Adding upstream version 125.0.1.upstream/125.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
author: Daniel Baumann <daniel.baumann@progress-linux.org> 2024-04-19 01:13:27 +0000
committer: Daniel Baumann <daniel.baumann@progress-linux.org> 2024-04-19 01:13:27 +0000
commit: 40a355a42d4a9444dc753c04c6608dade2f06a23 (patch)
tree: 871fc667d2de662f171103ce5ec067014ef85e61 /testing/web-platform/mozilla/tests
parent: Adding upstream version 124.0.1. (diff)
download: firefox-adbda400be353e676059e335c3c0aaf99e719475.tar.xz
firefox-adbda400be353e676059e335c3c0aaf99e719475.zip
106 files changed, 2947 insertions, 442 deletions
diff --git a/testing/web-platform/mozilla/tests/common/reftest-zoom.js b/testing/web-platform/mozilla/tests/common/reftest-zoom.js
new file mode 100644
index 0000000000..a20f2cc800
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/common/reftest-zoom.js
@@ -0,0 +1,29 @@
+// This JS file allows to emulate reftest-zoom.
+// See https://firefox-source-docs.mozilla.org/layout/Reftest.html#zoom-tests-reftest-zoom-float
+
+// Retrieve reftest-zoom attribute.
+const reftestZoom = "reftest-zoom";
+const root = document.documentElement;
+if (!root.hasAttribute(reftestZoom)) {
+  throw new Error(`${reftestZoom} attribute not found on the root element.`);
+}
+
+// Parse reftest-zoom value.
+let zoom = parseFloat(root.getAttribute(reftestZoom));
+if (Number.isNaN(zoom)) {
+  throw new Error(`${reftestZoom} is not a float number.`);
+}
+
+// Clamp reftest-zoom value.
+let minZoom = SpecialPowers.getIntPref("zoom.minPercent") / 100;
+let maxZoom = SpecialPowers.getIntPref("zoom.maxPercent") / 100;
+zoom = Math.min(Math.max(zoom, minZoom), maxZoom);
+
+// Ensure the original zoom level is restored after the screenshot.
+const originalZoom = SpecialPowers.getFullZoom(window);
+window.addEventListener("beforeunload", () => {
+  SpecialPowers.setFullZoom(window, originalZoom);
+});
+
+// Set the zoom level to the specified value.
+SpecialPowers.setFullZoom(window, zoom);
diff --git a/testing/web-platform/mozilla/tests/css/bug1833279-001.html b/testing/web-platform/mozilla/tests/css/bug1833279-001.html
new file mode 100644
index 0000000000..ecbdf934de
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/css/bug1833279-001.html
@@ -0,0 +1,38 @@
+<!DOCTYPE HTML>
+<meta charset="utf-8">
+<title>Test for bug 1833279</title>
+<link rel="author" title="Daniel Holbert" href="mailto:dholbert@mozilla.com">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1833279">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+  setup({ single_test: true });
+
+  // The following callback-function gets called twice by our iframe inner-doc:
+  // 1. when the iframe's document finishes printing.
+  // 2. when the iframe's document finishes loading its own <object> child-document.
+  // When those two steps have completed, we're past the situation that would
+  // trigger a fatal assertion when the object document gets cycle-collected.
+  // So at that point we remove our iframe, and (after a rAF tick) trigger a
+  // GC and CC, and then consider the test as having passed if we're still
+  // alive at that point.
+  const MAX_STEPS = 2;
+  let stepsComplete = 0;
+
+  function iframeStepComplete() {
+    stepsComplete++;
+    if (stepsComplete < MAX_STEPS) {
+      return;
+    }
+    requestAnimationFrame(()=> {
+      myIframe.remove();
+      requestAnimationFrame(()=> {
+        SpecialPowers.DOMWindowUtils.garbageCollect();
+        SpecialPowers.DOMWindowUtils.cycleCollect();
+        assert_true(true, "successfully completed without crashing");
+        done();
+      });
+    });
+  }
+</script>
+<iframe id="myIframe" src="resources/bug1833279-iframe.html"></iframe>
diff --git a/testing/web-platform/mozilla/tests/css/css-contain/content-visibility/content-visibility-auto-relevancy-updates-stop-ticking-002.html b/testing/web-platform/mozilla/tests/css/css-contain/content-visibility/content-visibility-auto-relevancy-updates-stop-ticking-002.html
new file mode 100644
index 0000000000..1b64e43a1d
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/css/css-contain/content-visibility/content-visibility-auto-relevancy-updates-stop-ticking-002.html
@@ -0,0 +1,55 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>Content Visibility: stop ticking after relevancy updates</title>
+<!--
+    Adapted from testing/web-platform/tests/css/css-contain/content-visibility/content-visibility-intrinsic-size-001.html
+-->
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1880928">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/rendering-utils.js"></script>
+
+<style>
+  #container {
+      position: sticky;
+  }
+  #container > div {
+      content-visibility: auto;
+      contain-intrinsic-size: 1px 5000px;
+  }
+</style>
+<div id="container">
+  <div>X</div>
+  <div id="target">XX</div>
+  <div>XXX</div>
+  <div>XXXX</div>
+</div>
+<script>
+  target.scrollIntoView();
+</script>
+
+<script>
+function hasPendingTick() {
+  return SpecialPowers.wrap(window).windowUtils.refreshDriverHasPendingTick;
+}
+
+// See comment in layout/base/tests/test_bug1756118.html about why the timeouts
+// etc.
+async function expectTicksToStop() {
+  for (let i = 0; i < 100; i++) {
+    await new Promise(r => setTimeout(r, 8));
+    if(!hasPendingTick()) {
+      break;
+    }
+  }
+  assert_false(hasPendingTick(), "refresh driver should have eventually stopped ticking");
+}
+
+promise_test(async function(t) {
+  await new Promise(resolve => { window.addEventListener("load", resolve); });
+  await SpecialPowers.pushPrefEnv({'set':
+                                   [['layout.keep_ticking_after_load_ms', 0]]});
+  await waitForAtLeastOneFrame();
+  await expectTicksToStop();
+});
+</script>
diff --git a/testing/web-platform/mozilla/tests/css/resources/bug1833279-iframe.html b/testing/web-platform/mozilla/tests/css/resources/bug1833279-iframe.html
new file mode 100644
index 0000000000..ac646e75d3
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/css/resources/bug1833279-iframe.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<script src="foo" type="text/javascript"></script>
+<script>
+// Note: this file gets loaded twice in the course of this test: first, in an
+// iframe hosted in the top-level test; and second, in an <object> inside that
+// iframe's document. (The object element gets created dynamically in the
+// script below.)
+window.onload = () => {
+  // For efficiency: check our window.location, to be sure we only run this
+  // logic in the iframe, and *not* in the <object> that ends up getting loaded
+  // with the same URL plus a "?" at the end:
+  let locationStr = "" + location;
+  if (!locationStr.endsWith("?")) {
+    window.print();
+
+    // Add an object whose location is set to '?' (which means our same
+    // base URL plus a "?" character):
+    let a = document.createElement("object");
+    a.data = "?";
+    document.documentElement.appendChild(a)
+  } else if (parent.parent && parent.parent.iframeStepComplete) {
+    // We're the nested document in the `<object>` tag that was created above.
+    // Signal the outer document (our grandparent) that we've completed the
+    // step of loading this inner object document.
+    parent.parent.iframeStepComplete();
+  }
+}
+
+window.onafterprint = () => {
+  // We've finished printing; signal to our outer document that we've completed
+  // that step.
+  parent.iframeStepComplete();
+}
+</script>
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/fetchpriority-adjustments.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/fetchpriority-adjustments.html
new file mode 100644
index 0000000000..71bfbcc0b5
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/fetchpriority-adjustments.html
@@ -0,0 +1,53 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>fetchpriority: verify basic invariants for adjustments</title>
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1880528"/>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+  const fetchpriorities = ["auto", "low", "high"];
+  const prioritiesWhenFetchpriorityDisabled = {
+      "link-preload-script": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGHEST,
+      "module-script": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL,
+      "async-or-defer-script": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL,
+      "script-in-head": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL,
+      "other-script": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL,
+      "link-preload-font": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH,
+      "link-preload-fetch": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL,
+      "deferred-style": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL,
+      "link-preload-style": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGHEST,
+      "non-deferred-style": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL,
+      "global-fetch-api": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL,
+      "images": SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW,
+  };
+  for (const name in prioritiesWhenFetchpriorityDisabled) {
+      let adjustments = {};
+      for (const fetchpriority of fetchpriorities) {
+	  adjustments[fetchpriority] = SpecialPowers.getIntPref(`network.fetchpriority.adjustments.${name}.${fetchpriority}`);
+      }
+      test(() => {
+	  // The higher the internal priority, the smaller the integer value.
+	  assert_less_than_equal(adjustments.high, adjustments.auto, "Internal priority for high is at most the one for auto");
+	  assert_less_than_equal(adjustments.auto, adjustments.low, "Internal priority for auto is at most the one for low");
+      }, `${name}: adjusted priorities for low/auto/high have proper ordering.`);
+
+      test(() => {
+	  assert_less_than(adjustments.high, adjustments.low, "Internal priority for high is less than the one for low");
+      }, `${name}: at least one of fetchpriority="high" or fetchpriority="low" has any effect.`);
+
+      test(() => {
+	  const priority = prioritiesWhenFetchpriorityDisabled[name];
+	  const predefinedPriorities = [
+	      SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGHEST,
+	      SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH,
+	      SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL,
+	      SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW,
+	      SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOWEST
+	  ];
+	  for (const fetchpriority of fetchpriorities) {
+	      const adjustedPriority = priority + adjustments[fetchpriority];
+	      assert_true(predefinedPriorities.includes(adjustedPriority), `Internal priority for ${fetchpriority} is in the predefined set of priorities.`);
+	  }
+      }, `${name}: adjusted priorities belong to the predefined set.`);
+  }
+</script>
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/fetch-tests-data.js b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/fetch-tests-data.js
index 4edb3ae171..7f5f77628c 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/fetch-tests-data.js
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/fetch-tests-data.js
@@ -1,36 +1,106 @@
 export const kTestFolderName = "fetch-tests";
 
+// Use RequestInit's priority if specified, or RequestionInfo's priority otherwise.
 const kExpectedRequestsOfFetchAPI = [
     {   fileNameAndSuffix: "dummy.css?1",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
     },
     {   fileNameAndSuffix: "dummy.css?2",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
     },
     {   fileNameAndSuffix: "dummy.css?3",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.css?4",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
     },
     {   fileNameAndSuffix: "dummy.css?5",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
     },
     {   fileNameAndSuffix: "dummy.css?6",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
     },
     {   fileNameAndSuffix: "dummy.css?7",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.css?8",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
     },
     {   fileNameAndSuffix: "dummy.css?9",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
     },
     {   fileNameAndSuffix: "dummy.css?10",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+    },
+    {   fileNameAndSuffix: "dummy.css?11",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?12",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?13",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
-    }
+    },
+    {   fileNameAndSuffix: "dummy.css?14",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+    },
+    {   fileNameAndSuffix: "dummy.css?15",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?16",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+];
+
+const kExpectedRequestsOfFetchAPIDisabled = [
+    {   fileNameAndSuffix: "dummy.css?1",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?2",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?3",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?4",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?5",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?6",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?7",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?8",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?9",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?10",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?11",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?12",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?13",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?14",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?15",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.css?16",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
 ];
 
 export const kTestData = [
@@ -38,3 +108,9 @@ export const kTestData = [
         expectedRequests: kExpectedRequestsOfFetchAPI
     }
 ];
+
+export const kTestDataDisabled = [
+    {   testFileName: "fetch-init.h2.html",
+        expectedRequests: kExpectedRequestsOfFetchAPIDisabled
+    }
+];
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/fetch-tests/fetch-init.h2.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/fetch-tests/fetch-init.h2.html
index 0e267b0a3a..d91dd5450f 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/fetch-tests/fetch-init.h2.html
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/fetch-tests/fetch-init.h2.html
@@ -10,51 +10,66 @@
   onload = function() {
     const kData = [
       {
-        description: 'fetch() with URL and request_init whose priority is "high" must be fetched with high load priority',
-        request_info: `${resource_url}?1`,
+        request_info: new Request(`${resource_url}?1`, {priority: 'low'}),
+        request_init: {priority: 'low'}
+      },
+      {
+        request_info: new Request(`${resource_url}?2`, {priority: 'low'}),
         request_init: {priority: 'high'}
       },
       {
-        description: 'fetch() with URL and request_init whose priority is "auto" must have no effect on resource load priority',
-        request_info: `${resource_url}?2`,
+        request_info: new Request(`${resource_url}?3`, {priority: 'low'}),
         request_init: {priority: 'auto'}
       },
       {
-        description: 'fetch() with URL and request_init whose priority is missing must have no effect on resource load priority',
-        request_info: `${resource_url}?3`,
-        request_init: {}
+        request_info: new Request(`${resource_url}?4`, {priority: 'low'})
       },
       {
-        description: 'fetch() with URL and request_init whose priority is "low" must be fetched with low resource load priority',
-        request_info: `${resource_url}?4`,
+        request_info: new Request(`${resource_url}?5`, {priority: 'high'}),
         request_init: {priority: 'low'}
       },
       {
-        description: 'fetch() with Request whose priority is "low" and request_init whose priority is "high" must have no effect on resource load priority',
-        request_info: new Request(`${resource_url}?5`, {priority: 'low'}),
+        request_info: new Request(`${resource_url}?6`, {priority: 'high'}),
         request_init: {priority: 'high'}
       },
       {
-        description: 'fetch() with Request whose priority is "high" and request_init whose priority is "low" must be fetched with low resource load priority',
-        request_info: new Request(`${resource_url}?6`, {priority: 'high'}),
+        request_info: new Request(`${resource_url}?7`, {priority: 'high'}),
+        request_init: {priority: 'auto'}
+      },
+      {
+        request_info: new Request(`${resource_url}?8`, {priority: 'high'})
+      },
+      {
+        request_info: new Request(`${resource_url}?9`, {priority: 'auto'}),
         request_init: {priority: 'low'}
       },
       {
-        description: 'fetch() with Request whose priority is "high" and no request_init must be fetched with high resource load priority',
-        request_info: new Request(`${resource_url}?7`, {priority: 'high'})
+        request_info: new Request(`${resource_url}?10`, {priority: 'auto'}),
+        request_init: {priority: 'high'}
+      },
+      {
+        request_info: new Request(`${resource_url}?11`, {priority: 'auto'}),
+        request_init: {priority: 'auto'}
+      },
+      {
+        request_info: new Request(`${resource_url}?12`, {priority: 'auto'}),
+      },
+      {
+        request_info: `${resource_url}?13`,
+        request_init: {priority: 'low'}
       },
       {
-        description: 'fetch() with Request whose priority is "auto" and no request_init must have no effect on resource load priority',
-        request_info: new Request(`${resource_url}?8`, {priority: 'auto'})
+        request_info: `${resource_url}?14`,
+        request_init: {priority: 'high'}
       },
       {
-        description: 'fetch() with Request whose priority is missing and no request_init must have no effect on resource load priority',
-        request_info: new Request(`${resource_url}?9`)
+        request_info: `${resource_url}?15`,
+        request_init: {priority: 'auto'}
       },
       {
-        description: 'fetch() with Request whose priority is "low" and no request_init must be fetched with low resource load priority',
-        request_info: new Request(`${resource_url}?10`, {priority: 'low'})
-      }
+        request_info: `${resource_url}?16`,
+        request_init: {}
+      },
     ];
     for (const data of kData) {
         const response = fetch(data.request_info, data.request_init);
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/image-tests/image-initial-load.h2.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/image-tests/image-initial-load.h2.html
index c3ee532d9e..9cc171b5dd 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/image-tests/image-initial-load.h2.html
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/image-tests/image-initial-load.h2.html
@@ -5,8 +5,8 @@
     <title>fetchpriority</title>
   </head>
   <body>
-    <img fetchpriority="low" src="../resources/square_25px_x_25px.png?2" alt="img">
-    <img fetchpriority="high" src="../resources/square_25px_x_25px.png?1" alt="img">
+    <img fetchpriority="low" src="../resources/square_25px_x_25px.png?1" alt="img">
+    <img fetchpriority="high" src="../resources/square_25px_x_25px.png?2" alt="img">
     <img fetchpriority="auto" src="../resources/square_25px_x_25px.png?3" alt="img">
     <img src="../resources/square_25px_x_25px.png?4" alt="img">
     <script>
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/link-tests-data.js b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/link-tests-data.js
index 16e59f2fd9..1606894e2e 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/link-tests-data.js
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/link-tests-data.js
@@ -2,28 +2,28 @@ export const kTestFolderName = "link-tests";
 
