From fbaf0bb26397aa498eb9156f06d5a6fe34dd7dd8 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Fri, 19 Apr 2024 03:14:29 +0200
Subject: Merging upstream version 125.0.1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 .../mrow/legacy-mstyle-attributes.html             | 136 ++++++++++++++++---
 .../mrow/semantics-001-ref.html                    |  22 ++++
 .../presentation-markup/mrow/semantics-001.html    |  24 ++++
 .../mrow/semantics-002-ref.html                    |  12 ++
 .../presentation-markup/mrow/semantics-002.html    |  16 +++
 .../mrow/semantics-003-ref.html                    |  13 ++
 .../presentation-markup/mrow/semantics-003.html    |  17 +++
 .../mrow/semantics-004-ref.html                    |  41 ++++++
 .../presentation-markup/mrow/semantics-004.html    |  47 +++++++
 .../mrow/semantics-005-ref.html                    |  11 ++
 .../presentation-markup/mrow/semantics-005.html    |  15 +++
 .../stretchy-largeop-with-default-font-1.html      |  64 +++++++++
 .../stretchy-largeop-with-default-font-2.html      | 132 +++++++++++++++++++
 .../stretchy-largeop-with-default-font-3.html      | 145 +++++++++++++++++++++
 .../scripts/mmultiscript-001-ref.html              |  15 +++
 .../scripts/mmultiscript-001.html                  |  17 +++
 .../scripts/mmultiscript-002-ref.html              |  16 +++
 .../scripts/mmultiscript-002.html                  |  18 +++
 .../scripts/mmultiscript-003-ref.html              |  42 ++++++
 .../scripts/mmultiscript-003.html                  |  42 ++++++
 .../munder-mover-align-accent-false-ref.html       |  70 ++++++++++
 .../scripts/munder-mover-align-accent-false.html   |  57 ++++++++
 .../munder-mover-align-accent-true-ref.html        |  70 ++++++++++
 .../scripts/munder-mover-align-accent-true.html    |  57 ++++++++
 .../scripts/munderover-align-accent-false-ref.html |  85 ++++++++++++
 .../scripts/munderover-align-accent-false.html     |  60 +++++++++
 .../scripts/munderover-align-accent-true-ref.html  |  85 ++++++++++++
 .../scripts/munderover-align-accent-true.html      |  60 +++++++++
 28 files changed, 1372 insertions(+), 17 deletions(-)
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-001-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-001.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-002-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-002.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-003-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-003.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-004-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-004.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-005-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-005.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-1.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-2.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-3.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-001-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-001.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-002-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-002.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-003-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-003.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-false-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-false.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-true-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-true.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-false-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-false.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-true-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-true.html

(limited to 'testing/web-platform/tests/mathml/presentation-markup')

diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/legacy-mstyle-attributes.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/legacy-mstyle-attributes.html
index 2463c40476..0b14ac5334 100644
--- a/testing/web-platform/tests/mathml/presentation-markup/mrow/legacy-mstyle-attributes.html
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/legacy-mstyle-attributes.html
@@ -35,11 +35,12 @@
 </head>
 <body>
   <div id="log"></div>
-  <!-- Note: mpadded attributes are not tested since MathML3 did not allow to
-       set them from mstyle. Also, it is not clear whether munderover's
-       accent/accentunder could be applied from mstyle, given that the former
-       clashes with mo@accent. Other legacy mstyle attributes not in MathML
-       Core or without visual effect are not tested.
+  <!-- Note: In earlier versions of MathML, putting some attributes on the
+       mstyle element was supposed to produce the same rendering as putting them
+       on the all descendants (with some exceptions). In MathML Core, relevant
+       style attributes are implemented as CSS properties and are no longer
+       specific to the mstyle element. The tests below verify that attributes
+       on mstyle that are not mapped to CSS have no effect.
     -->
   <p class="TestContainer" id="mspace">
     <math>
@@ -84,12 +85,12 @@
           <mn>3</mn>
         </munder>
       </mstyle>
-      <mstyle accent="false">
-        <mover>
-          <mn>4</mn>
-          <mo>⇀</mo>
-        </mover>
-      </mstyle>
+      <!-- Note: accent was a shared attribute name for mover and mo, so
+           make mstyle an ancestor of mo but not of mover. -->
+      <mover>
+        <mn>4</mn>
+        <mstyle accent="false"><mo>⇀</mo></mstyle>
+      </mover>
       <mstyle stretchy="false" symmetric="false" maxsize="20px">
         <mrow>
           <mo>|</mo>
@@ -102,6 +103,15 @@
           <mn>4</mn>
         </mrow>
       </mstyle>
+      <mstyle form="prefix">
+        <mrow>
+          <mn>1</mn>
+          <!-- Infix and prefix forms of − do not have the same lspace/rspace
+               values in the operator dictionary -->
+          <mo>−</mo>
+          <mn>2</mn>
+        </mrow>
+      </mstyle>
     </math>
     <math displaystyle="true">
       <mstyle>
@@ -115,12 +125,10 @@
           <mn>3</mn>
         </munder>
       </mstyle>
-      <mstyle>
-        <mover>
-          <mn>4</mn>
-          <mo>⇀</mo>
-        </mover>
-      </mstyle>
+      <mover>
+        <mn>4</mn>
+        <mstyle><mo>⇀</mo></mstyle>
+      </mover>
       <mstyle>
         <mrow>
           <mo>|</mo>
@@ -133,6 +141,13 @@
