packages/flutter_test/lib/src/widget_tester.dart - mirrors/flutter - Git at Google

 // 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 'dart:async';

 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart';
 import 'package:meta/meta.dart';
 import 'package:test/test.dart' as test_package;

 import 'all_elements.dart';
 import 'binding.dart';
 import 'controller.dart';
 import 'finders.dart';
 import 'test_async_utils.dart';

 export 'package:test/test.dart' hide expect;

 /// Signature for callback to [testWidgets] and [benchmarkWidgets].
 typedef Future<Null> WidgetTesterCallback(WidgetTester widgetTester);

 /// Runs the [callback] inside the Flutter test environment.
 ///
 /// Use this function for testing custom [StatelessWidget]s and
 /// [StatefulWidget]s.
 ///
 /// The callback can be asynchronous (using `async`/`await` or
 /// using explicit [Future]s).
 ///
 /// This function uses the [test] function in the test package to
 /// register the given callback as a test. The callback, when run,
 /// will be given a new instance of [WidgetTester]. The [find] object
 /// provides convenient widget [Finder]s for use with the
 /// [WidgetTester].
 ///
 /// Example:
 ///
 ///     testWidgets('MyWidget', (WidgetTester tester) async {
 ///       await tester.pumpWidget(new MyWidget());
 ///       await tester.tap(find.text('Save'));
 ///       expect(tester, hasWidget(find.text('Success')));
 ///     });
 void testWidgets(String description, WidgetTesterCallback callback, {
   bool skip: false,
   test_package.Timeout timeout
 }) {
   TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized();
   WidgetTester tester = new WidgetTester._(binding);
   timeout ??= binding.defaultTestTimeout;
   test_package.group('-', () {
     test_package.test(description, () => binding.runTest(() => callback(tester), tester._endOfTestVerifications), skip: skip);
     test_package.tearDown(binding.postTest);
   }, timeout: timeout);
 }

 /// Runs the [callback] inside the Flutter benchmark environment.
 ///
 /// Use this function for benchmarking custom [StatelessWidget]s and
 /// [StatefulWidget]s when you want to be able to use features from
 /// [TestWidgetsFlutterBinding]. The callback, when run, will be given
 /// a new instance of [WidgetTester]. The [find] object provides
 /// convenient widget [Finder]s for use with the [WidgetTester].
 ///
 /// The callback can be asynchronous (using `async`/`await` or using
 /// explicit [Future]s). If it is, then [benchmarkWidgets] will return
 /// a [Future] that completes when the callback's does. Otherwise, it
 /// will return a Future that is always complete.
 ///
 /// If the callback is asynchronous, make sure you `await` the call
 /// to [benchmarkWidgets], otherwise it won't run!
 ///
 /// Benchmarks must not be run in checked mode. To avoid this, this
 /// function will print a big message if it is run in checked mode.
 ///
 /// Example:
 ///
 ///     main() async {
 ///       assert(false); // fail in checked mode
 ///       await benchmarkWidgets((WidgetTester tester) async {
 ///         await tester.pumpWidget(new MyWidget());
 ///         final Stopwatch timer = new Stopwatch()..start();
 ///         for (int index = 0; index < 10000; index += 1) {
 ///           await tester.tap(find.text('Tap me'));
 ///           await tester.pump();
 ///         }
 ///         timer.stop();
 ///         debugPrint('Time taken: ${timer.elapsedMilliseconds}ms');
 ///       });
 ///       exit(0);
 ///     }
 Future<Null> benchmarkWidgets(WidgetTesterCallback callback) {
   assert(() {
     print('┏╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍┓');
     print('┇ ⚠ THIS BENCHMARK IS BEING RUN WITH ASSERTS ENABLED ⚠  ┇');
     print('┡╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍┦');
     print('│                                                       │');
     print('│  Numbers obtained from a benchmark while asserts are  │');
     print('│  enabled will not accurately reflect the performance  │');
     print('│  that will be experienced by end users using release  ╎');
     print('│  builds. Benchmarks should be run using this command  ┆');
     print('│  line:  flutter run --release benchmark.dart          ┊');
     print('│                                                        ');
     print('└─────────────────────────────────────────────────╌┄┈  🐢');
     return true;
   });
   TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized();
   assert(binding is! AutomatedTestWidgetsFlutterBinding);
   WidgetTester tester = new WidgetTester._(binding);
   return binding.runTest(() => callback(tester), tester._endOfTestVerifications) ?? new Future<Null>.value();
 }

