Add Tests for bottom_app_bar api examples (#156501)

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

It adds a test for

`examples/api/test/material/bottom_app_bar/bottom_app_bar.1_test.dart` and
`examples/api/test/material/bottom_app_bar/bottom_app_bar.2_test.dart`

This are tests of snippets used in [AutofillGroup class](https://api.flutter.dev/flutter/widgets/AutofillGroup-class.html)

dev/bots/check_code_samples.dart

@@ -309,8 +309,6 @@ class SampleChecker {
 // TODO(gspencergoog): implement the missing tests.
 // See https://github.com/flutter/flutter/issues/130459
 final Set<String> _knownMissingTests = <String>{
-  'examples/api/test/material/bottom_app_bar/bottom_app_bar.2_test.dart',
-  'examples/api/test/material/bottom_app_bar/bottom_app_bar.1_test.dart',
   'examples/api/test/material/selectable_region/selectable_region.0_test.dart',
   'examples/api/test/material/color_scheme/dynamic_content_color.0_test.dart',
   'examples/api/test/material/platform_menu_bar/platform_menu_bar.0_test.dart',

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

@@ -0,0 +1,70 @@
+// 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_app_bar/bottom_app_bar.1.dart'
+    as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets(
+    'BottomAppBarDemo shows FloatingActionButton and responds to toggle',
+    (WidgetTester tester) async {
+      await tester.pumpWidget(const example.BottomAppBarDemo());
+
+      expect(find.byType(FloatingActionButton), findsOneWidget);
+
+      // Tap the 'Floating Action Button' switch to hide the FAB.
+      await tester.tap(find.byType(SwitchListTile).first);
+      await tester.pumpAndSettle();
+
+      expect(find.byType(FloatingActionButton), findsNothing);
+    },
+  );
+
+  testWidgets('Notch can be toggled on and off', (WidgetTester tester) async {
+    await tester.pumpWidget(const example.BottomAppBarDemo());
+
+    // Check the BottomAppBar has a notch initially.
+    BottomAppBar bottomAppBar = tester.widget(find.byType(BottomAppBar));
+    expect(bottomAppBar.shape, isNotNull);
+
+    // Toggle the 'Notch' switch to remove the notch.
+    await tester.tap(find.byType(SwitchListTile).last);
+    await tester.pump();
+
+    bottomAppBar = tester.widget(find.byType(BottomAppBar));
+    expect(bottomAppBar.shape, isNull);
+  });
+
+  testWidgets('FAB location can be changed', (WidgetTester tester) async {
+    await tester.pumpWidget(const example.BottomAppBarDemo());
+
+    final Offset initialPosition =
+        tester.getCenter(find.byType(FloatingActionButton));
+
+    // Verify the initial position is near the right side (docked to the end).
+    final Size screenSize = tester.getSize(
+      find.byType(Scaffold),
+    );
+    expect(
+      initialPosition.dx,
+      greaterThan(screenSize.width * 0.5),
+    );
+
+    // Tap the radio button to move the FAB to centerDocked.
+    await tester.tap(find.text('Docked - Center'));
+    await tester.pumpAndSettle();
+
+    // Get the new FAB position (centerDocked).
+    final Offset newPosition = tester.getCenter(
+      find.byType(FloatingActionButton),
+    );
+
+    expect(
+      newPosition.dx,
+      closeTo(screenSize.width * 0.5, 10), // Center of the screen.
+    );
+  });
+}

examples/api/test/material/bottom_app_bar/bottom_app_bar.2_test.dart

@@ -0,0 +1,95 @@
+// 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_app_bar/bottom_app_bar.2.dart'
+    as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets(
+    'Floating Action Button visibility can be toggled',
+    (WidgetTester tester) async {
+      await tester.pumpWidget(
+        const example.BottomAppBarDemo(),
+      );
+
+      expect(find.byType(FloatingActionButton), findsOneWidget);
+
+      // Tap the switch to hide the FAB.
+      await tester.tap(find.byType(SwitchListTile).first);
+      await tester.pumpAndSettle();
+
+      expect(find.byType(FloatingActionButton), findsNothing);
+    },
+  );
+
+  testWidgets('BottomAppBar elevation can be toggled',
+      (WidgetTester tester) async {
+    // Build the app.
+    await tester.pumpWidget(const example.BottomAppBarDemo());
+
+    // Verify the BottomAppBar has elevation initially.
+    BottomAppBar bottomAppBar = tester.widget(
+      find.byType(BottomAppBar),
+    );
+    expect(bottomAppBar.elevation, isNot(0.0));
+
+    await tester.tap(find.text('Bottom App Bar Elevation'));
+    await tester.pumpAndSettle();
+
+    bottomAppBar = tester.widget(
+      find.byType(BottomAppBar),
+    );
+    expect(bottomAppBar.elevation, equals(0.0));
+  });
+
+  testWidgets(
+    'BottomAppBar hides on scroll down and shows on scroll up',
+    (WidgetTester tester) async {
+      await tester.pumpWidget(const example.BottomAppBarDemo());
+
+      // Ensure the BottomAppBar is visible initially.
+      expect(find.byType(BottomAppBar), findsOneWidget);
+
+      // Scroll down to hide the BottomAppBar.
+      await tester.drag(
+        find.byType(ListView),
+        const Offset(0, -300),
+      );
+      await tester.pumpAndSettle();
+
+      // Verify the BottomAppBar is hidden.
+      final Size hiddenSize = tester.getSize(
+        find.byType(AnimatedContainer),
+      );
+      expect(hiddenSize.height, equals(0.0)); // AnimatedContainer's height
+
+      // Scroll up to show the BottomAppBar again.
+      await tester.drag(find.byType(ListView), const Offset(0, 300));
+      await tester.pumpAndSettle();
+
+      // Verify the BottomAppBar is visible again.
+      final Size visibleSize = tester.getSize(
+        find.byType(AnimatedContainer),
+      );
+      expect(visibleSize.height, equals(80.0));
+    },
+  );
+
+  testWidgets(
+    'SnackBar is shown when Open popup menu is pressed',
+    (WidgetTester tester) async {
+      await tester.pumpWidget(const example.BottomAppBarDemo());
+
+      // Trigger the SnackBar.
+      await tester.tap(find.byTooltip('Open popup menu'));
+      await tester.pump();
+
+      expect(find.text('Yay! A SnackBar!'), findsOneWidget);
+
+      expect(find.text('Undo'), findsOneWidget);
+    },
+  );
+}