 const kExpectedRequestsOfLoadStylesheet = [
     {   fileNameAndSuffix: "dummy.css?1",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.css?2",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGHEST
     },
     {   fileNameAndSuffix: "dummy.css?3",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGHEST
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.css?4",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGHEST
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.css?5",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
     },
     {   fileNameAndSuffix: "dummy.css?6",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.css?7",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.css?8",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     // `media=print` doesn't match the environment
     // (https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#matches-the-environment)
@@ -32,13 +32,13 @@ const kExpectedRequestsOfLoadStylesheet = [
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
     },
     {   fileNameAndSuffix: "dummy.css?10",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.css?11",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.css?12",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
 ];
 
@@ -113,16 +113,16 @@ const kExpectedRequestsOfLinkPreloadFontDisabled = [
 
 const kExpectedRequestsOfLinkPreloadImage = [
     {   fileNameAndSuffix: "dummy.image?1",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW + 1
     },
     {   fileNameAndSuffix: "dummy.image?2",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH + 1
     },
     {   fileNameAndSuffix: "dummy.image?3",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW + 1
     },
     {   fileNameAndSuffix: "dummy.image?4",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW + 1
     },
 ];
 
@@ -176,13 +176,13 @@ const kExpectedRequestsOfPreloadScript = [
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
     },
     {   fileNameAndSuffix: "dummy.js?2",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGHEST
     },
     {   fileNameAndSuffix: "dummy.js?3",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGHEST
     },
     {   fileNameAndSuffix: "dummy.js?4",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGHEST
     },
 ];
 
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests-data.js b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests-data.js
index 8f3b2033ad..d712d8391a 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests-data.js
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests-data.js
@@ -17,10 +17,10 @@ const kExpectedRequestsForScriptsInHead = [
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
     },
     {   fileNameAndSuffix: kFetchPriorityAutoRequestFileNameAndSuffix,
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: kNoFetchPriorityRequestFileNameAndSuffix,
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     }
 ];
 
@@ -39,6 +39,7 @@ const kExpectedRequestsForScriptsInHeadDisabled = [
     }
 ];
 
+// TODO(bug 1872654): Should we align on Chromium for "early" in-body scripts?
 const kExpectedRequestsForScriptsInBody = [
     {   fileNameAndSuffix: "dummy.js?1",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
@@ -46,7 +47,6 @@ const kExpectedRequestsForScriptsInBody = [
     {   fileNameAndSuffix: "dummy.js?2",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
     },
-    // Bug 1872654: Chromium's behavior here differs.
     {   fileNameAndSuffix: "dummy.js?3",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
@@ -54,10 +54,10 @@ const kExpectedRequestsForScriptsInBody = [
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.js?5",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.js?6",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.js?7",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
@@ -65,6 +65,30 @@ const kExpectedRequestsForScriptsInBody = [
     {   fileNameAndSuffix: "dummy.js?8",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
+    {   fileNameAndSuffix: "dummy.js?9",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+    },
+    {   fileNameAndSuffix: "dummy.js?10",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+    },
+    {   fileNameAndSuffix: "dummy.js?11",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?12",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?13",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?14",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?15",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?16",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
 ]
 
 const kExpectedRequestsForScriptsInBodyDisabled = [
@@ -92,6 +116,30 @@ const kExpectedRequestsForScriptsInBodyDisabled = [
     {   fileNameAndSuffix: "dummy.js?8",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
+    {   fileNameAndSuffix: "dummy.js?9",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?10",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?11",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?12",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?13",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?14",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?15",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?16",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
 ]
 
 export const kTestFolderName = "script-tests";
@@ -104,10 +152,22 @@ const kExpectedRequestsForNonModuleAsyncAndDeferredScripts = [
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
     },
     {   fileNameAndSuffix: "dummy.js?3",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.js?4",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_LOW
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?5",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?6",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?7",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?8",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
 ]
 
@@ -124,6 +184,18 @@ const kExpectedRequestsForNonModuleAsyncAndDeferredScriptsDisabled = [
     {   fileNameAndSuffix: "dummy.js?4",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
+    {   fileNameAndSuffix: "dummy.js?5",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?6",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?7",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?8",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
 ]
 
 // Chromium's desired behavior is under discussion:
@@ -136,10 +208,22 @@ const kExpectedRequestsForModuleScripts = [
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
     },
     {   fileNameAndSuffix: "dummy.js?3",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
     {   fileNameAndSuffix: "dummy.js?4",
-        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_HIGH
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?5",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?6",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?7",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?8",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
 ]
 
@@ -156,6 +240,18 @@ const kExpectedRequestsForModuleScriptsDisabled = [
     {   fileNameAndSuffix: "dummy.js?4",
         internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
     },
+    {   fileNameAndSuffix: "dummy.js?5",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?6",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?7",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
+    {   fileNameAndSuffix: "dummy.js?8",
+        internalPriority: SpecialPowers.Ci.nsISupportsPriority.PRIORITY_NORMAL
+    },
 ]
 
 export const kTestData = [
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/async-module-script-initial-load.h2.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/async-module-script-initial-load.h2.html
index 6b8b0977b7..feb46d49f5 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/async-module-script-initial-load.h2.html
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/async-module-script-initial-load.h2.html
@@ -9,6 +9,10 @@
   <script type="module" async src="../resources/dummy.js?4"></script>
 </head>
 <body>
+  <svg><script type="module" async href="../resources/dummy.js?5" fetchpriority="low"></script></svg>
+  <svg><script type="module" async href="../resources/dummy.js?6" fetchpriority="high"></script></svg>
+  <svg><script type="module" async href="../resources/dummy.js?7" fetchpriority="auto"></script></svg>
+  <svg><script type="module" async href="../resources/dummy.js?8"></script></svg>
 <script>
   onload = function() {
     opener.postMessage("ChildLoaded", "*");
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/async-script-initial-load.h2.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/async-script-initial-load.h2.html
index f6ac1c9a4f..dbd26a8807 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/async-script-initial-load.h2.html
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/async-script-initial-load.h2.html
@@ -9,6 +9,10 @@
   <script async src="../resources/dummy.js?4"></script>
 </head>
 <body>
+  <svg><script async href="../resources/dummy.js?5" fetchpriority="low"></script></svg>
+  <svg><script async href="../resources/dummy.js?6" fetchpriority="high"></script></svg>
+  <svg><script async href="../resources/dummy.js?7" fetchpriority="auto"></script></svg>
+  <svg><script async href="../resources/dummy.js?8"></script></svg>
 <script>
   onload = function() {
     opener.postMessage("ChildLoaded", "*");
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/deferred-script-initial-load.h2.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/deferred-script-initial-load.h2.html
index 99a4b8b3b9..166e0999a1 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/deferred-script-initial-load.h2.html
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/deferred-script-initial-load.h2.html
@@ -9,6 +9,10 @@
   <script defer src="../resources/dummy.js?4"></script>
 </head>
 <body>
+  <svg><script defer href="../resources/dummy.js?5" fetchpriority="low"></script></svg>
+  <svg><script defer href="../resources/dummy.js?6" fetchpriority="high"></script></svg>
+  <svg><script defer href="../resources/dummy.js?7" fetchpriority="auto"></script></svg>
+  <svg><script defer href="../resources/dummy.js?8"></script></svg>
 <script>
   onload = function() {
     opener.postMessage("ChildLoaded", "*");
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/module-script-dynamic-insertion.h2.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/module-script-dynamic-insertion.h2.html
index 13e5b8c91d..572fe5ae7e 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/module-script-dynamic-insertion.h2.html
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/module-script-dynamic-insertion.h2.html
@@ -8,16 +8,33 @@
 <script>
   onload = function() {
     const kData = [
-        { src: "../resources/dummy.js?1", fetchPriority: "low"},
-        { src: "../resources/dummy.js?2", fetchPriority: "high"},
-        { src: "../resources/dummy.js?3", fetchPriority: "auto"},
-        { src: "../resources/dummy.js?4"}
+        { src: "../resources/dummy.js?1", fetchPriority: "low", svg: false},
+        { src: "../resources/dummy.js?2", fetchPriority: "high", svg: false},
+        { src: "../resources/dummy.js?3", fetchPriority: "auto", svg: false},
+        { src: "../resources/dummy.js?4", svg: false},
+        { src: "../resources/dummy.js?5", fetchPriority: "low", svg: true},
+        { src: "../resources/dummy.js?6", fetchPriority: "high", svg: true},
+        { src: "../resources/dummy.js?7", fetchPriority: "auto", svg: true},
+        { src: "../resources/dummy.js?8", svg: true},
     ];
 
     let allScriptElements = [];
     for (data of kData) {
-      let scriptElement = document.createElement("script");
-      scriptElement.src = data.src;
+      if (!data.svg) {
+        scriptElement = document.createElement("script");
+        scriptElement.src = data.src;
+        if ("fetchPriority" in data) {
+          scriptElement.fetchPriority = data.fetchPriority;
+        }
+      } else {
+        const namespaceURI = "http://www.w3.org/2000/svg";
+        scriptElement = document.createElementNS(namespaceURI, "script");
+        scriptElement.href.baseVal = data.src;
+        // Use setAttribute as SVGScriptElement has no fetchPriority property.
+        if ("fetchPriority" in data) {
+          scriptElement.setAttribute("fetchPriority", data.fetchPriority);
+        }
+      }
 
       scriptElement.type = "module";
 
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/module-script-initial-load.h2.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/module-script-initial-load.h2.html
index 52c5d0e9ca..c2ff305500 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/module-script-initial-load.h2.html
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/module-script-initial-load.h2.html
@@ -9,6 +9,10 @@
   <script type="module" src="../resources/dummy.js?4"></script>
 </head>
 <body>
+  <svg><script type="module" href="../resources/dummy.js?5" fetchpriority="low"></script></svg>
+  <svg><script type="module" href="../resources/dummy.js?6" fetchpriority="high"></script></svg>
+  <svg><script type="module" href="../resources/dummy.js?7" fetchpriority="auto"></script></svg>
+  <svg><script type="module" href="../resources/dummy.js?8"></script></svg>
 <script>
   onload = function() {
     opener.postMessage("ChildLoaded", "*");
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-dynamic-insertion.h2.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-dynamic-insertion.h2.html
index 27103c81c1..8ed2ae7e01 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-dynamic-insertion.h2.html
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-dynamic-insertion.h2.html
@@ -8,19 +8,34 @@
 <script>
   onload = function() {
     const kData = [
-        { src: "../resources/dummy.js?1", fetchPriority: "low"},
-        { src: "../resources/dummy.js?2", fetchPriority: "high"},
-        { src: "../resources/dummy.js?3", fetchPriority: "auto"},
-        { src: "../resources/dummy.js?4"}
+        { src: "../resources/dummy.js?1", fetchPriority: "low", svg: false},
+        { src: "../resources/dummy.js?2", fetchPriority: "high", svg: false},
+        { src: "../resources/dummy.js?3", fetchPriority: "auto", svg: false},
+        { src: "../resources/dummy.js?4", svg: false},
+        { src: "../resources/dummy.js?5", fetchPriority: "low", svg: true},
+        { src: "../resources/dummy.js?6", fetchPriority: "high", svg: true},
+        { src: "../resources/dummy.js?7", fetchPriority: "auto", svg: true},
+        { src: "../resources/dummy.js?8", svg: true},
     ];
 
     let allScriptElements = [];
     for (data of kData) {
-      let scriptElement = document.createElement("script");
-      scriptElement.src = data.src;
-
-      if ("fetchPriority" in data) {
-        scriptElement.fetchPriority = data.fetchPriority;
+      let scriptElement;
+      if (!data.svg) {
+        scriptElement = document.createElement("script");
+        scriptElement.src = data.src;
+        if ("fetchPriority" in data) {
+          scriptElement.fetchPriority = data.fetchPriority;
+        }
+      } else {
+        const namespaceURI = "http://www.w3.org/2000/svg";
+        scriptElement = document.createElementNS(namespaceURI, "script");
+        scriptElement.href.baseVal = data.src;
+        // Use setAttribute as SVGScriptElement has no fetchPriority property.
+        scriptElement.setAttribute("href", data.src);
+        if ("fetchPriority" in data) {
+          scriptElement.setAttribute("fetchPriority", data.fetchPriority);
+        }
       }
 