 /// Assert that `actual` matches `matcher`.
 ///
 /// See [test_package.expect] for details. This is a variant of that function
 /// that additionally verifies that there are no asynchronous APIs
 /// that have not yet resolved.
 void expect(dynamic actual, dynamic matcher, {
   String reason,
   bool verbose: false,
   dynamic formatter
 }) {
   TestAsyncUtils.guardSync();
   test_package.expect(actual, matcher, reason: reason, verbose: verbose, formatter: formatter);
 }

 /// Assert that `actual` matches `matcher`.
 ///
 /// See [test_package.expect] for details. This variant will _not_ check that
 /// there are no outstanding asynchronous API requests. As such, it can be
 /// called from, e.g., callbacks that are run during build or layout, or in the
 /// completion handlers of futures that execute in response to user input.
 ///
 /// Generally, it is better to use [expect], which does include checks to ensure
 /// that asynchronous APIs are not being called.
 void expectSync(dynamic actual, dynamic matcher, {
   String reason,
   bool verbose: false,
   dynamic formatter
 }) {
   test_package.expect(actual, matcher, reason: reason, verbose: verbose, formatter: formatter);
 }

 /// Class that programmatically interacts with widgets and the test environment.
 ///
 /// For convenience, instances of this class (such as the one provided by
 /// `testWidget`) can be used as the `vsync` for `AnimationController` objects.
 class WidgetTester extends WidgetController implements HitTestDispatcher, TickerProvider {
   WidgetTester._(TestWidgetsFlutterBinding binding) : super(binding) {
     if (binding is LiveTestWidgetsFlutterBinding)
       binding.deviceEventDispatcher = this;
   }

   /// The binding instance used by the testing framework.
   @override
   TestWidgetsFlutterBinding get binding => super.binding;

   /// Renders the UI from the given [widget].
   ///
   /// Calls [runApp] with the given widget, then triggers a frame and flushes
   /// microtasks, by calling [pump] with the same `duration` (if any). The
   /// supplied [EnginePhase] is the final phase reached during the pump pass; if
   /// not supplied, the whole pass is executed.
   Future<Null> pumpWidget(Widget widget, [
     Duration duration,
     EnginePhase phase = EnginePhase.sendSemanticsTree
   ]) {
     return TestAsyncUtils.guard(() {
       binding.attachRootWidget(widget);
       binding.scheduleFrame();
       return binding.pump(duration, phase);
     });
   }

   /// Triggers a frame after `duration` amount of time.
   ///
   /// This makes the framework act as if the application had janked (missed
   /// frames) for `duration` amount of time, and then received a v-sync signal
   /// to paint the application.
   ///
   /// This is a convenience function that just calls
   /// [TestWidgetsFlutterBinding.pump].
   @override
   Future<Null> pump([
     Duration duration,
     EnginePhase phase = EnginePhase.sendSemanticsTree
   ]) {
     return TestAsyncUtils.guard(() => binding.pump(duration, phase));
   }

   /// Repeatedly calls [pump] with the given `duration` until there are no
   /// longer any transient callbacks scheduled. If no transient callbacks are
   /// scheduled when the function is called, it returns without calling [pump].
   ///
   /// This essentially waits for all animations to have completed.
   ///
   /// This function will never return (and the test will hang and eventually
   /// time out and fail) if there is an infinite animation in progress (for
   /// example, if there is an indeterminate progress indicator spinning).
   ///
   /// If the function returns, it returns the number of pumps that it performed.
   ///
   /// In general, it is better practice to figure out exactly why each frame is
   /// needed, and then to [pump] exactly as many frames as necessary. This will
   /// help catch regressions where, for instance, an animation is being started
   /// one frame later than it should.
   ///
   /// Alternatively, one can check that the return value from this function
   /// matches the expected number of pumps.
   Future<int> pumpUntilNoTransientCallbacks([
     @required Duration duration,
     EnginePhase phase = EnginePhase.sendSemanticsTree
   ]) {
     assert(duration != null);
     assert(duration > Duration.ZERO);
     int count = 0;
     return TestAsyncUtils.guard(() async {
       while (binding.transientCallbackCount > 0) {
         await binding.pump(duration, phase);
         count += 1;
       }
     }).then/*<int>*/((Null _) => count);
   }

