Use @open-wc/testing

Bug: 1358229
Change-Id: I8b17750ee48501225f6e5846c128dc32ef8f9f3e
diff --git a/web/common_test.ts b/web/common_test.ts
index 1382cef..7056e63 100644
--- a/web/common_test.ts
+++ b/web/common_test.ts
@@ -5,7 +5,7 @@
  * found in the LICENSE file.
  */
 
-import './test/test-setup';
+import {assert} from '@open-wc/testing';
 
 import {getGerritHost, getTrailer} from './common';
 
diff --git a/web/self-review-warner_test.ts b/web/self-review-warner_test.ts
index 82b3b16..9016c38 100644
--- a/web/self-review-warner_test.ts
+++ b/web/self-review-warner_test.ts
@@ -5,8 +5,6 @@
  * found in the LICENSE file.
  */
 
-import './test/test-setup';
-
 import {REVIEW_LABEL} from './common';
 
 import {installOnSelfApproval} from './self-review-warner';
diff --git a/web/test/test-setup.ts b/web/test/test-setup.ts
deleted file mode 100644
index 5d31b8e..0000000
--- a/web/test/test-setup.ts
+++ /dev/null
@@ -1,22 +0,0 @@
-/**
- * @license
- * Copyright 2021 The Chromium Authors. All rights reserved.
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-import 'chai/chai';
-
-declare global {
-  interface Window {
-    assert: typeof chai.assert;
-    expect: typeof chai.expect;
-    sinon: typeof sinon;
-  }
-  let assert: typeof chai.assert;
-  let expect: typeof chai.expect;
-  let sinon: typeof sinon;
-}
-window.assert = chai.assert;
-window.expect = chai.expect;
-window.sinon = sinon;