Use @open-wc/testing

Bug: 1358229
Change-Id: I670ef3d68b31b32017eef43a528b09e40d8c3a16
diff --git a/web/landingwidget_test.ts b/web/landingwidget_test.ts
index 5a0bd2c..e6b79e5 100644
--- a/web/landingwidget_test.ts
+++ b/web/landingwidget_test.ts
@@ -1,4 +1,4 @@
-import './test/test-setup';
+import {assert} from '@open-wc/testing';
 import './landingwidget';
 import {ChromiumLandingWidget} from './landingwidget';
 
diff --git a/web/test/test-setup.ts b/web/test/test-setup.ts
deleted file mode 100644
index a408e76..0000000
--- a/web/test/test-setup.ts
+++ /dev/null
@@ -1,15 +0,0 @@
-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;