tests to assert futures complete as expected (#5947)

packages/flutter/lib/src/animation/animation_controller.dart

@@ -154,6 +154,8 @@ class AnimationController extends Animation<double>
   AnimationStatus _status;
 
   /// Starts running this animation forwards (towards the end).
+  ///
+  /// Returns a [Future] that completes when the animation is complete.
   Future<Null> forward({ double from }) {
     _direction = _AnimationDirection.forward;
     if (from != null)
@@ -162,6 +164,8 @@ class AnimationController extends Animation<double>
   }
 
   /// Starts running this animation in reverse (towards the beginning).
+  ///
+  /// Returns a [Future] that completes when the animation is complete.
   Future<Null> reverse({ double from }) {
     _direction = _AnimationDirection.reverse;
     if (from != null)
@@ -170,6 +174,8 @@ class AnimationController extends Animation<double>
   }
 
   /// Drives the animation from its current value to target.
+  ///
+  /// Returns a [Future] that completes when the animation is complete.
   Future<Null> animateTo(double target, { Duration duration, Curve curve: Curves.linear }) {
     Duration simulationDuration = duration;
     if (simulationDuration == null) {

packages/flutter/lib/src/widgets/scrollable.dart

@@ -472,6 +472,8 @@ class ScrollableState<T extends Scrollable> extends State<T> {
   /// This function does not accept a zero duration. To jump-scroll to
   /// the new offset, do not provide a duration, rather than providing
   /// a zero duration.
+  ///
+  /// The returned [Future] completes when the scrolling animation is complete.
   Future<Null> scrollTo(double newScrollOffset, {
     Duration duration,
     Curve curve: Curves.ease,
@@ -550,6 +552,8 @@ class ScrollableState<T extends Scrollable> extends State<T> {
   /// Calling this function starts a physics-based animation of the scroll
   /// offset with the given value as the initial velocity. The physics
   /// simulation is determined by the scroll behavior.
+  ///
+  /// The returned [Future] completes when the scrolling animation is complete.
   Future<Null> fling(double scrollVelocity) {
     if (scrollVelocity.abs() > kPixelScrollTolerance.velocity)
       return _startToEndAnimation(scrollVelocity);

packages/flutter/test/widget/bottom_sheet_test.dart

@@ -9,7 +9,6 @@ import 'package:flutter/widgets.dart';
 void main() {
   testWidgets('Verify that a tap dismisses a modal BottomSheet', (WidgetTester tester) async {
     BuildContext savedContext;
-    bool showBottomSheetThenCalled = false;
 
     await tester.pumpWidget(new MaterialApp(
       home: new Builder(
@@ -23,6 +22,7 @@ void main() {
     await tester.pump();
     expect(find.text('BottomSheet'), findsNothing);
 
+    bool showBottomSheetThenCalled = false;
     showModalBottomSheet/*<Null>*/(
       context: savedContext,
       builder: (BuildContext context) => new Text('BottomSheet')
@@ -44,14 +44,23 @@ void main() {
     await tester.pump(new Duration(seconds: 1)); // frame after the animation (sheet has been removed)
     expect(find.text('BottomSheet'), findsNothing);
 
-    showModalBottomSheet/*<Null>*/(context: savedContext, builder: (BuildContext context) => new Text('BottomSheet'));
+    showBottomSheetThenCalled = false;
+    showModalBottomSheet/*<Null>*/(
+      context: savedContext,
+      builder: (BuildContext context) => new Text('BottomSheet'),
+    ).then((Null result) {
+      expectSync(result, isNull);
+      showBottomSheetThenCalled = true;
+    });
     await tester.pump(); // bottom sheet show animation starts
     await tester.pump(new Duration(seconds: 1)); // animation done
     expect(find.text('BottomSheet'), findsOneWidget);
+    expect(showBottomSheetThenCalled, isFalse);
 
     // Tap above the the bottom sheet to dismiss it
     await tester.tapAt(new Point(20.0, 20.0));
     await tester.pump(); // bottom sheet dismiss animation starts
+    expect(showBottomSheetThenCalled, isTrue);
     await tester.pump(new Duration(seconds: 1)); // animation done
     await tester.pump(new Duration(seconds: 1)); // rebuild frame
     expect(find.text('BottomSheet'), findsNothing);

packages/flutter/test/widget/positioned_test.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
@@ -53,22 +55,31 @@ void main() {
       )
     ); // t=0
     recordMetrics();
-    controller.forward();
+    Completer<Null> completer = new Completer<Null>();
+    controller.forward().whenComplete(completer.complete);
+    expect(completer.isCompleted, isFalse);
     await tester.pump(); // t=0 again
+    expect(completer.isCompleted, isFalse);
     recordMetrics();
     await tester.pump(const Duration(seconds: 1)); // t=1
+    expect(completer.isCompleted, isFalse);
     recordMetrics();
     await tester.pump(const Duration(seconds: 1)); // t=2
+    expect(completer.isCompleted, isFalse);
     recordMetrics();
     await tester.pump(const Duration(seconds: 3)); // t=5
+    expect(completer.isCompleted, isFalse);
     recordMetrics();
     await tester.pump(const Duration(seconds: 5)); // t=10
+    expect(completer.isCompleted, isFalse);
     recordMetrics();
 