       allScriptElements.push(scriptElement);
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-initial-load-body.h2.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-initial-load-body.h2.html
index dd1c7eb60e..61453561b3 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-initial-load-body.h2.html
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-initial-load-body.h2.html
@@ -9,15 +9,23 @@
     <script src="../resources/dummy.js?2" fetchpriority="high"></script>
     <script src="../resources/dummy.js?3" fetchpriority="auto"></script>
     <script src="../resources/dummy.js?4"></script>
+    <svg><script href="../resources/dummy.js?5" fetchpriority="low"></script></svg>
+    <svg><script href="../resources/dummy.js?6" fetchpriority="high"></script></svg>
+    <svg><script href="../resources/dummy.js?7" fetchpriority="auto"></script></svg>
+    <svg><script href="../resources/dummy.js?8"></script></svg>
     <img src="../resources/square_25px_x_25px.png">
     <!-- The image makes the external in-body
     (https://html.spec.whatwg.org/#parsing-main-inbody) scripts considered "late"
     (https://web.dev/articles/fetch-priority#browser_priority_and_fetchpriority).
     -->
-    <script src="../resources/dummy.js?5" fetchpriority="low"></script>
-    <script src="../resources/dummy.js?6" fetchpriority="high"></script>
-    <script src="../resources/dummy.js?7" fetchpriority="auto"></script>
-    <script src="../resources/dummy.js?8"></script>
+    <script src="../resources/dummy.js?9" fetchpriority="low"></script>
+    <script src="../resources/dummy.js?10" fetchpriority="high"></script>
+    <script src="../resources/dummy.js?11" fetchpriority="auto"></script>
+    <script src="../resources/dummy.js?12"></script>
+    <svg><script href="../resources/dummy.js?13" fetchpriority="low"></script></svg>
+    <svg><script href="../resources/dummy.js?14" fetchpriority="high"></script></svg>
+    <svg><script href="../resources/dummy.js?15" fetchpriority="auto"></script></svg>
+    <svg><script href="../resources/dummy.js?16"></script></svg>
     <script>
     onload = function() {
         opener.postMessage("ChildLoaded");
diff --git a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-initial-load-head.h2.html b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-initial-load-head.h2.html
index 519bddf22f..5ca9d84db8 100644
--- a/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-initial-load-head.h2.html
+++ b/testing/web-platform/mozilla/tests/fetch/fetchpriority/support/script-tests/script-initial-load-head.h2.html
@@ -7,6 +7,9 @@
   <script src="../resources/dummy.js?2" fetchpriority="high"></script>
   <script src="../resources/dummy.js?3" fetchpriority="auto"></script>
   <script src="../resources/dummy.js?4"></script>
+  <!-- We don't test in-head SVG <script> elements. The HTML parser ignores
+       explicit SVG namespace on such elements and moves any <svg> wrapper
+       into the body. -->
 </head>
 <body>
 <script>
diff --git a/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-001-ref.html b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-001-ref.html
new file mode 100644
index 0000000000..1b394e0d4f
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-001-ref.html
@@ -0,0 +1,4 @@
+<!DOCTYPE html>
+<html style="zoom: .5">
+  <div style="width: 500px; height: 500px; background: green"></div>
+</html>
diff --git a/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-001.html b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-001.html
new file mode 100644
index 0000000000..83fc95510f
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-001.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html reftest-zoom="0">
+  <link rel="help" href="https://firefox-source-docs.mozilla.org/layout/Reftest.html#zoom-tests-reftest-zoom-float"/>
+  <link rel="match" href="clamp-full-zoom-001-ref.html"/>
+  <!-- zoom.minPercent is set to 50 in the corresponding ini file. -->
+  <meta name="assert" content="Zoom is at least by zoom.minPercent."/>
+  <script src="/_mozilla/common/reftest-zoom.js"></script>
+  <div style="width: 500px; height: 500px; background: green"></div>
+</html>
diff --git a/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-002-ref.html b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-002-ref.html
new file mode 100644
index 0000000000..e2dd42fc86
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-002-ref.html
@@ -0,0 +1,4 @@
+<!DOCTYPE html>
+<html style="zoom: 2">
+  <div style="width: 250px; height: 250px; background: green"></div>
+</html>
diff --git a/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-002.html b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-002.html
new file mode 100644
index 0000000000..4fbe7edca1
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/clamp-full-zoom-002.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html reftest-zoom="10">
+  <link rel="help" href="https://firefox-source-docs.mozilla.org/layout/Reftest.html#zoom-tests-reftest-zoom-float"/>
+  <link rel="match" href="clamp-full-zoom-002-ref.html"/>
+  <!-- zoom.maxPercent is set to 200 in the corresponding ini file. -->
+  <meta name="assert" content="Zoom is at most by zoom.maxPercent."/>
+  <script src="/_mozilla/common/reftest-zoom.js"></script>
+  <div style="width: 250px; height: 250px; background: green"></div>
+</html>
diff --git a/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-001-ref.html b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-001-ref.html
new file mode 100644
index 0000000000..1b394e0d4f
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-001-ref.html
@@ -0,0 +1,4 @@
+<!DOCTYPE html>
+<html style="zoom: .5">
+  <div style="width: 500px; height: 500px; background: green"></div>
+</html>
diff --git a/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-001.html b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-001.html
new file mode 100644
index 0000000000..15c07de20d
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-001.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html reftest-zoom=".5">
+  <link rel="help" href="https://firefox-source-docs.mozilla.org/layout/Reftest.html#zoom-tests-reftest-zoom-float"/>
+  <link rel="match" href="set-full-zoom-001-ref.html"/>
+  <meta name="assert" content="Zoom less than one scales down the rect."/>
+  <script src="/_mozilla/common/reftest-zoom.js"></script>
+  <div style="width: 500px; height: 500px; background: green"></div>
+</html>
diff --git a/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-002-ref.html b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-002-ref.html
new file mode 100644
index 0000000000..e2dd42fc86
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-002-ref.html
@@ -0,0 +1,4 @@
+<!DOCTYPE html>
+<html style="zoom: 2">
+  <div style="width: 250px; height: 250px; background: green"></div>
+</html>
diff --git a/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-002.html b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-002.html
new file mode 100644
index 0000000000..f5d5e6a777
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-002.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html reftest-zoom="2">
+  <link rel="help" href="https://firefox-source-docs.mozilla.org/layout/Reftest.html#zoom-tests-reftest-zoom-float"/>
+  <link rel="match" href="set-full-zoom-002-ref.html"/>
+  <meta name="assert" content="Zoom more than one scales up the rect."/>
+  <script src="/_mozilla/common/reftest-zoom.js"></script>
+  <div style="width: 250px; height: 250px; background: green"></div>
+</html>
diff --git a/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-003-ref.html b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-003-ref.html
new file mode 100644
index 0000000000..ab500f2a2e
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-003-ref.html
@@ -0,0 +1,4 @@
+<!DOCTYPE html>
+<html style="zoom: 1">
+  <div style="width: 250px; height: 250px; background: green"></div>
+</html>
diff --git a/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-003.html b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-003.html
new file mode 100644
index 0000000000..b4bf803a89
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/infrastructure/reftest-zoom/set-full-zoom-003.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html>
+  <link rel="match" href="set-full-zoom-003-ref.html"/>
+  <meta name="assert" content="Initial zoom is equal to one."/>
+  <!-- Note that when running all the tests by alphabetical order, this test
+       would fail if set-zoom-002.html does not reset the zoom to one.
+       It would pass when re-running after a browser restart, though. -->
+  <div style="width: 250px; height: 250px; background: green"></div>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/README.md b/testing/web-platform/mozilla/tests/mathml/README.md
index 092dae0251..d579f67987 100644
--- a/testing/web-platform/mozilla/tests/mathml/README.md
+++ b/testing/web-platform/mozilla/tests/mathml/README.md
@@ -46,6 +46,17 @@ any specification:
    interpretation is unclear in current version of MathML Core.
    See [issue 132](https://github.com/w3c/mathml-core/issues/132).
 
