Add a test for 5630 (#5768)

This issue got fixed by a recent check-in, but I had a test specifically
for this incarnation so we should probably keep it just in case.

Closes https://github.com/flutter/flutter/issues/5630

packages/flutter/test/widget/layout_builder_and_parent_data_test.dart

@@ -66,8 +66,7 @@ void main() {
       })
     ));
     frame += 1;
-    SizeChangerState state = tester.state(find.byType(SizeChanger));
-    state.trigger();
+    tester.state/*<SizeChangerState>*/(find.byType(SizeChanger)).trigger();
     await tester.pump();
   });
 }

packages/flutter/test/widget/remember_scroll_position_test.dart

@@ -57,8 +57,7 @@ Future<Null> performTest(WidgetTester tester, bool maintainState) async {
   expect(find.text('10'), findsNothing);
   expect(find.text('100'), findsNothing);
 
-  ScrollableState targetState = tester.state(find.byType(Scrollable));
-  targetState.scrollTo(1000.0);
+  tester.state/*<ScrollableState>*/(find.byType(Scrollable)).scrollTo(1000.0);
   await tester.pump(new Duration(seconds: 1));
 
   // we're 600 pixels high, each item is 100 pixels high, scroll position is

packages/flutter/test/widget/scrollable_dispose_test.dart

@@ -20,8 +20,7 @@ void main() {
     await tester.fling(find.byType(Scrollable), new Offset(0.0, -200.0), 1000.0);
     await tester.pump();
 
-    FlipWidgetState flipWidget = tester.state(find.byType(FlipWidget));
-    flipWidget.flip();
+    tester.state/*<FlipWidgetState>*/(find.byType(FlipWidget)).flip();
     await tester.pump(new Duration(hours: 5));
   });
 }

packages/flutter/test/widget/state_setting_in_scrollables_test.dart

+// Copyright 2016 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_test/flutter_test.dart' hide TypeMatcher;
+import 'package:flutter/widgets.dart';
+
+class Foo extends StatefulWidget {
+  @override
+  FooState createState() => new FooState();
+}
+
+class FooState extends State<Foo> {
+  final GlobalKey blockKey = new GlobalKey();
+  GlobalKey<ScrollableState> scrollableKey = new GlobalKey<ScrollableState>();
+
+  @override
+  Widget build(BuildContext context) {
+    return new LayoutBuilder(
+      builder: (BuildContext context, BoxConstraints constraints) {
+        return new ScrollConfiguration(
+          delegate: new FooScrollConfiguration(),
+          child: new Block(
+            scrollableKey: scrollableKey,
+            children: <Widget>[
+              new GestureDetector(
+                onTap: () {
+                  setState(() {});
+                  scrollableKey.currentState.scrollBy(200.0, duration: const Duration(milliseconds: 500));
+                },
+                child: new DecoratedBox(
+                  decoration: new BoxDecoration(backgroundColor: const Color(0)),
+                  child: new SizedBox(
+                    height: 200.0,
+                  ),
+                )
+              ),
+              new DecoratedBox(
+                decoration: new BoxDecoration(backgroundColor: const Color(0)),
+                child: new SizedBox(
+                  height: 200.0,
+                ),
+              ),
+              new DecoratedBox(
+                decoration: new BoxDecoration(backgroundColor: const Color(0)),
+                child: new SizedBox(
+                  height: 200.0,
+                ),
+              ),
+              new DecoratedBox(
+                decoration: new BoxDecoration(backgroundColor: const Color(0)),
+                child: new SizedBox(
+                  height: 200.0,
+                ),
+              ),
+              new DecoratedBox(
+                decoration: new BoxDecoration(backgroundColor: const Color(0)),
+                child: new SizedBox(
+                  height: 200.0,
+                ),
+              ),
+              new DecoratedBox(
+                decoration: new BoxDecoration(backgroundColor: const Color(0)),
+                child: new SizedBox(
+                  height: 200.0,
+                ),
+              ),
+            ],
+          )
+        );
+      }
+    );
+  }
+}
+
+class FooScrollConfiguration extends ScrollConfigurationDelegate {
+  @override
+  TargetPlatform get platform => defaultTargetPlatform;
+
+  @override
+  ExtentScrollBehavior createScrollBehavior() =>
+      new OverscrollWhenScrollableBehavior(platform: platform);
+
+  @override
+  bool updateShouldNotify(FooScrollConfiguration old) => true;
+}
+
+void main() {
+  testWidgets('https://github.com/flutter/flutter/issues/5630', (WidgetTester tester) async {
+    await tester.pumpWidget(new Foo());
+    expect(tester.state/*<ScrollableState>*/(find.byType(Scrollable)).scrollOffset, 0.0);
+    await tester.tap(find.byType(GestureDetector).first);
+    await tester.pump();
+    await tester.pump(const Duration(seconds: 1));
+    expect(tester.state/*<ScrollableState>*/(find.byType(Scrollable)).scrollOffset, 200.0);
+  });
+}

packages/flutter/test/widget/test_widgets.dart

@@ -54,6 +54,5 @@ class FlipWidgetState extends State<FlipWidget> {
 }
 
 void flipStatefulWidget(WidgetTester tester) {
-  FlipWidgetState state = tester.state(find.byType(FlipWidget));
-  state.flip();
+  tester.state/*<FlipWidgetState>*/(find.byType(FlipWidget)).flip();
 }

packages/flutter_test/lib/src/finders.dart

@@ -205,6 +205,14 @@ abstract class Finder {
     return false;
   }
 
+  /// Returns a variant of this finder that only matches the first element
+  /// matched by this finder.
+  Finder get first => new _FirstFinder(this);
+
+  /// Returns a variant of this finder that only matches the last element
+  /// matched by this finder.
+  Finder get last => new _LastFinder(this);
+
   @override
   String toString() {
     final String additional = skipOffstage ? ' (ignoring offstage widgets)' : '';
@@ -220,6 +228,34 @@ abstract class Finder {
   }
 }
 
+class _FirstFinder extends Finder {
+  _FirstFinder(this.parent);
+
+  final Finder parent;
+
+  @override
+  String get description => '${parent.description} (ignoring all but first)';
+
+  @override
+  Iterable<Element> apply(Iterable<Element> candidates) sync* {
+    yield parent.apply(candidates).first;
+  }
+}
+
+class _LastFinder extends Finder {
+  _LastFinder(this.parent);
+
+  final Finder parent;
+
+  @override
+  String get description => '${parent.description} (ignoring all but last)';
+
+  @override
+  Iterable<Element> apply(Iterable<Element> candidates) sync* {
+    yield parent.apply(candidates).last;
+  }
+}
+
 /// Searches a widget tree and returns nodes that match a particular
 /// pattern.
 abstract class MatchFinder extends Finder {