Add test for material_state_property.0.dart (#156719)

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

It adds a test for
- `examples/api/test/material/material_state/material_state_property.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/material_state/material_state_outlined_border.0_test.dart',
-  'examples/api/test/material/material_state/material_state_property.0_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/material_state/material_state_property.0_test.dart

@@ -0,0 +1,47 @@
+// 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_api_samples/material/material_state/material_state_property.0.dart'
+    as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  Color getButtonForegroundColor(WidgetTester tester) {
+    final Material widget = tester.widget(
+      find.descendant(
+        of: find.byType(example.MaterialStatePropertyExample),
+        matching:find.widgetWithText(Material, 'TextButton'),
+      ),
+    );
+    return widget.textStyle!.color!;
+  }
+
+  testWidgets(
+    'The foreground color of the TextButton should be red by default',
+    (WidgetTester tester) async {
+      await tester.pumpWidget(
+        const example.MaterialStatePropertyExampleApp(),
+      );
+
+      expect(getButtonForegroundColor(tester), Colors.red);
+    },
+  );
+
+  testWidgets(
+    'The foreground color of the TextButton should be blue when hovered',
+    (WidgetTester tester) async {
+      await tester.pumpWidget(
+        const example.MaterialStatePropertyExampleApp(),
+      );
+
+      final TestGesture gesture = await tester.createGesture(kind: PointerDeviceKind.mouse);
+      await gesture.addPointer(location: tester.getCenter(find.byType(TextButton)));
+      await tester.pump();
+
+      expect(getButtonForegroundColor(tester), Colors.blue);
+    },
+  );
+}