+- `operator-stretching`: Tests for operator stretching, using Gecko-specific
+   methods that are not part of the current version of MathML Core.
+
+- `rtl`: Tests for RTL MathML, for aspects not completely defined in
+   MathML Core or for which we use things like scale transform for
+   mirroring.
+   See [issue 67](https://github.com/w3c/mathml-core/issues/67).
+
+- `scripts`: Tests for MathML scripted elements, for Gecko features
+   that are not defined in MathML Core or in contradiction with the spec.
+
 - `tables`: Tests for
    [table features](https://www.w3.org/TR/MathML3/chapter3.html#presm.tabmat)
    that are in the initial version of MathML Core.
@@ -55,3 +66,5 @@ any specification:
    [whitespace trimming in token elements](https://www.w3.org/TR/MathML3/chapter2.html#fund.collapse)
    which is not described in the initial version of MathML Core.
    See [issue 149](https://github.com/w3c/mathml-core/issues/149).
+
+- `zoom`: Tests to check MathML rendering at different zoom levels.
diff --git a/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-seudo-units-001-ref.html b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-001-ref.html
index 0b6efcbafc..0b6efcbafc 100644
--- a/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-seudo-units-001-ref.html
+++ b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-001-ref.html
diff --git a/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-seudo-units-001.html b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-001.html
index 80ba835109..5f976e63de 100644
--- a/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-seudo-units-001.html
+++ b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-001.html
@@ -3,7 +3,7 @@
   <head>
     <title>Test mpadded</title>
     <meta name="assert" content="Verify basic rendering of mpadded with pseudo units.">
-    <link rel="match" href="mpadded-seudo-units-001-ref.html">
+    <link rel="match" href="mpadded-pseudo-units-001-ref.html">
   </head>
   <body>
     <math>
diff --git a/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-002-ref.html b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-002-ref.html
new file mode 100644
index 0000000000..50f14246ee
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-002-ref.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Test mpadded</title>
+  </head>
+  <body>
+    <math>
+      <mpadded mathbackground="red" height="100height" depth="0">
+        <mphantom>
+          <mtext>&#x1D687;<!-- Mathematical Monospace Capital X --></mtext>
+        </mphantom>
+      </mpadded>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-002.html b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-002.html
new file mode 100644
index 0000000000..62e72310c4
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-002.html
@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Test mpadded</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=685628">
+    <link rel="match" href="mpadded-pseudo-units-002-ref.html">
+    <meta name="assert" content="height pseudo unit in mpadded@height refers to logical (not ink) metrics.">
+  </head>
+  <body>
+    <math>
+      <!--height in term of height should not depend on the characters-->
+      <mpadded mathbackground="red" height="100height" depth="0">
+        <mphantom>
+          <mtext>&#x1D692;<!-- Mathematical Monospace Small I --></mtext>
+        </mphantom>
+      </mpadded>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-003-ref.html b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-003-ref.html
new file mode 100644
index 0000000000..e01e6498f2
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-003-ref.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Test mpadded</title>
+  </head>
+  <body>
+    <math>
+      <mpadded mathbackground="red" height="100width" depth="0">
+        <mphantom>
+          <mtext>&#x1D687;<!-- Mathematical Monospace Capital X --></mtext>
+        </mphantom>
+      </mpadded>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-003.html b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-003.html
new file mode 100644
index 0000000000..9089c2cd5e
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-003.html
@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Test mpadded</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=685628">
+    <link rel="match" href="mpadded-pseudo-units-003-ref.html">
+    <meta name="assert" content="width pseudo unit in mpadded@height refers to logical (not ink) metrics.">
+  </head>
+  <body>
+    <math>
+      <!--height in term of width should not depend on the characters-->
+      <mpadded mathbackground="red" height="100width" depth="0">
+        <mphantom>
+          <mtext>&#x1D692;<!-- Mathematical Monospace Small I --></mtext>
+        </mphantom>
+      </mpadded>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-004-ref.html b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-004-ref.html
new file mode 100644
index 0000000000..e2a4943edd
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-004-ref.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Test mpadded</title>
+  </head>
+  <body>
+    <math>
+      <mpadded mathbackground="red" width="100width">
+        <mphantom>
+          <mtext>&#x1D687;<!-- Mathematical Monospace Capital X --></mtext>
+        </mphantom>
+      </mpadded>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-004.html b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-004.html
new file mode 100644
index 0000000000..e2433ef045
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/mpadded/mpadded-pseudo-units-004.html
@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Test mpadded</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=685628">
+    <link rel="match" href="mpadded-pseudo-units-004-ref.html">
+    <meta name="assert" content="pseudo unit specified in mpadded@width does not affect the height/depth">
+  </head>
+  <body>
+    <math>
+      <!--with fixed width, height + depth should not depend on the characters-->
+      <mpadded mathbackground="red" width="100width">
+        <mphantom>
+          <mtext>&#x1D692;<!-- Mathematical Monospace Small I --></mtext>
+        </mphantom>
+      </mpadded>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/overbar-width-1-ref.xhtml b/testing/web-platform/mozilla/tests/mathml/operator-stretching/overbar-width-1-ref.xhtml
new file mode 100644
index 0000000000..64e89f403f
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/overbar-width-1-ref.xhtml
@@ -0,0 +1,26 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+  <head>
+    <style type="text/css">
+      html { background-color: grey; }
+      div { display: inline-block;
+            font-size: 30px;
+            line-height: 60px; /* Ensure space for overbar */
+            border: 1px solid white;
+            padding: 2px; /* 10% error allowed in char selection */
+            background-color: black;
+            color: red; }
+    </style>
+  </head>
+<body>
+  <div>
+    <math xmlns="http://www.w3.org/1998/Math/MathML">
+      <mphantom>
+	<mover>
+	  <mi>ai</mi>
+	  <mo>&#xaf;</mo>
+	</mover>
+      </mphantom>
+    </math>
+  </div>
+</body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/overbar-width-1.xhtml b/testing/web-platform/mozilla/tests/mathml/operator-stretching/overbar-width-1.xhtml
new file mode 100644
index 0000000000..317504a007
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/overbar-width-1.xhtml
@@ -0,0 +1,27 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+  <head>
+    <title>Check width of stretchy OverBar</title>
+    <link rel="match" href="overbar-width-1.xhtml"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=427666"/>
+    <style type="text/css">
+      html { background-color: grey; }
+      div { display: inline-block;
+            font-size: 30px;
+            line-height: 60px; /* Ensure space for overbar */
+            border: 1px solid white;
+            padding: 2px; /* 10% error allowed in char selection */
+            background-color: black;
+            color: black; }
+    </style>
+  </head>
+<body>
+  <div>
+    <math xmlns="http://www.w3.org/1998/Math/MathML">
+      <mover>
+	<mi>ai</mi>
+	<mo>&#xaf;</mo>
+      </mover>
+    </math>
+  </div>
+</body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-001-ref.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-001-ref.html
new file mode 100644
index 0000000000..36a2a574f8
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-001-ref.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Maximal size for a vertical arrow stretched by scaling</title>
+  </head>
+  <body>
+    <table style="position: absolute;">
+      <tr>
+        <td><div style="height: 200px; width: 5px; background: black"/></td>
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <mrow>
+              <mspace height="50px" depth="50px" width="5px"
+                      style="background: yellow" />
+              <mspace height="55px" depth="55px" width="50px"
+                      style="background: red;"/>
+            </mrow>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-001.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-001.html
new file mode 100644
index 0000000000..77b355f404
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-001.html
@@ -0,0 +1,48 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Maximal size for a vertical arrow stretched by scaling</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=414277">
+    <link rel="match" href="scale-stretchy-001-ref.html">
+    <meta name="assert" content="Verify maximal height of vertical operator stretched by scaling.">
+  </head>
+  <body>
+    <!-- This assumes that the system fonts do not provide a way to draw a
+         bigger U+290B DOWNWARDS TRIPLE ARROW and that preference
+         `mathml.scale_stretchy_operators` is enabled, so that we exercise
+         stretching of largeop using a scale. This test may still pass if
+         stretching is not performed via a scale though. -->
+    <table style="position: absolute;">
+      <tr>
+        <td><div style="height: 200px; width: 5px; background: black"/></td>
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <mrow>
+              <mspace height="50px" depth="50px" width="5px"
+                      style="background: yellow" />
+              <mo style="color: blue;">⤋</mo>
+            </mrow>
+          </math>
+        </td>
+      </tr>
+    </table>
+    <!-- The red rect is slightly taller than the target size so it should
+         completely cover the operator. -->
+    <table style="position: absolute;">
+      <tr>
+        <td><div style="height: 200px; width: 5px; background: black"/></td>
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <mrow>
+              <mspace height="50px" depth="50px" width="5px"
+                      style="background: yellow" />
+              <mspace height="55px" depth="55px" width="50px"
+                      style="background: red;"/>
+            </mrow>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-002-ref.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-002-ref.html
new file mode 100644
index 0000000000..7b0e084364
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-002-ref.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Minimal size for a vertical arrow stretched by scaling</title>
+  </head>
+  <body>
+    <table style="position: absolute;">
+      <tr>
+        <td><div style="height: 200px; width: 5px; background: black"/></td>
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <mrow>
+              <mspace height="50px" depth="50px" width="5px"
+                      style="background: yellow" />
+              <mspace height="44px" depth="44px" width="50px"
+                      style="background: green;"/>
+            </mrow>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-002.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-002.html
new file mode 100644
index 0000000000..db39cc97cc
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-002.html
@@ -0,0 +1,48 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Minimal size for a vertical arrow stretched by scaling</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=414277">
+    <link rel="mismatch" href="scale-stretchy-002-ref.html">
+    <meta name="assert" content="Verify minimal height of vertical operator stretched by scaling.">
+  </head>
+  <body>
+    <!-- This assumes that the system fonts do not provide a way to draw a
+         bigger U+290B DOWNWARDS TRIPLE ARROW and that preference
+         `mathml.scale_stretchy_operators` is enabled, so that we exercise
+         stretching of largeop using a scale. This test may still pass if
+         stretching is not performed via a scale though. -->
+    <table style="position: absolute;">
+      <tr>
+        <td><div style="height: 200px; width: 5px; background: black"/></td>
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <mrow>
+              <mspace height="50px" depth="50px" width="5px"
+                      style="background: yellow" />
+              <mo style="color: blue;">⤋</mo>
+            </mrow>
+          </math>
+        </td>
+      </tr>
+    </table>
+    <!-- The green rect is slightly shorter than the target size so it should
+         not completely cover the operator. -->
+    <table style="position: absolute;">
+      <tr>
+        <td><div style="height: 200px; width: 5px; background: black"/></td>
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <mrow>
+              <mspace height="50px" depth="50px" width="5px"
+                      style="background: yellow" />
+              <mspace height="44px" depth="44px" width="50px"
+                      style="background: green;"/>
+            </mrow>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-003-ref.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-003-ref.html
new file mode 100644
index 0000000000..b5935f306a
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-003-ref.html
@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Maximal size for a horizontal arrow stretched by scaling</title>
+  </head>
+  <body>
+    <table style="position: absolute;">
+      <tr align="center">
+        <td><div style="width: 200px; height: 5px; background: black"/></td>
+      </tr>
+      <tr align="center">
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <munder accentunder="false">
+              <mspace width="100px" height="5px" style="background: yellow"/>
+              <mspace width="110px" height="25px" depth="25px"
+                      style="background: red;"/>
+            </munder>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-003.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-003.html
new file mode 100644
index 0000000000..7191a329b4
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-003.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Maximal size for a horizontal arrow stretched by scaling</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=414277">
+    <link rel="match" href="scale-stretchy-003-ref.html">
+    <meta name="assert" content="Verify maximal height of horizontal operator stretched by scaling.">
+  </head>
+  <body>
+    <!-- This assumes that the system fonts do not provide a way to draw a
+         bigger U+21DB RIGHTWARDS TRIPLE ARROW and that preference
+         `mathml.scale_stretchy_operators` is enabled, so that we exercise
+         stretching of largeop using a scale. This test may still pass if
+         stretching is not performed via a scale though. -->
+    <table style="position: absolute;">
+      <tr align="center">
+        <td><div style="width: 200px; height: 5px; background: black"/></td>
+      </tr>
+      <tr align="center">
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <munder accentunder="false">
+              <mspace width="100px" height="5px" style="background: yellow"/>
+              <mo style="color: blue;">⇛</mo>
+            </munder>
+          </math>
+        </td>
+      </tr>
+    </table>
+    <!-- The red rect is slightly wider than the target size so it should
+         completely cover the operator. -->
+    <table style="position: absolute;">
+      <tr align="center">
+        <td><div style="width: 200px; height: 5px; background: black"/></td>
+      </tr>
+      <tr align="center">
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <munder accentunder="false">
+              <mspace width="100px" height="5px" style="background: yellow"/>
+              <mspace width="110px" height="25px" depth="25px"
+                      style="background: red;"/>
+            </munder>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-004-ref.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-004-ref.html
new file mode 100644
index 0000000000..ad797c46d1
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-004-ref.html
@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Minimal size for a horizontal arrow stretched by scaling (reference)</title>
+  </head>
+  <body>
+    <table style="position: absolute;">
+      <tr align="center">
+        <td><div style="width: 200px; height: 5px; background: black"/></td>
+      </tr>
+      <tr align="center">
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <munder>
+              <mspace width="100px" height="5px" style="background: yellow"/>
+              <mspace width="88px" height="25px" depth="25px"
+                      style="background: green;"/>
+            </munder>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-004.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-004.html
new file mode 100644
index 0000000000..f7d36b36e2
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-004.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Minimal size for a horizontal arrow stretched by scaling</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=414277">
+    <link rel="mismatch" href="scale-stretchy-004-ref.html">
+    <meta name="assert" content="Verify minimal width of horizontal operator stretched by scaling.">
+  </head>
+  <body>
+    <!-- This assumes that the system fonts do not provide a way to draw a
+         bigger U+21DB RIGHTWARDS TRIPLE ARROW and that preference
+         `mathml.scale_stretchy_operators` is enabled, so that we exercise
+         stretching of largeop using a scale. This test may still pass if
+         stretching is not performed via a scale though. -->
+    <table style="position: absolute;">
+      <tr align="center">
+        <td><div style="width: 200px; height: 5px; background: black"/></td>
+      </tr>
+      <tr align="center">
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <munder>
+              <mspace width="100px" height="5px" style="background: yellow"/>
+              <mo style="color: blue;">⇛</mo>
+            </munder>
+          </math>
+        </td>
+      </tr>
+    </table>
+    <!-- The green rect is slightly narrower than the target size so it should
+         not completely cover the operator. -->
+    <table style="position: absolute;">
+      <tr align="center">
+        <td><div style="width: 200px; height: 5px; background: black"/></td>
+      </tr>
+      <tr align="center">
+        <td>
+          <math xmlns="http://www.w3.org/1998/Math/MathML">
+            <munder>
+              <mspace width="100px" height="5px" style="background: yellow"/>
+              <mspace width="88px" height="25px" depth="25px"
+                      style="background: green;"/>
+            </munder>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-005-ref.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-005-ref.html
new file mode 100644
index 0000000000..c1bd50201b
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-005-ref.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Largeop in display mode stretched by scaling (reference)</title>
+  </head>
+  <body>
+    <math display="block">
+      <mo largeop="false">⨌</mo>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-005.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-005.html
new file mode 100644
index 0000000000..3f20eed587
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/scale-stretchy-005.html
@@ -0,0 +1,20 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Largeop in display mode stretched by scaling</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=414277">
+    <link rel="mismatch" href="scale-stretchy-005-ref.html">
+    <meta name="assert" content="Verify that a displaystyle largeop can be drawn bigger by scaling.">
+  </head>
+  <body>
+    <!-- This assumes that the system fonts do not provide a way to draw a
+         bigger U+2A0C QUADRUPLE INTEGRAL OPERATOR and that preference
+         `mathml.scale_stretchy_operators` is enabled, so that we exercise
+         stretching of largeop using a scale. This test may still pass if
+         stretching is not performed via a scale though. -->
+    <math display="block">
+      <mo largeop="true">⨌</mo>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/stretch-equal-sign-with-default-font-ref.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/stretch-equal-sign-with-default-font-ref.html
new file mode 100644
index 0000000000..074d0e0415
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/stretch-equal-sign-with-default-font-ref.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Horizontal stretching of equal of U+003D EQUAL SIGN with default font (reference)</title>
+  </head>
+  <body>
+    <math>
+      <munder>
+        <mi>AVERYLONGBASE</mi>
+        <mo stretchy="false">=</mo>
+      </munder>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/stretch-equal-sign-with-default-font.html b/testing/web-platform/mozilla/tests/mathml/operator-stretching/stretch-equal-sign-with-default-font.html
new file mode 100644
index 0000000000..2ddcdbe683
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/stretch-equal-sign-with-default-font.html
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Horizontal stretching of U+003D EQUAL SIGN with default font</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=854339">
+    <link rel="help" href="https://w3c.github.io/mathml-core/#unicode-based-glyph-assemblies">
+    <link rel="mismatch" href="stretch-equal-sign-with-default-font-ref.html">
+    <meta name="assert" content="Verify EQUAL SIGN can be stretched horizontally with default fonts.">
+  </head>
+  <body>
+    <math>
+      <munder>
+        <mi>AVERYLONGBASE</mi>
+        <mo stretchy="true">=</mo>
+      </munder>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/underbar-width-1-ref.xhtml b/testing/web-platform/mozilla/tests/mathml/operator-stretching/underbar-width-1-ref.xhtml
new file mode 100644
index 0000000000..737673ccb1
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/underbar-width-1-ref.xhtml
@@ -0,0 +1,26 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+  <head>
+    <style type="text/css">
+      html { background-color: grey; }
+      div { display: inline-block;
+            font-size: 30px;
+            line-height: 60px; /* Ensure space for underbar */
+            border: 1px solid white;
+            padding: 2px; /* 10% error allowed in char selection */
+            background-color: black;
+            color: red; }
+    </style>
+  </head>
+<body>
+  <div>
+    <math xmlns="http://www.w3.org/1998/Math/MathML">
+      <mphantom>
+	<munder>
+	  <mn>1</mn>
+	  <mo>&#x332;</mo>
+	</munder>
+      </mphantom>
+    </math>
+  </div>
+</body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/operator-stretching/underbar-width-1.xhtml b/testing/web-platform/mozilla/tests/mathml/operator-stretching/underbar-width-1.xhtml
new file mode 100644
index 0000000000..d2539d74ec
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/operator-stretching/underbar-width-1.xhtml
@@ -0,0 +1,27 @@
+<html xmlns="http://www.w3.org/1999/xhtml">
+  <head>
+    <title>Check width of stretchy UnderBar</title>
+    <link rel="match" href="underbar-width-1.xhtml"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=428863"/>
+    <style type="text/css">
+      html { background-color: grey; }
+      div { display: inline-block;
+            font-size: 30px;
+            line-height: 60px; /* Ensure space for underbar */
+            border: 1px solid white;
+            padding: 2px; /* 10% error allowed in char selection */
+            background-color: black;
+            color: black; }
+    </style>
+  </head>
+<body>
+  <div>
+    <math xmlns="http://www.w3.org/1998/Math/MathML">
+      <munder>
+	<mn>1</mn>
+	<mo>&#x332;</mo>
+      </munder>
+    </math>
+  </div>
+</body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-001-ref.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-001-ref.html
new file mode 100644
index 0000000000..9430d2d7f9
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-001-ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<math><mo>(</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-001.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-001.html
new file mode 100644
index 0000000000..38a322f725
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-001.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+<link rel="mismatch" href="mirror-op-001-ref.html">
+<meta name="assert" content="fence is mirrored in RTL mode">
+<math dir="rtl"><mo>(</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-002-ref.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-002-ref.html
new file mode 100644
index 0000000000..2273b3a1e5
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-002-ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<math><mo>)</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-002.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-002.html
