Manually update to https://github.com/lit/lit main

src/my-element.ts

@@ -1,19 +1,11 @@
 /**
  * @license
- * Copyright (c) 2019 The Polymer Project Authors. All rights reserved.
- * This code may only be used under the BSD style license found at
- * http://polymer.github.io/LICENSE.txt
- * The complete set of authors may be found at
- * http://polymer.github.io/AUTHORS.txt
- * The complete set of contributors may be found at
- * http://polymer.github.io/CONTRIBUTORS.txt
- * Code distributed by Google as part of the polymer project is also
- * subject to an additional IP rights grant found at
- * http://polymer.github.io/PATENTS.txt
+ * Copyright 2019 Google LLC
+ * SPDX-License-Identifier: BSD-3-Clause
  */
 
 import {LitElement, html, css} from 'lit';
-import {customElement, property} from 'lit/decorators';
+import {customElement, property} from 'lit/decorators.js';
 
 /**
  * An example element.

src/test/my-element_test.ts

@@ -1,3 +1,9 @@
+/**
+ * @license
+ * Copyright 2021 Google LLC
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
 import {MyElement} from '../my-element.js';
 
 import {fixture, html} from '@open-wc/testing';
@@ -48,4 +54,10 @@ suite('my-element', () => {
     `
     );
   });
+
+  test('styling applied', async () => {
+    const el = (await fixture(html`<my-element></my-element>`)) as MyElement;
+    await el.updateComplete;
+    assert.equal(getComputedStyle(el).paddingTop, '16px');
+  });
 });