Improve test coverage (#7430)

Also, make the exception handling for global key listeners slightly more
robust.

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

@@ -151,7 +151,7 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
   void _register(Element element) {
     assert(() {
       if (_registry.containsKey(this)) {
-        int oldCount = _debugDuplicates.putIfAbsent(this, () => 1);
+        final int oldCount = _debugDuplicates.putIfAbsent(this, () => 1);
         assert(oldCount >= 1);
         _debugDuplicates[this] = oldCount + 1;
       }
@@ -163,7 +163,7 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
   void _unregister(Element element) {
     assert(() {
       if (_registry.containsKey(this) && _debugDuplicates.containsKey(this)) {
-        int oldCount = _debugDuplicates[this];
+        final int oldCount = _debugDuplicates[this];
         assert(oldCount >= 2);
         if (oldCount == 2) {
           _debugDuplicates.remove(this);
@@ -257,17 +257,19 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
       for (GlobalKey key in _removedKeys) {
         if (!_registry.containsKey(key) && _removeListeners.containsKey(key)) {
           Set<GlobalKeyRemoveListener> localListeners = new HashSet<GlobalKeyRemoveListener>.from(_removeListeners[key]);
-          for (GlobalKeyRemoveListener listener in localListeners)
-            listener(key);
+          for (GlobalKeyRemoveListener listener in localListeners) {
+            try {
+              listener(key);
+            } catch (e, stack) {
+              _debugReportException('while notifying GlobalKey listener', e, stack);
+            }
+          }
         }
       }
-    } catch (e, stack) {
-      _debugReportException('while notifying GlobalKey listeners', e, stack);
     } finally {
       _removedKeys.clear();
     }
   }
-
 }
 
 /// A global key with a debugging label.

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

@@ -525,7 +525,6 @@ class _GestureSemantics extends SingleChildRenderObjectWidget {
         return;
       }
     }
-    assert(false);
   }
 
   void _handleVerticalDragUpdate(DragUpdateDetails updateDetails) {
@@ -553,7 +552,6 @@ class _GestureSemantics extends SingleChildRenderObjectWidget {
         return;
       }
     }
-    assert(false);
   }
 
   @override

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

@@ -72,6 +72,20 @@ class MediaQueryData {
     return size.width > size.height ? Orientation.landscape : Orientation.portrait;
   }
 
+  MediaQueryData copyWith({
+    Size size,
+    double devicePixelRatio,
+    double textScaleFactor,
+    EdgeInsets padding,
+  }) {
+    return new MediaQueryData(
+      size: size ?? this.size,
+      devicePixelRatio: devicePixelRatio ?? this.devicePixelRatio,
+      textScaleFactor: textScaleFactor ?? this.textScaleFactor,
+      padding: padding ?? this.padding,
+    );
+  }
+
   @override
   bool operator ==(Object other) {
     if (other.runtimeType != runtimeType)

packages/flutter/test/animation/animation_controller_test.dart

@@ -6,8 +6,6 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/animation.dart';
 import 'package:flutter/widgets.dart';
 
-import 'animation_tester.dart';
-
 void main() {
   setUp(() {
     WidgetsFlutterBinding.ensureInitialized();
@@ -206,17 +204,17 @@ void main() {
       duration: const Duration(milliseconds: 100),
       vsync: const TestVSync(),
     );
-    expect(controller.toString(), hasOneLineDescription);
+    expect(controller, hasOneLineDescription);
     controller.forward();
     WidgetsBinding.instance.handleBeginFrame(const Duration(milliseconds: 10));
     WidgetsBinding.instance.handleBeginFrame(const Duration(milliseconds: 20));
-    expect(controller.toString(), hasOneLineDescription);
+    expect(controller, hasOneLineDescription);
     WidgetsBinding.instance.handleBeginFrame(const Duration(milliseconds: 30));
-    expect(controller.toString(), hasOneLineDescription);
+    expect(controller, hasOneLineDescription);
     controller.reverse();
     WidgetsBinding.instance.handleBeginFrame(const Duration(milliseconds: 40));
     WidgetsBinding.instance.handleBeginFrame(const Duration(milliseconds: 50));
-    expect(controller.toString(), hasOneLineDescription);
+    expect(controller, hasOneLineDescription);
     controller.stop();
   });
 

packages/flutter/test/animation/animations_test.dart

@@ -6,8 +6,6 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/animation.dart';
 import 'package:flutter/widgets.dart';
 
