add tests for loader mock

Author: just-boris

src/app-layout/__tests__/widget-loader-mock.test.tsx

@@ -0,0 +1,35 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+import React from 'react';
+import { waitFor } from '@testing-library/react';
+
+import AppLayout from '../../../lib/components/app-layout';
+import { describeWithAppLayoutFeatureFlagEnabled } from '../../internal/widgets/__tests__/utils';
+import { describeEachAppLayout, renderComponent } from './utils';
+
+jest.mock('../../../lib/components/internal/widgets/loader-mock', () => {
+  // set this flag before the module is instantiated
+  (window as any)[Symbol.for('awsui-custom-flags')] = { appLayoutDelayedWidget: true };
+  return jest.requireActual('../../../lib/components/internal/widgets/loader-mock');
+});
+
+describeEachAppLayout({ themes: ['refresh-toolbar'], sizes: ['desktop'] }, () => {
+  test('renders instantly when widget is not activated', () => {
+    const { wrapper } = renderComponent(<AppLayout />);
+    expect(wrapper.findNavigation()).toBeTruthy();
+    expect(wrapper.findTools()).toBeTruthy();
+  });
+
+  describeWithAppLayoutFeatureFlagEnabled(() => {
+    test('renders app layout with a delay', async () => {
+      const { wrapper } = renderComponent(<AppLayout />);
+      expect(wrapper.findNavigation()).toBeFalsy();
+      expect(wrapper.findTools()).toBeFalsy();
+
+      await waitFor(() => {
+        expect(wrapper.findNavigation()).toBeTruthy();
+        expect(wrapper.findTools()).toBeTruthy();
+      });
+    });
+  });
+});