Adding upstream version 125.0.1.upstream/125.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

65 files changed, 1320 insertions, 191 deletions

diff --git a/accessible/tests/browser/atk/browser_role.js b/accessible/tests/browser/atk/browser_role.js
index 7b870b3337..47cc5ef28f 100644
--- a/accessible/tests/browser/atk/browser_role.js
+++ b/accessible/tests/browser/atk/browser_role.js
@@ -11,7 +11,7 @@ addAccessibleTask(
   `
 <p id="p">p</p>
   `,
-  async function (browser, docAcc) {
+  async function () {
     let role = await runPython(`
       global doc
       doc = getDoc()
diff --git a/accessible/tests/browser/atk/browser_table.js b/accessible/tests/browser/atk/browser_table.js
index 98b3270465..55452709e8 100644
--- a/accessible/tests/browser/atk/browser_table.js
+++ b/accessible/tests/browser/atk/browser_table.js
@@ -20,7 +20,7 @@ addAccessibleTask(
   </tr>
 </table>
   `,
-  async function (browser, docAcc) {
+  async function () {
     let result = await runPython(`
       global doc
       doc = getDoc()
diff --git a/accessible/tests/browser/bounds/browser_accessible_moved.js b/accessible/tests/browser/bounds/browser_accessible_moved.js
index 307c680000..a62f7ad8d0 100644
--- a/accessible/tests/browser/bounds/browser_accessible_moved.js
+++ b/accessible/tests/browser/bounds/browser_accessible_moved.js
@@ -12,10 +12,10 @@ function assertBoundsNonZero(acc) {
   let width = {};
   let height = {};
   acc.getBounds(x, y, width, height);
-  ok(x.value > 0, "x is non-0");
-  ok(y.value > 0, "y is non-0");
-  ok(width.value > 0, "width is non-0");
-  ok(height.value > 0, "height is non-0");
+  Assert.greater(x.value, 0, "x is non-0");
+  Assert.greater(y.value, 0, "y is non-0");
+  Assert.greater(width.value, 0, "width is non-0");
+  Assert.greater(height.value, 0, "height is non-0");
 }
 
 /**
diff --git a/accessible/tests/browser/bounds/browser_caret_rect.js b/accessible/tests/browser/bounds/browser_caret_rect.js
index ac0ee3aa50..9f5cac33a5 100644
--- a/accessible/tests/browser/bounds/browser_caret_rect.js
+++ b/accessible/tests/browser/bounds/browser_caret_rect.js
@@ -46,7 +46,7 @@ async function testCaretRect(browser, docAcc, id, offset) {
   );
   const [caretX, caretY, caretW, caretH] = await getCaretRect(browser, id);
   if (atEnd) {
-    ok(caretX > charX.value, "Caret x after last character x");
+    Assert.greater(caretX, charX.value, "Caret x after last character x");
   } else {
     is(caretX, charX.value, "Caret x same as character x");
   }
diff --git a/accessible/tests/browser/bounds/browser_test_display_contents.js b/accessible/tests/browser/bounds/browser_test_display_contents.js
index db1bfce178..4111ac5a81 100644
--- a/accessible/tests/browser/bounds/browser_test_display_contents.js
+++ b/accessible/tests/browser/bounds/browser_test_display_contents.js
@@ -16,7 +16,11 @@ async function testContentBounds(browser, acc) {
   is(x, expectedX, "Wrong x coordinate of " + prettyAccName);
   is(y, expectedY, "Wrong y coordinate of " + prettyAccName);
   is(width, expectedWidth, "Wrong width of " + prettyAccName);
-  ok(height >= expectedHeight, "Wrong height of " + prettyAccName);
+  Assert.greaterOrEqual(
+    height,
+    expectedHeight,
+    "Wrong height of " + prettyAccName
+  );
 }
 
 async function runTests(browser, accDoc) {
diff --git a/accessible/tests/browser/bounds/browser_test_iframe_transform.js b/accessible/tests/browser/bounds/browser_test_iframe_transform.js
index a44ab75faf..015d466da9 100644
--- a/accessible/tests/browser/bounds/browser_test_iframe_transform.js
+++ b/accessible/tests/browser/bounds/browser_test_iframe_transform.js
@@ -68,7 +68,7 @@ function testBoundsWithOffset(browser, iframeDocAcc, id, domElmBounds, offset) {
 
 addAccessibleTask(
   `<div id='${ELEM_ID}'>hello world</div>`,
-  async function (browser, iframeDocAcc, contentDocAcc) {
+  async function (browser, iframeDocAcc) {
     ok(iframeDocAcc, "IFRAME document accessible is present");
 
     await testBoundsWithContent(iframeDocAcc, ELEM_ID, browser);
@@ -143,7 +143,7 @@ addAccessibleTask(
  */
 addAccessibleTask(
   `<div id="div" style="width: 30px; height: 30px"></div>`,
-  async function (browser, accDoc, foo) {
+  async function (browser, accDoc) {
     const docWidth = () => {
       let width = {};
       accDoc.getBounds({}, {}, width, {});
diff --git a/accessible/tests/browser/bounds/browser_test_simple_transform.js b/accessible/tests/browser/bounds/browser_test_simple_transform.js
index 7197968b40..b5cb983e72 100644
--- a/accessible/tests/browser/bounds/browser_test_simple_transform.js
+++ b/accessible/tests/browser/bounds/browser_test_simple_transform.js
@@ -9,7 +9,7 @@ loadScripts({ name: "role.js", dir: MOCHITESTS_DIR });
 // test basic translation
 addAccessibleTask(
   `<p id="translate">hello world</p>`,
-  async function (browser, iframeDocAcc, contentDocAcc) {
+  async function (browser, iframeDocAcc) {
     ok(iframeDocAcc, "IFRAME document accessible is present");
     await testBoundsWithContent(iframeDocAcc, "translate", browser);
 
@@ -42,7 +42,7 @@ addAccessibleTask(
 // test basic rotation
 addAccessibleTask(
   `<p id="rotate">hello world</p>`,
-  async function (browser, iframeDocAcc, contentDocAcc) {
+  async function (browser, iframeDocAcc) {
     ok(iframeDocAcc, "IFRAME document accessible is present");
     await testBoundsWithContent(iframeDocAcc, "rotate", browser);
 
@@ -60,7 +60,7 @@ addAccessibleTask(
 // test basic scale
 addAccessibleTask(
   `<p id="scale">hello world</p>`,
-  async function (browser, iframeDocAcc, contentDocAcc) {
+  async function (browser, iframeDocAcc) {
     ok(iframeDocAcc, "IFRAME document accessible is present");
     await testBoundsWithContent(iframeDocAcc, "scale", browser);
 
diff --git a/accessible/tests/browser/bounds/browser_test_zoom.js b/accessible/tests/browser/bounds/browser_test_zoom.js
index ac84e485a4..1af84d61d8 100644
--- a/accessible/tests/browser/bounds/browser_test_zoom.js
+++ b/accessible/tests/browser/bounds/browser_test_zoom.js
@@ -16,7 +16,11 @@ async function testContentBounds(browser, acc) {
   is(x, expectedX, "Wrong x coordinate of " + prettyAccName);
   is(y, expectedY, "Wrong y coordinate of " + prettyAccName);
   is(width, expectedWidth, "Wrong width of " + prettyAccName);
-  ok(height >= expectedHeight, "Wrong height of " + prettyAccName);
+  Assert.greaterOrEqual(
+    height,
+    expectedHeight,
+    "Wrong height of " + prettyAccName
+  );
 }
 
 async function runTests(browser, accDoc) {
diff --git a/accessible/tests/browser/bounds/browser_zero_area.js b/accessible/tests/browser/bounds/browser_zero_area.js
index c0f9db2673..80954fbd1a 100644
--- a/accessible/tests/browser/bounds/browser_zero_area.js
+++ b/accessible/tests/browser/bounds/browser_zero_area.js
@@ -67,10 +67,10 @@ addAccessibleTask(
     const radio = findAccessibleChildByID(accDoc, "radio");
     const contentDPR = await getContentDPR(browser);
     const [x, y, width, height] = getBounds(radio, contentDPR);
-    ok(x < 0, "X coordinate should be negative");
-    ok(y > 0, "Y coordinate should be positive");
-    ok(width > 0, "Width should be positive");
-    ok(height > 0, "Height should be positive");
+    Assert.less(x, 0, "X coordinate should be negative");
+    Assert.greater(y, 0, "Y coordinate should be positive");
+    Assert.greater(width, 0, "Width should be positive");
+    Assert.greater(height, 0, "Height should be positive");
     // Note: the exact values of x, y, width, and height
     // are inconsistent with the DOM element values of those
     // fields, so we don't check our bounds against them with
diff --git a/accessible/tests/browser/browser_shutdown_acc_reference.js b/accessible/tests/browser/browser_shutdown_acc_reference.js
index 1768095f94..975eab55a0 100644
--- a/accessible/tests/browser/browser_shutdown_acc_reference.js
+++ b/accessible/tests/browser/browser_shutdown_acc_reference.js
@@ -36,7 +36,7 @@ add_task(async function () {
   const [a11yShutdownObserver, a11yShutdownPromise] = shutdownAccService();
   await a11yShutdownObserver;
   const a11yShutdown = new Promise((resolve, reject) =>
-    a11yShutdownPromise.then(flag =>
+    a11yShutdownPromise.then(() =>
       canShutdown
         ? resolve()
         : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/browser_shutdown_doc_acc_reference.js b/accessible/tests/browser/browser_shutdown_doc_acc_reference.js
index 8f7bf6d423..7d999d7d13 100644
--- a/accessible/tests/browser/browser_shutdown_doc_acc_reference.js
+++ b/accessible/tests/browser/browser_shutdown_doc_acc_reference.js
@@ -28,7 +28,7 @@ add_task(async function () {
   const [a11yShutdownObserver, a11yShutdownPromise] = shutdownAccService();
   await a11yShutdownObserver;
   const a11yShutdown = new Promise((resolve, reject) =>
-    a11yShutdownPromise.then(flag =>
+    a11yShutdownPromise.then(() =>
       canShutdown
         ? resolve()
         : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/browser_shutdown_multi_acc_reference_doc.js b/accessible/tests/browser/browser_shutdown_multi_acc_reference_doc.js
index 273fc7175d..1200e02116 100644
--- a/accessible/tests/browser/browser_shutdown_multi_acc_reference_doc.js
+++ b/accessible/tests/browser/browser_shutdown_multi_acc_reference_doc.js
@@ -39,7 +39,7 @@ add_task(async function () {
   const [a11yShutdownObserver, a11yShutdownPromise] = shutdownAccService();
   await a11yShutdownObserver;
   const a11yShutdown = new Promise((resolve, reject) =>
-    a11yShutdownPromise.then(flag =>
+    a11yShutdownPromise.then(() =>
       canShutdown
         ? resolve()
         : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/browser_shutdown_multi_acc_reference_obj.js b/accessible/tests/browser/browser_shutdown_multi_acc_reference_obj.js
index af21b3dc4c..346aa9b6c4 100644
--- a/accessible/tests/browser/browser_shutdown_multi_acc_reference_obj.js
+++ b/accessible/tests/browser/browser_shutdown_multi_acc_reference_obj.js
@@ -39,7 +39,7 @@ add_task(async function () {
   const [a11yShutdownObserver, a11yShutdownPromise] = shutdownAccService();
   await a11yShutdownObserver;
   const a11yShutdown = new Promise((resolve, reject) =>
-    a11yShutdownPromise.then(flag =>
+    a11yShutdownPromise.then(() =>
       canShutdown
         ? resolve()
         : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_doc.js b/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_doc.js
index e4091c5216..84429cf077 100644
--- a/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_doc.js
+++ b/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_doc.js
@@ -30,7 +30,7 @@ add_task(async function () {
         <body id="body"><div id="div"></div></body>
       </html>`,
     },
-    async function (browser) {
+    async function () {
       let docLoadedEvent = await docLoaded;
       let docAcc = docLoadedEvent.accessibleDocument;
       ok(docAcc, "Accessible document proxy is created");
@@ -46,7 +46,7 @@ add_task(async function () {
       const [a11yShutdownObserver, a11yShutdownPromise] = shutdownAccService();
       await a11yShutdownObserver;
       const a11yShutdown = new Promise((resolve, reject) =>
-        a11yShutdownPromise.then(flag =>
+        a11yShutdownPromise.then(() =>
           canShutdown
             ? resolve()
             : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_obj.js b/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_obj.js
index f6eca362b0..b7356f3e6f 100644
--- a/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_obj.js
+++ b/accessible/tests/browser/browser_shutdown_multi_proxy_acc_reference_obj.js
@@ -30,7 +30,7 @@ add_task(async function () {
         <body id="body"><div id="div"></div></body>
       </html>`,
     },
-    async function (browser) {
+    async function () {
       let docLoadedEvent = await docLoaded;
       let docAcc = docLoadedEvent.accessibleDocument;
       ok(docAcc, "Accessible document proxy is created");
@@ -46,7 +46,7 @@ add_task(async function () {
       const [a11yShutdownObserver, a11yShutdownPromise] = shutdownAccService();
       await a11yShutdownObserver;
       const a11yShutdown = new Promise((resolve, reject) =>
-        a11yShutdownPromise.then(flag =>
+        a11yShutdownPromise.then(() =>
           canShutdown
             ? resolve()
             : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/browser_shutdown_multi_reference.js b/accessible/tests/browser/browser_shutdown_multi_reference.js
index a92f6faf61..49ee822afa 100644
--- a/accessible/tests/browser/browser_shutdown_multi_reference.js
+++ b/accessible/tests/browser/browser_shutdown_multi_reference.js
@@ -31,7 +31,7 @@ add_task(async function () {
   const [a11yShutdownObserver, a11yShutdownPromise] = shutdownAccService();
   await a11yShutdownObserver;
   const a11yShutdown = new Promise((resolve, reject) =>
-    a11yShutdownPromise.then(flag =>
+    a11yShutdownPromise.then(() =>
       canShutdown
         ? resolve()
         : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/browser_shutdown_parent_own_reference.js b/accessible/tests/browser/browser_shutdown_parent_own_reference.js
index 472e977626..ffbe33f137 100644
--- a/accessible/tests/browser/browser_shutdown_parent_own_reference.js
+++ b/accessible/tests/browser/browser_shutdown_parent_own_reference.js
@@ -61,7 +61,7 @@ add_task(async function () {
         shutdownAccService(browser);
       await contentA11yShutdownObserver;
       const contentA11yShutdown = new Promise((resolve, reject) =>
-        contentA11yShutdownPromise.then(flag =>
+        contentA11yShutdownPromise.then(() =>
           contentCanShutdown
             ? resolve()
             : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/browser_shutdown_proxy_acc_reference.js b/accessible/tests/browser/browser_shutdown_proxy_acc_reference.js
index 7144cff019..47fa47da53 100644
--- a/accessible/tests/browser/browser_shutdown_proxy_acc_reference.js
+++ b/accessible/tests/browser/browser_shutdown_proxy_acc_reference.js
@@ -41,7 +41,7 @@ add_task(async function () {
       const [a11yShutdownObserver, a11yShutdownPromise] = shutdownAccService();
       await a11yShutdownObserver;
       const a11yShutdown = new Promise((resolve, reject) =>
-        a11yShutdownPromise.then(flag =>
+        a11yShutdownPromise.then(() =>
           canShutdown
             ? resolve()
             : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/browser_shutdown_proxy_doc_acc_reference.js b/accessible/tests/browser/browser_shutdown_proxy_doc_acc_reference.js
index 6d4ad71f1e..72a424b21f 100644
--- a/accessible/tests/browser/browser_shutdown_proxy_doc_acc_reference.js
+++ b/accessible/tests/browser/browser_shutdown_proxy_doc_acc_reference.js
@@ -30,7 +30,7 @@ add_task(async function () {
         <body id="body"></body>
       </html>`,
     },
-    async function (browser) {
+    async function () {
       let docLoadedEvent = await docLoaded;
       let docAcc = docLoadedEvent.accessibleDocument;
       ok(docAcc, "Accessible document proxy is created");
@@ -43,7 +43,7 @@ add_task(async function () {
       const [a11yShutdownObserver, a11yShutdownPromise] = shutdownAccService();
       await a11yShutdownObserver;
       const a11yShutdown = new Promise((resolve, reject) =>
-        a11yShutdownPromise.then(flag =>
+        a11yShutdownPromise.then(() =>
           canShutdown
             ? resolve()
             : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/browser_shutdown_remote_own_reference.js b/accessible/tests/browser/browser_shutdown_remote_own_reference.js
index a30d191b53..83c68689b7 100644
--- a/accessible/tests/browser/browser_shutdown_remote_own_reference.js
+++ b/accessible/tests/browser/browser_shutdown_remote_own_reference.js
@@ -108,7 +108,7 @@ add_task(async function () {
       const [contentA11yShutdownObserver, contentA11yShutdownPromise] =
         shutdownAccService(browser);
       const contentA11yShutdown = new Promise((resolve, reject) =>
-        contentA11yShutdownPromise.then(flag =>
+        contentA11yShutdownPromise.then(() =>
           contentCanShutdown
             ? resolve()
             : reject("Accessible service was shut down incorrectly")
diff --git a/accessible/tests/browser/e10s/browser.toml b/accessible/tests/browser/e10s/browser.toml
index dfac6b5219..914f839993 100644
--- a/accessible/tests/browser/e10s/browser.toml
+++ b/accessible/tests/browser/e10s/browser.toml
@@ -18,9 +18,12 @@ support-files = [
 ]
 prefs = [
   "javascript.options.asyncstack_capture_debuggee_only=false",
-  "dom.element.popover.enabled=true"
+  "dom.element.popover.enabled=true",
+  "accessibility.ARIAElementReflection.enabled=true"
 ]
 
