Migrate flutter_test (#66663)

dev/bots/test.dart

@@ -620,7 +620,7 @@ Future<void> _runFrameworkTests() async {
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_driver'), tableData: bigqueryApi?.tabledata, tests: <String>[path.join('test', 'src', 'real_tests')]);
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_goldens'), tableData: bigqueryApi?.tabledata);
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_localizations'), tableData: bigqueryApi?.tabledata);
-    await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_test'), tableData: bigqueryApi?.tabledata);
+    await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_test'), tableData: bigqueryApi?.tabledata, options: nullSafetyOptions);
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'fuchsia_remote_debug_protocol'), tableData: bigqueryApi?.tabledata);
     await _runFlutterTest(path.join(flutterRoot, 'dev', 'integration_tests', 'non_nullable'), options: nullSafetyOptions);
     await _runFlutterTest(

packages/flutter/test/cupertino/text_field_test.dart

@@ -3216,8 +3216,8 @@ void main() {
         ),
       );
 
-      tester.binding.window.physicalSizeTestValue = null;
-      tester.binding.window.devicePixelRatioTestValue = null;
+      tester.binding.window.clearPhysicalSizeTestValue();
+      tester.binding.window.clearDevicePixelRatioTestValue();
     });
 
     testWidgets('selecting multiple words works', (WidgetTester tester) async {
@@ -3287,8 +3287,8 @@ void main() {
         ),
       );
 
-      tester.binding.window.physicalSizeTestValue = null;
-      tester.binding.window.devicePixelRatioTestValue = null;
+      tester.binding.window.clearPhysicalSizeTestValue();
+      tester.binding.window.clearDevicePixelRatioTestValue();
     });
 
     testWidgets('selecting multiline works', (WidgetTester tester) async {
@@ -3362,8 +3362,8 @@ void main() {
         ),
       );
 
-      tester.binding.window.physicalSizeTestValue = null;
-      tester.binding.window.devicePixelRatioTestValue = null;
+      tester.binding.window.clearPhysicalSizeTestValue();
+      tester.binding.window.clearDevicePixelRatioTestValue();
     });
 
     // This is a regression test for

packages/flutter/test/material/app_test.dart

@@ -778,7 +778,7 @@ void main() {
     );
 
     expect(appliedTheme.primaryColor, Colors.blue);
-    tester.binding.window.accessibilityFeaturesTestValue = null;
+    tester.binding.window.clearAccessibilityFeaturesTestValue();
   });
 
   testWidgets('MaterialApp uses high contrast dark theme when appropriate', (WidgetTester tester) async {
@@ -811,7 +811,7 @@ void main() {
     );
 
     expect(appliedTheme.primaryColor, Colors.green);
-    tester.binding.window.accessibilityFeaturesTestValue = null;
+    tester.binding.window.clearAccessibilityFeaturesTestValue();
   });
 
   testWidgets('MaterialApp uses dark theme when no high contrast dark theme is provided', (WidgetTester tester) async {
@@ -838,8 +838,8 @@ void main() {
     );
 
     expect(appliedTheme.primaryColor, Colors.lightGreen);
-    tester.binding.window.accessibilityFeaturesTestValue = null;
-    tester.binding.window.platformBrightnessTestValue = null;
+    tester.binding.window.clearAccessibilityFeaturesTestValue();
+    tester.binding.window.clearPlatformBrightnessTestValue();
   });
 
   testWidgets('MaterialApp switches themes when the Window platformBrightness changes.', (WidgetTester tester) async {

packages/flutter/test/material/time_picker_test.dart

@@ -486,8 +486,8 @@ void _tests() {
     expect(minuteSize.width, greaterThanOrEqualTo(48.0));
     expect(minuteSize.height, greaterThanOrEqualTo(48.0));
 
-    tester.binding.window.physicalSizeTestValue = null;
-    tester.binding.window.devicePixelRatioTestValue = null;
+    tester.binding.window.clearPhysicalSizeTestValue();
+    tester.binding.window.clearDevicePixelRatioTestValue();
   });
 
   testWidgets('builder parameter', (WidgetTester tester) async {

packages/flutter_test/analysis_options.yaml

+# Use the parent analysis options settings and enable null-experiment.
+
+include: ../analysis_options.yaml
+
+analyzer:
+  enable-experiment:
+    - non-nullable
+  errors:
+    always_require_non_null_named_parameters: false # not needed with nnbd
+    unrelated_type_equality_checks: false # https://github.com/dart-lang/linter/issues/2196
+    void_checks: false # https://github.com/dart-lang/linter/issues/2185
+    unnecessary_null_comparison: false # https://github.com/dart-lang/language/issues/1018

packages/flutter_test/lib/src/_binding_web.dart

@@ -7,12 +7,12 @@ import 'package:flutter/widgets.dart';
 import 'binding.dart';
 