           <mn>4</mn>
         </mrow>
       </mstyle>
+      <mstyle>
+        <mrow>
+          <mn>1</mn>
+          <mo>−</mo>
+          <mn>2</mn>
+        </mrow>
+      </mstyle>
     </math>
   </p>
   <!-- notation attribute is from MathML3's menclose element -->
@@ -160,5 +175,92 @@
       </mstyle>
     </math>
   </p>
+  <p class="TestContainer" id="mpadded">
+    <math>
+      <mstyle width="100px" height="50px" depth="50px"
+              lspace="10px" voffset="15px">
+        <mpadded style="background: lightblue">
+          <mspace width="10px" height="10px" style="background: black"></mspace>
+        </mpadded>
+      </mstyle>
+    </math>
+    <math>
+      <mstyle>
+        <mpadded style="background: lightblue">
+          <mspace width="10px" height="10px" style="background: black"></mspace>
+        </mpadded>
+      </mstyle>
+    </math>
+  </p>
+  <p class="TestContainer" id="mover">
+    <math>
+      <mstyle accent="true">
+        <mover>
+          <mn>1</mn>
+          <mn>2</mn>
+        </mover>
+      </mstyle>
+    </math>
+    <math>
+      <mstyle>
+        <mover>
+          <mn>1</mn>
+          <mn>2</mn>
+        </mover>
+      </mstyle>
+    </math>
+  </p>
+  <p class="TestContainer" id="munder">
+    <math>
+      <mstyle accentunder="true">
+        <munder>
+          <mn>1</mn>
+          <mn>2</mn>
+        </munder>
+      </mstyle>
+    </math>
+    <math>
+      <mstyle>
+        <munder>
+          <mn>1</mn>
+          <mn>2</mn>
+        </munder>
+      </mstyle>
+    </math>
+  </p>
+  <p class="TestContainer" id="munderover">
+    <math>
+      <mstyle accent="true">
+        <munderover>
+          <mn>1</mn>
+          <mn>2</mn>
+          <mn>3</mn>
+        </munderover>
+      </mstyle>
+      <mstyle accentunder="true">
+        <munderover>
+          <mn>1</mn>
+          <mn>2</mn>
+          <mn>3</mn>
+        </munderover>
+      </mstyle>
+    </math>
+    <math>
+      <mstyle>
+        <munderover>
+          <mn>1</mn>
+          <mn>2</mn>
+          <mn>3</mn>
+        </munderover>
+      </mstyle>
+      <mstyle>
+        <munderover>
+          <mn>1</mn>
+          <mn>2</mn>
+          <mn>3</mn>
+        </munderover>
+      </mstyle>
+    </math>
+  </p>
 </body>
 </html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-001-ref.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-001-ref.html
new file mode 100644
index 0000000000..7d99e48c92
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-001-ref.html
@@ -0,0 +1,22 @@
+<!DOCTYPE html>
+<meta charset="utf-8"/>
+<title>&lt;semantics&gt - mozilla bug 468059 (reference)</title>
+<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+<style>
+  math, p {
+      font: 25px Ahem;
+  }
+</style>
+<p>
+  <math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
+    <semantics>
+      <mstyle displaystyle="true">
+        <munderover>
+          <mo movablelimits="true">pXp</mo>
+          <mtext>XpXpXp</mtext>
+          <mtext>XpXpXp</mtext>
+        </munderover>
+      </mstyle>
+    </semantics>
+  </math>
+</p>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-001.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-001.html
new file mode 100644
index 0000000000..63aa9a4da8
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-001.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<meta charset="utf-8"/>
+<title>&lt;semantics&gt - mozilla bug 468059</title>
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=468059">
+<link rel="help" href="https://w3c.github.io/mathml-core/#semantics-and-presentation">
+<link rel="match" href="semantics-001-ref.html">
+<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+<meta name="assert" content="MathML inside a semantics element inherits displaystyle.">
+<style>
+  math, p {
+      font: 25px Ahem;
+  }
+</style>
+<p>
+  <math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
+    <semantics>
+      <munderover>
+        <mo movablelimits="true">pXp</mo>
+        <mtext>XpXpXp</mtext>
+        <mtext>XpXpXp</mtext>
+      </munderover>
+    </semantics>
+  </math>
+</p>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-002-ref.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-002-ref.html
new file mode 100644
index 0000000000..8abdad93de
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-002-ref.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<title>semantics element and legacy rendering rules (reference)</title>
+<meta charset="utf-8"/>
+<p>Empty semantics: <math><mrow></mrow></math></p>
+<p>annotation: <math><mrow><annotation>annotation</annotation></mrow></math></p>
+<p>annotation-xml: <math><mrow><annotation-xml encoding="MathML-Presentation"><mtext>annotation-xml</mtext></annotation-xml></mrow></math></p>
+<p>presentation MathML (no annotations): <math><mrow><mtext>presentation MathML</mtext></mrow></math></p>
+<p>content MathML (no annotations): <math><mrow><csymbol>content MathML</csymbol></mrow></math></p>
+<p>presentation MathML ; annotation: <math><mrow><mtext>presentation MathML</mtext></mrow></math></p>
+<p>presentation MathML ; annotation-xml: <math><mrow><mtext>presentation MathML</mtext></mrow></math></p>
+<p>content MathML ; annotation: <math><mrow><csymbol>content MathML</csymbol></mrow></math></p>
+<p>content MathML ; annotation-xml: <math><mrow><csymbol>content MathML</csymbol></mrow></math></p>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-002.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-002.html
new file mode 100644
index 0000000000..62028fb863
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-002.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<title>semantics element and legacy rendering rules</title>
+<meta charset="utf-8"/>
+<link rel="help" href="https://developer.mozilla.org/en-US/docs/Web/MathML/Element/semantics">
+<link rel="help" href="https://w3c.github.io/mathml-core/#semantics-and-presentation">
+<link rel="match" href="semantics-002-ref.html">
+<meta name="assert" content="semantics element rendered as an mrow with only the first child displayed and does not rely on legacy rules to choose another child to display instead.">
+<p>Empty semantics: <math><semantics></semantics></math></p>
+<p>annotation: <math><semantics><annotation>annotation</annotation></semantics></math></p>
