calebdwilliams
diff --git a/Diff for: ‎jsdom-tests/index.html
+25 b/Diff for: ‎jsdom-tests/index.html
+25
diff --git a/Diff for: ‎jsdom-tests/jsdom.test.js
+36 b/Diff for: ‎jsdom-tests/jsdom.test.js
+36
@@ -0,0 +1,25 @@
+<!doctype html>
+<html>
+  <head>
+    <title>Test document in JSDOM</title>
+    <!--script>${polyfillContents};console.log(ElementInternals)</script-->
+    <script src="polyfill.js"></script>
+  </head>
+  <body>
+    <script>
+      class TestElement extends HTMLElement {
+        static get formAssociated() {
+          return true;
+        }
+
+        constructor() {
+          super();
+          this.internals = this.attachInternals();
+          this.internals.setFormValue('foo');
+        }
+      }
+
+      customElements.define('test-element', TestElement);
+    </script>
+  </body>
+</html>
@@ -0,0 +1,36 @@
+import { JSDOM } from 'jsdom';
+import { readFileSync } from 'fs';
+
+const polyfillContents = readFileSync('./dist/index.js', 'utf-8');
+
+function test(title, condition) {
+  if (!condition) {
+    throw new Error(`${title} failed with error ${error}`);
+  } else {
+    console.log(`${title} passed in JSDOM`);
+  }
+}
+
+JSDOM.fromFile('./jsdom-tests/index.html', {
+  runScripts: 'dangerously'
+}).then(async ({ window }) => {
+  const document = window._document;
+
+  const polyfill = document.createElement('script');
+  polyfill.textContent = polyfillContents;
+
+  document.body.append(polyfill);
+
+  const form = document.createElement('form');
+  const testElement = document.createElement('test-element');
+  testElement.setAttribute('name', 'test');
+
+  form.append(testElement);
+  document.body.append(form);
+
+  setImmediate(async () => {
+    test('ElementInternals is defined on the window', typeof window.ElementInternals !== 'undefined');
+    test('Polyfilled ElementInternals.prototype.form is working', testElement.internals.form === form);
+    test('Polyfilled form attachment is working', new window.FormData(form).get('test') === 'foo');
+  });
+});