diff --git a/Tests/LibWeb/Text/expected/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.txt b/Tests/LibWeb/Text/expected/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.txt
new file mode 100644
index 00000000000..9f79a071740
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.txt
@@ -0,0 +1,99 @@
+Harness status: OK
+
+Found 93 tests
+
+90 Pass
+3 Fail
+Pass	getAttributeType("dummy", "onabort", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onauxclick", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onbeforeinput", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onbeforematch", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onbeforetoggle", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onblur", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oncancel", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oncanplay", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oncanplaythrough", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onchange", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onclick", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onclose", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oncommand", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oncontextlost", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oncontextmenu", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oncontextrestored", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oncopy", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oncuechange", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oncut", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ondblclick", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ondrag", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ondragend", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ondragenter", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ondragleave", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ondragover", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ondragstart", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ondrop", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ondurationchange", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onemptied", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onended", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onerror", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onfocus", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onformdata", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oninput", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "oninvalid", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onkeydown", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onkeypress", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onkeyup", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onload", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onloadeddata", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onloadedmetadata", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onloadstart", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onmousedown", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onmouseenter", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onmouseleave", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onmousemove", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onmouseout", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onmouseover", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onmouseup", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onpaste", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onpause", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onplay", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onplaying", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onprogress", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onratechange", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onreset", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onresize", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onscroll", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onscrollend", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onsecuritypolicyviolation", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onseeked", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onseeking", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onselect", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onslotchange", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onstalled", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onsubmit", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onsuspend", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ontimeupdate", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ontoggle", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onvolumechange", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onwaiting", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onwheel", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onafterprint", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onbeforeprint", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onbeforeunload", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onhashchange", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onlanguagechange", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onmessage", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onmessageerror", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onoffline", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "ononline", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onpagehide", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onpagereveal", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onpageshow", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onpageswap", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onpopstate", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onrejectionhandled", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onstorage", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onunhandledrejection", "dummyNs", attrNs)
+Pass	getAttributeType("dummy", "onunload", "dummyNs", attrNs)
+Fail	getAttributeType("dummy", "onbegin", "dummyNs", attrNs)
+Fail	getAttributeType("dummy", "onend", "dummyNs", attrNs)
+Fail	getAttributeType("dummy", "onrepeat", "dummyNs", attrNs)
diff --git a/Tests/LibWeb/Text/expected/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-namespace.txt b/Tests/LibWeb/Text/expected/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-namespace.txt
new file mode 100644
index 00000000000..4be7a5aafd4
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-namespace.txt
@@ -0,0 +1,26 @@
+Harness status: OK
+
+Found 21 tests
+
+21 Pass
+Pass	0: getAttributeType with full namespace info.
+Pass	0: getAttributeType with element namespace and empty attribute namespace
+Pass	0: getAttributeType without namespaces.
+Pass	0: getAttributeType with undefined and empty namespace.
+Pass	0: getAttributeType with empty and undefined namespace.
+Pass	0: getAttributeType with empty namespaces.
+Pass	0: getAttributeType with element namespace and empty attribute namespace.
+Pass	1: getAttributeType with full namespace info.
+Pass	1: getAttributeType with element namespace and empty attribute namespace
+Pass	1: getAttributeType without namespaces.
+Pass	1: getAttributeType with undefined and empty namespace.
+Pass	1: getAttributeType with empty and undefined namespace.
+Pass	1: getAttributeType with empty namespaces.
+Pass	1: getAttributeType with element namespace and empty attribute namespace.
+Pass	2: getAttributeType with full namespace info.
+Pass	2: getAttributeType with element namespace and empty attribute namespace
+Pass	2: getAttributeType without namespaces.
+Pass	2: getAttributeType with undefined and empty namespace.
+Pass	2: getAttributeType with empty and undefined namespace.
+Pass	2: getAttributeType with empty namespaces.