+["browser_aria_activedescendant.js"]
+
 # Caching tests
 ["browser_caching_actions.js"]
 
diff --git a/accessible/tests/browser/e10s/browser_aria_activedescendant.js b/accessible/tests/browser/e10s/browser_aria_activedescendant.js
new file mode 100644
index 0000000000..f58c5aab39
--- /dev/null
+++ b/accessible/tests/browser/e10s/browser_aria_activedescendant.js
@@ -0,0 +1,485 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/* import-globals-from ../../mochitest/role.js */
+/* import-globals-from ../../mochitest/states.js */
+loadScripts(
+  { name: "role.js", dir: MOCHITESTS_DIR },
+  { name: "states.js", dir: MOCHITESTS_DIR }
+);
+
+async function synthFocus(browser, container, item) {
+  let focusPromise = waitForEvent(EVENT_FOCUS, item);
+  await invokeContentTask(browser, [container], _container => {
+    let elm = (
+      content.document._testGetElementById || content.document.getElementById
+    ).bind(content.document)(_container);
+    elm.focus();
+  });
+  await focusPromise;
+}
+
+async function changeARIAActiveDescendant(
+  browser,
+  container,
+  itemId,
+  prevItemId,
+  elementReflection
+) {
+  let expectedEvents = [[EVENT_FOCUS, itemId]];
+
+  if (prevItemId) {
+    info("A state change of the previous item precedes the new one.");
+    expectedEvents.push(
+      stateChangeEventArgs(prevItemId, EXT_STATE_ACTIVE, false, true)
+    );
+  }
+
+  expectedEvents.push(
+    stateChangeEventArgs(itemId, EXT_STATE_ACTIVE, true, true)
+  );
+
+  let expectedPromise = waitForEvents(expectedEvents);
+  await invokeContentTask(
+    browser,
+    [container, itemId, elementReflection],
+    (_container, _itemId, _elementReflection) => {
+      let getElm = (
+        content.document._testGetElementById || content.document.getElementById
+      ).bind(content.document);
+      let elm = getElm(_container);
+      if (_elementReflection) {
+        elm.ariaActiveDescendantElement = getElm(_itemId);
+      } else {
+        elm.setAttribute("aria-activedescendant", _itemId);
+      }
+    }
+  );
+
+  await expectedPromise;
+}
+
+async function clearARIAActiveDescendant(
+  browser,
+  container,
+  prevItemId,
+  defaultId,
+  elementReflection
+) {
+  let expectedEvents = [[EVENT_FOCUS, defaultId || container]];
+  if (prevItemId) {
+    expectedEvents.push(
+      stateChangeEventArgs(prevItemId, EXT_STATE_ACTIVE, false, true)
+    );
+  }
+
+  if (defaultId) {
+    expectedEvents.push(
+      stateChangeEventArgs(defaultId, EXT_STATE_ACTIVE, true, true)
+    );
+  }
+
+  let expectedPromise = waitForEvents(expectedEvents);
+  await invokeContentTask(
+    browser,
+    [container, elementReflection],
+    (_container, _elementReflection) => {
+      let elm = (
+        content.document._testGetElementById || content.document.getElementById
+      ).bind(content.document)(_container);
+      if (_elementReflection) {
+        elm.ariaActiveDescendantElement = null;
+      } else {
+        elm.removeAttribute("aria-activedescendant");
+      }
+    }
+  );
+
+  await expectedPromise;
+}
+
+async function insertItemNFocus(
+  browser,
+  container,
+  newItemID,
+  prevItemId,
+  elementReflection
+) {
+  let expectedEvents = [
+    [EVENT_SHOW, newItemID],
+    [EVENT_FOCUS, newItemID],
+  ];
+
+  if (prevItemId) {
+    info("A state change of the previous item precedes the new one.");
+    expectedEvents.push(
+      stateChangeEventArgs(prevItemId, EXT_STATE_ACTIVE, false, true)
+    );
+  }
+
+  expectedEvents.push(
+    stateChangeEventArgs(newItemID, EXT_STATE_ACTIVE, true, true)
+  );
+
+  let expectedPromise = waitForEvents(expectedEvents);
+
+  await invokeContentTask(
+    browser,
+    [container, newItemID, elementReflection],
+    (_container, _newItemID, _elementReflection) => {
+      let elm = (
+        content.document._testGetElementById || content.document.getElementById
+      ).bind(content.document)(_container);
+      let itemElm = content.document.createElement("div");
+      itemElm.setAttribute("id", _newItemID);
+      itemElm.setAttribute("role", "listitem");
+      itemElm.textContent = _newItemID;
+      elm.appendChild(itemElm);
+      if (_elementReflection) {
+        elm.ariaActiveDescendantElement = itemElm;
+      } else {
+        elm.setAttribute("aria-activedescendant", _newItemID);
+      }
+    }
+  );
+
+  await expectedPromise;
+}
+
+async function moveARIAActiveDescendantID(browser, fromID, toID) {
+  let expectedEvents = [
+    [EVENT_FOCUS, toID],
+    stateChangeEventArgs(toID, EXT_STATE_ACTIVE, true, true),
+  ];
+
+  let expectedPromise = waitForEvents(expectedEvents);
+  await invokeContentTask(browser, [fromID, toID], (_fromID, _toID) => {
+    let orig = (
+      content.document._testGetElementById || content.document.getElementById
+    ).bind(content.document)(_toID);
+    if (orig) {
+      orig.id = "";
+    }
+    (
+      content.document._testGetElementById || content.document.getElementById
+    ).bind(content.document)(_fromID).id = _toID;
+  });
+  await expectedPromise;
+}
+
+async function changeARIAActiveDescendantInvalid(
+  browser,
+  container,
+  invalidID = "invalid",
+  prevItemId = null
+) {
+  let expectedEvents = [[EVENT_FOCUS, container]];
+  if (prevItemId) {
+    expectedEvents.push(
+      stateChangeEventArgs(prevItemId, EXT_STATE_ACTIVE, false, true)
+    );
+  }
+
+  let expectedPromise = waitForEvents(expectedEvents);
+  await invokeContentTask(
+    browser,
+    [container, invalidID],
+    (_container, _invalidID) => {
+      let elm = (
+        content.document._testGetElementById || content.document.getElementById
+      ).bind(content.document)(_container);
+      elm.setAttribute("aria-activedescendant", _invalidID);
+    }
+  );
+
+  await expectedPromise;
+}
+
+const LISTBOX_MARKUP = `
+<div role="listbox" aria-activedescendant="item1" id="listbox" tabindex="1"
+aria-owns="item3">
+<div role="listitem" id="item1">item1</div>
+<div role="listitem" id="item2">item2</div>
+<div role="listitem" id="roaming" data-id="roaming">roaming</div>
+<div role="listitem" id="roaming2" data-id="roaming2">roaming2</div>
+</div>
+<div role="listitem" id="item3">item3</div>
+<div role="combobox" id="combobox">
+<input id="combobox_entry">
+<ul>
+  <li role="option" id="combobox_option1">option1</li>
+  <li role="option" id="combobox_option2">option2</li>
+</ul>
+</div>`;
+
+async function basicListboxTest(browser, elementReflection) {
+  await synthFocus(browser, "listbox", "item1");
+  await changeARIAActiveDescendant(
+    browser,
+    "listbox",
+    "item2",
+    "item1",
+    elementReflection
+  );
+  await changeARIAActiveDescendant(
+    browser,
+    "listbox",
+    "item3",
+    "item2",
+    elementReflection
+  );
+
+  info("Focus out of listbox");
+  await synthFocus(browser, "combobox_entry", "combobox_entry");
+  await changeARIAActiveDescendant(
+    browser,
+    "combobox",
+    "combobox_option2",
+    null,
+    elementReflection
+  );
+  await changeARIAActiveDescendant(
+    browser,
+    "combobox",
+    "combobox_option1",
+    null,
+    elementReflection
+  );
+
+  info("Focus back in listbox");
+  await synthFocus(browser, "listbox", "item3");
+  await insertItemNFocus(
+    browser,
+    "listbox",
+    "item4",
+    "item3",
+    elementReflection
+  );
+
+  await clearARIAActiveDescendant(
+    browser,
+    "listbox",
+    "item4",
+    null,
+    elementReflection
+  );
+  await changeARIAActiveDescendant(
+    browser,
+    "listbox",
+    "item1",
+    null,
+    elementReflection
+  );
+}
+
+addAccessibleTask(
+  LISTBOX_MARKUP,
+  async function (browser, docAcc) {
+    info("Test aria-activedescendant content attribute");
+    await basicListboxTest(browser, false);
+
+    await changeARIAActiveDescendantInvalid(
+      browser,
+      "listbox",
+      "invalid",
+      "item1"
+    );
+
+    await changeARIAActiveDescendant(browser, "listbox", "roaming");
+    await moveARIAActiveDescendantID(browser, "roaming2", "roaming");
+    await changeARIAActiveDescendantInvalid(
+      browser,
+      "listbox",
+      "roaming3",
+      "roaming"
+    );
+    await moveARIAActiveDescendantID(browser, "roaming", "roaming3");
+  },
+  { topLevel: true, chrome: true }
+);
+
+addAccessibleTask(
+  LISTBOX_MARKUP,
+  async function (browser, docAcc) {
+    info("Test ariaActiveDescendantElement element reflection");
+    await basicListboxTest(browser, true);
+  },
+  { topLevel: true, chrome: true }
+);
+
+addAccessibleTask(
+  `
+<input id="activedesc_nondesc_input" aria-activedescendant="activedesc_nondesc_option">
+<div role="listbox">
+  <div role="option" id="activedesc_nondesc_option">option</div>
+</div>`,
+  async function (browser, docAcc) {
+    info("Test aria-activedescendant non-descendant");
+    await synthFocus(
+      browser,
+      "activedesc_nondesc_input",
+      "activedesc_nondesc_option"
+    );
+  },
+  { topLevel: true, chrome: true }
+);
+
+addAccessibleTask(
+  `
+<div id="shadow"></div>
+<script>
+  let host = document.getElementById("shadow");
+  let shadow = host.attachShadow({mode: "open"});
+  let listbox = document.createElement("div");
+  listbox.id = "shadowListbox";
+  listbox.setAttribute("role", "listbox");
+  listbox.setAttribute("tabindex", "0");
+  shadow.appendChild(listbox);
+  let item = document.createElement("div");
+  item.id = "shadowItem1";
+  item.setAttribute("role", "option");
+  listbox.appendChild(item);
+  listbox.setAttribute("aria-activedescendant", "shadowItem1");
+  item = document.createElement("div");
+  item.id = "shadowItem2";
+  item.setAttribute("role", "option");
+  listbox.appendChild(item);
+</script>`,
+  async function (browser, docAcc) {
+    info("Test aria-activedescendant in shadow root");