     expect(sizes, equals(<Size>[const Size(10.0, 10.0), const Size(10.0, 10.0), const Size(10.0, 10.0), const Size(10.0, 10.0), const Size(10.0, 10.0), const Size(10.0, 10.0)]));
     expect(positions, equals(<Offset>[const Offset(10.0, 10.0), const Offset(10.0, 10.0), const Offset(17.0, 17.0), const Offset(24.0, 24.0), const Offset(45.0, 45.0), const Offset(80.0, 80.0)]));
 
     controller.stop();
+    await tester.pump();
+    expect(completer.isCompleted, isTrue);
   });
 
 }

packages/flutter/test/widget/remember_scroll_position_test.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:meta/meta.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
@@ -57,8 +59,11 @@ Future<Null> performTest(WidgetTester tester, bool maintainState) async {
   expect(find.text('10'), findsNothing);
   expect(find.text('100'), findsNothing);
 
-  tester.state/*<ScrollableState>*/(find.byType(Scrollable)).scrollTo(1000.0);
+  Completer<Null> completer = new Completer<Null>();
+  tester.state/*<ScrollableState>*/(find.byType(Scrollable)).scrollTo(1000.0).whenComplete(completer.complete);
+  expect(completer.isCompleted, isFalse);
   await tester.pump(new Duration(seconds: 1));
+  expect(completer.isCompleted, isTrue);
 
   // we're 600 pixels high, each item is 100 pixels high, scroll position is
   // 1000, so we should have exactly 6 items, 10..15.

packages/flutter/test/widget/scroll_events_test.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 
@@ -22,6 +24,14 @@ Widget _buildScroller({Key key, List<String> log}) {
 }
 
 void main() {
+  GlobalKey<ScrollableState<Scrollable>> scrollKey;
+
+  Completer<Null> scrollTo(double newScrollOffset, { Duration duration }) {
+    Completer<Null> completer = new Completer<Null>();
+    scrollKey.currentState.scrollTo(newScrollOffset, duration: duration).whenComplete(completer.complete);
+    return completer;
+  }
+
   testWidgets('Scroll event drag', (WidgetTester tester) async {
     List<String> log = <String>[];
     await tester.pumpWidget(_buildScroller(log: log));
@@ -42,12 +52,13 @@ void main() {
   });
 
   testWidgets('Scroll scrollTo animation', (WidgetTester tester) async {
-    GlobalKey<ScrollableState<Scrollable>> scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
+    scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
     List<String> log = <String>[];
     await tester.pumpWidget(_buildScroller(key: scrollKey, log: log));
 
     expect(log, equals(<String>[]));
-    scrollKey.currentState.scrollTo(100.0, duration: const Duration(seconds: 1));
+    Completer<Null> completer = scrollTo(100.0, duration: const Duration(seconds: 1));
+    expect(completer.isCompleted, isFalse);
     expect(log, equals(<String>['scrollstart']));
     await tester.pump(const Duration(milliseconds: 100));
     expect(log, equals(<String>['scrollstart']));
@@ -55,60 +66,74 @@ void main() {
     expect(log, equals(<String>['scrollstart', 'scroll']));
     await tester.pump(const Duration(milliseconds: 1500));
     expect(log, equals(<String>['scrollstart', 'scroll', 'scroll', 'scrollend']));
+    expect(completer.isCompleted, isTrue);
   });
 
   testWidgets('Scroll scrollTo no animation', (WidgetTester tester) async {
-    GlobalKey<ScrollableState<Scrollable>> scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
+    scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
     List<String> log = <String>[];
     await tester.pumpWidget(_buildScroller(key: scrollKey, log: log));
 
     expect(log, equals(<String>[]));
-    scrollKey.currentState.scrollTo(100.0);
+    Completer<Null> completer = scrollTo(100.0);
+    expect(completer.isCompleted, isFalse);
     expect(log, equals(<String>['scrollstart', 'scroll', 'scrollend']));
+    await tester.pump();
+    expect(completer.isCompleted, isTrue);
   });
 
   testWidgets('Scroll during animation', (WidgetTester tester) async {
-    GlobalKey<ScrollableState<Scrollable>> scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
+    scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
     List<String> log = <String>[];
     await tester.pumpWidget(_buildScroller(key: scrollKey, log: log));
 
