test: add property descriptor tests for Web API globals

test/fixtures/tz-version.txt

@@ -1 +1 @@
-2026e
+2026f

test/parallel/test-global-webapi-property-descriptors.js

@@ -0,0 +1,88 @@
+'use strict';
+
+// Verify that global Web API constructors (FormData, Headers, Request,
+// Response) have property descriptors that match the Web IDL specification.
+// Specifically, they should be data properties that are writable,
+// non-enumerable, and configurable.
+// See: https://webidl.spec.whatwg.org/#es-interfaces
+// Fixes: https://github.com/nodejs/node/issues/45099
+
+const common = require('../common');
+const assert = require('assert');
+
+// Web API interfaces exposed on globalThis per Web IDL spec
+const webAPIInterfaces = [
+  'Headers',
+  'Request',
+  'Response',
+  'FormData',
+];
+
+for (const name of webAPIInterfaces) {
+  const desc = Object.getOwnPropertyDescriptor(globalThis, name);
+
+  assert.notStrictEqual(desc, undefined,
+    `globalThis should have own property '${name}'`);
+
+  // Must be a data descriptor (has 'value'), not an accessor descriptor
+  assert.ok('value' in desc,
+    `globalThis.${name} descriptor should be a data property`);
+
+  // The value should be the constructor
+  assert.strictEqual(desc.value, globalThis[name],
+    `globalThis.${name} descriptor value should match globalThis.${name}`);
+
+  // Per Web IDL: writable = true
+  assert.strictEqual(desc.writable, true,
+    `globalThis.${name} should be writable`);
+
+  // Per Web IDL: enumerable = false
+  assert.strictEqual(desc.enumerable, false,
+    `globalThis.${name} should not be enumerable`);
+
+  // Per Web IDL: configurable = true
+  assert.strictEqual(desc.configurable, true,
+    `globalThis.${name} should be configurable`);
+
+  // Verify the value is actually a function (constructor)
+  assert.strictEqual(typeof desc.value, 'function',
+    `globalThis.${name} should be a function`);
+}
+
+// Also verify that these properties can be overwritten (writable)
+for (const name of webAPIInterfaces) {
+  const original = globalThis[name];
+  const replacement = function replacement() {};
+  globalThis[name] = replacement;
+  assert.strictEqual(globalThis[name], replacement,
+    `globalThis.${name} should be overwritable`);
+  // Restore original
+  globalThis[name] = original;
+}
+
+// Also verify that these properties can be deleted (configurable)
+for (const name of webAPIInterfaces) {
+  const original = globalThis[name];
+  assert.ok(delete globalThis[name],
+    `globalThis.${name} should be deletable`);
+  assert.strictEqual(globalThis[name], undefined,
+    `globalThis.${name} should be undefined after deletion`);
+  // Restore
+  Object.defineProperty(globalThis, name, {
+    __proto__: null,
+    writable: true,
+    enumerable: false,
+    configurable: true,
+    value: original,
+  });
+}
+
+// Verify these are not enumerable (should not appear in for-in)
+const enumerableKeys = [];
+for (const key in globalThis) {
+  if (webAPIInterfaces.includes(key)) {
+    enumerableKeys.push(key);
+  }
+}
+assert.deepStrictEqual(enumerableKeys, [],
+  'Web API interfaces should not be enumerable on globalThis');