  /// Ensure the [WidgetsBinding] is initialized.
-WidgetsBinding ensureInitialized([@visibleForTesting Map<String, String> environment]) {
+WidgetsBinding ensureInitialized([@visibleForTesting Map<String, String>? environment]) {
   if (WidgetsBinding.instance == null) {
     AutomatedTestWidgetsFlutterBinding();
   }
   assert(WidgetsBinding.instance is TestWidgetsFlutterBinding);
-  return WidgetsBinding.instance;
+  return WidgetsBinding.instance!;
 }
 
  /// This method is a noop on the web.

packages/flutter_test/lib/src/_goldens_io.dart

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.10
 import 'dart:async';
 import 'dart:io';
 import 'dart:math' as math;

packages/flutter_test/lib/src/_goldens_web.dart

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.10
 import 'dart:convert';
 import 'dart:html' as html;
 import 'dart:typed_data';

packages/flutter_test/lib/src/_matchers_io.dart

@@ -5,7 +5,7 @@
 import 'dart:typed_data';
 import 'dart:ui' as ui;
 
-import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:test_api/src/frontend/async_matcher.dart'; // ignore: implementation_imports
@@ -22,7 +22,8 @@ import 'goldens.dart';
 ///
 ///  * [OffsetLayer.toImage] which is the actual method being called.
 Future<ui.Image> captureImage(Element element) {
-  RenderObject renderObject = element.renderObject;
+  assert(element.renderObject != null);
+  RenderObject renderObject = element.renderObject!;
   while (!renderObject.isRepaintBoundary) {
     renderObject = renderObject.parent as RenderObject;
     assert(renderObject != null);
@@ -45,10 +46,10 @@ class MatchesGoldenFile extends AsyncMatcher {
   final Uri key;
 
   /// The [version] of the golden image.
-  final int version;
+  final int? version;
 
   @override
-  Future<String> matchAsync(dynamic item) async {
+  Future<String?> matchAsync(dynamic item) async {
     Future<ui.Image> imageFuture;
     if (item is Future<ui.Image>) {
       imageFuture = item;
@@ -68,9 +69,9 @@ class MatchesGoldenFile extends AsyncMatcher {
     final Uri testNameUri = goldenFileComparator.getTestUri(key, version);
 
     final TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized() as TestWidgetsFlutterBinding;
-    return binding.runAsync<String>(() async {
+    return binding.runAsync<String?>(() async {
       final ui.Image image = await imageFuture;
-      final ByteData bytes = await image.toByteData(format: ui.ImageByteFormat.png);
+      final ByteData? bytes = await image.toByteData(format: ui.ImageByteFormat.png);
       if (bytes == null)
         return 'could not encode screenshot.';
       if (autoUpdateGoldenFiles) {

packages/flutter_test/lib/src/_matchers_web.dart

@@ -32,15 +32,14 @@ class MatchesGoldenFile extends AsyncMatcher {
   final Uri key;
 
   /// The [version] of the golden image.
-  final int version;
+  final int? version;
 
   @override
-  Future<String> matchAsync(dynamic item) async {
+  Future<String?> matchAsync(dynamic item) async {
     if (item is! Finder) {
       return 'web goldens only supports matching finders.';
     }
-    final Finder finder = item as Finder;
-    final Iterable<Element> elements = finder.evaluate();
+    final Iterable<Element> elements = item.evaluate();
     if (elements.isEmpty) {
       return 'could not be rendered because no widget was found';
     } else if (elements.length > 1) {
@@ -50,14 +49,14 @@ class MatchesGoldenFile extends AsyncMatcher {
     final RenderObject renderObject = _findRepaintBoundary(element);
     final Size size = renderObject.paintBounds.size;
     final TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized() as TestWidgetsFlutterBinding;
-    final Element e = binding.renderViewElement;
+    final Element e = binding.renderViewElement!;
 
     // Unlike `flutter_tester`, we don't have the ability to render an element
     // to an image directly. Instead, we will use `window.render()` to render
     // only the element being requested, and send a request to the test server
     // requesting it to take a screenshot through the browser's debug interface.
     _renderElement(binding.window, renderObject);
-    final String result = await binding.runAsync<String>(() async {
+    final String? result = await binding.runAsync<String?>(() async {
       if (autoUpdateGoldenFiles) {
         await webGoldenComparator.update(size.width, size.height, key);
         return null;
@@ -81,7 +80,8 @@ class MatchesGoldenFile extends AsyncMatcher {
 }
 