-import 'animation_tester.dart';
-
 void main() {
   setUp(() {
     WidgetsFlutterBinding.ensureInitialized();
@@ -15,16 +13,16 @@ void main() {
   });
 
   test('toString control test', () {
-    expect(kAlwaysCompleteAnimation.toString(), hasOneLineDescription);
-    expect(kAlwaysDismissedAnimation.toString(), hasOneLineDescription);
-    expect(const AlwaysStoppedAnimation<double>(0.5).toString(), hasOneLineDescription);
+    expect(kAlwaysCompleteAnimation, hasOneLineDescription);
+    expect(kAlwaysDismissedAnimation, hasOneLineDescription);
+    expect(const AlwaysStoppedAnimation<double>(0.5), hasOneLineDescription);
     CurvedAnimation curvedAnimation = new CurvedAnimation(
       parent: kAlwaysDismissedAnimation,
       curve: Curves.ease
     );
-    expect(curvedAnimation.toString(), hasOneLineDescription);
+    expect(curvedAnimation, hasOneLineDescription);
     curvedAnimation.reverseCurve = Curves.elasticOut;
-    expect(curvedAnimation.toString(), hasOneLineDescription);
+    expect(curvedAnimation, hasOneLineDescription);
     AnimationController controller = new AnimationController(
       duration: const Duration(milliseconds: 500),
       vsync: const TestVSync(),
@@ -37,7 +35,7 @@ void main() {
       curve: Curves.ease,
       reverseCurve: Curves.elasticOut
     );
-    expect(curvedAnimation.toString(), hasOneLineDescription);
+    expect(curvedAnimation, hasOneLineDescription);
     controller.stop();
   });
 
@@ -45,9 +43,9 @@ void main() {
     ProxyAnimation animation = new ProxyAnimation();
     expect(animation.value, 0.0);
     expect(animation.status, AnimationStatus.dismissed);
-    expect(animation.toString(), hasOneLineDescription);
+    expect(animation, hasOneLineDescription);
     animation.parent = kAlwaysDismissedAnimation;
-    expect(animation.toString(), hasOneLineDescription);
+    expect(animation, hasOneLineDescription);
   });
 
   test('ProxyAnimation set parent generates value changed', () {
@@ -88,7 +86,7 @@ void main() {
     expect(didReceiveCallback, isFalse);
     controller.value = 0.7;
     expect(didReceiveCallback, isFalse);
-    expect(animation.toString(), hasOneLineDescription);
+    expect(animation, hasOneLineDescription);
   });
 
   test('TrainHoppingAnimation', () {
@@ -107,11 +105,11 @@ void main() {
       });
     expect(didSwitchTrains, isFalse);
     expect(animation.value, 0.5);
-    expect(animation.toString(), hasOneLineDescription);
+    expect(animation, hasOneLineDescription);
     nextTrain.value = 0.25;
     expect(didSwitchTrains, isTrue);
     expect(animation.value, 0.25);
-    expect(animation.toString(), hasOneLineDescription);
+    expect(animation, hasOneLineDescription);
     expect(animation.toString(), contains('no next'));
   });
 }

packages/flutter/test/animation/tween_test.dart

@@ -6,8 +6,6 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/animation.dart';
 import 'package:flutter/widgets.dart';
 
-import 'animation_tester.dart';
-
 void main() {
   test('Can chain tweens', () {
     Tween<double> tween = new Tween<double>(begin: 0.30, end: 0.50);

packages/flutter/test/painting/colors_test.dart

@@ -9,7 +9,7 @@ void main() {
   test('HSVColor control test', () {
     const HSVColor color = const HSVColor.fromAHSV(0.7, 28.0, 0.3, 0.6);
 