+<p>annotation-xml: <math><semantics><annotation-xml encoding="MathML-Presentation"><mtext>annotation-xml</mtext></annotation-xml></semantics></math></p>
+<p>presentation MathML (no annotations): <math><semantics><mtext>presentation MathML</mtext></semantics></math></p>
+<p>content MathML (no annotations): <math><semantics><csymbol>content MathML</csymbol></semantics></math></p>
+<p>presentation MathML ; annotation: <math><semantics><mtext>presentation MathML</mtext><annotation>annotation</annotation></semantics></math></p>
+<p>presentation MathML ; annotation-xml: <math><semantics><mtext>presentation MathML</mtext><annotation-xml encoding="application/mathml-presentation+xml"><mtext>annotation-xml</mtext></annotation-xml></semantics></math></p>
+<p>content MathML ; annotation: <math><semantics><csymbol>content MathML</csymbol><annotation>annotation</annotation></semantics></math></p>
+<p>content MathML ; annotation-xml: <math><semantics><csymbol>content MathML</csymbol><annotation-xml encoding="application/mathml-presentation+xml"><mtext>annotation-xml</mtext></annotation-xml></semantics></math></p>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-003-ref.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-003-ref.html
new file mode 100644
index 0000000000..7b6e21a3eb
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-003-ref.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<title>semantics element and legacy rendering rules (reference)</title>
+<meta charset="utf-8"/>
+<p>annotation 1: <math><mrow><csymbol>Content MathML</csymbol></mrow></math></p>
+<p>annotation 2: <math><mrow><csymbol>Content MathML</csymbol></mrow></math></p>
+<p>annotation 3: <math><mrow><csymbol>Content MathML</csymbol></mrow></math></p>
+<p>annotation-xml 1: <math><mrow><csymbol>Content MathML</csymbol></mrow></math></p>
+<p>annotation-xml 2: <math><mrow><csymbol>Content MathML</csymbol></mrow></math></p>
+<p>annotation-xml 3: <math><mrow><csymbol>Content MathML</csymbol></mrow></math></p>
+<p>annotation-xml 4: <math><mrow><csymbol>Content MathML</csymbol></mrow></math></p>
+<p>annotation-xml 5: <math><mrow><csymbol>Content MathML</csymbol></mrow></math></p>
+<p>annotation-xml 6: <math><mrow><csymbol>Content MathML</csymbol></mrow></math></p>
+<p>annotation-xml 7: <math><mrow><csymbol>Content MathML</csymbol></mrow></math></p>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-003.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-003.html
new file mode 100644
index 0000000000..83572f4c8c
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-003.html
@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<title>semantics element and legacy rendering rules</title>
+<meta charset="utf-8"/>
+<link rel="help" href="https://developer.mozilla.org/en-US/docs/Web/MathML/Element/semantics">
+<link rel="help" href="https://w3c.github.io/mathml-core/#semantics-and-presentation">
+<link rel="match" href="semantics-003-ref.html">
+<meta name="assert" content="semantics element rendered as an mrow with only the first child displayed and does not rely on legacy rules to choose another child to display instead.">
+<p>annotation 1: <math><semantics><csymbol>Content MathML</csymbol><annotation>annotation</annotation><annotation>error</annotation><annotation-xml encoding="application/mathml-presentation+xml"><mtext>error</mtext></annotation-xml></semantics></math></p>
+<p>annotation 2: <math><semantics><csymbol>Content MathML</csymbol><annotation encoding="application/x-tex">\sin x + 5</annotation><annotation>error</annotation><annotation-xml encoding="application/mathml-presentation+xml"><mtext>error</mtext></annotation-xml></semantics></math></p>
+<p>annotation 3: <math><semantics><csymbol>Content MathML</csymbol><annotation src="external-resource">error</annotation><annotation>annotation</annotation><annotation-xml encoding="application/mathml-presentation+xml"><mtext>error</mtext></annotation-xml></semantics></math></p>
+<p>annotation-xml 1: <math><semantics><csymbol>Content MathML</csymbol><annotation-xml encoding="application/mathml-presentation+xml"><mtext>application/mathml-presentation+xml</mtext></annotation-xml><annotation-xml encoding="application/mathml-presentation+xml"><mtext>error</mtext></annotation-xml><annotation>error</annotation></semantics></math></p>
+<p>annotation-xml 2: <math><semantics><csymbol>Content MathML</csymbol><annotation-xml encoding="MathML-Presentation"><mtext>MathML-Presentation</mtext></annotation-xml><annotation-xml encoding="application/mathml-presentation+xml"><mtext>error</mtext></annotation-xml><annotation>error</annotation></semantics></math></p>
+<p>annotation-xml 3: <math><semantics><csymbol>Content MathML</csymbol><annotation-xml encoding="image/svg+xml"><svg xmlns="http://www.w3.org/2000/svg" height="2em"><text y="1em">image/svg+xml</text></svg></annotation-xml><annotation-xml encoding="application/mathml-presentation+xml"><mtext>error</mtext></annotation-xml><annotation>error</annotation></semantics></math></p>
+<p>annotation-xml 4: <math><semantics><csymbol>Content MathML</csymbol><annotation-xml encoding="SVG1.1"><svg xmlns="http://www.w3.org/2000/svg" height="2em"><text y="1em">SVG1.1</text></svg></annotation-xml><annotation-xml encoding="application/mathml-presentation+xml"><mtext>error</mtext></annotation-xml><annotation>error</annotation></semantics></math></p>
+<p>annotation-xml 5: <math><semantics><csymbol>Content MathML</csymbol><annotation-xml encoding="application/xhtml+xml"><html xmlns="http://www.w3.org/1999/xhtml"><head><title>application/xhtml+xml</title></head><body><p>application/xhtml+xml</p></body></html></annotation-xml><annotation-xml encoding="application/mathml-presentation+xml"><mtext>error</mtext></annotation-xml><annotation>error</annotation></math></p>
+<p>annotation-xml 6: <math><semantics><csymbol>Content MathML</csymbol><annotation-xml encoding="text/html"><html><head><title>text/html</title></head><body><p>text/html</p></body></html></annotation-xml><annotation-xml encoding="application/mathml-presentation+xml"><mtext>error</mtext></annotation-xml><annotation>error</annotation></semantics></math></p>
+<p>annotation-xml 7: <math><semantics><csymbol>Content MathML</csymbol><annotation-xml encoding="unknown"><mtext>error</mtext></annotation-xml><annotation-xml encoding="application/mathml-presentation+xml"><mtext>annotation-xml</mtext></annotation-xml><annotation>error</annotation></semantics></math></p>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-004-ref.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-004-ref.html