     expect(log, equals(<String>[]));
-    scrollKey.currentState.scrollTo(100.0, duration: const Duration(seconds: 1));
+    Completer<Null> completer = scrollTo(100.0, duration: const Duration(seconds: 1));
+    expect(completer.isCompleted, isFalse);
     expect(log, equals(<String>['scrollstart']));
     await tester.pump(const Duration(milliseconds: 100));
     expect(log, equals(<String>['scrollstart']));
     await tester.pump(const Duration(milliseconds: 100));
     expect(log, equals(<String>['scrollstart', 'scroll']));
-    scrollKey.currentState.scrollTo(100.0);
+    expect(completer.isCompleted, isFalse);
+
+    completer = scrollTo(100.0);
+    expect(completer.isCompleted, isFalse);
     expect(log, equals(<String>['scrollstart', 'scroll', 'scroll']));
     await tester.pump(const Duration(milliseconds: 100));
     expect(log, equals(<String>['scrollstart', 'scroll', 'scroll', 'scrollend']));
     await tester.pump(const Duration(milliseconds: 1500));
     expect(log, equals(<String>['scrollstart', 'scroll', 'scroll', 'scrollend']));
+    expect(completer.isCompleted, isTrue);
   });
 
   testWidgets('Scroll during animation', (WidgetTester tester) async {
-    GlobalKey<ScrollableState<Scrollable>> scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
+    scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
     List<String> log = <String>[];
     await tester.pumpWidget(_buildScroller(key: scrollKey, log: log));
 
     expect(log, equals(<String>[]));
-    scrollKey.currentState.scrollTo(100.0, duration: const Duration(seconds: 1));
+    Completer<Null> completer = scrollTo(100.0, duration: const Duration(seconds: 1));
+    expect(completer.isCompleted, isFalse);
     expect(log, equals(<String>['scrollstart']));
     await tester.pump(const Duration(milliseconds: 100));
     expect(log, equals(<String>['scrollstart']));
     await tester.pump(const Duration(milliseconds: 100));
     expect(log, equals(<String>['scrollstart', 'scroll']));
-    scrollKey.currentState.scrollTo(100.0, duration: const Duration(seconds: 1));
+    expect(completer.isCompleted, isFalse);
+
+    completer = scrollTo(100.0, duration: const Duration(seconds: 1));
+    expect(completer.isCompleted, isFalse);
     expect(log, equals(<String>['scrollstart', 'scroll']));
     await tester.pump(const Duration(milliseconds: 100));
     expect(log, equals(<String>['scrollstart', 'scroll']));
     await tester.pump(const Duration(milliseconds: 1500));
     expect(log, equals(<String>['scrollstart', 'scroll', 'scroll', 'scrollend']));
+    expect(completer.isCompleted, isTrue);
   });
 
   testWidgets('fling, fling generates two start/end pairs', (WidgetTester tester) async {
-    GlobalKey<ScrollableState<Scrollable>> scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
+    scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
     List<String> log = <String>[];
     await tester.pumpWidget(_buildScroller(key: scrollKey, log: log));
 
@@ -127,7 +152,7 @@ void main() {
   });
 
   testWidgets('fling up ends', (WidgetTester tester) async {
-    GlobalKey<ScrollableState<Scrollable>> scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
+    scrollKey = new GlobalKey<ScrollableState<Scrollable>>();
     List<String> log = <String>[];
     await tester.pumpWidget(_buildScroller(key: scrollKey, log: log));
 

packages/flutter/test/widget/scrollable_lazy_list_test.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 
@@ -85,6 +87,11 @@ void main() {
       ),
       right: new Text('Not Today')
     );
+    Completer<Null> scrollTo(double newScrollOffset) {
+      Completer<Null> completer = new Completer<Null>();
+      scrollableKey.currentState.scrollTo(newScrollOffset).whenComplete(completer.complete);
+      return completer;
+    }
 
     await tester.pumpWidget(testWidget);
 
@@ -92,12 +99,14 @@ void main() {
 
     callbackTracker.clear();
 
-    scrollableKey.currentState.scrollTo(400.0);
+    Completer<Null> completer = scrollTo(400.0);
+    expect(completer.isCompleted, isFalse);
     // now only 3 should fit, numbered 2-4.
 
     await tester.pumpWidget(testWidget);
 
     expect(callbackTracker, equals(<int>[2, 3, 4]));
+    expect(completer.isCompleted, isTrue);
 
     callbackTracker.clear();
   });
@@ -134,6 +143,11 @@ void main() {
       ),
       right: new Text('Not Today')
     );
+    Completer<Null> scrollTo(double newScrollOffset) {
+      Completer<Null> completer = new Completer<Null>();
+      scrollableKey.currentState.scrollTo(newScrollOffset).whenComplete(completer.complete);
+      return completer;
+    }
 
     await tester.pumpWidget(testWidget);
 