+    // We want to retrieve elements using their IDs inside the shadow root, so
+    // we define a custom get element by ID method that our utility functions
+    // above call into if it exists.
+    await invokeContentTask(browser, [], () => {
+      content.document._testGetElementById = id =>
+        content.document.getElementById("shadow").shadowRoot.getElementById(id);
+    });
+
+    await synthFocus(browser, "shadowListbox", "shadowItem1");
+    await changeARIAActiveDescendant(
+      browser,
+      "shadowListbox",
+      "shadowItem2",
+      "shadowItem1"
+    );
+    info("Do it again with element reflection");
+    await changeARIAActiveDescendant(
+      browser,
+      "shadowListbox",
+      "shadowItem1",
+      "shadowItem2",
+      true
+    );
+  },
+  { topLevel: true, chrome: true }
+);
+
+addAccessibleTask(
+  `
+<div id="comboboxWithHiddenList" tabindex="0" role="combobox" aria-owns="hiddenList">
+</div>
+<div id="hiddenList" hidden role="listbox">
+  <div id="hiddenListOption" role="option"></div>
+</div>`,
+  async function (browser, docAcc) {
+    info("Test simultaneous insertion, relocation and aria-activedescendant");
+    await synthFocus(
+      browser,
+      "comboboxWithHiddenList",
+      "comboboxWithHiddenList"
+    );
+
+    testStates(
+      findAccessibleChildByID(docAcc, "comboboxWithHiddenList"),
+      STATE_FOCUSED
+    );
+    let evtProm = Promise.all([
+      waitForEvent(EVENT_FOCUS, "hiddenListOption"),
+      waitForStateChange("hiddenListOption", EXT_STATE_ACTIVE, true, true),
+    ]);
+    await invokeContentTask(browser, [], () => {
+      info("hiddenList is owned, so unhiding causes insertion and relocation.");
+      (
+        content.document._testGetElementById || content.document.getElementById
+      ).bind(content.document)("hiddenList").hidden = false;
+      content.document
+        .getElementById("comboboxWithHiddenList")
+        .setAttribute("aria-activedescendant", "hiddenListOption");
+    });
+    await evtProm;
+    testStates(
+      findAccessibleChildByID(docAcc, "hiddenListOption"),
+      STATE_FOCUSED
+    );
+  },
+  { topLevel: true, chrome: true }
+);
+
+addAccessibleTask(
+  `
+<custom-listbox id="custom-listbox1">
+  <div role="listitem" id="l1_1"></div>
+  <div role="listitem" id="l1_2"></div>
+  <div role="listitem" id="l1_3"></div>
+</custom-listbox>
+
+<custom-listbox id="custom-listbox2" aria-activedescendant="l2_1">
+  <div role="listitem" id="l2_1"></div>
+  <div role="listitem" id="l2_2"></div>
+  <div role="listitem" id="l2_3"></div>
+</custom-listbox>
+
+<script>
+customElements.define("custom-listbox",
+  class extends HTMLElement {
+    constructor() {
+      super();
+      this.tabIndex = "0"
+      this._internals = this.attachInternals();
+      this._internals.role = "listbox";
+      this._internals.ariaActiveDescendantElement = this.lastElementChild;
+    }
+    get internals() {
+      return this._internals;
+    }
+  }
+);
+</script>`,
+  async function (browser, docAcc) {
+    await synthFocus(browser, "custom-listbox1", "l1_3");
+
+    let evtProm = Promise.all([
+      waitForEvent(EVENT_FOCUS, "l1_2"),
+      waitForStateChange("l1_3", EXT_STATE_ACTIVE, false, true),
+      waitForStateChange("l1_2", EXT_STATE_ACTIVE, true, true),
+    ]);
+
+    await invokeContentTask(browser, [], () => {
+      content.document.getElementById(
+        "custom-listbox1"
+      ).internals.ariaActiveDescendantElement =
+        content.document.getElementById("l1_2");
+    });
+
+    await evtProm;
+
+    evtProm = Promise.all([
+      waitForEvent(EVENT_FOCUS, "custom-listbox1"),
+      waitForStateChange("l1_2", EXT_STATE_ACTIVE, false, true),
+    ]);
+
+    await invokeContentTask(browser, [], () => {
+      content.document.getElementById(
+        "custom-listbox1"
+      ).internals.ariaActiveDescendantElement = null;
+    });
+
+    await evtProm;
+
+    await synthFocus(browser, "custom-listbox2", "l2_1");
+    await clearARIAActiveDescendant(browser, "custom-listbox2", "l2_1", "l2_3");
+  }
+);
diff --git a/accessible/tests/browser/e10s/browser_caching_attributes.js b/accessible/tests/browser/e10s/browser_caching_attributes.js
index 139015061f..7a1f90ec13 100644
--- a/accessible/tests/browser/e10s/browser_caching_attributes.js
+++ b/accessible/tests/browser/e10s/browser_caching_attributes.js
@@ -733,7 +733,7 @@ addAccessibleTask(
  */
 addAccessibleTask(
   `<div id="popover" popover>popover</div>`,
-  async function testIspopup(browser, docAcc) {
+  async function testIspopup(browser) {
     info("Showing popover");
     let shown = waitForEvent(EVENT_SHOW, "popover");
     await invokeContentTask(browser, [], () => {
diff --git a/accessible/tests/browser/e10s/browser_caching_large_update.js b/accessible/tests/browser/e10s/browser_caching_large_update.js
index ccf8a86921..9a36ac7326 100644
--- a/accessible/tests/browser/e10s/browser_caching_large_update.js
+++ b/accessible/tests/browser/e10s/browser_caching_large_update.js
@@ -8,59 +8,56 @@
  * Test a large update which adds many thousands of Accessibles with a
  * lot of content in each.
  */
-addAccessibleTask(
-  `<main id="main" hidden></main>`,
-  async function (browser, docAcc) {
-    let shown = waitForEvent(EVENT_SHOW, "main");
-    await invokeContentTask(browser, [], () => {
-      // Make a long string.
-      let text = "";
-      for (let i = 0; i < 100; ++i) {
-        text += "a";
-      }
-      // Create lots of nodes which include the long string.
-      const contMain = content.document.getElementById("main");
-      // 15000 children of main.
-      for (let w = 0; w < 15000; ++w) {
-        // Each of those goes 9 deep.
-        let parent = contMain;
-        for (let d = 0; d < 10; ++d) {
-          const div = content.document.createElement("div");
-          div.setAttribute("aria-label", `${w} ${d} ${text}`);
-          parent.append(div);
-          parent = div;
-        }
-      }
-      contMain.hidden = false;
-    });
-    const main = (await shown).accessible;
-    is(main.childCount, 15000, "main has correct number of children");
-
-    // We don't want to output passes for every check, since that would output
-    // hundreds of thousands of lines, which slows the test to a crawl. Instead,
-    // output any failures and keep track of overall success/failure.
-    let treeOk = true;
-    function check(val, msg) {
-      if (!val) {
-        ok(false, msg);
-        treeOk = false;
-      }
+addAccessibleTask(`<main id="main" hidden></main>`, async function (browser) {
+  let shown = waitForEvent(EVENT_SHOW, "main");
+  await invokeContentTask(browser, [], () => {
+    // Make a long string.
+    let text = "";
+    for (let i = 0; i < 100; ++i) {
+      text += "a";
     }
-
-    info("Checking tree");
+    // Create lots of nodes which include the long string.
+    const contMain = content.document.getElementById("main");
+    // 15000 children of main.
     for (let w = 0; w < 15000; ++w) {
-      let acc = main.getChildAt(w);
-      let parent = main;
+      // Each of those goes 9 deep.
+      let parent = contMain;
       for (let d = 0; d < 10; ++d) {
-        check(acc, `Got child ${w} depth ${d}`);
-        const name = `${w} ${d}`;
-        check(acc.name.startsWith(name + " "), `${name}: correct name`);
-        check(acc.parent == parent, `${name}: correct parent`);
-        parent = acc;
-        acc = acc.firstChild;
+        const div = content.document.createElement("div");
+        div.setAttribute("aria-label", `${w} ${d} ${text}`);
+        parent.append(div);
+        parent = div;
       }
     }
-    // check() sets treeOk to false for any failure.
-    ok(treeOk, "Tree is correct");
+    contMain.hidden = false;
+  });
+  const main = (await shown).accessible;
+  is(main.childCount, 15000, "main has correct number of children");
+
+  // We don't want to output passes for every check, since that would output
+  // hundreds of thousands of lines, which slows the test to a crawl. Instead,
+  // output any failures and keep track of overall success/failure.
+  let treeOk = true;
+  function check(val, msg) {
+    if (!val) {
+      ok(false, msg);
+      treeOk = false;
+    }
+  }
+
+  info("Checking tree");
+  for (let w = 0; w < 15000; ++w) {
+    let acc = main.getChildAt(w);
+    let parent = main;
+    for (let d = 0; d < 10; ++d) {
+      check(acc, `Got child ${w} depth ${d}`);
+      const name = `${w} ${d}`;
+      check(acc.name.startsWith(name + " "), `${name}: correct name`);
+      check(acc.parent == parent, `${name}: correct parent`);
+      parent = acc;
+      acc = acc.firstChild;
+    }
   }
-);
+  // check() sets treeOk to false for any failure.
+  ok(treeOk, "Tree is correct");
+});
diff --git a/accessible/tests/browser/e10s/browser_caching_name.js b/accessible/tests/browser/e10s/browser_caching_name.js
index 55f506b85a..383d268d7d 100644
--- a/accessible/tests/browser/e10s/browser_caching_name.js
+++ b/accessible/tests/browser/e10s/browser_caching_name.js
@@ -477,7 +477,7 @@ markupTests.forEach(({ id, ruleset, markup, expected }) =>
     markup,
     async function (browser, accDoc) {
       const observer = {
-        observe(subject, topic, data) {
+        observe(subject) {
           const event = subject.QueryInterface(nsIAccessibleEvent);
           console.log(eventToString(event));
         },
diff --git a/accessible/tests/browser/e10s/browser_caching_relations_002.js b/accessible/tests/browser/e10s/browser_caching_relations_002.js
index 072656eb5e..61d92ba4ac 100644
--- a/accessible/tests/browser/e10s/browser_caching_relations_002.js
+++ b/accessible/tests/browser/e10s/browser_caching_relations_002.js
@@ -293,7 +293,7 @@ addAccessibleTask(
 );
 