new file mode 100644
index 0000000000..855d887bbc
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-004-ref.html
@@ -0,0 +1,41 @@
+<!DOCTYPE html>
+<meta charset="utf-8"/>
+<title>&lt;semantics&gt - mozilla bug 512418 (reference)</title>
+<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+<style>
+  math, p {
+      font: 25px Ahem;
+  }
+</style>
+<p>
+  XpXpXp<math xmlns="http://www.w3.org/1998/Math/MathML">
+    <mrow>
+      <mrow>
+        <mo>lcm</mo>
+        <mo>(</mo>
+        <mn>a</mn>
+        <mo>,</mo>
+        <mn>b</mn>
+        <mo>)</mo>
+      </mrow>
+      <mo>=</mo>
+      <mfrac>
+        <mrow>
+          <mo>(</mo>
+          <mn>a</mn>
+          <mo>&#x2062;</mo>
+          <mn>b</mn>
+          <mo>)</mo>
+        </mrow>
+        <mrow>
+          <mo>gcd</mo>
+          <mo>(</mo>
+          <mn>a</mn>
+          <mo>,</mo>
+          <mn>b</mn>
+          <mo>)</mo>
+        </mrow>
+      </mfrac>
+    </mrow>
+  </math>XpXpXp
+</p>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-004.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-004.html
new file mode 100644
index 0000000000..17f0f1ecd0
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-004.html
@@ -0,0 +1,47 @@
+<!DOCTYPE html>
+<meta charset="utf-8"/>
+<title>&lt;semantics&gt - mozilla bug 512418</title>
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=512418">
+<link rel="help" href="https://w3c.github.io/mathml-core/#semantics-and-presentation">
+<link rel="match" href="semantics-004-ref.html">
+<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+<meta name="assert" content="The semantics element shouldn't add space around it.">
+<style>
+  math, p {
+      font: 25px Ahem;
+  }
+</style>
+<p>
+  XpXpXp<math xmlns="http://www.w3.org/1998/Math/MathML">
+    <semantics>
+      <mrow>
+        <mrow>
+          <mo>lcm</mo>
+          <mo>(</mo>
+          <mn>a</mn>
+          <mo>,</mo>
+          <mn>b</mn>
+          <mo>)</mo>
+        </mrow>
+        <mo>=</mo>
+        <mfrac>
+          <mrow>
+            <mo>(</mo>
+            <mn>a</mn>
+            <mo>&#x2062;</mo>
+            <mn>b</mn>
+            <mo>)</mo>
+          </mrow>
+          <mrow>
+            <mo>gcd</mo>
+            <mo>(</mo>
+            <mn>a</mn>
+            <mo>,</mo>
+            <mn>b</mn>
+            <mo>)</mo>
+          </mrow>
+        </mfrac>
+      </mrow>
+    </semantics>
+  </math>XpXpXp
+</p>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-005-ref.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-005-ref.html
new file mode 100644
index 0000000000..cf722603e1
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-005-ref.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<title>&lt;semantics&gt - mozilla bug 21479 (reference)</title>
+<meta charset="utf-8"/>
+<p>
+  <math xmlns="http://www.w3.org/1998/Math/MathML">
+    <mover>
+      <mspace width="300px" height="10px" mathbackground="black"></mspace>
+      <mo>&#xaf;</mo>
+    </mover>
+  </math>
+</p>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-005.html b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-005.html
new file mode 100644
index 0000000000..e4fe611c47
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/mrow/semantics-005.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<title>&lt;semantics&gt - mozilla bug 21479</title>
+<meta charset="utf-8"/>
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=21479">
+<link rel="help" href="https://w3c.github.io/mathml-core/#semantics-and-presentation">
+<link rel="match" href="semantics-005-ref.html">
+<meta name="assert" content="The embellished operator made of a single mo inside a semantics element is treated the same as the mo alone.">
+<p>
+  <math xmlns="http://www.w3.org/1998/Math/MathML">
+    <mover>
+      <mspace width="300px" height="10px" mathbackground="black"></mspace>
+      <semantics><mo>&#xaf;</mo></semantics>
+    </mover>
+  </math>
+</p>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-1.html b/testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-1.html
new file mode 100644
index 0000000000..9f37cddc39
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-1.html
@@ -0,0 +1,64 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Stretchy/Largeop with default fonts</title>
+    <meta charset="utf-8"/>
+    <link rel="help" href="https://www.w3.org/TR/mathml-core/#layout-of-operators">
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1092053">
+    <script src="/resources/testharness.js"></script>
+    <script src="/resources/testharnessreport.js"></script>
+    <script type="text/javascript">
+      function heightOf(aElement) {
+        return document.getElementById(aElement).getBoundingClientRect().height;
+      }
+      promise_test(() => {
+        return new Promise(resolve => {
+          window.addEventListener("load", resolve);
+        }).then(() => {
+          assert_greater_than(heightOf("mo0"), heightOf("mo0a"));
+          assert_greater_than(heightOf("mo1"), heightOf("mo1a"));
+          assert_greater_than(heightOf("mo2"), heightOf("mo2a"));
+          assert_greater_than(heightOf("mo3"), heightOf("mo3a"));
+        });
+      }, "The size of displaystyle largeops is taken into account when stretching fences.");
+    </script>
+  </head>
+  <body>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mo id="mo0">(</mo>
+          <mo>∫</mo>
+          <mo id="mo1">)</mo>
+        <mrow>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mrow>
+          <mo id="mo0a">(</mo>
+          <mo>∫</mo>
+          <mo id="mo1a">)</mo>
+        <mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mo id="mo2">(</mo>
+          <mo>&Product;</mo>
+          <mo id="mo3">)</mo>
+        <mrow>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mrow>
+          <mo id="mo2a">(</mo>
+          <mo>&Product;</mo>
+          <mo id="mo3a">)</mo>
+        <mrow>
+      </math>
+    </p>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-2.html b/testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-2.html
new file mode 100644
index 0000000000..7c43c80acc
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-2.html
@@ -0,0 +1,132 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Stretchy/Largeop with default fonts</title>