-    expect(color.toString(), hasOneLineDescription);
+    expect(color, hasOneLineDescription);
     expect(color.hashCode, equals(new HSVColor.fromAHSV(0.7, 28.0, 0.3, 0.6).hashCode));
 
     expect(color.withAlpha(0.8), const HSVColor.fromAHSV(0.8, 28.0, 0.3, 0.6));

packages/flutter/test/painting/edge_insets_test.dart

@@ -9,7 +9,7 @@ void main() {
   test('EdgeInsets control test', () {
     const EdgeInsets insets = const EdgeInsets.fromLTRB(5.0, 7.0, 11.0, 13.0);
 
-    expect(insets.toString(), hasOneLineDescription);
+    expect(insets, hasOneLineDescription);
     expect(insets.hashCode, equals(new EdgeInsets.fromLTRB(5.0, 7.0, 11.0, 13.0).hashCode));
 
     expect(insets.topLeft, const Offset(5.0, 7.0));

packages/flutter/test/widgets/framework_test.dart

+// Copyright 2015 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';
+import 'package:flutter/widgets.dart';
+
+void main() {
+  testWidgets('UniqueKey control test', (WidgetTester tester) async {
+    Key key = new UniqueKey();
+    expect(key, hasOneLineDescription);
+    expect(key, isNot(equals(new UniqueKey())));
+  });
+
+  testWidgets('ObjectKey control test', (WidgetTester tester) async {
+    Object a = new Object();
+    Object b = new Object();
+    Key keyA = new ObjectKey(a);
+    Key keyA2 = new ObjectKey(a);
+    Key keyB = new ObjectKey(b);
+
+    expect(keyA, hasOneLineDescription);
+    expect(keyA, equals(keyA2));
+    expect(keyA.hashCode, equals(keyA2.hashCode));
+    expect(keyA, isNot(equals(keyB)));
+  });
+
+  testWidgets('GlobalKey duplication', (WidgetTester tester) async {
+    Key key = new GlobalKey(debugLabel: 'problematic');
+
+    await tester.pumpWidget(new Stack(
+      children: <Widget>[
+        new Container(
+          key: const ValueKey<int>(1),
+        ),
+        new Container(
+          key: const ValueKey<int>(2),
+        ),
+        new Container(
+          key: key
+        ),
+      ],
+    ));
+
+    await tester.pumpWidget(new Stack(
+      children: <Widget>[
+        new Container(
+          key: const ValueKey<int>(1),
+          child: new SizedBox(key: key),
+        ),
+        new Container(
+          key: const ValueKey<int>(2),
+          child: new Placeholder(key: key),
+        ),
+      ],
+    ));
+
+    expect(tester.takeException(), isNotNull);
+  });
+
+  testWidgets('GlobalKey notification exception handling', (WidgetTester tester) async {
+    GlobalKey key = new GlobalKey();
+
+    await tester.pumpWidget(new Container(key: key));
+
+    GlobalKey.registerRemoveListener(key, (GlobalKey key) {
+      throw new Exception('Misbehaving listener');
+    });
+
+    bool didReceiveCallback = false;
+    GlobalKey.registerRemoveListener(key, (GlobalKey key) {
+      expect(didReceiveCallback, isFalse);
+      didReceiveCallback = true;
+    });
+
+    await tester.pumpWidget(new Placeholder());
+
+    expect(tester.takeException(), isNotNull);
+    expect(didReceiveCallback, isTrue);
+  });
+}

packages/flutter/test/widgets/media_query_test.dart

@@ -14,7 +14,10 @@ void main() {
     await tester.pumpWidget(
       new Builder(
         builder: (BuildContext context) {
-          size = MediaQuery.of(context).size;
+          final MediaQueryData data = MediaQuery.of(context);
+          expect(data, hasOneLineDescription);
+          expect(data.hashCode, equals(data.copyWith().hashCode));
+          size = data.size;
           return new Container();
         }
       )

packages/flutter/test/widgets/performance_overlay_test.dart

+// 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_test/flutter_test.dart';
+import 'package:flutter/widgets.dart';
+
+void main() {
+  testWidgets('Performance overlay smoke test', (WidgetTester tester) async {
+    await tester.pumpWidget(new PerformanceOverlay());
+    await tester.pumpWidget(new PerformanceOverlay.allEnabled());
+  });
+}

