,7 @@ SimpleTest.waitForFocus(async () => {
           normalSel.collapse(editingHost.querySelector("p").firstChild, "It's beco".length);
           return 0;
         },
-        run: (editingHost) => {
+        run: () => {
           document.execCommand("insertParagraph");
           return 1;
         },