+    <meta charset="utf-8"/>
+    <link rel="help" href="https://www.w3.org/TR/mathml-core/#layout-of-operators">
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1092053">
+    <script src="/resources/testharness.js"></script>
+    <script src="/resources/testharnessreport.js"></script>
+    <script type="text/javascript">
+      function contentOf(aElement) {
+        return document.getElementById(aElement).textContent;
+      }
+      function heightOf(aElement) {
+        return document.getElementById(aElement).getBoundingClientRect().height;
+      }
+      promise_test(() => {
+        return new Promise(resolve => {
+          window.addEventListener("load", resolve);
+        }).then(() => {
+          const numTests = 10; // zero indexed
+          for (let i = 0; i < numTests; i++) {
+            const operatorName = contentOf(`mo${i}`);
+            assert_greater_than(heightOf(`mo${i}`), heightOf(`moRef${i}`), `size of largeop '${operatorName}'`);
+          }
+        });
+      }, "Test that non-stretchy largeops are bigger in display mode.");
+    </script>
+  </head>
+  <body>
+    <p>
+      <math displaystyle="true">
+        <mo id="mo0">&bigodot;</mo>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mo id="mo1">&bigoplus;</mo>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mo id="mo2">&#x2a03;</mo>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mo id="mo3">&#x2a05;</mo>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mo id="mo4">&#x2a07;</mo>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mo id="mo5">&#x2a08;</mo>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mo id="mo6">&#x2a09;</mo>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mo id="mo7">&#x2a0a;</mo>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mo id="mo8">&#x2afc;</mo>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mo id="mo9">&#x2aff;</mo>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mo id="moRef0">&bigodot;</mo>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mo id="moRef1">&bigoplus;</mo>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mo id="moRef2">&#x2a03;</mo>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mo id="moRef3">&#x2a05;</mo>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mo id="moRef4">&#x2a07;</mo>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mo id="moRef5">&#x2a08;</mo>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mo id="moRef6">&#x2a09;</mo>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mo id="moRef7">&#x2a0a;</mo>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mo id="moRef8">&#x2afc;</mo>
+      </math>
+    </p>
+    <p>
+      <math>
+        <mo id="moRef9">&#x2aff;</mo>
+      </math>
+    </p>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-3.html b/testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-3.html
new file mode 100644
index 0000000000..d588b9d4e0
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/operators/stretchy-largeop-with-default-font-3.html
@@ -0,0 +1,145 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Stretchy/Largeop with default fonts</title>
+    <meta charset="utf-8"/>
+    <link rel="help" href="https://www.w3.org/TR/mathml-core/#layout-of-operators">
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1092053">
+    <script src="/resources/testharness.js"></script>
+    <script src="/resources/testharnessreport.js"></script>
+    <script type="text/javascript">
+      function contentOf(aElement) {
+        return document.getElementById(aElement).textContent;
+      }
+      promise_test(() => {
+        return new Promise(resolve => {
+          window.addEventListener("load", resolve);
+        }).then(() => {
+          const numTests = 10; // zero indexed
+          const epsilon = 2;
+          for (let i = 0; i < numTests; i++) {
+            const operatorName = contentOf(`mo${i}`);
+            const box = document.getElementById(`mo${i}`).getBoundingClientRect();
+            const ref = document.getElementById(`moRef${i}`).getBoundingClientRect();
+            assert_approx_equals(box.width, ref.width, epsilon, `width of largeop '${operatorName}'`);
+            assert_approx_equals(box.height, ref.height, epsilon, `height of largeop '${operatorName}'`);
+          }
+        });
+      }, "Test that non-stretchy largeops do not stretch.");
+    </script>
+  </head>
+  <body>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mspace height="3em" />
+          <mo id="mo0">&bigodot;</mo>
+        </mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mspace height="3em" />
+          <mo id="mo1">&bigoplus;</mo>
+        </mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mspace height="3em" />
+          <mo id="mo2">&#x2a03;</mo>
+        </mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mspace height="3em" />
+          <mo id="mo3">&#x2a05;</mo>
+        </mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mspace height="3em" />
+          <mo id="mo4">&#x2a07;</mo>
+        </mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mspace height="3em" />
+          <mo id="mo5">&#x2a08;</mo>
+        </mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mspace height="3em" />
+          <mo id="mo6">&#x2a09;</mo>
+        </mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mspace height="3em" />
+          <mo id="mo7">&#x2a0a;</mo>
+        </mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mspace height="3em" />
+          <mo id="mo8">&#x2afc;</mo>
+        </mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mrow>
+          <mspace height="3em" />
+          <mo id="mo9">&#x2aff;</mo>
+        </mrow>
+      </math>
+    </p>
+    <p>
+      <math displaystyle="true">
+        <mo id="moRef0">&bigodot;</mo>
+      </math>
+      <math displaystyle="true">
+        <mo id="moRef1">&bigoplus;</mo>
+      </math>
+      <math displaystyle="true">
+        <mo id="moRef2">&#x2a03;</mo>
+      </math>
+      <math displaystyle="true">
+        <mo id="moRef3">&#x2a05;</mo>
+      </math>
+      <math displaystyle="true">
+        <mo id="moRef4">&#x2a07;</mo>
+      </math>
+      <math displaystyle="true">
+        <mo id="moRef5">&#x2a08;</mo>
+      </math>
+      <math displaystyle="true">
+        <mo id="moRef6">&#x2a09;</mo>
+      </math>
+      <math displaystyle="true">
