diff --git a/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html b/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html
index d8e82ab642b1a8..9dc9e7e6f0a9d2 100644
--- a/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html
+++ b/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html
@@ -6,61 +6,19 @@
 <meta name="timeout" content="long">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
-<script src="/resources/WebIDLParser.js"></script>
 <script src="support/namespaces.js"></script>
-<script>
-promise_setup(async function() {
-  let attributeNamesWithInterfaceName = [];
-  function addOnAttributes(IDL, interfaceName) {
-    // Parsing the whole IDL file is slow, so use a small regexp to extract only
-    // the part that is relevant for this test.
-    let regexp = new RegExp(`^.*\(partial \)?interface \(mixin \)?${interfaceName}[^{]*{[^{}]*};$`, "m");
-    let parsedIDL = WebIDL2.parse(IDL.match(regexp)[0]);
-    parsedIDL.find(idl => idl.name === interfaceName)
-      .members.map(member => member.name)
-      .filter(name => name.length >= 3 && name.startsWith("on") &&
-              !name.startsWith("onwebkit"))
-      .forEach(name => attributeNamesWithInterfaceName.push({name, interfaceName}));
-  }
-
-  const htmlIDL = await (await fetch("/interfaces/html.idl")).text();
-  // GlobalEventHandlers exist on HTMLElement, SVGElement, and MathMLElement.
-  // WindowEventHandlers exist on HTMLBodyElement, and HTMLFrameSetElement.
-  ["GlobalEventHandlers", "WindowEventHandlers"].forEach(interfaceName => {
-    addOnAttributes(htmlIDL, interfaceName);
-  });
-
-  const encryptedMediaIDL = await (await fetch("/interfaces/encrypted-media.idl")).text();
-  // HTMLMediaElement (the parent for <audio> and <video>) has extra event handlers.
-  addOnAttributes(encryptedMediaIDL, "HTMLMediaElement");
-
-  const svgAnimationsIDL = await (await fetch("/interfaces/svg-animations.idl")).text();
-  // SVGAnimationElement has extra event handlers.
-  addOnAttributes(svgAnimationsIDL, "SVGAnimationElement");
-
-  for (const attributeNameWithInterfaceName of attributeNamesWithInterfaceName) {
-    // Skip attributes that are not implemented in the browser.
-    if (attributeNameWithInterfaceName.interfaceName === 'GlobalEventHandlers' && !(attributeNameWithInterfaceName.name in HTMLElement.prototype)) {
-      continue;
-    }
-    if (attributeNameWithInterfaceName.interfaceName === 'WindowEventHandlers' && !(attributeNameWithInterfaceName.name in HTMLBodyElement.prototype)) {
-      continue;
-    }
-    if (attributeNameWithInterfaceName.interfaceName === 'HTMLMediaElement' && !(attributeNameWithInterfaceName.name in HTMLMediaElement.prototype)) {
-      continue;
+<script type="module">
+  import { getEventHandlerAttributeWithInterfaceNames } from './support/event-handler-attributes.mjs';
+  promise_setup(async function() {
+    for (const attr of await getEventHandlerAttributeWithInterfaceNames()) {
+      promise_test(async () => {
+        NSURI_ARRAY.forEach(attrNs => {
+          assert_equals(trustedTypes.getAttributeType(
+            "dummy", attr.name, "dummyNs", attrNs),
+            attrNs === NSURI_EMPTY ? "TrustedScript" : null,
+            `for attrNs='${attrNs}'`);
+        });
+      }, `getAttributeType("dummy", "${attr.name}", "dummyNs", attrNs)`);
     }
-    if (attributeNameWithInterfaceName.interfaceName === 'SVGAnimationElement' && !(attributeNameWithInterfaceName.name in SVGAnimationElement.prototype)) {
-      continue;
-    }
-
-    promise_test(async () => {
-      NSURI_ARRAY.forEach(attrNs => {
-        assert_equals(trustedTypes.getAttributeType(
-          "dummy", attributeNameWithInterfaceName.name, "dummyNs", attrNs),
-          attrNs === NSURI_EMPTY ? "TrustedScript" : null,
-          `for attrNs='${attrNs}'`);
-      });
-    }, `getAttributeType("dummy", "${attributeNameWithInterfaceName.name}", "dummyNs", attrNs)`);
-  }
-});
+  });
 </script>
diff --git a/trusted-types/set-event-handlers-content-attributes.tentative.html b/trusted-types/set-event-handlers-content-attributes.tentative.html
new file mode 100644
index 00000000000000..0dd5f8b3a08030
--- /dev/null
+++ b/trusted-types/set-event-handlers-content-attributes.tentative.html
@@ -0,0 +1,67 @@
+<!DOCTYPE html>
+<head>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="support/namespaces.js"></script>
+  <meta http-equiv="Content-Security-Policy" content="require-trusted-types-for 'script'">
+</head>
+<body>
+<script type="module">
+  import { getEventHandlerAttributeWithInterfaceNames } from './support/event-handler-attributes.mjs';
+
+  promise_setup(async function() {
+    const input_string = "unsafe_handler()";
+    const output_string = "safe_handler()";