+Pass	2: getAttributeType with element namespace and empty attribute namespace.
diff --git a/Tests/LibWeb/Text/expected/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-svg.txt b/Tests/LibWeb/Text/expected/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-svg.txt
new file mode 100644
index 00000000000..b37d7904646
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-svg.txt
@@ -0,0 +1,9 @@
+Harness status: OK
+
+Found 4 tests
+
+4 Pass
+Pass	trustedTypes.getAttributeType html script[href]
+Pass	trustedTypes.getAttributeType svg script[href]
+Pass	trustedTypes.getAttributeType svg script[href] xlink href
+Pass	trustedTypes.getAttributeType svg script[href] other href
diff --git a/Tests/LibWeb/Text/input/wpt-import/interfaces/encrypted-media.idl b/Tests/LibWeb/Text/input/wpt-import/interfaces/encrypted-media.idl
new file mode 100644
index 00000000000..c034cd0bf0d
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/interfaces/encrypted-media.idl
@@ -0,0 +1,132 @@
+// GENERATED CONTENT - DO NOT EDIT
+// Content was automatically extracted by Reffy into webref
+// (https://github.com/w3c/webref)
+// Source: Encrypted Media Extensions (https://w3c.github.io/encrypted-media/)
+
+[Exposed=Window]
+partial interface Navigator {
+  [SecureContext] Promise<MediaKeySystemAccess> requestMediaKeySystemAccess (
+      DOMString keySystem,
+      sequence<MediaKeySystemConfiguration> supportedConfigurations);
+};
+
+enum MediaKeysRequirement {
+  "required",
+  "optional",
+  "not-allowed"
+};
+
+dictionary MediaKeySystemConfiguration {
+  DOMString                               label = "";
+  sequence<DOMString>                     initDataTypes = [];
+  sequence<MediaKeySystemMediaCapability> audioCapabilities = [];
+  sequence<MediaKeySystemMediaCapability> videoCapabilities = [];
+  MediaKeysRequirement                    distinctiveIdentifier = "optional";
+  MediaKeysRequirement                    persistentState = "optional";
+  sequence<DOMString>                     sessionTypes;
+};
+
+dictionary MediaKeySystemMediaCapability {
+  DOMString contentType = "";
+  DOMString? encryptionScheme = null;
+  DOMString robustness = "";
+};
+
+[Exposed=Window, SecureContext] interface MediaKeySystemAccess {
+  readonly attribute DOMString keySystem;
+  MediaKeySystemConfiguration  getConfiguration ();
+  Promise<MediaKeys>           createMediaKeys ();
+};
+
+enum MediaKeySessionType {
+  "temporary",
+  "persistent-license"
+};
+
+[Exposed=Window, SecureContext] interface MediaKeys {
+    MediaKeySession createSession (optional MediaKeySessionType sessionType = "temporary");
+    Promise<MediaKeyStatus> getStatusForPolicy (optional MediaKeysPolicy policy = {});
+    Promise<boolean> setServerCertificate (BufferSource serverCertificate);
+};
+
+dictionary MediaKeysPolicy {
+    DOMString minHdcpVersion;
+};
+
+enum MediaKeySessionClosedReason {
+  "internal-error",
+  "closed-by-application",
+  "release-acknowledged",
+  "hardware-context-reset",
+  "resource-evicted"
+};
+
+[Exposed=Window, SecureContext] interface MediaKeySession : EventTarget {
+  readonly        attribute DOMString                            sessionId;
+  readonly        attribute unrestricted double                  expiration;
+  readonly        attribute Promise<MediaKeySessionClosedReason> closed;
+  readonly        attribute MediaKeyStatusMap                    keyStatuses;
+                  attribute EventHandler                         onkeystatuseschange;
+                  attribute EventHandler                         onmessage;
+  Promise<undefined>    generateRequest (DOMString initDataType, BufferSource initData);
+  Promise<boolean> load (DOMString sessionId);