+        <mo id="moRef7">&#x2a0a;</mo>
+      </math>
+      <math displaystyle="true">
+        <mo id="moRef8">&#x2afc;</mo>
+      </math>
+      <math displaystyle="true">
+        <mo id="moRef9">&#x2aff;</mo>
+      </math>
+    </p>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-001-ref.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-001-ref.html
new file mode 100644
index 0000000000..d814944f53
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-001-ref.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>mmultiscript with no scripts (reference)</title>
+  </head>
+  <body>
+    <math>
+      <mmultiscripts>
+        <mtext>base</mtext>
+        <none/>
+        <none/>
+      </mmultiscripts>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-001.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-001.html
new file mode 100644
index 0000000000..e55a04e128
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-001.html
@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>mmultiscript with no scripts</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+    <link rel="help" href="https://w3c.github.io/mathml-core/#base-with-prescripts-and-postscripts">
+    <link rel="match" href="mmultiscript-001-ref.html">
+    <meta name="assert" content="mmultiscript with no scripts renders the same as if it had two none post-scripts">
+  </head>
+  <body>
+    <math>
+      <mmultiscripts>
+        <mtext>base</mtext>
+      </mmultiscripts>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-002-ref.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-002-ref.html
new file mode 100644
index 0000000000..33f12d7cdf
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-002-ref.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>mmultiscript with mprescripts (reference)</title>
+  </head>
+  <body>
+    <math>
+      <mmultiscripts>
+        <mtext>base</mtext>
+        <none/>
+        <none/>
+        <mprescripts/>
+      </mmultiscripts>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-002.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-002.html
new file mode 100644
index 0000000000..c5e426008f
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-002.html
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>mmultiscript with mprescripts</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=208309">
+    <link rel="help" href="https://w3c.github.io/mathml-core/#base-with-prescripts-and-postscripts">
+    <link rel="match" href="mmultiscript-002-ref.html">
+    <meta name="assert" content="mmultiscript with no scripts and a mprescripts child renders the same as if it had two none pre-scripts">
+  </head>
+  <body>
+    <math>
+      <mmultiscripts>
+        <mtext>base</mtext>
+        <mprescripts/>
+      </mmultiscripts>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-003-ref.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-003-ref.html
new file mode 100644
index 0000000000..daac6b3346
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-003-ref.html
@@ -0,0 +1,42 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>alignment of mmultiscript sub/superscripts</title>
+  </head>
+  <body>
+    <math>
+      <mmultiscripts>
+        <mspace width="50px" height="50px" mathbackground="red"/>
+        <mrow>
+          <mspace width="50px" height="10px" mathbackground="blue"/>
+          <mspace width="50px" height="10px"/>
+        </mrow>
+        <mspace width="100px" height="10px" mathbackground="green"/>
+        <mprescripts/>
+        <mrow>
+          <mspace width="50px" height="10px"/>
+          <mspace width="50px" height="10px" mathbackground="blue"/>
+        </mrow>
+        <mspace width="100px" height="10px" mathbackground="green"/>
+      </mmultiscripts>
+    </math>
+    <br/>
+    <br/>
+    <math>
+      <mmultiscripts>
+        <mspace width="50px" height="50px" mathbackground="red"/>
+        <mspace width="100px" height="10px" mathbackground="green"/>
+        <mrow>
+          <mspace width="50px" height="10px" mathbackground="blue"/>
+          <mspace width="50px" height="10px"/>
+        </mrow>
+        <mprescripts/>
+        <mspace width="100px" height="10px" mathbackground="green"/>
+        <mrow>
+          <mspace width="50px" height="10px"/>
+          <mspace width="50px" height="10px" mathbackground="blue"/>
+        </mrow>
+      </mmultiscripts>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-003.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-003.html
new file mode 100644
index 0000000000..7de3e98b8a
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/mmultiscript-003.html
@@ -0,0 +1,42 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>alignment of mmultiscript sub/superscripts</title>
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=928675">
+    <link rel="help" href="https://w3c.github.io/mathml-core/#base-with-prescripts-and-postscripts">
+    <link rel="match" href="mmultiscript-003-ref.html">
+    <meta name="assert" content="In LTR mode, pre-scripts are right-aligned and post-scripts are left-aligned.">
+  </head>
+  <body>
+    <math>
+      <mmultiscripts>
+        <mspace width="50px" height="50px" mathbackground="red"/>
+        <mrow>
+          <mspace width="50px" height="10px" mathbackground="blue"/>
+        </mrow>
+        <mspace width="100px" height="10px" mathbackground="green"/>
+        <mprescripts/>
+        <mrow>
+          <mspace width="50px" height="10px" mathbackground="blue"/>
+        </mrow>
+        <mspace width="100px" height="10px" mathbackground="green"/>
+      </mmultiscripts>
+    </math>
+    <br/>
+    <br/>
+    <math>
+      <mmultiscripts>
+        <mspace width="50px" height="50px" mathbackground="red"/>
+        <mspace width="100px" height="10px" mathbackground="green"/>
+        <mrow>
+          <mspace width="50px" height="10px" mathbackground="blue"/>
+        </mrow>
+        <mprescripts/>
+        <mspace width="100px" height="10px" mathbackground="green"/>
+        <mrow>
+          <mspace width="50px" height="10px" mathbackground="blue"/>
+        </mrow>
+      </mmultiscripts>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-false-ref.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-false-ref.html
new file mode 100644
index 0000000000..db72d0c5e2
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-false-ref.html
