Write tests for API examples of BottomNavigationBar and IconButton (#138188)

This PR writes tests for a few of the API examples (not all), as requested in #130459. For the test names, I used the existing tests in the `api` folder as guide.

dev/bots/check_code_samples.dart

@@ -338,13 +338,9 @@ final Set<String> _knownMissingTests = <String>{
   'examples/api/test/material/snack_bar/snack_bar.0_test.dart',
   'examples/api/test/material/snack_bar/snack_bar.2_test.dart',
   'examples/api/test/material/snack_bar/snack_bar.1_test.dart',
-  'examples/api/test/material/bottom_navigation_bar/bottom_navigation_bar.0_test.dart',
-  'examples/api/test/material/bottom_navigation_bar/bottom_navigation_bar.1_test.dart',
   'examples/api/test/material/outlined_button/outlined_button.0_test.dart',
   'examples/api/test/material/icon_button/icon_button.2_test.dart',
   'examples/api/test/material/icon_button/icon_button.3_test.dart',
-  'examples/api/test/material/icon_button/icon_button.0_test.dart',
-  'examples/api/test/material/icon_button/icon_button.1_test.dart',
   'examples/api/test/material/expansion_panel/expansion_panel_list.expansion_panel_list_radio.0_test.dart',
   'examples/api/test/material/input_decorator/input_decoration.1_test.dart',
   'examples/api/test/material/input_decorator/input_decoration.prefix_icon_constraints.0_test.dart',

examples/api/test/material/bottom_navigation_bar/bottom_navigation_bar.0_test.dart

+// 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/bottom_navigation_bar/bottom_navigation_bar.0.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('BottomNavigationBar Updates Screen Content', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.BottomNavigationBarExampleApp(),
+    );
+
+    expect(find.widgetWithText(AppBar, 'BottomNavigationBar Sample'), findsOneWidget);
+    expect(find.byType(BottomNavigationBar), findsOneWidget);
+    expect(find.widgetWithText(Center, 'Index 0: Home'), findsOneWidget);
+
+    await tester.tap(find.byIcon(Icons.business));
+    await tester.pumpAndSettle();
+    expect(find.widgetWithText(Center, 'Index 1: Business'), findsOneWidget);
+
+    await tester.tap(find.byIcon(Icons.school));
+    await tester.pumpAndSettle();
+    expect(find.widgetWithText(Center, 'Index 2: School'), findsOneWidget);
+
+    // Verify we can go back
+    await tester.tap(find.byIcon(Icons.home));
+    await tester.pumpAndSettle();
+    expect(find.widgetWithText(Center, 'Index 0: Home'), findsOneWidget);
+  });
+}

examples/api/test/material/bottom_navigation_bar/bottom_navigation_bar.1_test.dart

+// 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/bottom_navigation_bar/bottom_navigation_bar.1.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('BottomNavigationBar Updates Screen Content', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.BottomNavigationBarExampleApp(),
+    );
+
+    expect(find.widgetWithText(AppBar, 'BottomNavigationBar Sample'), findsOneWidget);
+    expect(find.byType(BottomNavigationBar), findsOneWidget);
+    expect(find.widgetWithText(Center, 'Index 0: Home'), findsOneWidget);
+
+    await tester.tap(find.byIcon(Icons.business));
+    await tester.pumpAndSettle();
+    expect(find.widgetWithText(Center, 'Index 1: Business'), findsOneWidget);
+
+    await tester.tap(find.byIcon(Icons.school));
+    await tester.pumpAndSettle();
+    expect(find.widgetWithText(Center, 'Index 2: School'), findsOneWidget);
+
+    await tester.tap(find.byIcon(Icons.settings));
+    await tester.pumpAndSettle();
+    expect(find.widgetWithText(Center, 'Index 3: Settings'), findsOneWidget);
+
+    // Verify we can go back
+    await tester.tap(find.byIcon(Icons.home));
+    await tester.pumpAndSettle();
+    expect(find.widgetWithText(Center, 'Index 0: Home'), findsOneWidget);
+  });
+}

examples/api/test/material/icon_button/icon_button.0_test.dart

+// 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/icon_button/icon_button.0.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('IconButton increments volume when tapped', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.IconButtonExampleApp(),
+    );
+
+    expect(find.byIcon(Icons.volume_up), findsOneWidget);
+    expect(find.text('Volume : 0.0'), findsOneWidget);
+
+    await tester.tap(find.byType(IconButton));
+    await tester.pumpAndSettle();
+
+    expect(find.text('Volume : 10.0'), findsOneWidget);
+  });
+
+  testWidgets('IconButton shows tooltip when long pressed', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.IconButtonExampleApp(),
+    );
+
+    expect(find.text('Increase volume by 10'), findsNothing);
+    await tester.longPress(find.byType(IconButton));
+    await tester.pumpAndSettle();
+
+    expect(find.text('Increase volume by 10'), findsOneWidget);
+  });
+}

examples/api/test/material/icon_button/icon_button.1_test.dart

+// 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/icon_button/icon_button.1.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('IconButton', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.IconButtonExampleApp(),
+    );
+
+    await tester.pumpAndSettle();
+
+    expect(find.byIcon(Icons.android), findsOneWidget);
+    final Ink ink = tester.widget<Ink>(
+      find.ancestor(
+        of: find.byIcon(Icons.android),
+        matching: find.byType(Ink),
+      ),
+    );
+
+    final ShapeDecoration decoration = ink.decoration! as ShapeDecoration;
+    expect(decoration.color, Colors.lightBlue);
+    expect(decoration.shape, const CircleBorder());
+
+    final IconButton iconButton = ink.child! as IconButton;
+    expect(iconButton.color, Colors.white) ;
+  });
+}