   @override
   HitTestResult hitTestOnBinding(Point location) {
     location = binding.localToGlobal(location);
     return super.hitTestOnBinding(location);
   }

   @override
   Future<Null> sendEventToBinding(PointerEvent event, HitTestResult result) {
     return TestAsyncUtils.guard(() async {
       binding.dispatchEvent(event, result, source: TestBindingEventSource.test);
       return null;
     });
   }

   /// Handler for device events caught by the binding in live test mode.
   @override
   void dispatchEvent(PointerEvent event, HitTestResult result) {
     if (event is PointerDownEvent) {
       final RenderObject innerTarget = result.path.firstWhere(
         (HitTestEntry candidate) => candidate.target is RenderObject,
         orElse: () => null
       )?.target;
       if (innerTarget == null)
         return null;
       final Element innerTargetElement = collectAllElementsFrom(binding.renderViewElement, skipOffstage: true)
         .lastWhere((Element element) => element.renderObject == innerTarget);
       final List<Element> candidates = <Element>[];
       innerTargetElement.visitAncestorElements((Element element) {
         candidates.add(element);
         return true;
       });
       assert(candidates.isNotEmpty);
       String descendantText;
       int numberOfWithTexts = 0;
       int numberOfTypes = 0;
       int totalNumber = 0;
       debugPrint('Some possible finders for the widgets at ${binding.globalToLocal(event.position)}:');
       for (Element element in candidates) {
         if (totalNumber > 10)
           break;
         totalNumber += 1;

         if (element.widget is Text) {
           assert(descendantText == null);
           final Text widget = element.widget;
           final Iterable<Element> matches = find.text(widget.data).evaluate();
           descendantText = widget.data;
           if (matches.length == 1) {
             debugPrint('  find.text(\'${widget.data}\')');
             continue;
           }
         }

         if (element.widget.key is ValueKey<dynamic>) {
           final ValueKey<dynamic> key = element.widget.key;
           String keyLabel;
           if ((key is ValueKey<int> ||
                key is ValueKey<double> ||
                key is ValueKey<bool>)) {
             keyLabel = 'const ${element.widget.key.runtimeType}(${key.value})';
           } else if (key is ValueKey<String>) {
             keyLabel = 'const ${element.widget.key.runtimeType}(\'${key.value}\')';
           }
           if (keyLabel != null) {
             final Iterable<Element> matches = find.byKey(key).evaluate();
             if (matches.length == 1) {
               debugPrint('  find.byKey($keyLabel)');
               continue;
             }
           }
         }

         if (!_isPrivate(element.widget.runtimeType)) {
           if (numberOfTypes < 5) {
             final Iterable<Element> matches = find.byType(element.widget.runtimeType).evaluate();
             if (matches.length == 1) {
               debugPrint('  find.byType(${element.widget.runtimeType})');
               numberOfTypes += 1;
               continue;
             }
           }

           if (descendantText != null && numberOfWithTexts < 5) {
             final Iterable<Element> matches = find.widgetWithText(element.widget.runtimeType, descendantText).evaluate();
             if (matches.length == 1) {
               debugPrint('  find.widgetWithText(${element.widget.runtimeType}, \'$descendantText\')');
               numberOfWithTexts += 1;
               continue;
             }
           }
         }

         if (!_isPrivate(element.runtimeType)) {
           final Iterable<Element> matches = find.byElementType(element.runtimeType).evaluate();
           if (matches.length == 1) {
             debugPrint('  find.byElementType(${element.runtimeType})');
             continue;
           }
         }

         totalNumber -= 1; // if we got here, we didn't actually find something to say about it
       }
       if (totalNumber == 0)
         debugPrint('  <could not come up with any unique finders>');
     }
   }

   bool _isPrivate(Type type) {
     // used above so that we don't suggest matchers for private types
     return '_'.matchAsPrefix(type.toString()) != null;
   }

   /// Returns the exception most recently caught by the Flutter framework.
   ///
   /// See [TestWidgetsFlutterBinding.takeException] for details.
   dynamic takeException() {
     return binding.takeException();
   }

