Add test for selection_container_disabled.0.dart (#156934)

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

It adds a test for
- `examples/api/test/material/selection_container/selection_container_disabled.0_test.dart`

dev/bots/check_code_samples.dart

@@ -312,7 +312,6 @@ 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/selection_container/selection_container_disabled.0_test.dart',
   'examples/api/test/material/selection_container/selection_container.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/selection_container/selection_container_disabled.0_test.dart

@@ -0,0 +1,76 @@
+// 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/gestures.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
+import 'package:flutter_api_samples/material/selection_container/selection_container_disabled.0.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('A SelectionContainer.disabled should disable selections', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.SelectionContainerDisabledExampleApp(),
+    );
+
+    expect(find.widgetWithText(AppBar, 'SelectionContainer.disabled Sample'), findsOne);
+
+    final RenderParagraph paragraph1 = tester.renderObject<RenderParagraph>(
+      find.descendant(
+        of: find.text('Selectable text').first,
+        matching: find.byType(RichText),
+      ),
+    );
+    final Rect paragraph1Rect = tester.getRect(find.text('Selectable text').first);
+    final TestGesture gesture = await tester.startGesture(
+      paragraph1Rect.centerLeft,
+      kind: PointerDeviceKind.mouse,
+    );
+    addTearDown(gesture.removePointer);
+    await tester.pump();
+
+    await gesture.moveTo(paragraph1Rect.center);
+    await tester.pump();
+    expect(
+      paragraph1.selections.first,
+      const TextSelection(baseOffset: 0, extentOffset: 7),
+    );
+
+    final RenderParagraph paragraph2 = tester.renderObject<RenderParagraph>(
+      find.descendant(
+        of: find.text('Non-selectable text'),
+        matching: find.byType(RichText),
+      ),
+    );
+    final Rect paragraph2Rect = tester.getRect(find.text('Non-selectable text'));
+    await gesture.moveTo(paragraph2Rect.center);
+    // Should select the rest of paragraph 1.
+    expect(
+      paragraph1.selections.first,
+      const TextSelection(baseOffset: 0, extentOffset: 15),
+    );
+    // paragraph2 is in a disabled container.
+    expect(paragraph2.selections, isEmpty);
+
+    final RenderParagraph paragraph3 = tester.renderObject<RenderParagraph>(
+      find.descendant(
+        of: find.text('Selectable text').last,
+        matching: find.byType(RichText),
+      ),
+    );
+    final Rect paragraph3Rect = tester.getRect(find.text('Selectable text').last);
+    await gesture.moveTo(paragraph3Rect.center);
+    expect(
+      paragraph1.selections.first,
+      const TextSelection(baseOffset: 0, extentOffset: 15),
+    );
+    expect(paragraph2.selections, isEmpty);
+    expect(
+      paragraph3.selections.first,
+      const TextSelection(baseOffset: 0, extentOffset: 7),
+    );
+
+    await gesture.up();
+  });
+}