 /**
- * Test details relations on popovers and their invokers.
+ * Test details relations for the popovertarget content attribute.
  */
 addAccessibleTask(
   `
@@ -304,7 +304,7 @@ addAccessibleTask(
 <div id="popover" popover>popover</div>
 <div id="details">details</div>
   `,
-  async function testPopover(browser, docAcc) {
+  async function testPopoverContent(browser, docAcc) {
     // The popover is hidden, so nothing should be referring to it.
     const hide = findAccessibleChildByID(docAcc, "hide");
     await testCachedRelation(hide, RELATION_DETAILS, []);
@@ -330,7 +330,7 @@ addAccessibleTask(
     await testCachedRelation(toggleSibling, RELATION_DETAILS, []);
     await testCachedRelation(popover, RELATION_DETAILS_FOR, toggle1);
 
-    info("Setting toggle2 popovertargetaction");
+    info("Setting toggle2 popovertarget");
     await invokeSetAttribute(browser, "toggle2", "popovertarget", "popover");
     await testCachedRelation(toggle2, RELATION_DETAILS, popover);
     await testCachedRelation(popover, RELATION_DETAILS_FOR, [toggle1, toggle2]);
@@ -364,3 +364,106 @@ addAccessibleTask(
   },
   { chrome: false, topLevel: true }
 );
+
+/**
+ * Test details relations for the popoverTargetElement WebIDL attribute.
+ */
+addAccessibleTask(
+  `
+<button id="toggle1">toggle1</button>
+<button id="toggle2">toggle2</button>
+between
+<div id="popover1" popover>popover1</div>
+<button id="toggle3">toggle3</button>
+<div id="shadowHost"><template shadowrootmode="open">
+  <button id="toggle4">toggle4</button>
+  between
+  <div id="popover2" popover>popover2</div>
+  <button id="toggle5">toggle5</button>
+</template></div>
+<script>
+  const toggle1 = document.getElementById("toggle1");
+  const popover1 = document.getElementById("popover1");
+  toggle1.popoverTargetElement = popover1;
+  const toggle3 = document.getElementById("toggle3");
+  const shadow = document.getElementById("shadowHost").shadowRoot;
+  const toggle4 = shadow.getElementById("toggle4");
+  const popover2 = shadow.getElementById("popover2");
+  toggle3.popoverTargetElement = popover2;
+  toggle4.popoverTargetElement = popover2;
+  const toggle5 = shadow.getElementById("toggle5");
+  toggle5.popoverTargetElement = popover1;
+</script>
+  `,
+  async function testPopoverIdl(browser, docAcc) {
+    // No popover is showing, so there shouldn't be any details relations.
+    const toggle1 = findAccessibleChildByID(docAcc, "toggle1");
+    await testCachedRelation(toggle1, RELATION_DETAILS, []);
+    const toggle2 = findAccessibleChildByID(docAcc, "toggle2");
+    await testCachedRelation(toggle2, RELATION_DETAILS, []);
+    const toggle3 = findAccessibleChildByID(docAcc, "toggle3");
+    await testCachedRelation(toggle3, RELATION_DETAILS, []);
+    const toggle4 = findAccessibleChildByID(docAcc, "toggle4");
+    await testCachedRelation(toggle4, RELATION_DETAILS, []);
+    const toggle5 = findAccessibleChildByID(docAcc, "toggle5");
+    await testCachedRelation(toggle5, RELATION_DETAILS, []);
+
+    info("Showing popover1");
+    let shown = waitForEvent(EVENT_SHOW, "popover1");
+    toggle1.doAction(0);
+    const popover1 = (await shown).accessible;
+    await testCachedRelation(toggle1, RELATION_DETAILS, popover1);
+    // toggle5 is inside the shadow DOM and popover1 is outside, so the target
+    // is valid.
+    await testCachedRelation(toggle5, RELATION_DETAILS, popover1);
+    await testCachedRelation(popover1, RELATION_DETAILS_FOR, [
+      toggle1,
+      toggle5,
+    ]);
+    info("Setting toggle2's popover target to popover1");
+    await invokeContentTask(browser, [], () => {
+      const toggle2Dom = content.document.getElementById("toggle2");
+      const popover1Dom = content.document.getElementById("popover1");
+      toggle2Dom.popoverTargetElement = popover1Dom;
+    });
+    await testCachedRelation(toggle2, RELATION_DETAILS, popover1);
+    await testCachedRelation(popover1, RELATION_DETAILS_FOR, [
+      toggle1,
+      toggle2,
+      toggle5,
+    ]);
+    info("Clearing toggle2's popover target");
+    await invokeContentTask(browser, [], () => {
+      const toggle2Dom = content.document.getElementById("toggle2");
+      toggle2Dom.popoverTargetElement = null;
+    });
+    await testCachedRelation(toggle2, RELATION_DETAILS, []);
+    await testCachedRelation(popover1, RELATION_DETAILS_FOR, [
+      toggle1,
+      toggle5,
+    ]);
+    info("Hiding popover1");
+    let hidden = waitForEvent(EVENT_HIDE, popover1);
+    toggle1.doAction(0);
+    await hidden;
+    await testCachedRelation(toggle1, RELATION_DETAILS, []);
+    await testCachedRelation(toggle2, RELATION_DETAILS, []);
+    await testCachedRelation(toggle5, RELATION_DETAILS, []);
+
+    info("Showing popover2");
+    shown = waitForEvent(EVENT_SHOW, "popover2");
+    toggle4.doAction(0);
+    const popover2 = (await shown).accessible;
+    // toggle4 is in the same shadow DOM as popover2.
+    await testCachedRelation(toggle4, RELATION_DETAILS, popover2);
+    // toggle3 is outside popover2's shadow DOM, so the target isn't valid.
+    await testCachedRelation(toggle3, RELATION_DETAILS, []);
+    await testCachedRelation(popover2, RELATION_DETAILS_FOR, [toggle4]);
+    info("Hiding popover2");
+    hidden = waitForEvent(EVENT_HIDE, popover2);
+    toggle4.doAction(0);
+    await hidden;
+    await testCachedRelation(toggle4, RELATION_DETAILS, []);
+  },
+  { chrome: true, topLevel: true }
+);
diff --git a/accessible/tests/browser/e10s/browser_caching_states.js b/accessible/tests/browser/e10s/browser_caching_states.js
index 37f8c46966..7292228f25 100644
--- a/accessible/tests/browser/e10s/browser_caching_states.js
+++ b/accessible/tests/browser/e10s/browser_caching_states.js
@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
+requestLongerTimeout(2);
 
 /* import-globals-from ../../mochitest/role.js */
 /* import-globals-from ../../mochitest/states.js */
@@ -484,7 +485,7 @@ addAccessibleTask(
 );
 
 /**
- * Test caching of the expanded state for popover target element.
+ * Test caching of the expanded state for the popovertarget content attribute.
  */
 addAccessibleTask(
   `
@@ -550,3 +551,157 @@ addAccessibleTask(
   },
   { chrome: true, topLevel: true, remoteIframe: true }
 );
+
+/**
+ * Test caching of the expanded state for the popoverTargetElement WebIDL
+ * attribute.
+ */
+addAccessibleTask(
+  `
+<button id="toggle1">toggle</button>
+<div id="popover1" popover>popover1</div>
+<button id="toggle2">toggle2</button>
+<button id="toggle3">toggle3</button>
+<div id="shadowHost"><template shadowrootmode="open">
+  <button id="toggle4">toggle4</button>
+  <div id="popover2" popover>popover2</div>
+  <button id="toggle5">toggle5</button>
+</template></div>
+<script>
+  const toggle1 = document.getElementById("toggle1");
+  const popover1 = document.getElementById("popover1");
+  toggle1.popoverTargetElement = popover1;
+  const toggle3 = document.getElementById("toggle3");
+  const shadow = document.getElementById("shadowHost").shadowRoot;
+  const toggle4 = shadow.getElementById("toggle4");
+  const popover2 = shadow.getElementById("popover2");
+  toggle3.popoverTargetElement = popover2;
+  toggle4.popoverTargetElement = popover2;
+  const toggle5 = shadow.getElementById("toggle5");
+  toggle5.popoverTargetElement = popover1;
+</script>
+  `,
+  async function (browser, docAcc) {
+    const toggle1 = findAccessibleChildByID(docAcc, "toggle1");
+    // toggle1's popover target is set and connected to the document.
+    testStates(toggle1, STATE_COLLAPSED);
+
+    const toggle2 = findAccessibleChildByID(docAcc, "toggle2");
+    // toggle2's popover target isn't set yet.
+    testStates(
+      toggle2,
+      0,
+      0,
+      STATE_EXPANDED | STATE_COLLAPSED,
+      EXT_STATE_EXPANDABLE
+    );
+    info("Setting toggle2's popoverTargetElement");
+    let changed = waitForStateChange(toggle2, EXT_STATE_EXPANDABLE, true, true);
+    await invokeContentTask(browser, [], () => {
+      const toggle2Dom = content.document.getElementById("toggle2");
+      const popover1 = content.document.getElementById("popover1");
+      toggle2Dom.popoverTargetElement = popover1;
+    });
+    await changed;
+    testStates(toggle2, STATE_COLLAPSED);
+
+    const toggle5 = findAccessibleChildByID(docAcc, "toggle5");
+    // toggle5 is inside the shadow DOM and popover1 is outside, so the target
+    // is valid.
+    testStates(toggle5, STATE_COLLAPSED);
+
+    // Changes to the popover should fire events on all invokers.
+    const changeEvents = [
+      [EVENT_STATE_CHANGE, toggle1],
+      [EVENT_STATE_CHANGE, toggle2],
+      [EVENT_STATE_CHANGE, toggle5],
+    ];
+    info("Showing popover1");
+    changed = waitForEvents(changeEvents);
+    toggle1.doAction(0);
+    await changed;
+    testStates(toggle1, STATE_EXPANDED);
+    testStates(toggle2, STATE_EXPANDED);
+
+    info("Hiding popover1");
+    changed = waitForEvents(changeEvents);
+    toggle1.doAction(0);
+    await changed;
+    testStates(toggle1, STATE_COLLAPSED);
+    testStates(toggle2, STATE_COLLAPSED);
+
+    info("Clearing toggle1's popover target");
+    changed = waitForStateChange(toggle1, EXT_STATE_EXPANDABLE, false, true);
+    await invokeContentTask(browser, [], () => {
+      const toggle1Dom = content.document.getElementById("toggle1");
+      toggle1Dom.popoverTargetElement = null;
+    });
+    await changed;
+    testStates(
+      toggle1,
+      0,
+      0,
+      STATE_EXPANDED | STATE_COLLAPSED,
+      EXT_STATE_EXPANDABLE
+    );
+
+    info("Setting toggle2's popover target to a disconnected node");
+    changed = waitForStateChange(toggle2, EXT_STATE_EXPANDABLE, false, true);
+    await invokeContentTask(browser, [], () => {
+      const toggle2Dom = content.document.getElementById("toggle2");
+      const popover3 = content.document.createElement("div");
+      popover3.popover = "auto";
+      popover3.textContent = "popover3";
+      // We don't append popover3 anywhere, so it is disconnected.
+      toggle2Dom.popoverTargetElement = popover3;
+    });
+    await changed;
+    testStates(
+      toggle2,
+      0,
+      0,
+      STATE_EXPANDED | STATE_COLLAPSED,
+      EXT_STATE_EXPANDABLE
+    );
+
+    const toggle3 = findAccessibleChildByID(docAcc, "toggle3");
+    // toggle3 is outside popover2's shadow DOM, so the target isn't valid.
+    testStates(
+      toggle3,
+      0,
+      0,
+      STATE_EXPANDED | STATE_COLLAPSED,
+      EXT_STATE_EXPANDABLE
+    );
+    const toggle4 = findAccessibleChildByID(docAcc, "toggle4");
+    // toggle4 is in the same shadow DOM as popover2.
+    testStates(toggle4, STATE_COLLAPSED);
+  },
+  { chrome: true, topLevel: true }
+);
+
+/**
+ * Test the mixed state of indeterminate HTML checkboxes.
+ */
+addAccessibleTask(
+  `<input type="checkbox" id="checkbox">`,
+  async function testHTMLCheckboxMixed(browser, docAcc) {
+    const checkbox = findAccessibleChildByID(docAcc, "checkbox");
+    testStates(checkbox, 0, 0, STATE_MIXED);
+    info("Setting indeterminate on checkbox");
+    let changed = waitForStateChange(checkbox, STATE_MIXED, true);
+    await invokeContentTask(browser, [], () => {
+      content.document.getElementById("checkbox").indeterminate = true;
+    });
+    await changed;
+    testStates(checkbox, STATE_MIXED);
+    info("Clearing indeterminate on checkbox");
+    changed = waitForStateChange(checkbox, STATE_MIXED, false);
+    await invokeContentTask(browser, [], () => {
+      content.document.getElementById("checkbox").indeterminate = false;
+    });
+    await changed;
+    testStates(checkbox, 0, 0, STATE_MIXED);
+  },
+  { chrome: true, topLevel: true, iframe: true, remoteIframe: true }
+);
diff --git a/accessible/tests/browser/e10s/browser_caching_table.js b/accessible/tests/browser/e10s/browser_caching_table.js
index 9c8bcb9616..0329e6411b 100644
--- a/accessible/tests/browser/e10s/browser_caching_table.js
+++ b/accessible/tests/browser/e10s/browser_caching_table.js
@@ -482,7 +482,7 @@ addAccessibleTask(
  */
 addAccessibleTask(
   `<table><tr id="tr"></tr></table>`,
-  async function (browser, docAcc) {
+  async function (browser) {
     let reordered = waitForEvent(EVENT_REORDER, "tr");
     await invokeContentTask(browser, [], () => {
       const iframe = content.document.createElement("iframe");
diff --git a/accessible/tests/browser/e10s/browser_caching_text_bounds.js b/accessible/tests/browser/e10s/browser_caching_text_bounds.js
index 3e37bf7490..486e28df53 100644
--- a/accessible/tests/browser/e10s/browser_caching_text_bounds.js
+++ b/accessible/tests/browser/e10s/browser_caching_text_bounds.js
@@ -138,9 +138,13 @@ async function testLineWithNonRenderedSpace(docAcc, browser, id, length) {
     const w = {};
     const h = {};
     acc.getCharacterExtents(offset, x, y, w, h, COORDTYPE_SCREEN_RELATIVE);
-    ok(x.value > prevX, `${id}: offset ${offset} x is larger (${x.value})`);
+    Assert.greater(
+      x.value,
+      prevX,
+      `${id}: offset ${offset} x is larger (${x.value})`
+    );
     prevX = x.value;
-    ok(w.value > 0, `${id}: offset ${offset} width > 0`);
+    Assert.greater(w.value, 0, `${id}: offset ${offset} width > 0`);
   }
 }
 