@@ -141,12 +155,14 @@ void main() {
 
     callbackTracker.clear();
 
-    scrollableKey.currentState.scrollTo(400.0);
+    Completer<Null> completer = scrollTo(400.0);
+    expect(completer.isCompleted, isFalse);
     // now only 4 should fit, numbered 2-5.
 
     await tester.pumpWidget(testWidget);
 
     expect(callbackTracker, equals(<int>[2, 3, 4, 5]));
+    expect(completer.isCompleted, isTrue);
 
     callbackTracker.clear();
   });
@@ -174,24 +190,35 @@ void main() {
       itemExtent: 300.0,
       itemCount: 10
     );
+    Completer<Null> scrollTo(double newScrollOffset) {
+      Completer<Null> completer = new Completer<Null>();
+      scrollableKey.currentState.scrollTo(newScrollOffset).whenComplete(completer.complete);
+      return completer;
+    }
 
     await tester.pumpWidget(testWidget);
     expect(callbackTracker, equals(<int>[0, 1]));
     callbackTracker.clear();
 
-    scrollableKey.currentState.scrollTo(150.0);
+    Completer<Null> completer = scrollTo(150.0);
+    expect(completer.isCompleted, isFalse);
     await tester.pumpWidget(testWidget);
     expect(callbackTracker, equals(<int>[0, 1, 2]));
+    expect(completer.isCompleted, isTrue);
     callbackTracker.clear();
 
-    scrollableKey.currentState.scrollTo(600.0);
+    completer = scrollTo(600.0);
+    expect(completer.isCompleted, isFalse);
     await tester.pumpWidget(testWidget);
     expect(callbackTracker, equals(<int>[2, 3]));
+    expect(completer.isCompleted, isTrue);
     callbackTracker.clear();
 
-    scrollableKey.currentState.scrollTo(750.0);
+    completer = scrollTo(750.0);
+    expect(completer.isCompleted, isFalse);
     await tester.pumpWidget(testWidget);
     expect(callbackTracker, equals(<int>[2, 3, 4]));
+    expect(completer.isCompleted, isTrue);
     callbackTracker.clear();
   });
 

packages/flutter/test/widget/snap_scrolling_test.dart

@@ -46,8 +46,10 @@ set scrollOffset(double value) {
   scrollableState.scrollTo(value);
 }
 
-Future<Null> fling(double velocity) {
-  return scrollableState.fling(velocity);
+Completer<Null> fling(double velocity) {
+  Completer<Null> completer = new Completer<Null>();
+  scrollableState.fling(velocity).whenComplete(completer.complete);
+  return completer;
 }
 
 void main() {
@@ -60,49 +62,55 @@ void main() {
 
     Duration dt = const Duration(seconds: 2);
 
-    fling(1000.0);
+    Completer<Null> completer = fling(1000.0);
+    expect(completer.isCompleted, isFalse);
     await tester.pump(); // Start the scheduler at 0.0
     await tester.pump(dt);
     expect(scrollOffset, closeTo(200.0, 1.0));
+    expect(completer.isCompleted, isTrue);
 
     scrollOffset = 0.0;
     await tester.pump();
     expect(scrollOffset, 0.0);
 
-    fling(2000.0);
+    completer = fling(2000.0);
+    expect(completer.isCompleted, isFalse);
     await tester.pump();
     await tester.pump(dt);
     expect(scrollOffset, closeTo(400.0, 1.0));
+    expect(completer.isCompleted, isTrue);
 
     scrollOffset = 400.0;
     await tester.pump();
     expect(scrollOffset, 400.0);
 
-    fling(-800.0);
+    completer = fling(-800.0);
+    expect(completer.isCompleted, isFalse);
     await tester.pump();
     await tester.pump(dt);
     expect(scrollOffset, closeTo(0.0, 1.0));
+    expect(completer.isCompleted, isTrue);
 
     scrollOffset = 800.0;
     await tester.pump();
     expect(scrollOffset, 800.0);
 
-    fling(-2000.0);
+    completer = fling(-2000.0);
+    expect(completer.isCompleted, isFalse);
     await tester.pump();
     await tester.pump(dt);
     expect(scrollOffset, closeTo(200.0, 1.0));
+    expect(completer.isCompleted, isTrue);
 
     scrollOffset = 800.0;
     await tester.pump();
     expect(scrollOffset, 800.0);
 
-    bool completed = false;
-    fling(-2000.0).then((_) {
-      completed = true;
-      expectSync(scrollOffset, closeTo(200.0, 1.0));
-    });
+    completer = fling(-2000.0);
+    expect(completer.isCompleted, isFalse);
     await tester.pump();
     await tester.pump(dt);
-    expect(completed, true);
+    expect(completer.isCompleted, isTrue);
+    expectSync(scrollOffset, closeTo(200.0, 1.0));
   });
 }