packages/flutter/test/widgets/placeholder_test.dart

+// 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_test/flutter_test.dart';
+import 'package:flutter/widgets.dart';
+
+void main() {
+  testWidgets('Placeholder control test', (WidgetTester tester) async {
+    GlobalKey<PlaceholderState> key = new GlobalKey<PlaceholderState>();
+
+    await tester.pumpWidget(new Placeholder(key: key));
+
+    key.currentState.child = new Text('target');
+
+    expect(find.text('target'), findsNothing);
+
+    await tester.pump();
+
+    expect(find.text('target'), findsOneWidget);
+  });
+}

packages/flutter/test/widgets/raw_keyboard_listener_test.dart

@@ -18,6 +18,7 @@ void sendFakeKeyEvent(Map<String, dynamic> data) {
 
 void main() {
   testWidgets('Can dispose without keyboard', (WidgetTester tester) async {
+    await tester.pumpWidget(new RawKeyboardListener(child: new Container()));
     await tester.pumpWidget(new RawKeyboardListener(child: new Container()));
     await tester.pumpWidget(new Container());
   });

packages/flutter/test/widgets/routes_test.dart

@@ -96,6 +96,11 @@ Future<Null> runNavigatorTest(
 }
 
 void main() {
+  testWidgets('Route settings', (WidgetTester tester) async {
+    RouteSettings settings = const RouteSettings(name: 'A');
+    expect(settings, hasOneLineDescription);
+  });
+
   testWidgets('Route management - push, replace, pop', (WidgetTester tester) async {
     GlobalKey<NavigatorState> navigatorKey = new GlobalKey<NavigatorState>();
     await tester.pumpWidget(new Navigator(
@@ -320,6 +325,7 @@ void main() {
         'B: didChangeNext C',
       ]
     );
+    expect(routeC.isActive, isTrue);
     TestRoute routeB;
     await runNavigatorTest(
       tester,

packages/flutter/test/widgets/semantics_debugger_test.dart

@@ -14,13 +14,13 @@ void main() {
         children: <Widget>[
           new Semantics(),
           new Semantics(
-            container: true
+            container: true,
           ),
           new Semantics(
-            label: 'label'
+            label: 'label',
           ),
-        ]
-      )
+        ],
+      ),
     );
 
     await tester.pumpWidget(
@@ -29,20 +29,21 @@ void main() {
           children: <Widget>[
             new Semantics(),
             new Semantics(
-              container: true
+              container: true,
             ),
             new Semantics(
-              label: 'label'
+              label: 'label',
             ),
-          ]
-        )
-      )
+          ],
+        ),
+      ),
     );
 
     expect(true, isTrue); // expect that we reach here without crashing
   });
 
-  testWidgets('SemanticsDebugger reparents subtree', (WidgetTester tester) async {
+  testWidgets('SemanticsDebugger reparents subtree',
+      (WidgetTester tester) async {
     GlobalKey key = new GlobalKey();
 
     await tester.pumpWidget(
@@ -51,12 +52,16 @@ void main() {
           children: <Widget>[
             new Semantics(label: 'label1'),
             new Positioned(
-              key: key, left: 0.0, top: 0.0, width: 100.0, height: 100.0,
-              child: new Semantics(label: 'label2')
+              key: key,
+              left: 0.0,
+              top: 0.0,
+              width: 100.0,
+              height: 100.0,
+              child: new Semantics(label: 'label2'),
             ),
-          ]
-        )
-      )
+          ],
+        ),
+      ),
     );
 
     await tester.pumpWidget(
@@ -69,16 +74,20 @@ void main() {
               child: new Stack(
                 children: <Widget>[
                   new Positioned(
-                    key: key, left: 0.0, top: 0.0, width: 100.0, height: 100.0,
-                    child: new Semantics(label: 'label2')
+                    key: key,
+                    left: 0.0,
+                    top: 0.0,
+                    width: 100.0,
+                    height: 100.0,
+                    child: new Semantics(label: 'label2'),
                   ),
                   new Semantics(label: 'label3'),
-                ]
-              )
-            )
-          ]
-        )
-      )
+                ],
+              ),
+            ),
+          ],
+        ),
+      ),
     );
 
