Add:创建 flutter go web 版

packages/flutter_web/test/widgets/scrollable_animations_test.dart

@@ -0,0 +1,97 @@
+// Copyright 2017 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_test/flutter_web_test.dart';
+import 'package:flutter_web/scheduler.dart';
+import 'package:flutter_web/widgets.dart';
+
+void main() {
+  testWidgets('Does not animate if already at target position',
+      (WidgetTester tester) async {
+    final List<Widget> textWidgets = <Widget>[];
+    for (int i = 0; i < 80; i++)
+      textWidgets.add(new Text('$i', textDirection: TextDirection.ltr));
+    final ScrollController controller = new ScrollController();
+    await tester.pumpWidget(
+      new Directionality(
+        textDirection: TextDirection.ltr,
+        child: new ListView(
+          children: textWidgets,
+          controller: controller,
+        ),
+      ),
+    );
+
+    expectNoAnimation();
+    final double currentPosition = controller.position.pixels;
+    controller.position.animateTo(currentPosition,
+        duration: const Duration(seconds: 10), curve: Curves.linear);
+
+    expectNoAnimation();
+    expect(controller.position.pixels, currentPosition);
+  });
+
+  testWidgets('Does not animate if already at target position within tolerance',
+      (WidgetTester tester) async {
+    final List<Widget> textWidgets = <Widget>[];
+    for (int i = 0; i < 80; i++)
+      textWidgets.add(new Text('$i', textDirection: TextDirection.ltr));
+    final ScrollController controller = new ScrollController();
+    await tester.pumpWidget(
+      new Directionality(
+        textDirection: TextDirection.ltr,
+        child: new ListView(
+          children: textWidgets,
+          controller: controller,
+        ),
+      ),
+    );
+
+    expectNoAnimation();
+
+    final double halfTolerance =
+        controller.position.physics.tolerance.distance / 2;
+    expect(halfTolerance, isNonZero);
+    final double targetPosition = controller.position.pixels + halfTolerance;
+    controller.position.animateTo(targetPosition,
+        duration: const Duration(seconds: 10), curve: Curves.linear);
+
+    expectNoAnimation();
+    expect(controller.position.pixels, targetPosition);
+  });
+
+  testWidgets('Animates if going to a position outside of tolerance',
+      (WidgetTester tester) async {
+    final List<Widget> textWidgets = <Widget>[];
+    for (int i = 0; i < 80; i++)
+      textWidgets.add(new Text('$i', textDirection: TextDirection.ltr));
+    final ScrollController controller = new ScrollController();
+    await tester.pumpWidget(
+      new Directionality(
+        textDirection: TextDirection.ltr,
+        child: new ListView(
+          children: textWidgets,
+          controller: controller,
+        ),
+      ),
+    );
+
+    expectNoAnimation();
+
+    final double doubleTolerance =
+        controller.position.physics.tolerance.distance * 2;
+    expect(doubleTolerance, isNonZero);
+    final double targetPosition = controller.position.pixels + doubleTolerance;
+    controller.position.animateTo(targetPosition,
+        duration: const Duration(seconds: 10), curve: Curves.linear);
+
+    expect(SchedulerBinding.instance.transientCallbackCount, equals(1),
+        reason: 'Expected an animation.');
+  });
+}
+
+void expectNoAnimation() {
+  expect(SchedulerBinding.instance.transientCallbackCount, equals(0),
+      reason: 'Expected no animation.');
+}