[federated_plugin_sample] Initial commit (#497)

experimental/federated_plugin/federated_plugin/test/federated_plugin_test.dart

@@ -0,0 +1,27 @@
+// 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/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:federated_plugin/federated_plugin.dart';
+
+void main() {
+  const channel = MethodChannel('federated_plugin');
+
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  setUp(() {
+    channel.setMockMethodCallHandler((methodCall) async {
+      return '42';
+    });
+  });
+
+  tearDown(() {
+    channel.setMockMethodCallHandler(null);
+  });
+
+  test('getPlatformVersion', () async {
+    expect(await FederatedPlugin.platformVersion, '42');
+  });
+}