new file mode 100644
index 0000000000..82f0b0d669
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-002.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+<link rel="mismatch" href="mirror-op-002-ref.html">
+<meta name="assert" content="fence is mirrored in RTL mode">
+<math dir="rtl"><mo>)</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-003-ref.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-003-ref.html
new file mode 100644
index 0000000000..83522ce6bd
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-003-ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<math><mo>[</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-003.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-003.html
new file mode 100644
index 0000000000..773f44a71d
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-003.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+<link rel="mismatch" href="mirror-op-003-ref.html">
+<meta name="assert" content="fence is mirrored in RTL mode">
+<math dir="rtl"><mo>[</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-004-ref.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-004-ref.html
new file mode 100644
index 0000000000..1bc501a43e
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-004-ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<math><mo>]</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-004.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-004.html
new file mode 100644
index 0000000000..0292d8e976
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-004.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+<link rel="mismatch" href="mirror-op-004-ref.html">
+<meta name="assert" content="fence is mirrored in RTL mode">
+<math dir="rtl"><mo>]</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-005-ref.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-005-ref.html
new file mode 100644
index 0000000000..5dec3e3c0a
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-005-ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<math><mo>{</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-005.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-005.html
new file mode 100644
index 0000000000..121928e03f
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-005.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+<link rel="mismatch" href="mirror-op-005-ref.html">
+<meta name="assert" content="fence is mirrored in RTL mode">
+<math dir="rtl"><mo>{</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-006-ref.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-006-ref.html
new file mode 100644
index 0000000000..765c29e858
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-006-ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<math><mo>}</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-006.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-006.html
new file mode 100644
index 0000000000..431e636ba9
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-006.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+<link rel="mismatch" href="mirror-op-006-ref.html">
+<meta name="assert" content="fence is mirrored in RTL mode">
+<math dir="rtl"><mo>}</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-007-ref.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-007-ref.html
new file mode 100644
index 0000000000..efe4bf1f89
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-007-ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<math><mo>∑</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-007.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-007.html
new file mode 100644
index 0000000000..4266e71a97
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-007.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+<link rel="mismatch" href="mirror-op-007-ref.html">
+<meta name="assert" content="sum is mirrored in RTL mode">
+<math dir="rtl"><mo>∑</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-008-ref.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-008-ref.html
new file mode 100644
index 0000000000..813900251d
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-008-ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<math><mo>√</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-008.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-008.html
new file mode 100644
index 0000000000..edee9f5f14
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-008.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+<link rel="mismatch" href="mirror-op-008-ref.html">
+<meta name="assert" content="square root is mirrored in RTL mode">
+<math dir="rtl"><mo>√</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-009-ref.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-009-ref.html
new file mode 100644
index 0000000000..efc9648228
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-009-ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<math><mo>∫</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-009.html b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-009.html
new file mode 100644
index 0000000000..d90e4701a3
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/rtl/mirror-op-009.html
@@ -0,0 +1,6 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+<link rel="mismatch" href="mirror-op-009-ref.html">
+<meta name="assert" content="integral is mirrored in RTL mode">
+<math dir="rtl"><mo>∫</mo></math>
diff --git a/testing/web-platform/mozilla/tests/mathml/scripts/mmultiscripts-empty-scripts-ref.html b/testing/web-platform/mozilla/tests/mathml/scripts/mmultiscripts-empty-scripts-ref.html
new file mode 100644
index 0000000000..2b47eb4d1b
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/scripts/mmultiscripts-empty-scripts-ref.html
@@ -0,0 +1,75 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
+    <title>Comparison of script elements</title>
+  </head>
+  <body>
+    msubsup:
+    <math>
+      <mmultiscripts style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+        <mtext style="background-color: rgba(0, 255, 0, 0.4);">ccc</mtext>
+      </mmultiscripts>
+    </math>
+
+    <br><br>
+
+    msubsup:
+    <math>
+      <mmultiscripts style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+        <none/>
+      </mmultiscripts>
+    </math>
+
+    <br><br>
+
+    msup / msubsup:
+    <math>
+      <mmultiscripts style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <none/>
+        <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+      </mmultiscripts>
+    </math>
+
+    <math>
+      <mmultiscripts style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <none/>
+        <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+      </mmultiscripts>
+    </math>
+
+    <br><br>
+
+
+    mrow / msub:
+    <math>
+      <mrow style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+      </mrow>
+    </math>
+
+    <math>
+      <mrow style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+      </mrow>
+    </math>
+
+    <br><br>
+
+    msupsub:
+    <math>
+      <mmultiscripts style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <none />
+        <none />
+      </mmultiscripts>
+    </math>
+
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/scripts/mmultiscripts-empty-scripts.html b/testing/web-platform/mozilla/tests/mathml/scripts/mmultiscripts-empty-scripts.html
new file mode 100644
index 0000000000..31473c2a72
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/scripts/mmultiscripts-empty-scripts.html
@@ -0,0 +1,77 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Comparison of script elements</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=669932">
+    <link rel="match" href="mmultiscripts-empty-scripts-ref.html">
+    <meta name="assert" content="Verify elements with empty sub/sup scripts render the same as equivalent elements with less scripts.">
+  </head>
+  <body>
+    msubsup:
+    <math>
+      <msubsup style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+        <mtext style="background-color: rgba(0, 255, 0, 0.4);">ccc</mtext>
+      </msubsup>
+    </math>
+
+    <br><br>
+
+    <!-- Different rules apply to msub, so it won't provide equivalent output -->
+    msubsup:
+    <math>
+      <msubsup style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+        <mrow></mrow>
+      </msubsup>
+    </math>
+
+    <br><br>
+
+    msup / msubsup:
+    <math>
+      <msup style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+      </msup>
+    </math>
+
+    <math>
+      <msubsup style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <mrow></mrow>
+        <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+      </msubsup>
+    </math>
+
+    <br><br>
+
+    mrow / msub:
+    <math>
+      <mrow style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+      </mrow>
+    </math>
+
+    <math>
+      <msub style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <mrow></mrow>
+      </msub>
+    </math>
+
+    <br><br>
+
+    msupsub:
+    <math>
+      <msubsup style="background: red;">
+        <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        <mrow></mrow>
+        <mrow></mrow>
+      </msubsup>
+    </math>
+
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/scripts/munderover-empty-scripts-ref.html b/testing/web-platform/mozilla/tests/mathml/scripts/munderover-empty-scripts-ref.html
new file mode 100644
index 0000000000..5e0ba0bac1
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/scripts/munderover-empty-scripts-ref.html
@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Test munderover with empty scripts</title>
+  </head>
+  <body>
+
+    <p>munder / munderover with empty overscript:
+      <math>
+        <munderover style="background: red;">
+          <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+          <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+          <mspace></mspace>
+        </munderover>
+      </math>
+    </p>
+
+    <p>mover / munderover with empty underscript:
+      <math>
+        <munderover style="background: red;">
+          <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+          <mspace></mspace>
+          <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+        </munderover>
+      </math>
+    </p>
+
+    <p>mrow / munder with empty scripts:
+      <math>
+        <munderover style="background: red;">
+          <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+          <mspace></mspace>
+          <mspace></mspace>
+        </munderover>
+      </math>
+    </p>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/scripts/munderover-empty-scripts.html b/testing/web-platform/mozilla/tests/mathml/scripts/munderover-empty-scripts.html
new file mode 100644
index 0000000000..671c889211
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/scripts/munderover-empty-scripts.html
@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Test munderover with empty scripts</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=669932">
+    <link rel="match" href="munderover-empty-scripts-ref.html">
+    <meta name="assert" content="Verify elements with empty under/over scripts render the same as equivalent elements with less scripts.">
+  </head>
+  <body>
+
+    <p>munder / munderover with empty overscript:
+      <math>
+        <munder style="background: red;">
+          <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+          <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+        </munder>
+      </math>
+    </p>
+
+    <p>mover / munderover with empty underscript:
+      <math>
+        <mover style="background: red;">
+          <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+          <mtext style="background-color: rgba(0, 255, 0, 0.4);">bbb</mtext>
+        </mover>
+      </math>
+    </p>
+
+    <p>mrow / munder with empty scripts:
+      <math>
+        <mrow style="background: red;">
+          <mtext style="background-color: rgba(0, 0, 255, 0.4);">AAA</mtext>
+        </mrow>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/scripts/scriptlevel-movablelimits-accent-ref.html b/testing/web-platform/mozilla/tests/mathml/scripts/scriptlevel-movablelimits-accent-ref.html
new file mode 100644
index 0000000000..20a0f65ec7
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/scripts/scriptlevel-movablelimits-accent-ref.html
@@ -0,0 +1,28 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <title>Test accent/accentunder (reference)</title>
+  </head>
+  <body>
+    <math displaystyle="false">
+      <munderover>
+        <mo>∑</mo>
+        <mi>a</mi>
+        <mi>b</mi>
+      </munderover>
+    </math>
+    <math displaystyle="false">
+      <munder>
+        <mo>∑</mo>
+        <mi>a</mi>
+      </munder>
+    </math>
+    <math displaystyle="false">
+      <mover>
+        <mo>∑</mo>
+        <mi>a</mi>
+      </mover>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/scripts/scriptlevel-movablelimits-accent.html b/testing/web-platform/mozilla/tests/mathml/scripts/scriptlevel-movablelimits-accent.html
new file mode 100644
index 0000000000..4da97dadbf
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/scripts/scriptlevel-movablelimits-accent.html
@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <title>Test accent/accentunder</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=669713">
+    <link rel="help" href="https://www.w3.org/TR/MathML3/chapter3.html#presm.munder">
+    <link rel="help" href="https://www.w3.org/TR/MathML3/chapter3.html#presm.mover">
+    <link rel="help" href="https://www.w3.org/TR/MathML3/chapter3.html#presm.munderover">
+    <link rel="match" href="scriptlevel-movablelimits-accent-ref.html">
+    <meta name="assert" content="Verify accentunder='true' or accent='true' is ignored when an underover element is laid out as a subsup element.">
+  </head>
+  <body>
+    <!-- Per MathML3, setting accentunder/accent to true prevents scriptlevel
+         from being incremented, however such attributes should be ignored when
+         scripts are drawn as subcript/superscript, which is the case here
+         because U+2211 N-ARY SUMMATION defaults to movablelimits="true". -->
+    <math displaystyle="false">
+      <munderover accentunder="true" accent="true">
+        <mo>∑</mo>
+        <mi>a</mi>
+        <mi>b</mi>
+      </munderover>
+    </math>
+    <math displaystyle="false">
+      <munder accentunder="true">
+        <mo>∑</mo>
+        <mi>a</mi>
+      </munder>
+    </math>
+    <math displaystyle="false">
+      <mover accent="true">
+        <mo>∑</mo>
+        <mi>a</mi>
+      </mover>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/scripts/subscript-italic-correction.html b/testing/web-platform/mozilla/tests/mathml/scripts/subscript-italic-correction.html
new file mode 100644
index 0000000000..2c39d825ff
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/scripts/subscript-italic-correction.html
@@ -0,0 +1,62 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>italic correction for subscripts</title>
+    <meta charset="utf-8"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=945254">
+    <link rel="help" href="https://w3c.github.io/mathml-core/#dfn-italic-correction">
+    <script src="/resources/testharness.js"></script>
+    <script src="/resources/testharnessreport.js"></script>
+    <script type="text/javascript">
+      function verifyItalicCorrections()
+      {
+        var epsilon = 2;
+        for (var i = 0; i < 8; i += 2) {
+          var sub = document.getElementById("s" + i);
+          var sup = document.getElementById("s" + (i+1));
+          var italicCorrection =
+           sup.getBoundingClientRect().left - sub.getBoundingClientRect().left;
+          assert_greater_than(italicCorrection, epsilon);
+        }
+      }
+
+      promise_test(() => {
+        return new Promise(resolve => {
+          window.addEventListener("load", resolve);
+        }).then(verifyItalicCorrections);
+      }, "Italic correction of base is used to place subscripts.");
+    </script>
+    <style>
+      math { font-size: 50px; }
+    </style>
+  </head>
+  <body>
+
+    <div>
+      <math>
+        <msubsup>
+          <mi mathbackground="#5f5">f</mi>
+          <mspace id="s0" width="50px" height="50px" mathbackground="blue"/>
+          <mspace id="s1" width="50px" height="50px" mathbackground="blue"/>
+        </msubsup>
+      </math>
+    </div>
+
+    <br/>
+
+    <div>
+      <math>
+        <mmultiscripts>
+          <mi mathbackground="#5f5">f</mi>
+          <mspace id="s2" width="50px" height="50px" mathbackground="blue"/>
+          <mspace id="s3" width="50px" height="50px" mathbackground="blue"/>
+          <mspace id="s4" width="50px" height="50px" mathbackground="blue"/>
+          <mspace id="s5" width="50px" height="50px" mathbackground="blue"/>
+          <mspace id="s6" width="50px" height="50px" mathbackground="blue"/>
+          <mspace id="s7" width="50px" height="50px" mathbackground="blue"/>
+        </mmultiscripts>
+      </math>
+    </div>
+
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1.html
new file mode 100644
index 0000000000..1882b78275
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="hidden">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="hidden">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="visible">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1a.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1a.html
new file mode 100644
index 0000000000..9d48a0971f
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1a.html
@@ -0,0 +1,51 @@
+<!DOCTYPE html>
+<html reftest-zoom=".5">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="hidden">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="hidden">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="visible">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1b.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1b.html
new file mode 100644
index 0000000000..d72cb252c7
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1b.html
@@ -0,0 +1,51 @@
+<!DOCTYPE html>
+<html reftest-zoom=".4">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="hidden">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="hidden">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="visible">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1c.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1c.html
new file mode 100644
index 0000000000..d0708973f0
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1c.html
@@ -0,0 +1,51 @@
+<!DOCTYPE html>
+<html reftest-zoom=".3">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="hidden">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="hidden">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="visible">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1d.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1d.html
new file mode 100644
index 0000000000..91004d1acd
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-1d.html
@@ -0,0 +1,51 @@
+<!DOCTYPE html>
+<html reftest-zoom=".2">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="hidden">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="hidden">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="visible">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2.html
new file mode 100644
index 0000000000..2b5df8e97b
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="hidden">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="visible">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="hidden">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2a.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2a.html
new file mode 100644
index 0000000000..33368521ad
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2a.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html reftest-zoom="0.5">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="hidden">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="visible">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="hidden">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2b.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2b.html
new file mode 100644
index 0000000000..b88f094c79
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2b.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html reftest-zoom="0.4">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="hidden">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="visible">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="hidden">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2c.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2c.html
new file mode 100644
index 0000000000..b9c83c19a3
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2c.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html reftest-zoom="0.3">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="hidden">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="visible">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="hidden">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2d.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2d.html
new file mode 100644
index 0000000000..836f12b4e9
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-2d.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html reftest-zoom="0.2">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="hidden">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="visible">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="hidden">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3.html
new file mode 100644
index 0000000000..245a1d6b6b
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="visible">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="hidden">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="hidden">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3a.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3a.html
new file mode 100644
index 0000000000..30017437e5
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3a.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html reftest-zoom="0.5">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="visible">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="hidden">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="hidden">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3b.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3b.html
new file mode 100644
index 0000000000..2f6ac92624
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3b.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html reftest-zoom="0.4">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="visible">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="hidden">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="hidden">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3c.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3c.html
new file mode 100644
index 0000000000..5886cfeb63
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3c.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html reftest-zoom="0.3">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="visible">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="hidden">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="hidden">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3d.html b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3d.html
new file mode 100644
index 0000000000..2802cb343e
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/mathml/zoom/radicalbar-3d.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html reftest-zoom="0.2">
+  <head>
+    <link rel="mismatch" href="about:blank"/>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1011020"/>
+    <script src="/_mozilla/common/reftest-zoom.js"></script>
+    <!-- Default to invisible text -->
+    <style type="text/css" media="screen, print">
+      .hidden {
+          color: white;
+      }
+      .visible {
+          color: black;
+      }
+    </style>
+  </head>
+  <body>
+    <!-- Nest successive radicals and test that the horizontal bar of one of them is drawn.
+         Because the comparison is for inequality with about:blank, at most one can be visible -->
+    <math>
+      <mrow>
+        <msqrt class="hidden">
+          <mspace width="1em" height="1em" />
+          <msqrt class="hidden">
+            <mspace width="1em" height="1em" />
+            <msqrt class="hidden">
+              <mspace width="1em" height="1em" />
+              <msqrt class="hidden">
+                <mspace width="1em" height="1em" />
+                <msqrt class="visible">
+                  <mspace width="1em" height="1em" />
+                  <msqrt class="hidden">
+                    <mspace width="1em" height="1em" />
+                    <msqrt class="hidden">
+                      <mspace width="20em" height="1em" />
+                    </msqrt>
+                  </msqrt>
+                </msqrt>
+              </msqrt>
+            </msqrt>
+          </msqrt>
+        </msqrt>
+      </mrow>
+    </math>
+
+    <!-- Block out all but the horizontal bar of the visible radical -->
+    <div style="position: absolute; top: 5px; left: 0px;
+                width: 20em; height: 10em; background: white;"></div>
+  </body>
+</html>
diff --git a/testing/web-platform/mozilla/tests/webdriver/bidi/browsing_context/navigate/error.py b/testing/web-platform/mozilla/tests/webdriver/bidi/browsing_context/navigate/error.py
index 374359d1ae..ea76b13727 100644
--- a/testing/web-platform/mozilla/tests/webdriver/bidi/browsing_context/navigate/error.py
+++ b/testing/web-platform/mozilla/tests/webdriver/bidi/browsing_context/navigate/error.py
@@ -1,4 +1,3 @@
-import os
 from copy import deepcopy
 