@@ -0,0 +1,70 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Horizontal alignment of base with munder/mover scripts (accent="false")</title>
+  </head>
+  <body>
+    <table border="1">
+      <tr>
+        <th colspan="2">mover</th>
+        <th colspan="2">munder</th>
+      </tr>
+      <tr>
+        <td align="center">Over &lt; Base</td>
+        <td align="center">Over &gt; Base</td>
+        <td align="center">Under &lt; Base</td>
+        <td align="center">Under &gt; Base</td>
+      </tr>
+      <tr>
+        <td align="center">
+          <math>
+            <mover>
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+            </mover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <mover>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="blue"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </mover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munder>
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+            </munder>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munder>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="blue"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munder>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-false.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-false.html
new file mode 100644
index 0000000000..0d4205410a
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-false.html
@@ -0,0 +1,57 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Horizontal alignment of base with munder/mover scripts (accent="false")</title>
+    <link rel="help" href="https://w3c.github.io/mathml-core/#underscripts-and-overscripts-munder-mover-munderover">
+    <link rel="match" href="munder-mover-align-accent-false-ref.html">
+    <meta name="assert" content="base, underscript and overscript should be horizontally aligned.">
+  </head>
+  <body>
+    <table border="1">
+      <tr>
+        <th colspan="2">mover</th>
+        <th colspan="2">munder</th>
+      </tr>
+      <tr>
+        <td align="center">Over &lt; Base</td>
+        <td align="center">Over &gt; Base</td>
+        <td align="center">Under &lt; Base</td>
+        <td align="center">Under &gt; Base</td>
+      </tr>
+      <tr>
+        <td align="center">
+          <math>
+            <mover>
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+            </mover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <mover>
+              <mspace height="15px" width="25px" mathbackground="blue"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </mover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munder>
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+            </munder>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munder>
+              <mspace height="15px" width="25px" mathbackground="blue"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munder>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-true-ref.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-true-ref.html
new file mode 100644
index 0000000000..da1033563e
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-true-ref.html
@@ -0,0 +1,70 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Horizontal alignment of base with munder/mover scripts (accent="true")</title>
+  </head>
+  <body>
+    <table border="1">
+      <tr>
+        <th colspan="2">mover</th>
+        <th colspan="2">munder</th>
+      </tr>
+      <tr>
+        <td align="center">Over &lt; Base</td>
+        <td align="center">Over &gt; Base</td>
+        <td align="center">Under &lt; Base</td>
+        <td align="center">Under &gt; Base</td>
+      </tr>
+      <tr>
+        <td align="center">
+          <math>
+            <mover accent="true">
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+            </mover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <mover accent="true">
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="blue"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </mover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munder accentunder="true">
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+            </munder>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munder accentunder="true">
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="blue"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munder>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-true.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-true.html
new file mode 100644
index 0000000000..aa70d244f3
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/munder-mover-align-accent-true.html
@@ -0,0 +1,57 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Horizontal alignment of base with munder/mover scripts (accent="true")</title>
+    <link rel="help" href="https://w3c.github.io/mathml-core/#underscripts-and-overscripts-munder-mover-munderover">
+    <link rel="match" href="munder-mover-align-accent-true-ref.html">
+    <meta name="assert" content="base, underscript and overscript should be horizontally aligned.">
+  </head>
+  <body>
+    <table border="1">
+      <tr>
+        <th colspan="2">mover</th>
+        <th colspan="2">munder</th>
+      </tr>
+      <tr>
+        <td align="center">Over &lt; Base</td>
+        <td align="center">Over &gt; Base</td>
+        <td align="center">Under &lt; Base</td>
+        <td align="center">Under &gt; Base</td>
+      </tr>
+      <tr>
+        <td align="center">
+          <math>
+            <mover accent="true">
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+            </mover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <mover accent="true">
+              <mspace height="15px" width="25px" mathbackground="blue"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </mover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munder accentunder="true">
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+            </munder>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munder accentunder="true">
+              <mspace height="15px" width="25px" mathbackground="blue"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munder>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-false-ref.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-false-ref.html
new file mode 100644
index 0000000000..c339149c25
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-false-ref.html