+  Promise<undefined>    update (BufferSource response);
+  Promise<undefined>    close ();
+  Promise<undefined>    remove ();
+};
+
+[Exposed=Window, SecureContext] interface MediaKeyStatusMap {
+  iterable<BufferSource,MediaKeyStatus>;
+  readonly attribute unsigned long size;
+  boolean has (BufferSource keyId);
+  (MediaKeyStatus or undefined) get (BufferSource keyId);
+};
+
+enum MediaKeyStatus {
+  "usable",
+  "expired",
+  "released",
+  "output-restricted",
+  "output-downscaled",
+  "usable-in-future",
+  "status-pending",
+  "internal-error"
+};
+
+enum MediaKeyMessageType {
+  "license-request",
+  "license-renewal",
+  "license-release",
+  "individualization-request"
+};
+
+[Exposed=Window, SecureContext]
+interface MediaKeyMessageEvent : Event {
+  constructor(DOMString type, MediaKeyMessageEventInit eventInitDict);
+  readonly attribute MediaKeyMessageType messageType;
+  readonly attribute ArrayBuffer         message;
+};
+
+dictionary MediaKeyMessageEventInit : EventInit {
+  required MediaKeyMessageType messageType;
+  required ArrayBuffer         message;
+};
+
+[Exposed=Window] partial interface HTMLMediaElement {
+  [SecureContext] readonly        attribute MediaKeys?   mediaKeys;
+                                  attribute EventHandler onencrypted;
+                                  attribute EventHandler onwaitingforkey;
+  [SecureContext] Promise<undefined> setMediaKeys (MediaKeys? mediaKeys);
+};
+
+[Exposed=Window]
+interface MediaEncryptedEvent : Event {
+    constructor(DOMString type, optional MediaEncryptedEventInit eventInitDict = {});
+    readonly        attribute DOMString    initDataType;
+    readonly        attribute ArrayBuffer? initData;
+};
+
+dictionary MediaEncryptedEventInit : EventInit {
+  DOMString    initDataType = "";
+  ArrayBuffer? initData = null;
+};
diff --git a/Tests/LibWeb/Text/input/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html b/Tests/LibWeb/Text/input/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html
new file mode 100644
index 00000000000..88a18bf695a
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<link rel="help" href="https://w3c.github.io/trusted-types/dist/spec/#dom-trustedtypepolicyfactory-getattributetype">
+<link rel="help" href="https://w3c.github.io/trusted-types/dist/spec/#abstract-opdef-get-trusted-type-data-for-attribute">
+<link rel="help" href="https://github.com/w3c/trusted-types/issues/520">
+<meta name="assert" content="getAttributeType() with empty attributeNs returns 'TrustedScript' for event handler content attributes.">
+<meta name="timeout" content="long">
+<script src="../resources/testharness.js"></script>
+<script src="../resources/testharnessreport.js"></script>
+<script src="support/namespaces.js"></script>
+<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, NSURI_HTML, attrNs),
+            attrNs === NSURI_EMPTY ? "TrustedScript" : null,
+            `for attrNs='${attrNs}'`);
+        });
+      }, `getAttributeType("dummy", "${attr.name}", "dummyNs", attrNs)`);
+    }
+  });
+</script>
diff --git a/Tests/LibWeb/Text/input/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-namespace.html b/Tests/LibWeb/Text/input/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-namespace.html
new file mode 100644
index 00000000000..27e7d2442f6
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-namespace.html
@@ -0,0 +1,62 @@
+<!DOCTYPE html>
+<script src="../resources/testharness.js" ></script>
+<script src="../resources/testharnessreport.js"></script>
+<body>
+<script>
+// Tests for getAttributeType with namespaces, based on
+// https://crbug.com/1305293 (attachment on comment 0).