 import pytest
@@ -7,13 +6,12 @@ from tests.bidi.browsing_context.navigate import navigate_and_assert
 pytestmark = pytest.mark.asyncio
 
 
-async def test_insecure_certificate(configuration, url, custom_profile, geckodriver):
-    try:
-        # Create a new profile and remove the certificate storage so that
-        # loading a HTTPS page will cause an insecure certificate error
-        os.remove(os.path.join(custom_profile.profile, "cert9.db"))
-    except Exception:
-        pass
+async def test_insecure_certificate(
+    configuration, url, create_custom_profile, geckodriver
+):
+    # Create a fresh profile without any item in the certificate storage so that
+    # loading a HTTPS page will cause an insecure certificate error
+    custom_profile = create_custom_profile(clone=False)
 
     config = deepcopy(configuration)
     config["capabilities"]["moz:firefoxOptions"]["args"] = [
diff --git a/testing/web-platform/mozilla/tests/webdriver/bidi/storage/delete_cookies/__init__.py b/testing/web-platform/mozilla/tests/webdriver/bidi/storage/delete_cookies/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/webdriver/bidi/storage/delete_cookies/__init__.py
diff --git a/testing/web-platform/mozilla/tests/webdriver/bidi/storage/delete_cookies/partition.py b/testing/web-platform/mozilla/tests/webdriver/bidi/storage/delete_cookies/partition.py
new file mode 100644
index 0000000000..d8e2729fe2
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/webdriver/bidi/storage/delete_cookies/partition.py
@@ -0,0 +1,114 @@
+import pytest
+from tests.bidi import recursive_compare
+from tests.support.helpers import get_origin_from_url
+from webdriver.bidi.modules.network import NetworkStringValue
+from webdriver.bidi.modules.storage import (
+    BrowsingContextPartitionDescriptor,
+    PartialCookie,
+)
+
+pytestmark = pytest.mark.asyncio
+
+
+@pytest.mark.parametrize(
+    "with_document_cookie",
+    [True, False],
+    ids=["with document cookie", "with set cookie"],
+)
+async def test_partition_context(
+    bidi_session,
+    new_tab,
+    test_page,
+    domain_value,
+    add_cookie,
+    set_cookie,
+    with_document_cookie,
+):
+    await bidi_session.browsing_context.navigate(
+        context=new_tab["context"], url=test_page, wait="complete"
+    )
+
+    cookie_name = "foo"
+    cookie_value = "bar"
+    source_origin = get_origin_from_url(test_page)
+    partition = BrowsingContextPartitionDescriptor(new_tab["context"])
+    if with_document_cookie:
+        await add_cookie(new_tab["context"], cookie_name, cookie_value)
+    else:
+        await set_cookie(
+            cookie=PartialCookie(
+                domain=domain_value(),
+                name=cookie_name,
+                value=NetworkStringValue(cookie_value),
+            ),
+            partition=partition,
+        )
+
+    result = await bidi_session.storage.delete_cookies(partition=partition)
+    recursive_compare({"partitionKey": {"sourceOrigin": source_origin}}, result)
+
+    result = await bidi_session.storage.get_cookies(partition=partition)
+    assert result["cookies"] == []
+
+
+@pytest.mark.parametrize("domain", ["", "alt"], ids=["same_origin", "cross_origin"])
+async def test_partition_context_iframe_with_set_cookie(
+    bidi_session, new_tab, inline, domain_value, domain, set_cookie
+):
+    iframe_url = inline("<div id='in-iframe'>foo</div>", domain=domain)
+    page_url = inline(f"<iframe src='{iframe_url}'></iframe>")
+    await bidi_session.browsing_context.navigate(
+        context=new_tab["context"], url=page_url, wait="complete"
+    )
+    source_origin = get_origin_from_url(iframe_url)
+
+    contexts = await bidi_session.browsing_context.get_tree(root=new_tab["context"])
+    iframe_context = contexts[0]["children"][0]
+
+    cookie_name = "foo"
+    cookie_value = "bar"
+    frame_partition = BrowsingContextPartitionDescriptor(iframe_context["context"])
+    await set_cookie(
+        cookie=PartialCookie(
+            domain=domain_value(domain),
+            name=cookie_name,
+            value=NetworkStringValue(cookie_value),
+        ),
+        partition=frame_partition,
+    )
+
+    result = await bidi_session.storage.delete_cookies(partition=frame_partition)
+    recursive_compare({"partitionKey": {"sourceOrigin": source_origin}}, result)
+
+    result = await bidi_session.storage.get_cookies(partition=frame_partition)
+    assert result["cookies"] == []
+
+
+# Because of Dynamic First-Party Isolation, adding the cookie with `document.cookie`
+# works only with same-origin iframes.
+async def test_partition_context_same_origin_iframe_with_document_cookie(
+    bidi_session,
+    new_tab,
+    inline,
+    add_cookie,
+):
+    iframe_url = inline("<div id='in-iframe'>foo</div>")
+    page_url = inline(f"<iframe src='{iframe_url}'></iframe>")
+    await bidi_session.browsing_context.navigate(
+        context=new_tab["context"], url=page_url, wait="complete"
+    )
+    source_origin = get_origin_from_url(iframe_url)
+
+    contexts = await bidi_session.browsing_context.get_tree(root=new_tab["context"])
+    iframe_context = contexts[0]["children"][0]
+
+    cookie_name = "foo"
+    cookie_value = "bar"
+    frame_partition = BrowsingContextPartitionDescriptor(iframe_context["context"])
+    await add_cookie(iframe_context["context"], cookie_name, cookie_value)
+
+    result = await bidi_session.storage.delete_cookies(partition=frame_partition)
+    recursive_compare({"partitionKey": {"sourceOrigin": source_origin}}, result)
+
+    result = await bidi_session.storage.get_cookies(partition=frame_partition)
+    assert result["cookies"] == []
diff --git a/testing/web-platform/mozilla/tests/webdriver/bidi/storage/get_cookies/partition.py b/testing/web-platform/mozilla/tests/webdriver/bidi/storage/get_cookies/partition.py
index b037c30038..5503f13224 100644
--- a/testing/web-platform/mozilla/tests/webdriver/bidi/storage/get_cookies/partition.py
+++ b/testing/web-platform/mozilla/tests/webdriver/bidi/storage/get_cookies/partition.py
@@ -59,18 +59,22 @@ async def test_partition_context(
     )
 
     recursive_compare(
-        {"cookies": [], "partitionKey": {"sourceOrigin": source_origin_2}}, cookies
+        {
+            "cookies": [],
+            "partitionKey": {"sourceOrigin": source_origin_2, "userContext": "default"},
+        },
+        cookies,
     )
 
 
-@pytest.mark.parametrize("domain", ["", "alt"], ids=["same_origin", "cross_origin"])
-async def test_partition_context_iframe(
-    bidi_session, new_tab, inline, domain_value, domain, add_cookie
+# Because of Dynamic First-Party Isolation, adding the cookie with `document.cookie`
+# works only with same-origin iframes.
+async def test_partition_context_same_origin_iframe(
+    bidi_session, new_tab, inline, domain_value, add_cookie
 ):
-    iframe_url = inline("<div id='in-iframe'>foo</div>", domain=domain)
-    source_origin_for_iframe = get_origin_from_url(iframe_url)
+    iframe_url = inline("<div id='in-iframe'>foo</div>")
+    source_origin = get_origin_from_url(iframe_url)
     page_url = inline(f"<iframe src='{iframe_url}'></iframe>")
-    source_origin_for_page = get_origin_from_url(page_url)
     await bidi_session.browsing_context.navigate(
         context=new_tab["context"], url=page_url, wait="complete"
     )
@@ -89,7 +93,7 @@ async def test_partition_context_iframe(
 
     expected_cookies = [
         {
-            "domain": domain_value(domain=domain),
+            "domain": domain_value(),
             "httpOnly": False,
             "name": cookie_name,
             "path": "/webdriver/tests/support",
@@ -99,10 +103,11 @@ async def test_partition_context_iframe(
             "value": {"type": "string", "value": cookie_value},
         }
     ]
+
     recursive_compare(
         {
             "cookies": expected_cookies,
-            "partitionKey": {"sourceOrigin": source_origin_for_iframe},
+            "partitionKey": {"sourceOrigin": source_origin},
         },
         cookies,
     )
@@ -110,22 +115,16 @@ async def test_partition_context_iframe(
     cookies = await bidi_session.storage.get_cookies(
         partition=BrowsingContextPartitionDescriptor(new_tab["context"])
     )
-    # When the iframe is on the different domain we can verify that top context has no iframe cookie.
-    if domain == "alt":
-        recursive_compare(
-            {
-                "cookies": [],
-                "partitionKey": {"sourceOrigin": source_origin_for_page},
-            },
-            cookies,
-        )
-    else:
-        # When the iframe is on the same domain, since the browsing context partition is defined by user context and origin,
-        # which will be the same for the page, we get the same cookies as for the iframe
-        recursive_compare(
-            {
-                "cookies": expected_cookies,
-                "partitionKey": {"sourceOrigin": source_origin_for_page},
+
+    # When the iframe is on the same domain, since the browsing context partition is defined by user context and origin,
+    # which will be the same for the page, we get the same cookies as for the iframe.
+    recursive_compare(
+        {
+            "cookies": expected_cookies,
+            "partitionKey": {
+                "sourceOrigin": source_origin,
+                "userContext": "default",
             },
-            cookies,
-        )
+        },
+        cookies,
+    )
diff --git a/testing/web-platform/mozilla/tests/webdriver/bidi/storage/set_cookie/partition.py b/testing/web-platform/mozilla/tests/webdriver/bidi/storage/set_cookie/partition.py
index f8e2823dbc..a9b5d3a43a 100644
--- a/testing/web-platform/mozilla/tests/webdriver/bidi/storage/set_cookie/partition.py
+++ b/testing/web-platform/mozilla/tests/webdriver/bidi/storage/set_cookie/partition.py
@@ -42,7 +42,9 @@ async def test_partition_context(
         partition=new_tab_partition,
     )
 
-    assert set_cookie_result == {"partitionKey": {"sourceOrigin": source_origin_1}}
+    assert set_cookie_result == {
+        "partitionKey": {"sourceOrigin": source_origin_1, "userContext": "default"}
+    }
 
     # Check that added cookies are present on the right context.
     cookies = await bidi_session.storage.get_cookies(partition=new_tab_partition)
@@ -72,7 +74,11 @@ async def test_partition_context(
     )
 
     recursive_compare(
-        {"cookies": [], "partitionKey": {"sourceOrigin": source_origin_2}}, cookies
+        {
+            "cookies": [],
+            "partitionKey": {"sourceOrigin": source_origin_2, "userContext": "default"},
+        },
+        cookies,
     )
 