@@ -566,7 +570,11 @@ c</textarea>
       {},
       COORDTYPE_SCREEN_RELATIVE
     );
-    ok(newY.value < oldY.value, "y coordinate smaller after scrolling down");
+    Assert.less(
+      newY.value,
+      oldY.value,
+      "y coordinate smaller after scrolling down"
+    );
   },
   { chrome: true, topLevel: true, iframe: !true }
 );
diff --git a/accessible/tests/browser/e10s/browser_file_input.js b/accessible/tests/browser/e10s/browser_file_input.js
index 238e48740e..4c68e8e6da 100644
--- a/accessible/tests/browser/e10s/browser_file_input.js
+++ b/accessible/tests/browser/e10s/browser_file_input.js
@@ -34,7 +34,7 @@ addAccessibleTask(
     function chooseFile(id) {
       return invokeContentTask(browser, [id], contentId => {
         const MockFilePicker = content.SpecialPowers.MockFilePicker;
-        MockFilePicker.init(content);
+        MockFilePicker.init(content.browsingContext);
         MockFilePicker.useBlobFile();
         MockFilePicker.returnValue = MockFilePicker.returnOK;
         const input = content.document.getElementById(contentId);
diff --git a/accessible/tests/browser/e10s/browser_treeupdate_select_dropdown.js b/accessible/tests/browser/e10s/browser_treeupdate_select_dropdown.js
index a82fc4c04d..8ccbe58751 100644
--- a/accessible/tests/browser/e10s/browser_treeupdate_select_dropdown.js
+++ b/accessible/tests/browser/e10s/browser_treeupdate_select_dropdown.js
@@ -24,7 +24,7 @@ const snippet = `
 
 addAccessibleTask(
   snippet,
-  async function (browser, accDoc) {
+  async function (browser) {
     await invokeFocus(browser, "select");
     // Expand the select. A dropdown item should get focus.
     // Note that the dropdown is rendered in the parent process.
diff --git a/accessible/tests/browser/events/browser_test_docload.js b/accessible/tests/browser/events/browser_test_docload.js
index 78ac77fd8c..12076b3002 100644
--- a/accessible/tests/browser/events/browser_test_docload.js
+++ b/accessible/tests/browser/events/browser_test_docload.js
@@ -30,7 +30,7 @@ function urlChecker(url) {
   };
 }
 
-async function runTests(browser, accDoc) {
+async function runTests(browser) {
   let onLoadEvents = waitForEvents({
     expected: [
       [EVENT_REORDER, getAccessible(browser)],
diff --git a/accessible/tests/browser/events/browser_test_focus_browserui.js b/accessible/tests/browser/events/browser_test_focus_browserui.js
index 969d336c74..2f67cb3681 100644
--- a/accessible/tests/browser/events/browser_test_focus_browserui.js
+++ b/accessible/tests/browser/events/browser_test_focus_browserui.js
@@ -11,7 +11,7 @@ loadScripts(
   { name: "role.js", dir: MOCHITESTS_DIR }
 );
 
-async function runTests(browser, accDoc) {
+async function runTests(browser) {
   await SpecialPowers.pushPrefEnv({
     // If Fission is disabled, the pref is no-op.
     set: [["fission.bfcacheInParent", true]],
diff --git a/accessible/tests/browser/events/browser_test_focus_dialog.js b/accessible/tests/browser/events/browser_test_focus_dialog.js
index 71485a678d..03a1b82dc1 100644
--- a/accessible/tests/browser/events/browser_test_focus_dialog.js
+++ b/accessible/tests/browser/events/browser_test_focus_dialog.js
@@ -11,7 +11,7 @@ loadScripts(
   { name: "role.js", dir: MOCHITESTS_DIR }
 );
 
-async function runTests(browser, accDoc) {
+async function runTests(browser) {
   let onFocus = waitForEvent(EVENT_FOCUS, "button");
   await SpecialPowers.spawn(browser, [], () => {
     content.document.getElementById("button").focus();
diff --git a/accessible/tests/browser/events/browser_test_focus_urlbar.js b/accessible/tests/browser/events/browser_test_focus_urlbar.js
index 68b2b07f3c..647b837e9f 100644
--- a/accessible/tests/browser/events/browser_test_focus_urlbar.js
+++ b/accessible/tests/browser/events/browser_test_focus_urlbar.js
@@ -68,10 +68,10 @@ class TipTestProvider extends UrlbarProvider {
   get type() {
     return UrlbarUtils.PROVIDER_TYPE.PROFILE;
   }
-  isActive(context) {
+  isActive() {
     return true;
   }
-  isRestricting(context) {
+  isRestricting() {
     return true;
   }
   async startQuery(context, addCallback) {
diff --git a/accessible/tests/browser/events/browser_test_scrolling.js b/accessible/tests/browser/events/browser_test_scrolling.js
index 9678ee767b..d9425721bf 100644
--- a/accessible/tests/browser/events/browser_test_scrolling.js
+++ b/accessible/tests/browser/events/browser_test_scrolling.js
@@ -25,13 +25,15 @@ c</textarea>
     });
     let [scrollEvent1, scrollEndEvent1] = await onScrolling;
     scrollEvent1.QueryInterface(nsIAccessibleScrollingEvent);
-    ok(
-      scrollEvent1.maxScrollY >= scrollEvent1.scrollY,
+    Assert.greaterOrEqual(
+      scrollEvent1.maxScrollY,
+      scrollEvent1.scrollY,
       "scrollY is within max"
     );
     scrollEndEvent1.QueryInterface(nsIAccessibleScrollingEvent);
-    ok(
-      scrollEndEvent1.maxScrollY >= scrollEndEvent1.scrollY,
+    Assert.greaterOrEqual(
+      scrollEndEvent1.maxScrollY,
+      scrollEndEvent1.scrollY,
       "scrollY is within max"
     );
 
@@ -44,13 +46,15 @@ c</textarea>
     });
     let [scrollEvent2, scrollEndEvent2] = await onScrolling;
     scrollEvent2.QueryInterface(nsIAccessibleScrollingEvent);
-    ok(
-      scrollEvent2.scrollY > scrollEvent1.scrollY,
+    Assert.greater(
+      scrollEvent2.scrollY,
+      scrollEvent1.scrollY,
       `${scrollEvent2.scrollY} > ${scrollEvent1.scrollY}`
     );
     scrollEndEvent2.QueryInterface(nsIAccessibleScrollingEvent);
-    ok(
-      scrollEndEvent2.maxScrollY >= scrollEndEvent2.scrollY,
+    Assert.greaterOrEqual(
+      scrollEndEvent2.maxScrollY,
+      scrollEndEvent2.scrollY,
       "scrollY is within max"
     );
 
@@ -63,17 +67,20 @@ c</textarea>
     });
     let [scrollEvent3, scrollEndEvent3] = await onScrolling;
     scrollEvent3.QueryInterface(nsIAccessibleScrollingEvent);
-    ok(
-      scrollEvent3.maxScrollX >= scrollEvent3.scrollX,
+    Assert.greaterOrEqual(
+      scrollEvent3.maxScrollX,
+      scrollEvent3.scrollX,
       "scrollX is within max"
     );
     scrollEndEvent3.QueryInterface(nsIAccessibleScrollingEvent);
-    ok(
-      scrollEndEvent3.maxScrollX >= scrollEndEvent3.scrollX,
+    Assert.greaterOrEqual(
+      scrollEndEvent3.maxScrollX,
+      scrollEndEvent3.scrollX,
       "scrollY is within max"
     );
-    ok(
-      scrollEvent3.scrollX > scrollEvent2.scrollX,
+    Assert.greater(
+      scrollEvent3.scrollX,
+      scrollEvent2.scrollX,
       `${scrollEvent3.scrollX} > ${scrollEvent2.scrollX}`
     );
 
@@ -87,13 +94,15 @@ c</textarea>
     });
     let [scrollEvent4, scrollEndEvent4] = await onScrolling;
     scrollEvent4.QueryInterface(nsIAccessibleScrollingEvent);
-    ok(
-      scrollEvent4.maxScrollY >= scrollEvent4.scrollY,
+    Assert.greaterOrEqual(
+      scrollEvent4.maxScrollY,
+      scrollEvent4.scrollY,
       "scrollY is within max"
     );
     scrollEndEvent4.QueryInterface(nsIAccessibleScrollingEvent);
-    ok(
-      scrollEndEvent4.maxScrollY >= scrollEndEvent4.scrollY,
+    Assert.greaterOrEqual(
+      scrollEndEvent4.maxScrollY,
+      scrollEndEvent4.scrollY,
       "scrollY is within max"
     );
 
@@ -119,7 +128,7 @@ addAccessibleTask(
     <p>b</p>
     <p id="c">c</p>
   `,
-  async function (browser, accDoc) {
+  async function (browser) {
     let onScrollingStart = waitForEvent(EVENT_SCROLLING_START, "c");
     await SpecialPowers.spawn(browser, [], () => {
       content.location.hash = "#c";
@@ -137,7 +146,7 @@ addAccessibleTask(
   <h1 style="height: 300%;" id="inside-scrollable">test</h1>
 </div>
   `,
-  async function (browser, accDoc) {
+  async function (browser) {
     let onScrollingStart = waitForEvent(
       EVENT_SCROLLING_START,
       "inside-scrollable"
diff --git a/accessible/tests/browser/mac/browser_app.js b/accessible/tests/browser/mac/browser_app.js
index bedefae440..e7e18b5ddd 100644
--- a/accessible/tests/browser/mac/browser_app.js
+++ b/accessible/tests/browser/mac/browser_app.js
@@ -138,7 +138,7 @@ add_task(async () => {
       gBrowser,
       url: "about:license",
     },
-    async browser => {
+    async () => {
       let root = await getMacAccessible(document);
       let rootChildCount = () => root.getAttributeValue("AXChildren").length;
 
@@ -206,8 +206,10 @@ add_task(async () => {
       is(rootChildCount(), baseRootChildCount + 1, "Root has another child");
 
       // Close popup
+      let hide = waitForMacEvent("AXUIElementDestroyed");
       EventUtils.synthesizeKey("KEY_Escape");
       await BrowserTestUtils.waitForPopupEvent(identityPopup, "hidden");
+      await hide;
 
       // We're back to the base child count
       is(rootChildCount(), baseRootChildCount, "Root has the base child count");
@@ -225,7 +227,7 @@ add_task(async () => {
       // eslint-disable-next-line @microsoft/sdl/no-insecure-url
       url: "http://example.com",
     },
-    async browser => {
+    async () => {
       let input = await getMacAccessible("urlbar-input");
       is(
         input.getAttributeValue("AXValue"),
@@ -238,6 +240,38 @@ add_task(async () => {
 });
 