+
+const parser = new DOMParser();
+[
+  parser.parseFromString(
+    '<!doctype html><html><head><script src="./foo.js"><'+'/script></head></html>',
+    'text/html'),
+  parser.parseFromString(
+    '<html xmlns="http://www.w3.org/1999/xhtml"><head><script src="./foo.js" /></head></html>',
+    'application/xhtml+xml'),
+  parser.parseFromString(
+  '<xml xmlns:html="http://www.w3.org/1999/xhtml"><html:script src="./foo.js" /></xml>',
+  'application/xml')
+].forEach((doc, index) => {
+  const element = doc.getElementsByTagNameNS("http://www.w3.org/1999/xhtml", 'script')[0];
+  const attribute = element.getAttributeNode("src");
+
+  test(_ => {
+    assert_equals(trustedTypes.getAttributeType(
+      element.localName, attribute.name, element.namespaceURI, attribute.namespaceURI),
+      "TrustedScriptURL");
+  }, `${index}: getAttributeType with full namespace info.`);
+
+  test(_ => {
+    assert_equals(trustedTypes.getAttributeType(
+      element.localName, attribute.name, element.namespaceURI, undefined),
+      "TrustedScriptURL");
+  },`${index}: getAttributeType with element namespace and empty attribute namespace`);
+
+  test(_ => {
+    assert_equals(trustedTypes.getAttributeType(
+        element.localName, attribute.name, undefined, undefined), "TrustedScriptURL");
+  }, `${index}: getAttributeType without namespaces.`);
+
+  test(_ => {
+    assert_equals(trustedTypes.getAttributeType(
+        element.localName, attribute.name, undefined, ""), "TrustedScriptURL");
+  }, `${index}: getAttributeType with undefined and empty namespace.`);
+
+  test(_ => {
+    assert_equals(trustedTypes.getAttributeType(
+      element.localName, attribute.name, "", undefined), "TrustedScriptURL");
+  }, `${index}: getAttributeType with empty and undefined namespace.`);
+
+  test(_ => {
+    assert_equals(trustedTypes.getAttributeType(
+        element.localName, attribute.name, "", ""), "TrustedScriptURL");
+  }, `${index}: getAttributeType with empty namespaces.`);
+
+  test(_ => {
+    assert_equals(trustedTypes.getAttributeType(
+        element.localName, attribute.name, element.namespaceURI, ""), "TrustedScriptURL");
+  }, `${index}: getAttributeType with element namespace and empty attribute namespace.`);
+});
+</script>
+</body>
diff --git a/Tests/LibWeb/Text/input/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-svg.html b/Tests/LibWeb/Text/input/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-svg.html
new file mode 100644
index 00000000000..194c4ba9b75
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/trusted-types/TrustedTypePolicyFactory-getAttributeType-svg.html
@@ -0,0 +1,22 @@
+<!DOCTYPE html>
+<script src="../resources/testharness.js" ></script>
+<script src="../resources/testharnessreport.js"></script>
+<script src="support/helper.sub.js"></script>
+
+<body>
+<div id="target"></div>
+<script>
+  test(t => {
+    assert_equals(trustedTypes.getAttributeType("script", "href"), null);
+  }, "trustedTypes.getAttributeType html script[href]");
+  test(t => {
+    assert_equals(trustedTypes.getAttributeType("script", "href", "http://www.w3.org/2000/svg"), "TrustedScriptURL");
+  }, "trustedTypes.getAttributeType svg script[href]");
+  test(t => {
+    assert_equals(trustedTypes.getAttributeType("script", "href", "http://www.w3.org/2000/svg", "http://www.w3.org/1999/xlink"), "TrustedScriptURL");
+  }, "trustedTypes.getAttributeType svg script[href] xlink href");
+  test(t => {
+    assert_equals(trustedTypes.getAttributeType("script", "href", "http://www.w3.org/2000/svg", "http://www.w3.org/other"), null);
+  }, "trustedTypes.getAttributeType svg script[href] other href");
+</script>
+</body>
diff --git a/Tests/LibWeb/Text/input/wpt-import/trusted-types/support/event-handler-attributes.mjs b/Tests/LibWeb/Text/input/wpt-import/trusted-types/support/event-handler-attributes.mjs
new file mode 100644
index 00000000000..e3484f19317
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/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;
+}
