improve web-platform test harness

Author: anonrig

src/wpt/harness/assertions.ts

@@ -81,9 +81,14 @@ declare global {
     maybeDescription?: string
   ): Promise<unknown>;
 
+  function assert_own_property(
+    object: object,
+    property_name: string | symbol,
+    description?: string
+  ): void;
   function assert_not_own_property(
     object: object,
-    property_name: string,
+    property_name: string | symbol,
     description?: string
   ): void;
   function promise_rejects_js(
@@ -439,6 +444,21 @@ globalThis.promise_rejects_dom = (
     });
 };
 
+/**
+ * Assert that ``object`` has an own property with name ``property_name``.
+ *
+ * @param object - Object that should have the given property.
+ * @param property_name - Property name to test.
+ * @param [description] - Description of the condition being tested.
+ */
+globalThis.assert_own_property = (object, property_name, description): void => {
+  ok(
+    Object.prototype.hasOwnProperty.call(object, property_name),
+    `expected property ${String(property_name)} missing on object: ` +
+      (description ?? '')
+  );
+};
+
 /**
  * Assert that ``object`` does not have an own property with name ``property_name``.
  *
@@ -453,7 +473,7 @@ globalThis.assert_not_own_property = (
 ): void => {
   ok(
     !Object.prototype.hasOwnProperty.call(object, property_name),
-    `unexpected property ${property_name} is found on object: ` +
+    `unexpected property ${String(property_name)} is found on object: ` +
       (description ?? '')
   );
 };

src/wpt/harness/globals.ts

@@ -29,6 +29,15 @@ import { getBindingPath } from './common';
 // @ts-expect-error We're just exposing enough stuff for the tests to pass; it's not a perfect match
 globalThis.self = globalThis;
 
+// WPT tests use self.URL which requires URL to be an own property of globalThis
+globalThis.URL = URL;
+
+// Some WPT tests reference addEventListener at the top level during file evaluation.
+// workerd doesn't have addEventListener on the global (it uses module exports instead),
+// so we provide a no-op stub to allow test files to load without throwing.
+// Tests that actually need addEventListener functionality should be marked as omitted.
+globalThis.addEventListener = (): void => {};
+
 // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment,@typescript-eslint/no-unsafe-member-access --  We're just exposing enough stuff for the tests to pass; it's not a perfect match
 globalThis.Window = Object.getPrototypeOf(globalThis).constructor;