   /// Acts as if the application went idle.
   ///
   /// Runs all remaining microtasks, including those scheduled as a result of
   /// running them, until there are no more microtasks scheduled.
   ///
   /// Does not run timers. May result in an infinite loop or run out of memory
   /// if microtasks continue to recursively schedule new microtasks.
   Future<Null> idle() {
     return TestAsyncUtils.guard(() => binding.idle());
   }

   Set<Ticker> _tickers;

   @override
   Ticker createTicker(TickerCallback onTick) {
     _tickers ??= new Set<_TestTicker>();
     final _TestTicker result = new _TestTicker(onTick, _removeTicker);
     _tickers.add(result);
     return result;
   }

   void _removeTicker(_TestTicker ticker) {
     assert(_tickers != null);
     assert(_tickers.contains(ticker));
     _tickers.remove(ticker);
   }

   /// Throws an exception if any tickers created by the [WidgetTester] are still
   /// active when the method is called.
   ///
   /// An argument can be specified to provide a string that will be used in the
   /// error message. It should be an adverbial phrase describing the current
   /// situation, such as "at the end of the test".
   void verifyTickersWereDisposed([ String when = 'when none should have been' ]) {
     assert(when != null);
     if (_tickers != null) {
       for (Ticker ticker in _tickers) {
         if (ticker.isActive) {
           throw new FlutterError(
             'A Ticker was active $when.\n'
             'All Tickers must be disposed. Tickers used by AnimationControllers '
             'should be disposed by calling dispose() on the AnimationController itself. '
             'Otherwise, the ticker will leak.\n'
             'The offending ticker was: ${ticker.toString(debugIncludeStack: true)}'
           );
         }
       }
     }
   }

   void _endOfTestVerifications() {
     verifyTickersWereDisposed('at the end of the test');
   }
 }

 typedef void _TickerDisposeCallback(_TestTicker ticker);

 class _TestTicker extends Ticker {
   _TestTicker(TickerCallback onTick, this._onDispose) : super(onTick);

   _TickerDisposeCallback _onDispose;

   @override
   void dispose() {
     if (_onDispose != null)
       _onDispose(this);
     super.dispose();
   }
 }
	// 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 'dart:async';

	import 'package:flutter/gestures.dart';
	import 'package:flutter/rendering.dart';
	import 'package:flutter/scheduler.dart';
	import 'package:flutter/widgets.dart';
	import 'package:meta/meta.dart';
	import 'package:test/test.dart' as test_package;

	import 'all_elements.dart';
	import 'binding.dart';
	import 'controller.dart';
	import 'finders.dart';
	import 'test_async_utils.dart';

	export 'package:test/test.dart' hide expect;

	/// Signature for callback to [testWidgets] and [benchmarkWidgets].
	typedef Future<Null> WidgetTesterCallback(WidgetTester widgetTester);

	/// Runs the [callback] inside the Flutter test environment.
	///
	/// Use this function for testing custom [StatelessWidget]s and
	/// [StatefulWidget]s.
	///
	/// The callback can be asynchronous (using `async`/`await` or
	/// using explicit [Future]s).
	///
	/// This function uses the [test] function in the test package to
	/// register the given callback as a test. The callback, when run,
	/// will be given a new instance of [WidgetTester]. The [find] object
	/// provides convenient widget [Finder]s for use with the
	/// [WidgetTester].
	///
	/// Example:
	///
	/// testWidgets('MyWidget', (WidgetTester tester) async {
	/// await tester.pumpWidget(new MyWidget());
	/// await tester.tap(find.text('Save'));
	/// expect(tester, hasWidget(find.text('Success')));
	/// });
	void testWidgets(String description, WidgetTesterCallback callback, {
	bool skip: false,
	test_package.Timeout timeout
	}) {
	TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized();
	WidgetTester tester = new WidgetTester._(binding);
	timeout ??= binding.defaultTestTimeout;
	test_package.group('-', () {
	test_package.test(description, () => binding.runTest(() => callback(tester), tester._endOfTestVerifications), skip: skip);
	test_package.tearDown(binding.postTest);
	}, timeout: timeout);
	}

