Add tests for about_list_tile.0.dart (#150181)

Contributes to https://github.com/flutter/flutter/issues/130459

It adds a test for
- `examples/api/lib/material/about/about_list_tile.0.dart`

dev/bots/check_code_samples.dart

@@ -339,7 +339,6 @@ final Set<String> _knownMissingTests = <String>{
   'examples/api/test/material/search_anchor/search_anchor.0_test.dart',
   'examples/api/test/material/search_anchor/search_anchor.1_test.dart',
   'examples/api/test/material/search_anchor/search_anchor.2_test.dart',
-  'examples/api/test/material/about/about_list_tile.0_test.dart',
   'examples/api/test/material/selection_area/selection_area.0_test.dart',
   'examples/api/test/material/scaffold/scaffold_messenger.of.0_test.dart',
   'examples/api/test/material/scaffold/scaffold_messenger.0_test.dart',

examples/api/test/material/about/about_list_tile.0_test.dart

@@ -0,0 +1,67 @@
+// Copyright 2014 The Flutter 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 'package:flutter/material.dart';
+import 'package:flutter_api_samples/material/about/about_list_tile.0.dart'
+    as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('It should show the about dialog after clicking on the button', (WidgetTester tester) async {
+    await tester.pumpWidget(const example.AboutListTileExampleApp());
+
+    expect(find.widgetWithText(AppBar, 'Show About Example'), findsOne);
+
+    await tester.tap(find.widgetWithText(ElevatedButton, 'Show About Example'));
+    await tester.pumpAndSettle();
+
+    expect(find.byType(AboutDialog), findsOne);
+    expect(find.widgetWithText(AboutDialog, 'Show About Example'), findsOne);
+    expect(find.text('August 2019'), findsOne);
+    expect(find.byType(FlutterLogo), findsOne);
+    expect(find.text('\u{a9} 2014 The Flutter Authors'), findsOne);
+    expect(
+      find.text(
+        "Flutter is Google's UI toolkit for building beautiful, "
+        'natively compiled applications for mobile, web, and desktop '
+        'from a single codebase. Learn more about Flutter at '
+        'https://flutter.dev.',
+        findRichText: true,
+      ),
+      findsOne,
+    );
+  });
+
+  testWidgets('It should show the about dialog after clicking on about list tile in the drawer', (WidgetTester tester) async {
+    await tester.pumpWidget(const example.AboutListTileExampleApp());
+
+    expect(find.widgetWithText(AppBar, 'Show About Example'), findsOne);
+
+    await tester.tap(find.byType(DrawerButton));
+    await tester.pumpAndSettle();
+
+    expect(find.byType(Drawer), findsOne);
+    expect(find.widgetWithText(AboutListTile, 'About Show About Example'), findsOne);
+    expect(find.widgetWithIcon(AboutListTile, Icons.info), findsOne);
+
+    await tester.tap(find.widgetWithIcon(AboutListTile, Icons.info));
+    await tester.pumpAndSettle();
+
+    expect(find.byType(AboutDialog), findsOne);
+    expect(find.widgetWithText(AboutDialog, 'Show About Example'), findsOne);
+    expect(find.text('August 2019'), findsOne);
+    expect(find.byType(FlutterLogo), findsOne);
+    expect(find.text('\u{a9} 2014 The Flutter Authors'), findsOne);
+    expect(
+      find.text(
+        "Flutter is Google's UI toolkit for building beautiful, "
+        'natively compiled applications for mobile, web, and desktop '
+        'from a single codebase. Learn more about Flutter at '
+        'https://flutter.dev.',
+        findRichText: true,
+      ),
+      findsOne,
+    );
+  });
+}