 RenderObject _findRepaintBoundary(Element element) {
-  RenderObject renderObject = element.renderObject;
+  assert(element.renderObject != null);
+  RenderObject renderObject = element.renderObject!;
   while (!renderObject.isRepaintBoundary) {
     renderObject = renderObject.parent as RenderObject;
     assert(renderObject != null);
@@ -90,7 +90,8 @@ RenderObject _findRepaintBoundary(Element element) {
 }
 
 void _renderElement(ui.Window window, RenderObject renderObject) {
-  final Layer layer = renderObject.debugLayer;
+  assert(renderObject.debugLayer != null);
+  final Layer layer = renderObject.debugLayer!;
   final ui.SceneBuilder sceneBuilder = ui.SceneBuilder();
   if (layer is OffsetLayer) {
     sceneBuilder.pushOffset(-layer.offset.dx, -layer.offset.dy);

packages/flutter_test/lib/src/all_elements.dart

@@ -18,7 +18,7 @@ import 'package:flutter/widgets.dart';
 /// are also cached.
 Iterable<Element> collectAllElementsFrom(
   Element rootElement, {
-  @required bool skipOffstage,
+  required bool skipOffstage,
 }) {
   return CachingIterable<Element>(_DepthFirstChildIterator(rootElement, skipOffstage));
 }
@@ -29,7 +29,7 @@ class _DepthFirstChildIterator implements Iterator<Element> {
 
   final bool skipOffstage;
 
-  Element _current;
+  late Element _current;
 
   final List<Element> _stack;
 

packages/flutter_test/lib/src/animation_sheet.dart

@@ -8,7 +8,6 @@ import 'dart:ui' as ui;
 import 'package:flutter/rendering.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart';
-import 'package:flutter_test/flutter_test.dart';
 
 /// Records the frames of an animating widget, and later displays the frames as a
 /// grid in an animation sheet.
@@ -92,7 +91,7 @@ class AnimationSheetBuilder {
   ///
   /// The [frameSize] is a tight constraint for the child to be recorded, and must not
   /// be null.
-  AnimationSheetBuilder({@required this.frameSize}) : assert(frameSize != null);
+  AnimationSheetBuilder({required this.frameSize}) : assert(frameSize != null);
 
   /// The size of the child to be recorded.
   ///
@@ -133,7 +132,7 @@ class AnimationSheetBuilder {
   ///  * [WidgetTester.pumpFrames], which renders a widget in a series of frames
   ///    with a fixed time interval.
   Widget record(Widget child, {
-    Key key,
+    Key? key,
     bool recording = true,
   }) {
     assert(child != null);
@@ -160,7 +159,7 @@ class AnimationSheetBuilder {
   /// The `key` is applied to the root widget.
   ///
   /// This method can only be called if at least one frame has been recorded.
-  Future<Widget> display({Key key}) async {
+  Future<Widget> display({Key? key}) async {
     assert(_recordedFrames.isNotEmpty);
     final List<ui.Image> frames = await _frames;
     return _CellSheet(
@@ -209,12 +208,12 @@ typedef _RecordedHandler = void Function(Future<ui.Image> image);
 class _AnimationSheetRecorder extends StatefulWidget {
   const _AnimationSheetRecorder({
     this.handleRecorded,
-    this.child,
-    this.size,
-    Key key,
+    required this.child,
+    required this.size,
+    Key? key,
   }) : super(key: key);
 
-  final _RecordedHandler handleRecorded;
+  final _RecordedHandler? handleRecorded;
   final Widget child;
   final Size size;
 
@@ -226,8 +225,9 @@ class _AnimationSheetRecorderState extends State<_AnimationSheetRecorder> {
   GlobalKey boundaryKey = GlobalKey();
 
   void _record(Duration duration) {
-    final RenderRepaintBoundary boundary = boundaryKey.currentContext.findRenderObject() as RenderRepaintBoundary;
-    widget.handleRecorded(boundary.toImage());
+    assert(widget.handleRecorded != null);
+    final RenderRepaintBoundary boundary = boundaryKey.currentContext!.findRenderObject()! as RenderRepaintBoundary;
+    widget.handleRecorded!(boundary.toImage());
   }
 