diff --git a/Tests/LibWeb/Text/input/wpt-import/trusted-types/support/helper.sub.js b/Tests/LibWeb/Text/input/wpt-import/trusted-types/support/helper.sub.js
new file mode 100644
index 00000000000..b680256b7a2
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/trusted-types/support/helper.sub.js
@@ -0,0 +1,172 @@
+const INPUTS = {
+  HTML: "Hi, I want to be transformed!",
+  SCRIPT: "Hi, I want to be transformed!",
+  SCRIPTURL: "http://this.is.a.scripturl.test/",
+};
+
+const RESULTS = {
+  HTML: "Quack, I want to be a duck!",
+  SCRIPT: "Meow, I want to be a cat!",
+  SCRIPTURL: "http://this.is.a.successful.test/",
+};
+
+function createHTMLJS(html) {
+  return html.replace("Hi", "Quack")
+      .replace("transformed", "a duck");
+}
+
+function createScriptJS(script) {
+  return script.replace("Hi", "Meow")
+      .replace("transformed", "a cat");
+}
+
+function createScriptURLJS(scripturl) {
+  return scripturl.replace("scripturl", "successful");
+}
+
+function createHTMLJSWithThreeArguments(html0, html1, html2) {
+  return html0 + html1 + html2;
+}
+
+function createScriptJSWithThreeArguments(script0, script1, script2) {
+  return script0 + script1 + script2;
+}
+
+function createScriptURLJSWithThreeArguments(scripturl0, scripturl1, scripturl2) {
+  return scripturl0 + scripturl1 + scripturl2;
+}
+
+function createHTML_policy(win, c) {
+  return win.trustedTypes.createPolicy('SomeHTMLPolicyName' + c, { createHTML: createHTMLJS });
+}
+
+function createScript_policy(win, c) {
+  return win.trustedTypes.createPolicy('SomeScriptPolicyName' + c, { createScript: createScriptJS });
+}
+
+function createScriptURL_policy(win, c) {
+  return win.trustedTypes.createPolicy('SomeScriptURLPolicyName' + c, { createScriptURL: createScriptURLJS });
+}
+
+function assert_element_accepts_trusted_html(win, c, t, tag, attribute, expected) {
+  let p = createHTML_policy(win, c);
+  let html = p.createHTML(INPUTS.HTML);
+  assert_element_accepts_trusted_type(tag, attribute, html, expected);
+}
+
+function assert_element_accepts_trusted_script(win, c, t, tag, attribute, expected) {
+  let p = createScript_policy(win, c);
+  let script = p.createScript(INPUTS.SCRIPT);
+  assert_element_accepts_trusted_type(tag, attribute, script, expected);
+}
+
+function assert_element_accepts_trusted_script_url(win, c, t, tag, attribute, expected) {
+  let p = createScriptURL_policy(win, c);
+  let scripturl = p.createScriptURL(INPUTS.SCRIPTURL);
+  assert_element_accepts_trusted_type(tag, attribute, scripturl, expected);
+}
+
+function assert_element_accepts_trusted_type(tag, attribute, value, expected) {
+  let elem = document.createElement(tag);
+  elem[attribute] = value;
+  assert_equals(elem[attribute] + "", expected);
+}
+
+function assert_throws_no_trusted_type(tag, attribute, value) {
+  let elem = document.createElement(tag);
+  let prev = elem[attribute];
+  assert_throws_js(TypeError, _ => {
+    elem[attribute] = value;
+  });
+  assert_equals(elem[attribute], prev);
+}
+
+function assert_element_accepts_trusted_html_explicit_set(win, c, t, tag, attribute, expected) {
+  let p = createHTML_policy(win, c);
+  let html = p.createHTML(INPUTS.HTML);
+  assert_element_accepts_trusted_type_explicit_set(tag, attribute, html, expected);
+}
+
+function assert_element_accepts_trusted_script_explicit_set(win, c, t, tag, attribute, expected) {
+  let p = createScript_policy(win, c);
+  let script = p.createScript(INPUTS.SCRIPT);
+  assert_element_accepts_trusted_type_explicit_set(tag, attribute, script, expected);
+}
+
+function assert_element_accepts_trusted_script_url_explicit_set(win, c, t, tag, attribute, expected) {
+  let p = createScriptURL_policy(win, c);
+  let scripturl = p.createScriptURL(INPUTS.SCRIPTURL);
+  assert_element_accepts_trusted_type_explicit_set(tag, attribute, scripturl, expected);
+}
+
+function assert_element_accepts_trusted_type_explicit_set(tag, attribute, value, expected) {
+  let elem = document.createElement(tag);
+  elem.setAttribute(attribute, value);
+  if (!/^on/.test(attribute)) { // "on" attributes are converted to functions.