@@ -0,0 +1,85 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Horizontal alignment of base with munder/mover scripts (accent="false")</title>
+  </head>
+  <body>
+    <table border="1">
+      <tr>
+        <th colspan="6">munderover</th>
+      </tr>
+      <tr>
+        <td align="center">Over &lt; Base &lt; Under</td>
+        <td align="center">Over &gt; Base &gt; Under</td>
+        <td align="center">Over = Under &lt; Base</td>
+        <td align="center">Over = Under &gt; Base</td>
+      </tr>
+      <tr>
+        <td align="center">
+          <math>
+            <munderover accent="false" accentunder="false">
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="50px" mathbackground="blue"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover accent="false" accentunder="false">
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="50px" mathbackground="blue"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover accent="false" accentunder="false">
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover accent="false" accentunder="false">
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="blue"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-false.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-false.html
new file mode 100644
index 0000000000..2c082612a2
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-false.html
@@ -0,0 +1,60 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Horizontal alignment of base with munder/mover scripts (accent="false")</title>
+    <link rel="help" href="https://w3c.github.io/mathml-core/#underscripts-and-overscripts-munder-mover-munderover">
+    <link rel="match" href="munderover-align-accent-false-ref.html">
+    <meta name="assert" content="base, underscript and overscript should be horizontally aligned.">
+  </head>
+  <body>
+    <table border="1">
+      <tr>
+        <th colspan="4">munderover</th>
+      </tr>
+      <tr>
+        <td align="center">Over &lt; Base &lt; Under</td>
+        <td align="center">Over &gt; Base &gt; Under</td>
+        <td align="center">Over = Under &lt; Base</td>
+        <td align="center">Over = Under &gt; Base</td>
+      </tr>
+      <tr>
+        <td align="center">
+          <math>
+            <munderover>
+              <mspace height="15px" width="50px" mathbackground="blue"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover>
+              <mspace height="15px" width="50px" mathbackground="blue"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover>
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover>
+              <mspace height="15px" width="25px" mathbackground="blue"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-true-ref.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-true-ref.html
new file mode 100644
index 0000000000..aababcb17b
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-true-ref.html
@@ -0,0 +1,85 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Horizontal alignment of base with munder/mover scripts (accent="true")</title>
+  </head>
+  <body>
+    <table border="1">
+      <tr>
+        <th colspan="6">munderover</th>
+      </tr>
+      <tr>
+        <td align="center">Over &lt; Base &lt; Under</td>
+        <td align="center">Over &gt; Base &gt; Under</td>
+        <td align="center">Over = Under &lt; Base</td>
+        <td align="center">Over = Under &gt; Base</td>
+      </tr>
+      <tr>
+        <td align="center">
+          <math>
+            <munderover accent="true" accentunder="true">
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="50px" mathbackground="blue"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover accent="true" accentunder="true">
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="50px" mathbackground="blue"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover accent="true" accentunder="true">
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="red"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover accent="true" accentunder="true">
+              <mrow>
+                <mspace height="15px" width="25px"/>
+                <mspace height="15px" width="25px" mathbackground="blue"/>
+                <mspace height="15px" width="25px"/>
+              </mrow>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-true.html b/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-true.html
new file mode 100644
index 0000000000..e6578ade52
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/scripts/munderover-align-accent-true.html
@@ -0,0 +1,60 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Horizontal alignment of base with munder/mover scripts (accent="true")</title>
+    <link rel="help" href="https://w3c.github.io/mathml-core/#underscripts-and-overscripts-munder-mover-munderover">
+    <link rel="match" href="munderover-align-accent-true-ref.html">
+    <meta name="assert" content="base, underscript and overscript should be horizontally aligned.">
+  </head>
+  <body>
+    <table border="1">
+      <tr>
+        <th colspan="4">munderover</th>
+      </tr>
+      <tr>
+        <td align="center">Over &lt; Base &lt; Under</td>
+        <td align="center">Over &gt; Base &gt; Under</td>
+        <td align="center">Over = Under &lt; Base</td>
+        <td align="center">Over = Under &gt; Base</td>
+      </tr>
+      <tr>
+        <td align="center">
+          <math>
+            <munderover accent="true" accentunder="true">
+              <mspace height="15px" width="50px" mathbackground="blue"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover accent="true" accentunder="true">
+              <mspace height="15px" width="50px" mathbackground="blue"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover accent="true" accentunder="true">
+              <mspace height="15px" width="75px" mathbackground="blue"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+              <mspace height="15px" width="25px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+        <td align="center">
+          <math>
+            <munderover accent="true" accentunder="true">
+              <mspace height="15px" width="25px" mathbackground="blue"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+              <mspace height="15px" width="75px" mathbackground="red"/>
+            </munderover>
+          </math>
+        </td>
+      </tr>
+    </table>
+  </body>
+</html>
-- 
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