Add:创建 flutter go web 版

packages/flutter_web/test/widgets/fade_transition_test.dart

@@ -0,0 +1,35 @@
+// Copyright 2018 The Chromium 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_web/foundation.dart';
+import 'package:flutter_web/widgets.dart';
+import 'package:flutter_web_test/flutter_web_test.dart';
+
+void main() {
+  testWidgets('FadeTransition', (WidgetTester tester) async {
+    final DebugPrintCallback oldPrint = debugPrint;
+    final List<String> log = <String>[];
+    debugPrint = (String message, {int wrapWidth}) {
+      log.add(message);
+    };
+    debugPrintBuildScope = true;
+    final AnimationController controller = AnimationController(
+      vsync: const TestVSync(),
+      duration: const Duration(seconds: 2),
+    );
+    await tester.pumpWidget(FadeTransition(
+      opacity: controller,
+      child: const Placeholder(),
+    ));
+    expect(log, hasLength(2));
+    expect(log.last, 'buildScope finished');
+    await tester.pump();
+    expect(log, hasLength(2));
+    controller.forward();
+    await tester.pumpAndSettle();
+    expect(log, hasLength(2));
+    debugPrint = oldPrint;
+    debugPrintBuildScope = false;
+  });
+}