 /**
+ * Tests attributed text in nav bar has no invisible AXAttachments
+ */
+add_task(async () => {
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      url: "http://example.com",
+    },
+    async () => {
+      let root = await getMacAccessible(document);
+      let navBar = await getMacAccessible("nav-bar");
+      let elemRange = root.getParameterizedAttributeValue(
+        "AXTextMarkerRangeForUIElement",
+        navBar
+      );
+      let attributedString = root.getParameterizedAttributeValue(
+        "AXAttributedStringForTextMarkerRange",
+        elemRange
+      );
+      let attachmentRoles = attributedString.map(s =>
+        s.AXAttachment ? s.AXAttachment.getAttributeValue("AXRole") : null
+      );
+      ok(
+        !attachmentRoles.includes("AXMenu"),
+        "Collapsed menu should be embedded in attributed text"
+      );
+    }
+  );
+});
+
+/**
  * Test context menu
  */
 add_task(async () => {
diff --git a/accessible/tests/browser/mac/browser_bounds.js b/accessible/tests/browser/mac/browser_bounds.js
index 09343d7c9d..bc7939cfe0 100644
--- a/accessible/tests/browser/mac/browser_bounds.js
+++ b/accessible/tests/browser/mac/browser_bounds.js
@@ -21,22 +21,26 @@ addAccessibleTask(
     // test them here instead of calling AXFrame directly.
     const [helloWidth, helloHeight] = hello.getAttributeValue("AXSize");
     const [worldWidth, worldHeight] = world.getAttributeValue("AXSize");
-    ok(helloWidth > 0, "Hello has a positive width");
-    ok(helloHeight > 0, "Hello has a positive height");
-    ok(worldWidth > 0, "World has a positive width");
-    ok(worldHeight > 0, "World has a positive height");
-    ok(helloHeight < worldHeight, "Hello has a smaller height than world");
-    ok(helloWidth < worldWidth, "Hello has a smaller width than world");
+    Assert.greater(helloWidth, 0, "Hello has a positive width");
+    Assert.greater(helloHeight, 0, "Hello has a positive height");
+    Assert.greater(worldWidth, 0, "World has a positive width");
+    Assert.greater(worldHeight, 0, "World has a positive height");
+    Assert.less(
+      helloHeight,
+      worldHeight,
+      "Hello has a smaller height than world"
+    );
+    Assert.less(helloWidth, worldWidth, "Hello has a smaller width than world");
 
     // Note: these are mac screen coords, so our origin is bottom left
     const [helloX, helloY] = hello.getAttributeValue("AXPosition");
     const [worldX, worldY] = world.getAttributeValue("AXPosition");
-    ok(helloX > 0, "Hello has a positive X");
-    ok(helloY > 0, "Hello has a positive Y");
-    ok(worldX > 0, "World has a positive X");
-    ok(worldY > 0, "World has a positive Y");
-    ok(helloY > worldY, "Hello has a larger Y than world");
-    ok(helloX == worldX, "Hello and world have the same X");
+    Assert.greater(helloX, 0, "Hello has a positive X");
+    Assert.greater(helloY, 0, "Hello has a positive Y");
+    Assert.greater(worldX, 0, "World has a positive X");
+    Assert.greater(worldY, 0, "World has a positive Y");
+    Assert.greater(helloY, worldY, "Hello has a larger Y than world");
+    Assert.equal(helloX, worldX, "Hello and world have the same X");
   }
 );
 
@@ -57,21 +61,25 @@ addAccessibleTask(
     // test them here instead of calling AXFrame directly.
     const [helloWidth, helloHeight] = hello.getAttributeValue("AXSize");
     const [worldWidth, worldHeight] = world.getAttributeValue("AXSize");
-    ok(helloWidth > 0, "Hello has a positive width");
-    ok(helloHeight > 0, "Hello has a positive height");
-    ok(worldWidth > 0, "World has a positive width");
-    ok(worldHeight > 0, "World has a positive height");
-    ok(helloHeight < worldHeight, "Hello has a smaller height than world");
-    ok(helloWidth < worldWidth, "Hello has a smaller width than world");
+    Assert.greater(helloWidth, 0, "Hello has a positive width");
+    Assert.greater(helloHeight, 0, "Hello has a positive height");
+    Assert.greater(worldWidth, 0, "World has a positive width");
+    Assert.greater(worldHeight, 0, "World has a positive height");
+    Assert.less(
+      helloHeight,
+      worldHeight,
+      "Hello has a smaller height than world"
+    );
+    Assert.less(helloWidth, worldWidth, "Hello has a smaller width than world");
 
     // Note: these are mac screen coords, so our origin is bottom left
     const [helloX, helloY] = hello.getAttributeValue("AXPosition");
     const [worldX, worldY] = world.getAttributeValue("AXPosition");
-    ok(helloX < 0, "Hello has a negative X");
-    ok(helloY > 0, "Hello has a positive Y");
-    ok(worldX < 0, "World has a negative X");
-    ok(worldY > 0, "World has a positive Y");
-    ok(helloY > worldY, "Hello has a larger Y than world");
-    ok(helloX == worldX, "Hello and world have the same X");
+    Assert.less(helloX, 0, "Hello has a negative X");
+    Assert.greater(helloY, 0, "Hello has a positive Y");
+    Assert.less(worldX, 0, "World has a negative X");
+    Assert.greater(worldY, 0, "World has a positive Y");
+    Assert.greater(helloY, worldY, "Hello has a larger Y than world");
+    Assert.equal(helloX, worldX, "Hello and world have the same X");
   }
 );
diff --git a/accessible/tests/browser/mac/browser_live_regions.js b/accessible/tests/browser/mac/browser_live_regions.js
index 10a03120f8..aa07f003df 100644
--- a/accessible/tests/browser/mac/browser_live_regions.js
+++ b/accessible/tests/browser/mac/browser_live_regions.js
@@ -131,7 +131,7 @@ addAccessibleTask(
   <button id="button" aria-label="Start"></button>
   </div>
   `,
-  async (browser, accDoc) => {
+  async browser => {
     let liveRegionChanged = waitForMacEvent("AXLiveRegionChanged", "live");
     await SpecialPowers.spawn(browser, [], () => {
       content.document.getElementById("time").textContent = "4:56pm";
diff --git a/accessible/tests/browser/mac/browser_menulist.js b/accessible/tests/browser/mac/browser_menulist.js
index b26a0be782..3b0fe8b210 100644
--- a/accessible/tests/browser/mac/browser_menulist.js
+++ b/accessible/tests/browser/mac/browser_menulist.js
@@ -74,7 +74,7 @@ addAccessibleTask(
       "First menu item is selected"
     );
     // focus the second item, and verify it is selected
-    event = waitForMacEvent("AXFocusedUIElementChanged", (iface, data) => {
+    event = waitForMacEvent("AXFocusedUIElementChanged", iface => {
       try {
         return iface.getAttributeValue("AXTitle") == "100%";
       } catch (e) {
diff --git a/accessible/tests/browser/mac/browser_roles_elements.js b/accessible/tests/browser/mac/browser_roles_elements.js
index 791598fed6..b6049e7afd 100644
--- a/accessible/tests/browser/mac/browser_roles_elements.js
+++ b/accessible/tests/browser/mac/browser_roles_elements.js
@@ -47,6 +47,7 @@ addAccessibleTask(
   <div id="complementary" role="complementary"></div>
   <div id="contentinfo" role="contentinfo"></div>
   <div id="form" role="form"></div>
+  <div id="form_label" aria-label="form" role="form"></div>
   <div id="main" role="main"></div>
   <div id="navigation" role="navigation"></div>
   <div id="search" role="search"></div>
@@ -149,7 +150,8 @@ addAccessibleTask(
       "AXLandmarkComplementary"
     );
     testRoleAndSubRole(accDoc, "contentinfo", null, "AXLandmarkContentInfo");
-    testRoleAndSubRole(accDoc, "form", null, "AXLandmarkForm");
+    testRoleAndSubRole(accDoc, "form", null, "AXApplicationGroup");
+    testRoleAndSubRole(accDoc, "form_label", null, "AXLandmarkForm");
     testRoleAndSubRole(accDoc, "main", null, "AXLandmarkMain");
     testRoleAndSubRole(accDoc, "navigation", null, "AXLandmarkNavigation");
     testRoleAndSubRole(accDoc, "search", null, "AXLandmarkSearch");
diff --git a/accessible/tests/browser/mac/browser_rotor.js b/accessible/tests/browser/mac/browser_rotor.js
index 3f13506757..87ac40592d 100644
--- a/accessible/tests/browser/mac/browser_rotor.js
+++ b/accessible/tests/browser/mac/browser_rotor.js
@@ -269,7 +269,7 @@ addAccessibleTask(
       "AXUIElementCountForSearchPredicate",
       NSDictionary(searchPred)
     );
-    is(4, tableCount, "Found four tables");
+    is(tableCount, 3, "Found three tables");
 
     const tables = webArea.getParameterizedAttributeValue(
       "AXUIElementsForSearchPredicate",
@@ -278,7 +278,6 @@ addAccessibleTask(
     const shapes = getNativeInterface(accDoc, "shapes");
     const food = getNativeInterface(accDoc, "food");
     const ariaTable = getNativeInterface(accDoc, "ariaTable");
-    const grid = getNativeInterface(accDoc, "grid");
 
     is(
       shapes.getAttributeValue("AXColumnCount"),
@@ -295,11 +294,6 @@ addAccessibleTask(
       tables[2].getAttributeValue("AXColumnCount"),
       "Found correct third table"
     );
-    is(
-      grid.getAttributeValue("AXColumnCount"),
-      tables[3].getAttributeValue("AXColumnCount"),
-      "Found correct fourth table"
-    );
   }
 );
 
diff --git a/accessible/tests/browser/mac/browser_text_leaf.js b/accessible/tests/browser/mac/browser_text_leaf.js
index 21deed6212..c65e8c6ebe 100644
--- a/accessible/tests/browser/mac/browser_text_leaf.js
+++ b/accessible/tests/browser/mac/browser_text_leaf.js
@@ -77,7 +77,11 @@ addAccessibleTask(
       NSRange(3, 8)
     );
 
-    ok(smallBounds.size[0] < largeBounds.size[0], "longer range is wider");
+    Assert.less(
+      smallBounds.size[0],
+      largeBounds.size[0],
+      "longer range is wider"
+    );
   },
   { chrome: true, iframe: true, remoteIframe: true }
 );
diff --git a/accessible/tests/browser/mac/browser_text_selection.js b/accessible/tests/browser/mac/browser_text_selection.js
index a914adba8e..7e2145631c 100644
--- a/accessible/tests/browser/mac/browser_text_selection.js
+++ b/accessible/tests/browser/mac/browser_text_selection.js
@@ -82,7 +82,7 @@ addAccessibleTask(
   Hello <a href="#" id="link">World</a>,
   I <a href="#" style="user-select: none;" id="unselectable_link">love</a>
   <button id="button">you</button></p>`,
-  async (browser, accDoc) => {
+  async browser => {
     // Set up an AXSelectedTextChanged listener here. It will get resolved
     // on the first non-root event it encounters, so if we test its data at the end
     // of this test it will show us the first text-selectable object that was focused,
diff --git a/accessible/tests/browser/mac/browser_toggle_radio_check.js b/accessible/tests/browser/mac/browser_toggle_radio_check.js
index 1695d73b0d..f9094ac3d7 100644
--- a/accessible/tests/browser/mac/browser_toggle_radio_check.js
+++ b/accessible/tests/browser/mac/browser_toggle_radio_check.js
@@ -128,7 +128,7 @@ addAccessibleTask(
 
     // Changing from checked to mixed fires two events. Make sure we wait until
     // the second so we're asserting based on the latest state.
-    evt = waitForMacEvent("AXValueChanged", (iface, data) => {
+    evt = waitForMacEvent("AXValueChanged", iface => {
       return (
         iface.getAttributeValue("AXDOMIdentifier") == "checkbox" &&
         iface.getAttributeValue("AXValue") == 2
diff --git a/accessible/tests/browser/mac/browser_webarea.js b/accessible/tests/browser/mac/browser_webarea.js
index ac6122de14..4872c58845 100644
--- a/accessible/tests/browser/mac/browser_webarea.js
+++ b/accessible/tests/browser/mac/browser_webarea.js
@@ -8,8 +8,8 @@
 loadScripts({ name: "role.js", dir: MOCHITESTS_DIR });
 
 // Test web area role and AXLoadComplete event
-addAccessibleTask(``, async (browser, accDoc) => {
-  let evt = waitForMacEvent("AXLoadComplete", (iface, data) => {
+addAccessibleTask(``, async browser => {
+  let evt = waitForMacEvent("AXLoadComplete", iface => {
     return iface.getAttributeValue("AXDescription") == "webarea test";
   });
   await SpecialPowers.spawn(browser, [], () => {
@@ -29,16 +29,16 @@ addAccessibleTask(``, async (browser, accDoc) => {
 });
 
 // Test iframe web area role and AXLayoutComplete event
-addAccessibleTask(`<title>webarea test</title>`, async (browser, accDoc) => {
+addAccessibleTask(`<title>webarea test</title>`, async browser => {
   // If the iframe loads before the top level document finishes loading, we'll
   // get both an AXLayoutComplete event for the iframe and an AXLoadComplete
   // event for the document. Otherwise, if the iframe loads after the
   // document, we'll get one AXLoadComplete event.
   let eventPromise = Promise.race([
-    waitForMacEvent("AXLayoutComplete", (iface, data) => {
+    waitForMacEvent("AXLayoutComplete", iface => {
       return iface.getAttributeValue("AXDescription") == "iframe document";
     }),
-    waitForMacEvent("AXLoadComplete", (iface, data) => {
+    waitForMacEvent("AXLoadComplete", iface => {
       return iface.getAttributeValue("AXDescription") == "webarea test";
     }),
   ]);
diff --git a/accessible/tests/browser/scroll/browser_test_scroll_bounds.js b/accessible/tests/browser/scroll/browser_test_scroll_bounds.js
index 31de002cda..33a99266db 100644
--- a/accessible/tests/browser/scroll/browser_test_scroll_bounds.js
+++ b/accessible/tests/browser/scroll/browser_test_scroll_bounds.js
@@ -238,7 +238,11 @@ addAccessibleTask(
       newTopBounds[0],
       "x of non-fixed element remains accurate."
     );
-    ok(newTopBounds[1] < 0, "y coordinate shows item scrolled off page");
+    Assert.less(
+      newTopBounds[1],
+      0,
+      "y coordinate shows item scrolled off page"
+    );
     is(
       origTopBounds[2],
       newTopBounds[2],
@@ -254,7 +258,11 @@ addAccessibleTask(
       newDBounds[0],
       "x of non-fixed container element remains accurate."
     );
-    ok(newDBounds[1] < 0, "y coordinate shows container scrolled off page");
+    Assert.less(
+      newDBounds[1],
+      0,
+      "y coordinate shows container scrolled off page"
+    );
     // Removing the position styling on this acc causes it to be bound by
     // its parent's bounding box, which alters its width as a block element.
     // We don't particularly care about width in this test, so skip it.
@@ -481,7 +489,7 @@ addAccessibleTask(
         newBounds[0],
         `x coord of non-sticky element remains accurate.`
       );
-      ok(newBounds[1] < 0, "y coordinate shows item scrolled off page");
+      Assert.less(newBounds[1], 0, "y coordinate shows item scrolled off page");
 