	/// Runs the [callback] inside the Flutter benchmark environment.
	///
	/// Use this function for benchmarking custom [StatelessWidget]s and
	/// [StatefulWidget]s when you want to be able to use features from
	/// [TestWidgetsFlutterBinding]. The callback, when run, will be given
	/// a new instance of [WidgetTester]. The [find] object provides
	/// convenient widget [Finder]s for use with the [WidgetTester].
	///
	/// The callback can be asynchronous (using `async`/`await` or using
	/// explicit [Future]s). If it is, then [benchmarkWidgets] will return
	/// a [Future] that completes when the callback's does. Otherwise, it
	/// will return a Future that is always complete.
	///
	/// If the callback is asynchronous, make sure you `await` the call
	/// to [benchmarkWidgets], otherwise it won't run!
	///
	/// Benchmarks must not be run in checked mode. To avoid this, this
	/// function will print a big message if it is run in checked mode.
	///
	/// Example:
	///
	/// main() async {
	/// assert(false); // fail in checked mode
	/// await benchmarkWidgets((WidgetTester tester) async {
	/// await tester.pumpWidget(new MyWidget());
	/// final Stopwatch timer = new Stopwatch()..start();
	/// for (int index = 0; index < 10000; index += 1) {
	/// await tester.tap(find.text('Tap me'));
	/// await tester.pump();
	/// }
	/// timer.stop();
	/// debugPrint('Time taken: ${timer.elapsedMilliseconds}ms');
	/// });
	/// exit(0);
	/// }
	Future<Null> benchmarkWidgets(WidgetTesterCallback callback) {
	assert(() {
	print('┏╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍┓');
	print('┇ ⚠ THIS BENCHMARK IS BEING RUN WITH ASSERTS ENABLED ⚠ ┇');
	print('┡╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍╍┦');
	print('│ │');
	print('│ Numbers obtained from a benchmark while asserts are │');
	print('│ enabled will not accurately reflect the performance │');
	print('│ that will be experienced by end users using release ╎');
	print('│ builds. Benchmarks should be run using this command ┆');
	print('│ line: flutter run --release benchmark.dart ┊');
	print('│ ');
	print('└─────────────────────────────────────────────────╌┄┈ 🐢');
	return true;
	});
	TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized();
	assert(binding is! AutomatedTestWidgetsFlutterBinding);
	WidgetTester tester = new WidgetTester._(binding);
	return binding.runTest(() => callback(tester), tester._endOfTestVerifications) ?? new Future<Null>.value();
	}

	/// Assert that `actual` matches `matcher`.
	///
	/// See [test_package.expect] for details. This is a variant of that function
	/// that additionally verifies that there are no asynchronous APIs
	/// that have not yet resolved.
	void expect(dynamic actual, dynamic matcher, {
	String reason,
	bool verbose: false,
	dynamic formatter
	}) {
	TestAsyncUtils.guardSync();
	test_package.expect(actual, matcher, reason: reason, verbose: verbose, formatter: formatter);
	}

	/// Assert that `actual` matches `matcher`.
	///
	/// See [test_package.expect] for details. This variant will _not_ check that
	/// there are no outstanding asynchronous API requests. As such, it can be
	/// called from, e.g., callbacks that are run during build or layout, or in the
	/// completion handlers of futures that execute in response to user input.
	///
	/// Generally, it is better to use [expect], which does include checks to ensure
	/// that asynchronous APIs are not being called.
	void expectSync(dynamic actual, dynamic matcher, {
	String reason,
	bool verbose: false,
	dynamic formatter
	}) {
	test_package.expect(actual, matcher, reason: reason, verbose: verbose, formatter: formatter);
	}

	/// Class that programmatically interacts with widgets and the test environment.
	///
	/// For convenience, instances of this class (such as the one provided by
	/// `testWidget`) can be used as the `vsync` for `AnimationController` objects.
	class WidgetTester extends WidgetController implements HitTestDispatcher, TickerProvider {
	WidgetTester._(TestWidgetsFlutterBinding binding) : super(binding) {
	if (binding is LiveTestWidgetsFlutterBinding)
	binding.deviceEventDispatcher = this;
	}

	/// The binding instance used by the testing framework.
	@override
	TestWidgetsFlutterBinding get binding => super.binding;