     await tester.pumpWidget(
@@ -91,19 +100,180 @@ void main() {
               child: new Stack(
                 children: <Widget>[
                   new Positioned(
-                    key: key, left: 0.0, top: 0.0, width: 100.0, height: 100.0,
-                    child: new Semantics(label: 'label2')
-                  ),
+                      key: key,
+                      left: 0.0,
+                      top: 0.0,
+                      width: 100.0,
+                      height: 100.0,
+                      child: new Semantics(label: 'label2')),
                   new Semantics(label: 'label3'),
                   new Semantics(label: 'label4'),
-                ]
-              )
-            )
-          ]
-        )
-      )
+                ],
+              ),
+            ),
+          ],
+        ),
+      ),
     );
 
     expect(tester.takeException(), isNull);
   });
+
+  testWidgets('SemanticsDebugger interaction test',
+      (WidgetTester tester) async {
+    final List<String> log = <String>[];
+
+    await tester.pumpWidget(
+      new SemanticsDebugger(
+        child: new Material(
+          child: new Block(children: <Widget>[
+            new RaisedButton(
+              onPressed: () {
+                log.add('top');
+              },
+              child: new Text('TOP'),
+            ),
+            new RaisedButton(
+              onPressed: () {
+                log.add('bottom');
+              },
+              child: new Text('BOTTOM'),
+            ),
+          ]),
+        ),
+      ),
+    );
+
+    await tester.tap(find.text('TOP'));
+    expect(log, equals(<String>['top']));
+    log.clear();
+
+    await tester.tap(find.text('BOTTOM'));
+    expect(log, equals(<String>['bottom']));
+    log.clear();
+  });
+
+  testWidgets('SemanticsDebugger scroll test', (WidgetTester tester) async {
+    Key childKey = new UniqueKey();
+
+    await tester.pumpWidget(
+      new SemanticsDebugger(
+        child: new Block(
+          children: <Widget>[
+            new Container(
+              key: childKey,
+              height: 5000.0,
+              decoration:
+                new BoxDecoration(backgroundColor: Colors.green[500]),
+            ),
+          ],
+        ),
+      ),
+    );
+
+    expect(tester.getTopLeft(find.byKey(childKey)).y, equals(0.0));
+
+    await tester.fling(find.byType(Block), const Offset(0.0, -200.0), 200.0);
+    await tester.pump();
+
+    expect(tester.getTopLeft(find.byKey(childKey)).y, equals(-480.0));
+
+    await tester.fling(find.byType(Block), const Offset(200.0, 0.0), 200.0);
+    await tester.pump();
+
+    expect(tester.getTopLeft(find.byKey(childKey)).y, equals(-480.0));
+
+    await tester.fling(find.byType(Block), const Offset(-200.0, 0.0), 200.0);
+    await tester.pump();
+
+    expect(tester.getTopLeft(find.byKey(childKey)).y, equals(-480.0));
+
+    await tester.fling(find.byType(Block), const Offset(0.0, 200.0), 200.0);
+    await tester.pump();
+
+    expect(tester.getTopLeft(find.byKey(childKey)).y, equals(0.0));
+  });
+
+  testWidgets('SemanticsDebugger long press', (WidgetTester tester) async {
+    bool didLongPress = false;
+
+    await tester.pumpWidget(
+      new SemanticsDebugger(
+        child: new GestureDetector(
+          onLongPress: () {
+            expect(didLongPress, isFalse);
+            didLongPress = true;
+          },
+          child: new Text('target'),
+        ),
+      ),
+    );
+
+    await tester.longPress(find.text('target'));
+    expect(didLongPress, isTrue);
+  });
+
+  testWidgets('SemanticsDebugger slider', (WidgetTester tester) async {
+    double value = 0.75;
+
+    await tester.pumpWidget(
+      new SemanticsDebugger(
+        child: new Material(
+          child: new Center(
+            child: new Slider(
+              value: value,
+              onChanged: (double newValue) {
+                value = newValue;
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    await tester.fling(find.byType(Slider), const Offset(-100.0, 0.0), 100.0);
+    expect(value, equals(0.65));
+  });
+
+  testWidgets('SemanticsDebugger checkbox', (WidgetTester tester) async {
+    Key keyTop = new UniqueKey();
+    Key keyBottom = new UniqueKey();
+
+    bool valueTop = false;
+    bool valueBottom = true;
+
+    await tester.pumpWidget(
+      new SemanticsDebugger(
+        child: new Material(
+          child: new Block(
+            children: <Widget>[
+              new Checkbox(
+                key: keyTop,
+                value: valueTop,
+                onChanged: (bool newValue) {
+                  valueTop = newValue;
+                },
+              ),
+              new Checkbox(
+                key: keyBottom,
+                value: valueBottom,
+                onChanged: null,
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+
+    await tester.tap(find.byKey(keyTop));
+
+    expect(valueTop, isTrue);
+    valueTop = false;
+    expect(valueTop, isFalse);
+
+    await tester.tap(find.byKey(keyBottom));
+
+    expect(valueTop, isFalse);
+    expect(valueTop, isFalse);
+  });
 }