       // Removing the position styling on this acc causes it to be bound by
       // its parent's bounding box, which alters its width as a block element.
diff --git a/accessible/tests/browser/scroll/browser_test_scroll_substring.js b/accessible/tests/browser/scroll/browser_test_scroll_substring.js
index e8426d00ca..031b8a5124 100644
--- a/accessible/tests/browser/scroll/browser_test_scroll_substring.js
+++ b/accessible/tests/browser/scroll/browser_test_scroll_substring.js
@@ -45,8 +45,9 @@ The only thing I found in the fridge was a dead dove in a bag.
       text.getCharacterExtents(7, {}, objY, {}, {}, COORDTYPE_SCREEN_RELATIVE);
       return objY.value;
     };
-    ok(
-      containerHeight < getCharY(),
+    Assert.less(
+      containerHeight,
+      getCharY(),
       "Character is outside of container bounds"
     );
     text.scrollSubstringTo(7, 8, SCROLL_TYPE_TOP_EDGE);
diff --git a/accessible/tests/browser/selectable/browser_test_select.js b/accessible/tests/browser/selectable/browser_test_select.js
index f86a371d81..6a51fd4f3b 100644
--- a/accessible/tests/browser/selectable/browser_test_select.js
+++ b/accessible/tests/browser/selectable/browser_test_select.js
@@ -313,7 +313,7 @@ addAccessibleTask(
   </select>
 </form>
   `,
-  async function (browser, docAcc) {
+  async function (browser) {
     let selected = waitForEvent(EVENT_SELECTION_WITHIN, "select");
     await invokeContentTask(browser, [], () => {
       const form = content.document.getElementById("form");
diff --git a/accessible/tests/browser/shared-head.js b/accessible/tests/browser/shared-head.js
index fe87a77765..c238a5a7a0 100644
--- a/accessible/tests/browser/shared-head.js
+++ b/accessible/tests/browser/shared-head.js
@@ -830,7 +830,7 @@ const CACHE_WAIT_TIMEOUT_MS = 5000;
  * be used to record a pass or fail in the test.
  */
 function untilCacheCondition(conditionFunc, argsFunc) {
-  return new Promise((resolve, reject) => {
+  return new Promise(resolve => {
     let args = argsFunc();
     if (conditionFunc(...args)) {
       resolve(args);
@@ -838,7 +838,7 @@ function untilCacheCondition(conditionFunc, argsFunc) {
     }
 
     let cacheObserver = {
-      observe(subject) {
+      observe() {
         args = argsFunc();
         if (conditionFunc(...args)) {
           clearTimeout(this.timer);
@@ -945,7 +945,7 @@ function runPython(code) {
       "ws://mochi.test:8888/browser/accessible/tests/browser/python_runner"
     );
     if (gPythonSocket.readyState != WebSocket.OPEN) {
-      gPythonSocket.onopen = evt => {
+      gPythonSocket.onopen = () => {
         gPythonSocket.send(code);
         gPythonSocket.onopen = null;
       };
diff --git a/accessible/tests/browser/text/browser_text_paragraph_boundary.js b/accessible/tests/browser/text/browser_text_paragraph_boundary.js
index 04e64520e8..b206829398 100644
--- a/accessible/tests/browser/text/browser_text_paragraph_boundary.js
+++ b/accessible/tests/browser/text/browser_text_paragraph_boundary.js
@@ -8,7 +8,7 @@
 // boundary on an Accessible which has remote ProxyAccessible descendants.
 addAccessibleTask(
   `test`,
-  async function testParagraphBoundaryWithRemoteDescendants(browser, accDoc) {
+  async function testParagraphBoundaryWithRemoteDescendants() {
     const root = getRootAccessible(document).QueryInterface(
       Ci.nsIAccessibleText
     );
diff --git a/accessible/tests/browser/text/head.js b/accessible/tests/browser/text/head.js
index fa4b095892..72195ddbb0 100644
--- a/accessible/tests/browser/text/head.js
+++ b/accessible/tests/browser/text/head.js
@@ -142,7 +142,7 @@ function testBoundarySequence(
 // Editable text
 
 async function waitForCopy(browser) {
-  await BrowserTestUtils.waitForContentEvent(browser, "copy", false, evt => {
+  await BrowserTestUtils.waitForContentEvent(browser, "copy", false, () => {
     return true;
   });
 
diff --git a/accessible/tests/browser/tree/browser_aria_owns.js b/accessible/tests/browser/tree/browser_aria_owns.js
index 0ca55ed357..904597cc66 100644
--- a/accessible/tests/browser/tree/browser_aria_owns.js
+++ b/accessible/tests/browser/tree/browser_aria_owns.js
@@ -176,7 +176,7 @@ addAccessibleTask(
 addAccessibleTask(
   `
   <select id="container" aria-owns="boom" multiple></select>`,
-  async function (browser, accDoc) {
+  async function () {
     ok(true, "Did not crash");
   }
 );
diff --git a/accessible/tests/browser/tree/browser_browser_element.js b/accessible/tests/browser/tree/browser_browser_element.js
index 82be24d93c..d6ece6676e 100644
--- a/accessible/tests/browser/tree/browser_browser_element.js
+++ b/accessible/tests/browser/tree/browser_browser_element.js
@@ -8,7 +8,7 @@ loadScripts({ name: "role.js", dir: MOCHITESTS_DIR });
 
 // Test that the tree is correct for browser elements containing remote
 // documents.
-addAccessibleTask(`test`, async function (browser, docAcc) {
+addAccessibleTask(`test`, async function (browser) {
   // testAccessibleTree also verifies childCount, indexInParent and parent.
   testAccessibleTree(browser, {
     INTERNAL_FRAME: [{ DOCUMENT: [{ TEXT_LEAF: [] }] }],
diff --git a/accessible/tests/browser/tree/browser_lazy_tabs.js b/accessible/tests/browser/tree/browser_lazy_tabs.js
index f7aa9bdeb2..46e10d0bac 100644
--- a/accessible/tests/browser/tree/browser_lazy_tabs.js
+++ b/accessible/tests/browser/tree/browser_lazy_tabs.js
@@ -5,7 +5,7 @@
 
 // Test that lazy background tabs aren't unintentionally loaded when building
 // the a11y tree (bug 1700708).
-addAccessibleTask(``, async function (browser, accDoc) {
+addAccessibleTask(``, async function () {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.sessionstore.restore_on_demand", true]],
   });
diff --git a/accessible/tests/browser/tree/browser_test_nsIAccessibleDocument_URL.js b/accessible/tests/browser/tree/browser_test_nsIAccessibleDocument_URL.js
index 623f2640f0..e6b55d0fd3 100644
--- a/accessible/tests/browser/tree/browser_test_nsIAccessibleDocument_URL.js
+++ b/accessible/tests/browser/tree/browser_test_nsIAccessibleDocument_URL.js
@@ -25,7 +25,7 @@ async function promiseEventDocumentLoadComplete(expectedURL) {
 add_task(async function testInDataURI() {
   const kURL = "data:text/html,Some text";
   const waitForDocumentLoadComplete = promiseEventDocumentLoadComplete("");
-  await BrowserTestUtils.withNewTab(kURL, async browser => {
+  await BrowserTestUtils.withNewTab(kURL, async () => {
     is(
       (await waitForDocumentLoadComplete).URL,
       "",
@@ -44,7 +44,7 @@ add_task(async function testInHTTPSURIContainingPrivateThings() {
     "https://example.com/browser/toolkit/content/tests/browser/file_empty.html?query=some#ref";
   const waitForDocumentLoadComplete =
     promiseEventDocumentLoadComplete(kURLWithoutUserPass);
-  await BrowserTestUtils.withNewTab(kURL, async browser => {
+  await BrowserTestUtils.withNewTab(kURL, async () => {
     is(
       (await waitForDocumentLoadComplete).URL,
       kURLWithoutUserPass,
diff --git a/accessible/tests/browser/windows/a11y_setup.py b/accessible/tests/browser/windows/a11y_setup.py
index d6dc19f0fb..726eea07a4 100644
--- a/accessible/tests/browser/windows/a11y_setup.py
+++ b/accessible/tests/browser/windows/a11y_setup.py
@@ -9,19 +9,28 @@ import ctypes
 import os
 from ctypes import POINTER, byref
 from ctypes.wintypes import BOOL, HWND, LPARAM, POINT  # noqa: F401
+from dataclasses import dataclass
 
+import comtypes.automation
 import comtypes.client
 import psutil
 from comtypes import COMError, IServiceProvider
 
+CHILDID_SELF = 0
+COWAIT_DEFAULT = 0
+EVENT_OBJECT_FOCUS = 0x8005
+GA_ROOT = 2
+NAVRELATION_EMBEDS = 0x1009
+OBJID_CLIENT = -4
+RPC_S_CALLPENDING = -2147417835
+WINEVENT_OUTOFCONTEXT = 0
+WM_CLOSE = 0x0010
+
 user32 = ctypes.windll.user32
 oleacc = ctypes.oledll.oleacc
 oleaccMod = comtypes.client.GetModule("oleacc.dll")
 IAccessible = oleaccMod.IAccessible
 del oleaccMod
-OBJID_CLIENT = -4
-CHILDID_SELF = 0
-NAVRELATION_EMBEDS = 0x1009
 # This is the path if running locally.
 ia2Tlb = os.path.join(
     os.getcwd(),
@@ -65,6 +74,13 @@ def AccessibleObjectFromWindow(hwnd, objectID=OBJID_CLIENT):
     return p
 
 
+def getWindowClass(hwnd):
+    MAX_CHARS = 257
+    buffer = ctypes.create_unicode_buffer(MAX_CHARS)
+    user32.GetClassNameW(hwnd, buffer, MAX_CHARS)
+    return buffer.value
+
+
 def getFirefoxHwnd():
     """Search all top level windows for the Firefox instance being
     tested.
@@ -78,9 +94,7 @@ def getFirefoxHwnd():
 
     @ctypes.WINFUNCTYPE(BOOL, HWND, LPARAM)
     def callback(hwnd, lParam):
-        name = ctypes.create_unicode_buffer(100)
-        user32.GetClassNameW(hwnd, name, 100)
-        if name.value != "MozillaWindowClass":
+        if getWindowClass(hwnd) != "MozillaWindowClass":
             return True
         pid = ctypes.wintypes.DWORD()
         user32.GetWindowThreadProcessId(hwnd, byref(pid))
@@ -127,6 +141,106 @@ def findIa2ByDomId(root, id):
             return descendant
 