+    let seenSinkName;
+    function resetSeenSinkName() { seenSinkName = undefined; }
+    trustedTypes.createPolicy("default", {
+      createScript: (input, trustedTypeName, sinkName) => {
+        assert_equals(input, input_string);
+        assert_equals(trustedTypeName, "TrustedScript");
+        assert_equals(seenSinkName, undefined);
+        seenSinkName = sinkName;
+        return output_string;
+      }
+    });
+    function elementsImplementingInterface(interfaceName) {
+      switch (interfaceName) {
+      case 'GlobalEventHandlers':
+          return [document.createElement("div"),
+                  document.createElementNS(NSURI_SVG, "g"),
+                  document.createElementNS(NSURI_MATHML, "mrow")];
+      case 'WindowEventHandlers':
+          return [document.createElement("body"),
+                  document.createElement("frameset")];
+      case 'HTMLMediaElement':
+          return [document.createElement("audio"),
+                  document.createElement("video")];
+      case 'SVGAnimationElement':
+         return [document.createElementNS(NSURI_SVG, "animation")];
+      default:
+        throw "Unknown interface";
+      }
+    }
+
+    for (const attr of await getEventHandlerAttributeWithInterfaceNames()) {
+      elementsImplementingInterface(attr.interfaceName).forEach(element => {
+         function cleanup() {
+           resetSeenSinkName();
+           element.removeAttribute(attr.name);
+         }
+         promise_test(async t => {
+           t.add_cleanup(cleanup);
+           element.setAttribute(attr.name, input_string);
+           assert_equals(seenSinkName, `Element ${attr.name}`);
+           assert_equals(element.getAttribute(attr.name),output_string);
+         }, `${element.tagName}.setAttribute(${attr.name}, "${input_string}") calls default policy`);
+         promise_test(async t => {
+           t.add_cleanup(cleanup);
+           element.setAttributeNS(null, attr.name, input_string);
+           assert_equals(seenSinkName, `Element ${attr.name}`);
+           assert_equals(element.getAttribute(attr.name),output_string);
+         }, `${element.tagName}.setAttributeNS(${attr.name}, "${input_string}") calls default policy`);
+      });
+    }
+  });
+</script>
+</body>
diff --git a/trusted-types/support/event-handler-attributes.mjs b/trusted-types/support/event-handler-attributes.mjs
new file mode 100644
index 00000000000000..8d54524950b9c0
--- /dev/null
+++ b/trusted-types/support/event-handler-attributes.mjs
@@ -0,0 +1,47 @@
+import '/resources/WebIDLParser.js';
+
+export async function getEventHandlerAttributeWithInterfaceNames() {
+  let attributeNamesWithInterfaceName = [];
+  function isAttributeImplemented(interfaceName, name) {
+    switch (interfaceName) {
+      case 'GlobalEventHandlers':
+        return name in HTMLElement.prototype;
+      case 'WindowEventHandlers':
+        return name in HTMLBodyElement.prototype;
+      case 'HTMLMediaElement':
+        return name in HTMLMediaElement.prototype;
+      case 'SVGAnimationElement':
+        return name in SVGAnimationElement.prototype;
+      default:
+       throw "Unknown interface";
+    }
+  }
+  function addOnAttributes(IDL, interfaceName) {
+    // Parsing the whole IDL file is slow, so use a small regexp to extract only
+    // the part that is relevant for this test.
+    let regexp = new RegExp(`^.*\(partial \)?interface \(mixin \)?${interfaceName}[^{]*{[^{}]*};$`, "m");
+    let parsedIDL = WebIDL2.parse(IDL.match(regexp)[0]);
+    parsedIDL.find(idl => idl.name === interfaceName)
+      .members.map(member => member.name)
+      .filter(name => name.length >= 3 && name.startsWith("on") &&
+              !name.startsWith("onwebkit") &&
+              isAttributeImplemented(interfaceName, name))
+      .forEach(name => attributeNamesWithInterfaceName.push({name, interfaceName}));
+  }
+  const htmlIDL = await (await fetch("/interfaces/html.idl")).text();
+  // GlobalEventHandlers exist on HTMLElement, SVGElement, and MathMLElement.
+  // WindowEventHandlers exist on HTMLBodyElement, and HTMLFrameSetElement.
+  ["GlobalEventHandlers", "WindowEventHandlers"].forEach(interfaceName => {
+    addOnAttributes(htmlIDL, interfaceName);
+  });
+
+  const encryptedMediaIDL = await (await fetch("/interfaces/encrypted-media.idl")).text();
+  // HTMLMediaElement (the parent for <audio> and <video>) has extra event handlers.
+  addOnAttributes(encryptedMediaIDL, "HTMLMediaElement");
+
+  const svgAnimationsIDL = await (await fetch("/interfaces/svg-animations.idl")).text();
+  // SVGAnimationElement has extra event handlers.
+  addOnAttributes(svgAnimationsIDL, "SVGAnimationElement");
+
+  return attributeNamesWithInterfaceName;
+}