1 files changed, 58 insertions, 0 deletions
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/tabindex-001.html b/testing/web-platform/tests/mathml/relations/html5-tree/tabindex-001.html
new file mode 100644
index 0000000000..3aaf0d955a
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+++ b/testing/web-platform/tests/mathml/relations/html5-tree/tabindex-001.html
@@ -0,0 +1,58 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8"/>
+<title>MathML tabIndex attribute</title>
+<link rel="help" href="https://w3c.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://w3c.github.io/mathml-core/#the-top-level-math-element">
+<meta name="assert" content="Verify default values for the tabIndex attribute">
+
+<script src="/mathml/support/mathml-fragments.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+  <div id="log"></div>
+  <math>
+  </math>
+  <script>
+    const htmlLinkableElements =
+      new Set([
+        'mi', 'mo', 'mn', 'ms', 'mtext', 'mrow'
+      ]);
+
+    Object.keys(MathMLFragments).forEach(elName => {
+        const mathEl = document.querySelector('math');
+
+        mathEl.innerHTML = `
+        <${elName} id="el" onfocus="alert('fail')"></${elName}>
+        <${elName} id="el-link" href="javascript:alert('fail')" onfocus="alert('fail')"></${elName}>
+        `;
+
+        const el = mathEl.querySelector('#el');
+        const elLink = mathEl.querySelector('#el-link');
+
+        const expectedDefault = (htmlLinkableElements.has(elName)) ? 0 : -1;
+
+        test(() => {
+            assert_equals(el.tabIndex, expectedDefault, "no attribute");
+            el.setAttribute("tabindex", "invalid");
+            assert_equals(el.getAttribute("tabindex"), "invalid");
+            assert_equals(el.tabIndex, expectedDefault, "invalid");
+            el.setAttribute("tabindex", "9999999999");
+            assert_equals(el.getAttribute("tabindex"), "9999999999");
+            assert_equals(el.tabIndex, expectedDefault, "too large integer");
+        }, `default and invalid values for ${elName} without href`);
+        test(() => {
+            assert_equals(elLink.tabIndex, expectedDefault, "no attribute");
+            elLink.setAttribute("tabindex", "invalid");
+            assert_equals(elLink.getAttribute("tabindex"), "invalid");
+            assert_equals(elLink.tabIndex, expectedDefault, "invalid");
+            elLink.setAttribute("tabindex", "9999999999");
+            assert_equals(elLink.getAttribute("tabindex"), "9999999999");
+            assert_equals(elLink.tabIndex, expectedDefault, "too large integer");
+        }, `default and invalid values for ${elName} with href`);
+    });
+  </script>
+</body>
+</html>