	/// Renders the UI from the given [widget].
	///
	/// Calls [runApp] with the given widget, then triggers a frame and flushes
	/// microtasks, by calling [pump] with the same `duration` (if any). The
	/// supplied [EnginePhase] is the final phase reached during the pump pass; if
	/// not supplied, the whole pass is executed.
	Future<Null> pumpWidget(Widget widget, [
	Duration duration,
	EnginePhase phase = EnginePhase.sendSemanticsTree
	]) {
	return TestAsyncUtils.guard(() {
	binding.attachRootWidget(widget);
	binding.scheduleFrame();
	return binding.pump(duration, phase);
	});
	}

	/// Triggers a frame after `duration` amount of time.
	///
	/// This makes the framework act as if the application had janked (missed
	/// frames) for `duration` amount of time, and then received a v-sync signal
	/// to paint the application.
	///
	/// This is a convenience function that just calls
	/// [TestWidgetsFlutterBinding.pump].
	@override
	Future<Null> pump([
	Duration duration,
	EnginePhase phase = EnginePhase.sendSemanticsTree
	]) {
	return TestAsyncUtils.guard(() => binding.pump(duration, phase));
	}

	/// Repeatedly calls [pump] with the given `duration` until there are no
	/// longer any transient callbacks scheduled. If no transient callbacks are
	/// scheduled when the function is called, it returns without calling [pump].
	///
	/// This essentially waits for all animations to have completed.
	///
	/// This function will never return (and the test will hang and eventually
	/// time out and fail) if there is an infinite animation in progress (for
	/// example, if there is an indeterminate progress indicator spinning).
	///
	/// If the function returns, it returns the number of pumps that it performed.
	///
	/// In general, it is better practice to figure out exactly why each frame is
	/// needed, and then to [pump] exactly as many frames as necessary. This will
	/// help catch regressions where, for instance, an animation is being started
	/// one frame later than it should.
	///
	/// Alternatively, one can check that the return value from this function
	/// matches the expected number of pumps.
	Future<int> pumpUntilNoTransientCallbacks([
	@required Duration duration,
	EnginePhase phase = EnginePhase.sendSemanticsTree
	]) {
	assert(duration != null);
	assert(duration > Duration.ZERO);
	int count = 0;
	return TestAsyncUtils.guard(() async {
	while (binding.transientCallbackCount > 0) {
	await binding.pump(duration, phase);
	count += 1;
	}
	}).then/<int>/((Null _) => count);
	}

	@override
	HitTestResult hitTestOnBinding(Point location) {
	location = binding.localToGlobal(location);
	return super.hitTestOnBinding(location);
	}

	@override
	Future<Null> sendEventToBinding(PointerEvent event, HitTestResult result) {
	return TestAsyncUtils.guard(() async {
	binding.dispatchEvent(event, result, source: TestBindingEventSource.test);
	return null;
	});
	}

	/// Handler for device events caught by the binding in live test mode.
	@override
	void dispatchEvent(PointerEvent event, HitTestResult result) {
	if (event is PointerDownEvent) {
	final RenderObject innerTarget = result.path.firstWhere(
	(HitTestEntry candidate) => candidate.target is RenderObject,
	orElse: () => null
	)?.target;
	if (innerTarget == null)
	return null;
	final Element innerTargetElement = collectAllElementsFrom(binding.renderViewElement, skipOffstage: true)
	.lastWhere((Element element) => element.renderObject == innerTarget);
	final List<Element> candidates = <Element>[];
	innerTargetElement.visitAncestorElements((Element element) {
	candidates.add(element);
	return true;
	});
	assert(candidates.isNotEmpty);
	String descendantText;
	int numberOfWithTexts = 0;
	int numberOfTypes = 0;
	int totalNumber = 0;
	debugPrint('Some possible finders for the widgets at ${binding.globalToLocal(event.position)}:');
	for (Element element in candidates) {
	if (totalNumber > 10)
	break;
	totalNumber += 1;

	if (element.widget is Text) {
	assert(descendantText == null);
	final Text widget = element.widget;
	final Iterable<Element> matches = find.text(widget.data).evaluate();
	descendantText = widget.data;
	if (matches.length == 1) {
	debugPrint(' find.text(\'${widget.data}\')');
	continue;
	}
	}