 
@@ -121,7 +127,10 @@ async def test_partition_context_iframe(
     recursive_compare(
         {
             "cookies": expected_cookies,
-            "partitionKey": {"sourceOrigin": source_origin_for_iframe},
+            "partitionKey": {
+                "sourceOrigin": source_origin_for_iframe,
+                "userContext": "default",
+            },
         },
         cookies,
     )
@@ -134,7 +143,10 @@ async def test_partition_context_iframe(
         recursive_compare(
             {
                 "cookies": [],
-                "partitionKey": {"sourceOrigin": source_origin_for_page},
+                "partitionKey": {
+                    "sourceOrigin": source_origin_for_page,
+                    "userContext": "default",
+                },
             },
             cookies,
         )
@@ -144,7 +156,10 @@ async def test_partition_context_iframe(
         recursive_compare(
             {
                 "cookies": expected_cookies,
-                "partitionKey": {"sourceOrigin": source_origin_for_page},
+                "partitionKey": {
+                    "sourceOrigin": source_origin_for_page,
+                    "userContext": "default",
+                },
             },
             cookies,
         )
diff --git a/testing/web-platform/mozilla/tests/webdriver/cdp/port_file.py b/testing/web-platform/mozilla/tests/webdriver/cdp/port_file.py
index aa294deb24..23c31906fa 100644
--- a/testing/web-platform/mozilla/tests/webdriver/cdp/port_file.py
+++ b/testing/web-platform/mozilla/tests/webdriver/cdp/port_file.py
@@ -4,7 +4,7 @@ from support.network import websocket_request
 
 
 def test_devtools_active_port_file(browser):
-    current_browser = browser(use_cdp=True)
+    current_browser = browser(use_cdp=True, clone_profile=False)
 
     assert current_browser.remote_agent_port != 0
     assert current_browser.debugger_address.startswith("/devtools/browser/")
@@ -12,9 +12,6 @@ def test_devtools_active_port_file(browser):
     port_file = os.path.join(current_browser.profile.profile, "DevToolsActivePort")
     assert os.path.exists(port_file)
 
-    current_browser.quit(clean_profile=False)
-    assert not os.path.exists(port_file)
-
 
 def test_connect(browser):
     current_browser = browser(use_cdp=True)
diff --git a/testing/web-platform/mozilla/tests/webdriver/classic/new_session/conftest.py b/testing/web-platform/mozilla/tests/webdriver/classic/new_session/conftest.py
index 1cab6784c2..63abd19f6a 100644
--- a/testing/web-platform/mozilla/tests/webdriver/classic/new_session/conftest.py
+++ b/testing/web-platform/mozilla/tests/webdriver/classic/new_session/conftest.py
@@ -2,7 +2,7 @@ import pytest
 from webdriver.transport import HTTPWireProtocol
 
 
-@pytest.fixture(name="configuration")
+@pytest.fixture(name="configuration", scope="session")
 def fixture_configuration(configuration):
     """Remove "acceptInsecureCerts" from capabilities if it exists.
 
diff --git a/testing/web-platform/mozilla/tests/webdriver/classic/new_session/profile_root.py b/testing/web-platform/mozilla/tests/webdriver/classic/new_session/profile_root.py
index fc3607bed9..97cb835e2c 100644
--- a/testing/web-platform/mozilla/tests/webdriver/classic/new_session/profile_root.py
+++ b/testing/web-platform/mozilla/tests/webdriver/classic/new_session/profile_root.py
@@ -4,7 +4,7 @@ import os
 import pytest
 
 
-def test_profile_root(tmp_path, configuration, geckodriver, user_prefs):
+def test_profile_root(tmp_path, configuration, geckodriver, default_preferences):
     profile_path = os.path.join(tmp_path, "geckodriver-test")
     os.makedirs(profile_path)
 
@@ -12,7 +12,7 @@ def test_profile_root(tmp_path, configuration, geckodriver, user_prefs):
 
     # Pass all the wpt preferences from the default profile's user.js via
     # capabilities to allow geckodriver to create a new valid profile itself.
-    config["capabilities"]["moz:firefoxOptions"]["prefs"] = user_prefs
+    config["capabilities"]["moz:firefoxOptions"]["prefs"] = default_preferences
 
     # Ensure we don't set a profile in command line arguments
     del config["capabilities"]["moz:firefoxOptions"]["args"]
diff --git a/testing/web-platform/mozilla/tests/webdriver/classic/protocol/marionette_port.py b/testing/web-platform/mozilla/tests/webdriver/classic/protocol/marionette_port.py
index 09951abc43..20b4e03324 100644
--- a/testing/web-platform/mozilla/tests/webdriver/classic/protocol/marionette_port.py
+++ b/testing/web-platform/mozilla/tests/webdriver/classic/protocol/marionette_port.py
@@ -14,9 +14,10 @@ def test_marionette_port(geckodriver, port):
 
 
 def test_marionette_port_outdated_active_port_file(
-    configuration, geckodriver, custom_profile
+    configuration, create_custom_profile, geckodriver
 ):
     config = deepcopy(configuration)
+    custom_profile = create_custom_profile()
     extra_args = ["--marionette-port", "0"]
 
     # Prepare a Marionette active port file that contains a port which will
diff --git a/testing/web-platform/mozilla/tests/webdriver/harness/preferences.py b/testing/web-platform/mozilla/tests/webdriver/harness/preferences_marionette.py
index b5cf36bd5e..e5d18aeb6b 100644
--- a/testing/web-platform/mozilla/tests/webdriver/harness/preferences.py
+++ b/testing/web-platform/mozilla/tests/webdriver/harness/preferences_marionette.py
@@ -2,5 +2,5 @@ from support.fixtures import get_pref
 
 
 def test_recommended_preferences(session):
-    has_recommended_prefs = get_pref(session, "remote.prefs.recommended")
+    has_recommended_prefs = get_pref(session, "remote.prefs.recommended.applied")
     assert has_recommended_prefs is True
diff --git a/testing/web-platform/mozilla/tests/webdriver/harness/preferences_remote_agent.py b/testing/web-platform/mozilla/tests/webdriver/harness/preferences_remote_agent.py
new file mode 100644
index 0000000000..59db5fa0e3
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/webdriver/harness/preferences_remote_agent.py
@@ -0,0 +1,37 @@
+import pytest
+from support.helpers import read_user_preferences
+from tests.support.sync import Poll
+
+
+@pytest.mark.parametrize(
+    "value",
+    [
+        {"pref_value": 1, "use_cdp": False, "use_bidi": True},
+        {"pref_value": 2, "use_cdp": True, "use_bidi": False},
+        {"pref_value": 3, "use_cdp": True, "use_bidi": True},
+    ],
+    ids=["bidi only", "cdp only", "bidi and cdp"],
+)
+def test_remote_agent_recommended_preferences_applied(browser, value):
+    # Marionette cannot be enabled for this test because it will also set the
+    # recommended preferences. Therefore only enable Remote Agent protocols.
+    current_browser = browser(
+        extra_prefs={
+            "remote.active-protocols": value["pref_value"],
+        },
+        use_cdp=value["use_cdp"],
+        use_bidi=value["use_bidi"],
+    )
+
+    def pref_is_set(_):
+        preferences = read_user_preferences(current_browser.profile.profile, "prefs.js")
+        return preferences.get("remote.prefs.recommended.applied", False)
+
+    # Without Marionette enabled preferences cannot be retrieved via script evaluation yet.
+    wait = Poll(
+        None,
+        timeout=5,
+        ignored_exceptions=FileNotFoundError,
+        message="""Preference "remote.prefs.recommended.applied" is not true""",
+    )
+    wait.until(pref_is_set)
diff --git a/testing/web-platform/mozilla/tests/webdriver/support/fixtures.py b/testing/web-platform/mozilla/tests/webdriver/support/fixtures.py
index e9dbf1cdfe..b788d874e5 100644
--- a/testing/web-platform/mozilla/tests/webdriver/support/fixtures.py
+++ b/testing/web-platform/mozilla/tests/webdriver/support/fixtures.py
@@ -1,40 +1,18 @@
-import argparse
-import json
-import os
-import re
-import socket
-import subprocess
-import threading
-import time
-from contextlib import suppress
-from urllib.parse import urlparse
-
 import pytest
-import webdriver
-from mozprofile import Preferences, Profile
-from mozrunner import FirefoxRunner
-
-from .context import using_context
-
-
-def get_arg_value(arg_names, args):
-    """Get an argument value from a list of arguments
 
-    This assumes that argparse argument parsing is close enough to the target
-    to be compatible, at least with the set of inputs we have.
-
-    :param arg_names: - List of names for the argument e.g. ["--foo", "-f"]
-    :param args: - List of arguments to parse
-    :returns: - Optional string argument value
-    """
-    parser = argparse.ArgumentParser()
-    parser.add_argument(*arg_names, action="store", dest="value", default=None)
-    parsed, _ = parser.parse_known_args(args)
-    return parsed.value
+from .helpers import (
+    Browser,
+    Geckodriver,
+    create_custom_profile,
+    get_pref,
+    get_profile_folder,
+    read_user_preferences,
+    set_pref,
+)
 
 
 @pytest.fixture(scope="module")
-def browser(full_configuration):
+def browser(configuration, firefox_options):
     """Start a Firefox instance without using geckodriver.
 
     geckodriver will automatically use the --remote-allow-hosts and
@@ -46,7 +24,13 @@ def browser(full_configuration):
     """
     current_browser = None
 
-    def _browser(use_bidi=False, use_cdp=False, extra_args=None, extra_prefs=None):
+    def _browser(
+        use_bidi=False,
+        use_cdp=False,
+        extra_args=None,
+        extra_prefs=None,
+        clone_profile=True,
+    ):
         nonlocal current_browser
 
         # If the requested preferences and arguments match the ones for the
@@ -66,12 +50,18 @@ def browser(full_configuration):
             # to create a new instance for the provided preferences.
             current_browser.quit()
 
-        binary = full_configuration["browser"]["binary"]
-        env = full_configuration["browser"]["env"]
-        firefox_options = full_configuration["capabilities"]["moz:firefoxOptions"]
+        binary = configuration["browser"]["binary"]
+        env = configuration["browser"]["env"]
+
+        profile_path = get_profile_folder(firefox_options)
+        default_prefs = read_user_preferences(profile_path)
+        profile = create_custom_profile(
+            profile_path, default_prefs, clone=clone_profile
+        )
+
         current_browser = Browser(
             binary,
-            firefox_options,
+            profile,
             use_bidi=use_bidi,
             use_cdp=use_cdp,
             extra_args=extra_args,
@@ -89,20 +79,32 @@ def browser(full_configuration):
         current_browser = None
 
 
-@pytest.fixture
-def profile_folder(configuration):
-    firefox_options = configuration["capabilities"]["moz:firefoxOptions"]
-    return get_arg_value(["--profile"], firefox_options["args"])
+@pytest.fixture(name="create_custom_profile")
+def fixture_create_custom_profile(default_preferences, profile_folder):
+    profile = None
+
+    def _create_custom_profile(clone=True):
+        profile = create_custom_profile(
+            profile_folder, default_preferences, clone=clone
+        )
+
+        return profile
+
+    yield _create_custom_profile
+
+    # if profile is not None:
+    if profile:
+        profile.cleanup()
 
 
 @pytest.fixture
-def custom_profile(profile_folder):
-    # Clone the known profile for automation preferences
-    profile = Profile.clone(profile_folder)
+def default_preferences(profile_folder):
+    return read_user_preferences(profile_folder)
 
-    yield profile
 
-    profile.cleanup()
+@pytest.fixture(scope="session")
+def firefox_options(configuration):
+    return configuration["capabilities"]["moz:firefoxOptions"]
 
 
 @pytest.fixture
@@ -128,277 +130,8 @@ def geckodriver(configuration):
 
