[federated_plugin_sample] Initial commit (#497)

experimental/federated_plugin/federated_plugin/example/test/widget_test.dart

@@ -0,0 +1,24 @@
+// Copyright 2020 The Flutter team. 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_test/flutter_test.dart';
+
+import 'package:federated_plugin_example/main.dart';
+
+void main() {
+  testWidgets('Verify Platform version', (tester) async {
+    // Build our app and trigger a frame.
+    await tester.pumpWidget(MyApp());
+
+    // Verify that platform version is retrieved.
+    expect(
+      find.byWidgetPredicate(
+        (widget) => widget is Text &&
+                           widget.data.startsWith('Running on:'),
+      ),
+      findsOneWidget,
+    );
+  });
+}