	if (element.widget.key is ValueKey<dynamic>) {
	final ValueKey<dynamic> key = element.widget.key;
	String keyLabel;
	if ((key is ValueKey<int> \|\|
	key is ValueKey<double> \|\|
	key is ValueKey<bool>)) {
	keyLabel = 'const ${element.widget.key.runtimeType}(${key.value})';
	} else if (key is ValueKey<String>) {
	keyLabel = 'const ${element.widget.key.runtimeType}(\'${key.value}\')';
	}
	if (keyLabel != null) {
	final Iterable<Element> matches = find.byKey(key).evaluate();
	if (matches.length == 1) {
	debugPrint(' find.byKey($keyLabel)');
	continue;
	}
	}
	}

	if (!_isPrivate(element.widget.runtimeType)) {
	if (numberOfTypes < 5) {
	final Iterable<Element> matches = find.byType(element.widget.runtimeType).evaluate();
	if (matches.length == 1) {
	debugPrint(' find.byType(${element.widget.runtimeType})');
	numberOfTypes += 1;
	continue;
	}
	}

	if (descendantText != null && numberOfWithTexts < 5) {
	final Iterable<Element> matches = find.widgetWithText(element.widget.runtimeType, descendantText).evaluate();
	if (matches.length == 1) {
	debugPrint(' find.widgetWithText(${element.widget.runtimeType}, \'$descendantText\')');
	numberOfWithTexts += 1;
	continue;
	}
	}
	}

	if (!_isPrivate(element.runtimeType)) {
	final Iterable<Element> matches = find.byElementType(element.runtimeType).evaluate();
	if (matches.length == 1) {
	debugPrint(' find.byElementType(${element.runtimeType})');
	continue;
	}
	}

	totalNumber -= 1; // if we got here, we didn't actually find something to say about it
	}
	if (totalNumber == 0)
	debugPrint(' <could not come up with any unique finders>');
	}
	}

	bool _isPrivate(Type type) {
	// used above so that we don't suggest matchers for private types
	return '_'.matchAsPrefix(type.toString()) != null;
	}

	/// Returns the exception most recently caught by the Flutter framework.
	///
	/// See [TestWidgetsFlutterBinding.takeException] for details.
	dynamic takeException() {
	return binding.takeException();
	}

	/// Acts as if the application went idle.
	///
	/// Runs all remaining microtasks, including those scheduled as a result of
	/// running them, until there are no more microtasks scheduled.
	///
	/// Does not run timers. May result in an infinite loop or run out of memory
	/// if microtasks continue to recursively schedule new microtasks.
	Future<Null> idle() {
	return TestAsyncUtils.guard(() => binding.idle());
	}

	Set<Ticker> _tickers;

	@override
	Ticker createTicker(TickerCallback onTick) {
	_tickers ??= new Set<_TestTicker>();
	final _TestTicker result = new _TestTicker(onTick, _removeTicker);
	_tickers.add(result);
	return result;
	}

	void _removeTicker(_TestTicker ticker) {
	assert(_tickers != null);
	assert(_tickers.contains(ticker));
	_tickers.remove(ticker);
	}

	/// Throws an exception if any tickers created by the [WidgetTester] are still
	/// active when the method is called.
	///
	/// An argument can be specified to provide a string that will be used in the
	/// error message. It should be an adverbial phrase describing the current
	/// situation, such as "at the end of the test".
	void verifyTickersWereDisposed([ String when = 'when none should have been' ]) {
	assert(when != null);
	if (_tickers != null) {
	for (Ticker ticker in _tickers) {
	if (ticker.isActive) {
	throw new FlutterError(
	'A Ticker was active $when.\n'
	'All Tickers must be disposed. Tickers used by AnimationControllers '
	'should be disposed by calling dispose() on the AnimationController itself. '
	'Otherwise, the ticker will leak.\n'
	'The offending ticker was: ${ticker.toString(debugIncludeStack: true)}'
	);
	}
	}
	}
	}

	void _endOfTestVerifications() {
	verifyTickersWereDisposed('at the end of the test');
	}
	}

	typedef void _TickerDisposeCallback(_TestTicker ticker);

	class _TestTicker extends Ticker {
	_TestTicker(TickerCallback onTick, this._onDispose) : super(onTick);

	_TickerDisposeCallback _onDispose;

	@override
	void dispose() {
	if (_onDispose != null)
	_onDispose(this);
	super.dispose();
	}
	}