 
 @pytest.fixture
-def user_prefs(profile_folder):
-    user_js = os.path.join(profile_folder, "user.js")
-
-    prefs = {}
-    for pref_name, pref_value in Preferences().read_prefs(user_js):
-        prefs[pref_name] = pref_value
-
-    return prefs
-
-
-class Browser:
-    def __init__(
-        self,
-        binary,
-        firefox_options,
-        use_bidi=False,
-        use_cdp=False,
-        extra_args=None,
-        extra_prefs=None,
-        env=None,
-    ):
-        self.use_bidi = use_bidi
-        self.bidi_port_file = None
-        self.use_cdp = use_cdp
-        self.cdp_port_file = None
-        self.extra_args = extra_args
-        self.extra_prefs = extra_prefs
-
-        self.debugger_address = None
-        self.remote_agent_host = None
-        self.remote_agent_port = None
-
-        # Prepare temporary profile
-        _profile_arg, profile_folder = firefox_options["args"]
-        self.profile = Profile.clone(profile_folder)
-        if self.extra_prefs is not None:
-            self.profile.set_preferences(self.extra_prefs)
-
-        if use_cdp:
-            self.cdp_port_file = os.path.join(
-                self.profile.profile, "DevToolsActivePort"
-            )
-            with suppress(FileNotFoundError):
-                os.remove(self.cdp_port_file)
-        if use_bidi:
-            self.webdriver_bidi_file = os.path.join(
-                self.profile.profile, "WebDriverBiDiServer.json"
-            )
-            with suppress(FileNotFoundError):
-                os.remove(self.webdriver_bidi_file)
-
-        cmdargs = ["-no-remote"]
-        if self.use_bidi or self.use_cdp:
-            cmdargs.extend(["--remote-debugging-port", "0"])
-        if self.extra_args is not None:
-            cmdargs.extend(self.extra_args)
-        self.runner = FirefoxRunner(
-            binary=binary, profile=self.profile, cmdargs=cmdargs, env=env
-        )
-
-    @property
-    def is_running(self):
-        return self.runner.is_running()
-
-    def start(self):
-        # Start Firefox.
-        self.runner.start()
-
-        if self.use_bidi:
-            # Wait until the WebDriverBiDiServer.json file is ready
-            while not os.path.exists(self.webdriver_bidi_file):
-                time.sleep(0.1)
-
-            # Read the connection details from file
-            data = json.loads(open(self.webdriver_bidi_file).read())
-            self.remote_agent_host = data["ws_host"]
-            self.remote_agent_port = int(data["ws_port"])
-
-        if self.use_cdp:
-            # Wait until the DevToolsActivePort file is ready
-            while not os.path.exists(self.cdp_port_file):
-                time.sleep(0.1)
-
-            # Read the port if needed and the debugger address from the
-            # DevToolsActivePort file
-            lines = open(self.cdp_port_file).readlines()
-            assert len(lines) == 2
-
-            if self.remote_agent_port is None:
-                self.remote_agent_port = int(lines[0].strip())
-            self.debugger_address = lines[1].strip()
-
-    def quit(self, clean_profile=True):
-        if self.is_running:
-            self.runner.stop()
-            self.runner.cleanup()
-
-        if clean_profile:
-            self.profile.cleanup()
-
-    def wait(self):
-        if self.is_running is True:
-            self.runner.wait()
-
-
-class Geckodriver:
-    PORT_RE = re.compile(b".*Listening on [^ :]*:(\d+)")
-
-    def __init__(self, configuration, hostname=None, extra_args=None):
-        self.config = configuration["webdriver"]
-        self.requested_capabilities = configuration["capabilities"]
-        self.hostname = hostname or configuration["host"]
-        self.extra_args = extra_args or []
-        self.env = configuration["browser"]["env"]
-
-        self.command = None
-        self.proc = None
-        self.port = None
-        self.reader_thread = None
-
-        self.capabilities = {"alwaysMatch": self.requested_capabilities}
-        self.session = None
-
-    @property
-    def remote_agent_port(self):
-        webSocketUrl = self.session.capabilities.get("webSocketUrl")
-        assert webSocketUrl is not None
-
-        return urlparse(webSocketUrl).port
-
-    def start(self):
-        self.command = (
-            [self.config["binary"], "--port", "0"]
-            + self.config["args"]
-            + self.extra_args
-        )
-
-        print(f"Running command: {' '.join(self.command)}")
-        self.proc = subprocess.Popen(self.command, env=self.env, stdout=subprocess.PIPE)
-
-        self.reader_thread = threading.Thread(
-            target=readOutputLine,
-            args=(self.proc.stdout, self.processOutputLine),
-            daemon=True,
-        )
-        self.reader_thread.start()
-        # Wait for the port to become ready
-        end_time = time.time() + 10
-        while time.time() < end_time:
-            returncode = self.proc.poll()
-            if returncode is not None:
-                raise ChildProcessError(
-                    f"geckodriver terminated with code {returncode}"
-                )
-            if self.port is not None:
-                with socket.socket() as sock:
-                    if sock.connect_ex((self.hostname, self.port)) == 0:
-                        break
-            else:
-                time.sleep(0.1)
-        else:
-            if self.port is None:
-                raise OSError(
-                    f"Failed to read geckodriver port started on {self.hostname}"
-                )
-            raise ConnectionRefusedError(
-                f"Failed to connect to geckodriver on {self.hostname}:{self.port}"
-            )
-
-        self.session = webdriver.Session(
-            self.hostname, self.port, capabilities=self.capabilities
-        )
-
-        return self
-
-    def processOutputLine(self, line):
-        if self.port is None:
-            m = self.PORT_RE.match(line)
-            if m is not None:
-                self.port = int(m.groups()[0])
-
-    def stop(self):
-        if self.session is not None:
-            self.delete_session()
-        if self.proc:
-            self.proc.kill()
-        self.port = None
-        if self.reader_thread is not None:
-            self.reader_thread.join()
-
-    def new_session(self):
-        self.session.start()
-
-    def delete_session(self):
-        self.session.end()
-
-
-def readOutputLine(stream, callback):
-    while True:
-        line = stream.readline()
-        if not line:
-            break
-
-        callback(line)
-
-
-def clear_pref(session, pref):
-    """Clear the user-defined value from the specified preference.
-
-    :param pref: Name of the preference.
-    """
-    with using_context(session, "chrome"):
-        session.execute_script(
-            """
-           const { Preferences } = ChromeUtils.importESModule(
-             "resource://gre/modules/Preferences.sys.mjs"
-           );
-           Preferences.reset(arguments[0]);
-           """,
-            args=(pref,),
-        )
-
-
-def get_pref(session, pref):
-    """Get the value of the specified preference.
-
-    :param pref: Name of the preference.
-    """
-    with using_context(session, "chrome"):
-        pref_value = session.execute_script(
-            """
-            const { Preferences } = ChromeUtils.importESModule(
-              "resource://gre/modules/Preferences.sys.mjs"
-            );
-
-            let pref = arguments[0];
-
-            prefs = new Preferences();
-            return prefs.get(pref, null);
-            """,
-            args=(pref,),
-        )
-        return pref_value
-
-
-def set_pref(session, pref, value):
-    """Set the value of the specified preference.
-
-    :param pref: Name of the preference.
-    :param value: The value to set the preference to. If the value is None,
-                  reset the preference to its default value. If no default
-                  value exists, the preference will cease to exist.
-    """
-    if value is None:
-        clear_pref(session, pref)
-        return
-
-    with using_context(session, "chrome"):
-        session.execute_script(
-            """
-            const { Preferences } = ChromeUtils.importESModule(
-              "resource://gre/modules/Preferences.sys.mjs"
-            );
-
-            const [pref, value] = arguments;
-
-            prefs = new Preferences();
-            prefs.set(pref, value);
-            """,
-            args=(pref, value),
-        )
+def profile_folder(firefox_options):
+    return get_profile_folder(firefox_options)
 
 
 @pytest.fixture
diff --git a/testing/web-platform/mozilla/tests/webdriver/support/helpers.py b/testing/web-platform/mozilla/tests/webdriver/support/helpers.py
new file mode 100644
index 0000000000..6577289983
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/webdriver/support/helpers.py
@@ -0,0 +1,324 @@
+import argparse
+import json
+import os
+import re
+import socket
+import subprocess
+import tempfile
+import threading
+import time
+from contextlib import suppress
+from urllib.parse import urlparse
+
+import webdriver
+from mozprofile import Preferences, Profile
+from mozrunner import FirefoxRunner
+
+from .context import using_context
+
+
+class Browser:
+    def __init__(
+        self,
+        binary,
+        profile,
+        use_bidi=False,
+        use_cdp=False,
+        extra_args=None,
+        extra_prefs=None,
+        env=None,
+    ):
+        self.profile = profile
+        self.use_bidi = use_bidi
+        self.bidi_port_file = None
+        self.use_cdp = use_cdp
+        self.cdp_port_file = None
+        self.extra_args = extra_args
+        self.extra_prefs = extra_prefs
+
+        self.debugger_address = None
+        self.remote_agent_host = None
+        self.remote_agent_port = None
+
+        if self.extra_prefs is not None:
+            self.profile.set_preferences(self.extra_prefs)
+
+        if use_cdp:
+            self.cdp_port_file = os.path.join(
+                self.profile.profile, "DevToolsActivePort"
+            )
+            with suppress(FileNotFoundError):
+                os.remove(self.cdp_port_file)
+
+        if use_bidi:
+            self.webdriver_bidi_file = os.path.join(
+                self.profile.profile, "WebDriverBiDiServer.json"
+            )
+            with suppress(FileNotFoundError):
+                os.remove(self.webdriver_bidi_file)
+
+        cmdargs = ["-no-remote"]
+        if self.use_bidi or self.use_cdp:
+            cmdargs.extend(["--remote-debugging-port", "0"])
+        if self.extra_args is not None:
+            cmdargs.extend(self.extra_args)
+        self.runner = FirefoxRunner(
+            binary=binary, profile=self.profile, cmdargs=cmdargs, env=env
+        )
+
+    @property
+    def is_running(self):
+        return self.runner.is_running()
+
+    def start(self):
+        # Start Firefox.
+        self.runner.start()
+
+        if self.use_bidi:
+            # Wait until the WebDriverBiDiServer.json file is ready
+            while not os.path.exists(self.webdriver_bidi_file):
+                time.sleep(0.1)
+
+            # Read the connection details from file
+            data = json.loads(open(self.webdriver_bidi_file).read())
+            self.remote_agent_host = data["ws_host"]
+            self.remote_agent_port = int(data["ws_port"])
+
+        if self.use_cdp:
+            # Wait until the DevToolsActivePort file is ready
+            while not os.path.exists(self.cdp_port_file):
+                time.sleep(0.1)
+
+            # Read the port if needed and the debugger address from the
+            # DevToolsActivePort file
+            lines = open(self.cdp_port_file).readlines()
+            assert len(lines) == 2
+
+            if self.remote_agent_port is None:
+                self.remote_agent_port = int(lines[0].strip())
+            self.debugger_address = lines[1].strip()
+
+    def quit(self, clean_profile=True):
+        if self.is_running:
+            self.runner.stop()
+            self.runner.cleanup()
+
+        if clean_profile:
+            self.profile.cleanup()
+
+    def wait(self):
+        if self.is_running is True:
+            self.runner.wait()
+
+
+class Geckodriver:
+    PORT_RE = re.compile(rb".*Listening on [^ :]*:(\d+)")
+
+    def __init__(self, configuration, hostname=None, extra_args=None):
+        self.config = configuration["webdriver"]
+        self.requested_capabilities = configuration["capabilities"]
+        self.hostname = hostname or configuration["host"]
+        self.extra_args = extra_args or []
+        self.env = configuration["browser"]["env"]
+
+        self.command = None
+        self.proc = None
+        self.port = None
+        self.reader_thread = None
+
+        self.capabilities = {"alwaysMatch": self.requested_capabilities}
+        self.session = None
+
+    @property
+    def remote_agent_port(self):
+        webSocketUrl = self.session.capabilities.get("webSocketUrl")
+        assert webSocketUrl is not None
+
+        return urlparse(webSocketUrl).port
+
+    def start(self):
+        self.command = (
+            [self.config["binary"], "--port", "0"]
+            + self.config["args"]
+            + self.extra_args
+        )
+
+        print(f"Running command: {' '.join(self.command)}")
+        self.proc = subprocess.Popen(self.command, env=self.env, stdout=subprocess.PIPE)
+
+        self.reader_thread = threading.Thread(
+            target=readOutputLine,
+            args=(self.proc.stdout, self.processOutputLine),
+            daemon=True,
+        )
+        self.reader_thread.start()
+        # Wait for the port to become ready
+        end_time = time.time() + 10
+        while time.time() < end_time:
+            returncode = self.proc.poll()
+            if returncode is not None:
+                raise ChildProcessError(
+                    f"geckodriver terminated with code {returncode}"
+                )
+            if self.port is not None:
+                with socket.socket() as sock:
+                    if sock.connect_ex((self.hostname, self.port)) == 0:
+                        break
+            else:
+                time.sleep(0.1)
+        else:
+            if self.port is None:
+                raise OSError(
+                    f"Failed to read geckodriver port started on {self.hostname}"
+                )
+            raise ConnectionRefusedError(
+                f"Failed to connect to geckodriver on {self.hostname}:{self.port}"
+            )
+
+        self.session = webdriver.Session(
+            self.hostname, self.port, capabilities=self.capabilities
+        )
+
+        return self
+
+    def processOutputLine(self, line):
+        if self.port is None:
+            m = self.PORT_RE.match(line)
+            if m is not None:
+                self.port = int(m.groups()[0])
+
+    def stop(self):
+        if self.session is not None:
+            self.delete_session()
+        if self.proc:
+            self.proc.kill()
+        self.port = None
+        if self.reader_thread is not None:
+            self.reader_thread.join()
+
+    def new_session(self):
+        self.session.start()
+
+    def delete_session(self):
+        self.session.end()
+
+
+def clear_pref(session, pref):
+    """Clear the user-defined value from the specified preference.
+
+    :param pref: Name of the preference.
+    """
+    with using_context(session, "chrome"):
+        session.execute_script(
+            """
+           const { Preferences } = ChromeUtils.importESModule(
+             "resource://gre/modules/Preferences.sys.mjs"
+           );
+           Preferences.reset(arguments[0]);
+           """,
+            args=(pref,),
+        )
+
+
+def create_custom_profile(base_profile, default_preferences, clone=True):
+    if clone:
+        # Clone the current profile and remove the prefs.js file to only
+        # keep default preferences as set in user.js.
+        profile = Profile.clone(base_profile)
+        prefs_path = os.path.join(profile.profile, "prefs.js")
+        if os.path.exists(prefs_path):
+            os.remove(prefs_path)
+    else:
+        profile = Profile(tempfile.mkdtemp(prefix="wdspec-"))
+        profile.set_preferences(default_preferences)
+
+    return profile
+
+
+def get_arg_value(arg_names, args):
+    """Get an argument value from a list of arguments
+
+    This assumes that argparse argument parsing is close enough to the target
+    to be compatible, at least with the set of inputs we have.
+
+    :param arg_names: - List of names for the argument e.g. ["--foo", "-f"]
+    :param args: - List of arguments to parse
+    :returns: - Optional string argument value
+    """
+    parser = argparse.ArgumentParser()
+    parser.add_argument(*arg_names, action="store", dest="value", default=None)
+    parsed, _ = parser.parse_known_args(args)
+    return parsed.value
+
+
+def get_pref(session, pref):
+    """Get the value of the specified preference.
+
+    :param pref: Name of the preference.
+    """
+    with using_context(session, "chrome"):
+        pref_value = session.execute_script(
+            """
+            const { Preferences } = ChromeUtils.importESModule(
+              "resource://gre/modules/Preferences.sys.mjs"
+            );
+
+            let pref = arguments[0];
+
+            prefs = new Preferences();
+            return prefs.get(pref, null);
+            """,
+            args=(pref,),
+        )
+        return pref_value
+
+
+def get_profile_folder(firefox_options):
+    return get_arg_value(["--profile"], firefox_options["args"])
+
+
+def readOutputLine(stream, callback):
+    while True:
+        line = stream.readline()
+        if not line:
+            break
+
+        callback(line)
+
+
+def read_user_preferences(profile_path, filename="user.js"):
+    prefs_file = os.path.join(profile_path, filename)
+
+    prefs = {}
+    for pref_name, pref_value in Preferences().read_prefs(prefs_file):
+        prefs[pref_name] = pref_value
+
+    return prefs
+
+
+def set_pref(session, pref, value):
+    """Set the value of the specified preference.
+
+    :param pref: Name of the preference.
+    :param value: The value to set the preference to. If the value is None,
+                  reset the preference to its default value. If no default
+                  value exists, the preference will cease to exist.
+    """
+    if value is None:
+        clear_pref(session, pref)
+        return
+
+    with using_context(session, "chrome"):
+        session.execute_script(
+            """
+            const { Preferences } = ChromeUtils.importESModule(
+              "resource://gre/modules/Preferences.sys.mjs"
+            );
+
+            const [pref, value] = arguments;
+
+            prefs = new Preferences();
+            prefs.set(pref, value);
+            """,
+            args=(pref, value),
+        )
author	Daniel Baumann <daniel.baumann@progress-linux.org>	2024-04-19 01:13:27 +0000
committer	Daniel Baumann <daniel.baumann@progress-linux.org>	2024-04-19 01:13:27 +0000
commit	40a355a42d4a9444dc753c04c6608dade2f06a23 (patch)
tree	871fc667d2de662f171103ce5ec067014ef85e61 /testing/web-platform/mozilla/tests
parent	Adding upstream version 124.0.1. (diff)
download	firefox-adbda400be353e676059e335c3c0aaf99e719475.tar.xz firefox-adbda400be353e676059e335c3c0aaf99e719475.zip