 
+@dataclass
+class WinEvent:
+    event: int
+    hwnd: int
+    objectId: int
+    childId: int
+
+    def getIa2(self):
+        acc = ctypes.POINTER(IAccessible)()
+        child = comtypes.automation.VARIANT()
+        ctypes.oledll.oleacc.AccessibleObjectFromEvent(
+            self.hwnd,
+            self.objectId,
+            self.childId,
+            ctypes.byref(acc),
+            ctypes.byref(child),
+        )
+        if child.value != CHILDID_SELF:
+            # This isn't an IAccessible2 object.
+            return None
+        return toIa2(acc)
+
+
+class WaitForWinEvent:
+    """Wait for a win event, usually for IAccessible2.
+    This should be used as follows:
+    1. Create an instance to wait for the desired event.
+    2. Perform the action that should fire the event.
+    3. Call wait() on the instance you created in 1) to wait for the event.
+    """
+
+    def __init__(self, eventId, match):
+        """event is the event id to wait for.
+        match is either None to match any object, an str containing the DOM id
+        of the desired object, or a function taking a WinEvent which should
+        return True if this is the requested event.
+        """
+        self._matched = None
+        # A kernel event used to signal when we get the desired event.
+        self._signal = ctypes.windll.kernel32.CreateEventW(None, True, False, None)
+
+        # We define this as a nested function because it has to be a static
+        # function, but we need a reference to self.
+        @ctypes.WINFUNCTYPE(
+            None,
+            ctypes.wintypes.HANDLE,
+            ctypes.wintypes.DWORD,
+            ctypes.wintypes.HWND,
+            ctypes.wintypes.LONG,
+            ctypes.wintypes.LONG,
+            ctypes.wintypes.DWORD,
+            ctypes.wintypes.DWORD,
+        )
+        def winEventProc(hook, eventId, hwnd, objectId, childId, thread, time):
+            event = WinEvent(eventId, hwnd, objectId, childId)
+            if isinstance(match, str):
+                try:
+                    ia2 = event.getIa2()
+                    if f"id:{match};" in ia2.attributes:
+                        self._matched = event
+                except (comtypes.COMError, TypeError):
+                    pass
+            elif callable(match):
+                try:
+                    if match(event):
+                        self._matched = event
+                except Exception as e:
+                    self._matched = e
+            if self._matched:
+                ctypes.windll.kernel32.SetEvent(self._signal)
+
+        self._hook = user32.SetWinEventHook(
+            eventId, eventId, None, winEventProc, 0, 0, WINEVENT_OUTOFCONTEXT
+        )
+        # Hold a reference to winEventProc so it doesn't get destroyed.
+        self._proc = winEventProc
+
+    def wait(self):
+        """Wait for and return the desired WinEvent."""
+        # Pump Windows messages until we get the desired event, which will be
+        # signalled using a kernel event.
+        handles = (ctypes.c_void_p * 1)(self._signal)
+        index = ctypes.wintypes.DWORD()
+        TIMEOUT = 10000
+        try:
+            ctypes.oledll.ole32.CoWaitForMultipleHandles(
+                COWAIT_DEFAULT, TIMEOUT, 1, handles, ctypes.byref(index)
+            )
+        except WindowsError as e:
+            if e.winerror == RPC_S_CALLPENDING:
+                raise TimeoutError("Timeout before desired event received")
+            raise
+        finally:
+            user32.UnhookWinEvent(self._hook)
+            self._proc = None
+        if isinstance(self._matched, Exception):
+            raise self._matched from self._matched
+        return self._matched
+
+
 def getDocUia():
     """Get the IUIAutomationElement for the document being tested."""
     # We start with IAccessible2 because there's no efficient way to
diff --git a/accessible/tests/browser/windows/ia2/browser.toml b/accessible/tests/browser/windows/ia2/browser.toml
index d72b5f8a2d..d6226b73cc 100644
--- a/accessible/tests/browser/windows/ia2/browser.toml
+++ b/accessible/tests/browser/windows/ia2/browser.toml
@@ -6,4 +6,6 @@ skip-if = [
 ]
 support-files = ["head.js"]
 
+["browser_osPicker.js"]
+
 ["browser_role.js"]
diff --git a/accessible/tests/browser/windows/ia2/browser_osPicker.js b/accessible/tests/browser/windows/ia2/browser_osPicker.js
new file mode 100644
index 0000000000..b14f2d0a5f
--- /dev/null
+++ b/accessible/tests/browser/windows/ia2/browser_osPicker.js
@@ -0,0 +1,51 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+addAccessibleTask(
+  `<input id="file" type="file">`,
+  async function (browser, docAcc) {
+    info("Focusing file input");
+    await runPython(`
+      global focused
+      focused = WaitForWinEvent(EVENT_OBJECT_FOCUS, "file")
+    `);
+    const file = findAccessibleChildByID(docAcc, "file");
+    file.takeFocus();
+    await runPython(`
+      focused.wait()
+    `);
+    ok(true, "file input got focus");
+    info("Opening file picker");
+    await runPython(`
+      global focused
+      focused = WaitForWinEvent(
+        EVENT_OBJECT_FOCUS,
+        lambda evt: getWindowClass(evt.hwnd) == "Edit"
+      )
+    `);
+    file.doAction(0);
+    await runPython(`
+      global event
+      event = focused.wait()
+    `);
+    ok(true, "Picker got focus");
+    info("Dismissing picker");
+    await runPython(`
+      # If the picker is dismissed too quickly, it seems to re-enable the root
+      # window before we do. This sleep isn't ideal, but it's more likely to
+      # reproduce the case that our root window gets focus before it is enabled.
+      # See bug 1883568 for further details.
+      import time
+      time.sleep(1)
+      focused = WaitForWinEvent(EVENT_OBJECT_FOCUS, "file")
+      # Sending key presses to the picker is unreliable, so use WM_CLOSE.
+      pickerRoot = user32.GetAncestor(event.hwnd, GA_ROOT)
+      user32.SendMessageW(pickerRoot, WM_CLOSE, 0, 0)
+      focused.wait()
+    `);
+    ok(true, "file input got focus");
+  }
+);
diff --git a/accessible/tests/browser/windows/ia2/browser_role.js b/accessible/tests/browser/windows/ia2/browser_role.js
index 08e44c280f..89b560ab49 100644
--- a/accessible/tests/browser/windows/ia2/browser_role.js
+++ b/accessible/tests/browser/windows/ia2/browser_role.js
@@ -12,7 +12,7 @@ addAccessibleTask(
   `
 <p id="p">p</p>
   `,
-  async function (browser, docAcc) {
+  async function () {
     let role = await runPython(`
       global doc
       doc = getDocIa2()
diff --git a/accessible/tests/browser/windows/uia/browser.toml b/accessible/tests/browser/windows/uia/browser.toml
index f7974d69c7..d1513c1822 100644
--- a/accessible/tests/browser/windows/uia/browser.toml
+++ b/accessible/tests/browser/windows/uia/browser.toml
@@ -9,3 +9,5 @@ support-files = ["head.js"]
 ["browser_controlType.js"]
 
 ["browser_elementFromPoint.js"]
+
+["browser_tree.js"]
diff --git a/accessible/tests/browser/windows/uia/browser_controlType.js b/accessible/tests/browser/windows/uia/browser_controlType.js
index 16db892581..3bb994f437 100644
--- a/accessible/tests/browser/windows/uia/browser_controlType.js
+++ b/accessible/tests/browser/windows/uia/browser_controlType.js
@@ -9,11 +9,11 @@ const UIA_ButtonControlTypeId = 50000;
 const UIA_DocumentControlTypeId = 50030;
 /* eslint-enable camelcase */
 
-addAccessibleTask(
+addUiaTask(
   `
 <button id="button">button</button>
   `,
-  async function (browser, docAcc) {
+  async function () {
     let controlType = await runPython(`
       global doc
       doc = getDocUia()
diff --git a/accessible/tests/browser/windows/uia/browser_elementFromPoint.js b/accessible/tests/browser/windows/uia/browser_elementFromPoint.js
index e2fda4ab30..acf6fe91c7 100644
--- a/accessible/tests/browser/windows/uia/browser_elementFromPoint.js
+++ b/accessible/tests/browser/windows/uia/browser_elementFromPoint.js
@@ -4,12 +4,12 @@
 
 "use strict";
 
-addAccessibleTask(
+addUiaTask(
   `
 <button id="button">button</p>
 <a id="a" href="#">a</a>
   `,
-  async function (browser, docAcc) {
+  async function () {
     ok(
       await runPython(`
         global doc
diff --git a/accessible/tests/browser/windows/uia/browser_tree.js b/accessible/tests/browser/windows/uia/browser_tree.js
new file mode 100644
index 0000000000..778609bedb
--- /dev/null
+++ b/accessible/tests/browser/windows/uia/browser_tree.js
@@ -0,0 +1,104 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+async function testIsControl(pyVar, isControl) {
+  const result = await runPython(`bool(${pyVar}.CurrentIsControlElement)`);
+  if (isControl) {
+    ok(result, `${pyVar} is a control element`);
+  } else {
+    ok(!result, `${pyVar} isn't a control element`);
+  }
+}
+
+/**
+ * Define a global Python variable and assign it to a given Python expression.
+ */
+function definePyVar(varName, expression) {
+  return runPython(`
+    global ${varName}
+    ${varName} = ${expression}
+  `);
+}
+
+/**
+ * Get the UIA element with the given id and assign it to a global Python
+ * variable using the id as the variable name.
+ */
+function assignPyVarToUiaWithId(id) {
+  return definePyVar(id, `findUiaByDomId(doc, "${id}")`);
+}
+
+addUiaTask(
+  `
+<p id="p">paragraph</p>
+<div id="div">div</div>
+<!-- The spans are because the UIA -> IA2 proxy seems to remove a single text
+   leaf child from even the raw tree.
+  -->
+<a id="link" href="#">link<span> </span>></a>
+<h1 id="h1">h1<span> </span></h1>
+<h1 id="h1WithDiv"><div>h1 with div<span> </span></div></h1>
+<input id="range" type="range">
+<div onclick=";" id="clickable">clickable</div>
+<div id="editable" contenteditable>editable</div>
+<table id="table"><tr><th>th</th></tr></table>
+  `,
+  async function (browser, docAcc) {
+    await definePyVar("doc", `getDocUia()`);
+    await assignPyVarToUiaWithId("p");
+    await testIsControl("p", false);
+    await definePyVar(
+      "pTextLeaf",
+      `uiaClient.RawViewWalker.GetFirstChildElement(p)`
+    );
+    await testIsControl("pTextLeaf", true);
+    await assignPyVarToUiaWithId("div");
+    await testIsControl("div", false);
+    await definePyVar(
+      "divTextLeaf",
+      `uiaClient.RawViewWalker.GetFirstChildElement(div)`
+    );
+    await testIsControl("divTextLeaf", true);
+    await assignPyVarToUiaWithId("link");
+    await testIsControl("link", true);
+    await assignPyVarToUiaWithId("range");
+    await testIsControl("range", true);
+    await assignPyVarToUiaWithId("editable");
+    await testIsControl("editable", true);
+    await assignPyVarToUiaWithId("table");
+    await testIsControl("table", true);
+    if (!gIsUiaEnabled) {
+      // The remaining tests are broken with the UIA -> IA2 proxy.
+      return;
+    }
+    await definePyVar(
+      "linkTextLeaf",
+      `uiaClient.RawViewWalker.GetFirstChildElement(link)`
+    );
+    await testIsControl("linkTextLeaf", false);
+    await assignPyVarToUiaWithId("h1");
+    await testIsControl("h1", true);
+    await definePyVar(
+      "h1TextLeaf",
+      `uiaClient.RawViewWalker.GetFirstChildElement(h1)`
+    );
+    await testIsControl("h1TextLeaf", false);
+    await assignPyVarToUiaWithId("h1WithDiv");
+    await testIsControl("h1WithDiv", true);
+    // h1WithDiv's text leaf is its grandchild.
+    await definePyVar(
+      "h1WithDivTextLeaf",
+      `uiaClient.RawViewWalker.GetFirstChildElement(
+        uiaClient.RawViewWalker.GetFirstChildElement(
+          h1WithDiv
+        )
+      )`
+    );
+    await testIsControl("h1WithDivTextLeaf", false);
+    await assignPyVarToUiaWithId("clickable");
+    await testIsControl("clickable", true);
+  }
+);
diff --git a/accessible/tests/browser/windows/uia/head.js b/accessible/tests/browser/windows/uia/head.js
index afc50984bd..e659354c7c 100644
--- a/accessible/tests/browser/windows/uia/head.js
+++ b/accessible/tests/browser/windows/uia/head.js
@@ -4,6 +4,8 @@
 
 "use strict";
 
+/* exported gIsUiaEnabled, addUiaTask */
+
 // Load the shared-head file first.
 Services.scriptloader.loadSubScript(
   "chrome://mochitests/content/browser/accessible/tests/browser/shared-head.js",
@@ -16,3 +18,38 @@ loadScripts(
   { name: "common.js", dir: MOCHITESTS_DIR },
   { name: "promisified-events.js", dir: MOCHITESTS_DIR }
 );
+
+let gIsUiaEnabled = false;
+
+/**
+ * This is like addAccessibleTask, but takes two additional boolean options:
+ * - uiaEnabled: Whether to run a variation of this test with Gecko UIA enabled.
+ * - uiaDisabled: Whether to run a variation of this test with UIA disabled. In
+ *   this case, UIA will rely entirely on the IA2 -> UIA proxy.
+ * If both are set, the test will be run twice with different configurations.
+ * You can determine which variant is currently running using the gIsUiaEnabled
+ * variable. This is useful for conditional tests; e.g. if Gecko UIA supports
+ * something that the IA2 -> UIA proxy doesn't support.
+ */
+function addUiaTask(doc, task, options = {}) {
+  const { uiaEnabled = true, uiaDisabled = true } = options;
+
+  function addTask(shouldEnable) {
+    async function uiaTask(browser, docAcc, topDocAcc) {
+      await SpecialPowers.pushPrefEnv({
+        set: [["accessibility.uia.enable", shouldEnable]],
+      });
+      gIsUiaEnabled = shouldEnable;
+      info(shouldEnable ? "Gecko UIA enabled" : "Gecko UIA disabled");
+      await task(browser, docAcc, topDocAcc);
+    }
+    addAccessibleTask(doc, uiaTask, options);
+  }
+
+  if (uiaEnabled) {
+    addTask(true);
+  }
+  if (uiaDisabled) {
+    addTask(false);
+  }
+}