packages/flutter/test/widgets/status_transitions_test.dart

+// 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_test/flutter_test.dart';
+import 'package:flutter/widgets.dart';
+
+class TestStatusTransitionWidget extends StatusTransitionWidget {
+  TestStatusTransitionWidget({
+    Key key,
+    this.builder,
+    Animation<double> animation,
+  }) : super(key: key, animation: animation);
+
+  final WidgetBuilder builder;
+
+  @override
+  Widget build(BuildContext context) => builder(context);
+}
+
+void main() {
+  testWidgets('Status transition control test', (WidgetTester tester) async {
+    bool didBuild = false;
+    final AnimationController controller = new AnimationController(
+      duration: const Duration(seconds: 1),
+      vsync: const TestVSync(),
+    );
+
+    await tester.pumpWidget(new TestStatusTransitionWidget(
+      animation: controller,
+      builder: (BuildContext context) {
+        expect(didBuild, isFalse);
+        didBuild = true;
+        return new Container();
+      },
+    ));
+
+    expect(didBuild, isTrue);
+    didBuild = false;
+
+    controller.forward();
+
+    expect(didBuild, isFalse);
+    await tester.pump();
+    expect(didBuild, isTrue);
+    didBuild = false;
+    await tester.pump(const Duration(milliseconds: 100));
+    expect(didBuild, isFalse);
+    await tester.pump(const Duration(milliseconds: 850));
+    expect(didBuild, isFalse);
+    await tester.pump(const Duration(milliseconds: 100));
+    expect(didBuild, isTrue);
+    didBuild = false;
+    controller.forward();
+    await tester.pump(const Duration(milliseconds: 100));
+    expect(didBuild, isFalse);
+    controller.stop();
+    await tester.pump(const Duration(milliseconds: 100));
+    expect(didBuild, isFalse);
+
+    final AnimationController anotherController = new AnimationController(
+      duration: const Duration(seconds: 1),
+      vsync: const TestVSync(),
+    );
+
+    await tester.pumpWidget(new TestStatusTransitionWidget(
+      animation: anotherController,
+      builder: (BuildContext context) {
+        expect(didBuild, isFalse);
+        didBuild = true;
+        return new Container();
+      },
+    ));
+
+    expect(didBuild, isTrue);
+    didBuild = false;
+    controller.reverse();
+    await tester.pump(const Duration(milliseconds: 100));
+    expect(didBuild, isFalse);
+    anotherController.forward();
+    await tester.pump(const Duration(milliseconds: 100));
+    expect(didBuild, isTrue);
+    didBuild = false;
+
+    controller.stop();
+    anotherController.stop();
+  });
+}

packages/flutter_test/lib/flutter_test.dart

@@ -15,4 +15,5 @@ export 'src/matchers.dart';
 export 'src/test_async_utils.dart';
 export 'src/stack_manipulation.dart';
 export 'src/test_pointer.dart';
+export 'src/test_vsync.dart';
 export 'src/widget_tester.dart';

packages/flutter/test/animation/animation_tester.dart → packages/flutter_test/lib/src/test_vsync.dart

@@ -4,7 +4,12 @@
 
 import 'package:flutter/scheduler.dart';
 
+/// A [TickerProvider] that creates a standalone ticker.
+///
+/// Useful in tests that create an [AnimationController] outside of the widget
+/// tree.
 class TestVSync implements TickerProvider {
+  /// Creates a ticker provider that creates standalone tickers.
   const TestVSync();
 
   @override