+    assert_equals(elem[attribute] + "", expected);
+  }
+  assert_equals(elem.getAttribute(attribute), expected);
+}
+
+function assert_throws_no_trusted_type_explicit_set(tag, attribute, value) {
+  let elem = document.createElement(tag);
+  let prev = elem[attribute];
+  assert_throws_js(TypeError, _ => {
+    elem.setAttribute(attribute, value);
+  });
+  assert_equals(elem[attribute], prev);
+  assert_equals(elem.getAttribute(attribute), null);
+}
+
+function assert_element_accepts_non_trusted_type_explicit_set(tag, attribute, value, expected) {
+  let elem = document.createElement(tag);
+  elem.setAttribute(attribute, value);
+  assert_equals(elem[attribute] + "", expected);
+  assert_equals(elem.getAttribute(attribute), expected);
+}
+
+let namespace = null;
+function assert_element_accepts_trusted_html_set_ns(win, c, t, tag, attribute, expected) {
+  let p = createHTML_policy(win, c);
+  let html = p.createHTML(INPUTS.HTML);
+  assert_element_accepts_trusted_type_set_ns(tag, attribute, html, expected);
+}
+
+function assert_element_accepts_trusted_script_set_ns(win, c, t, tag, attribute, expected) {
+  let p = createScript_policy(win, c);
+  let script = p.createScript(INPUTS.SCRIPT);
+  assert_element_accepts_trusted_type_set_ns(tag, attribute, script, expected);
+}
+
+function assert_element_accepts_trusted_script_url_set_ns(win, c, t, tag, attribute, expected) {
+  let p = createScriptURL_policy(win, c);
+  let scripturl = p.createScriptURL(INPUTS.SCRIPTURL);
+  assert_element_accepts_trusted_type_set_ns(tag, attribute, scripturl, expected);
+}
+
+function assert_element_accepts_trusted_type_set_ns(tag, attribute, value, expected) {
+  let elem = document.createElement(tag);
+  elem.setAttributeNS(namespace, attribute, value);
+  let attr_node = elem.getAttributeNodeNS(namespace, attribute);
+  assert_equals(attr_node.value + "", expected);
+}
+
+function assert_throws_no_trusted_type_set_ns(tag, attribute, value) {
+  let elem = document.createElement(tag);
+  assert_throws_js(TypeError, _ => {
+    elem.setAttributeNS(namespace, attribute, value);
+  });
+}
+
+function assert_element_accepts_value_set_ns(tag, attribute, value, expected,
+                                                        elementNamespace, attributeNamespace) {
+  let elem = document.createElementNS(elementNamespace, tag);
+  elem.setAttributeNS(attributeNamespace, attribute, value);
+  let attr_node = elem.getAttributeNodeNS(attributeNamespace, attribute);
+  assert_equals(attr_node.value + "", expected);
+}
+
+function getGlobalThisStr() {
+  // `globalThis.toString()` is of the form "[Object <someName>]".
+  return globalThis.toString().split(" ")[1].slice(0, -1);
+}
diff --git a/Tests/LibWeb/Text/input/wpt-import/trusted-types/support/namespaces.js b/Tests/LibWeb/Text/input/wpt-import/trusted-types/support/namespaces.js
new file mode 100644
index 00000000000..72271293bae
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/trusted-types/support/namespaces.js
@@ -0,0 +1,24 @@
+const NSURI_EMPTY = '';
+const NSURI_FOO = 'https://example.com/namespace';
+const NSURI_HTML = 'http://www.w3.org/1999/xhtml';
+const NSURI_MATHML = 'http://www.w3.org/1998/Math/MathML';
+const NSURI_RDF = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'
+const NSURI_SVG = 'http://www.w3.org/2000/svg';
+const NSURI_XLINK = 'http://www.w3.org/1999/xlink';
+const NSURI_XML = 'http://www.w3.org/XML/1998/namespace';
+const NSURI_XMLNS = 'http://www.w3.org/XML/1998/namespace';
+const NSURI_XSLT = 'http://www.w3.org/1999/XSL/Transform';
+const NSURI_XUL = 'http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul';
+const NSURI_ARRAY = [
+  NSURI_EMPTY,
+  NSURI_FOO,
+  NSURI_HTML,
+  NSURI_MATHML,
+  NSURI_RDF,
+  NSURI_SVG,
+  NSURI_XLINK,
+  NSURI_XML,
+  NSURI_XMLNS,
+  NSURI_XSLT,
+  NSURI_XUL,
+];