   @override
@@ -258,12 +258,12 @@ class _AnimationSheetRecorderState extends State<_AnimationSheetRecorder> {
 // If `callback` is null, `_PostFrameCallbacker` is equivalent to a proxy box.
 class _PostFrameCallbacker extends SingleChildRenderObjectWidget {
   const _PostFrameCallbacker({
-    Key key,
-    Widget child,
+    Key? key,
+    Widget? child,
     this.callback,
   }) : super(key: key, child: child);
 
-  final FrameCallback callback;
+  final FrameCallback? callback;
 
   @override
   _RenderPostFrameCallbacker createRenderObject(BuildContext context) => _RenderPostFrameCallbacker(
@@ -278,12 +278,12 @@ class _PostFrameCallbacker extends SingleChildRenderObjectWidget {
 
 class _RenderPostFrameCallbacker extends RenderProxyBox {
   _RenderPostFrameCallbacker({
-    FrameCallback callback,
+    FrameCallback? callback,
   }) : _callback = callback;
 
-  FrameCallback get callback => _callback;
-  FrameCallback _callback;
-  set callback(FrameCallback value) {
+  FrameCallback? get callback => _callback;
+  FrameCallback? _callback;
+  set callback(FrameCallback? value) {
     _callback = value;
     if (value != null) {
       markNeedsPaint();
@@ -293,8 +293,8 @@ class _RenderPostFrameCallbacker extends RenderProxyBox {
   @override
   void paint(PaintingContext context, Offset offset) {
     if (callback != null) {
-      SchedulerBinding.instance.addPostFrameCallback(callback == null ? null : (Duration duration) {
-        callback(duration);
+      SchedulerBinding.instance!.addPostFrameCallback((Duration duration) {
+        callback!(duration);
         markNeedsPaint();
       });
     }
@@ -314,9 +314,9 @@ class _RenderPostFrameCallbacker extends RenderProxyBox {
 // positioned from top left to bottom right in a row-major order.
 class _CellSheet extends StatelessWidget {
   _CellSheet({
-    Key key,
-    @required this.cellSize,
-    @required this.children,
+    Key? key,
+    required this.cellSize,
+    required this.children,
   }) : assert(cellSize != null),
        assert(children != null && children.isNotEmpty),
        super(key: key);

packages/flutter_test/lib/src/buffer_matcher.dart

@@ -19,10 +19,10 @@ class _BufferGoldenMatcher extends AsyncMatcher {
   final Uri key;
 
   /// The [version] of the golden image.
-  final int version;
+  final int? version;
 
   @override
-  Future<String> matchAsync(dynamic item) async {
+  Future<String?> matchAsync(dynamic item) async {
     Uint8List buffer;
     if (item is List<int>) {
       buffer = Uint8List.fromList(item);
@@ -69,6 +69,6 @@ class _BufferGoldenMatcher extends AsyncMatcher {
 /// );
 /// ```
 /// {@end-tool}
-AsyncMatcher bufferMatchesGoldenFile(String key, {int version}) {
+AsyncMatcher bufferMatchesGoldenFile(String key, {int? version}) {
    return _BufferGoldenMatcher(Uri.parse(key), version);
 }

packages/flutter_test/lib/src/controller.dart

@@ -96,7 +96,7 @@ abstract class WidgetController {
   /// using [Iterator.moveNext].
   Iterable<Element> get allElements {
     TestAsyncUtils.guardSync();
-    return collectAllElementsFrom(binding.renderViewElement, skipOffstage: false);
+    return collectAllElementsFrom(binding.renderViewElement!, skipOffstage: false);
   }
 
   /// The matching element in the widget tree.
@@ -193,7 +193,7 @@ abstract class WidgetController {
   /// their own render object.
   Iterable<RenderObject> get allRenderObjects {
     TestAsyncUtils.guardSync();
-    return allElements.map<RenderObject>((Element element) => element.renderObject);
+    return allElements.map<RenderObject>((Element element) => element.renderObject!);
   }
 
   /// The render object of the matching widget in the widget tree.
@@ -232,13 +232,13 @@ abstract class WidgetController {
   }
 
   /// Returns a list of all the [Layer] objects in the rendering.
-  List<Layer> get layers => _walkLayers(binding.renderView.debugLayer).toList();
+  List<Layer> get layers => _walkLayers(binding.renderView.debugLayer!).toList();
   Iterable<Layer> _walkLayers(Layer layer) sync* {
     TestAsyncUtils.guardSync();
     yield layer;
     if (layer is ContainerLayer) {
       final ContainerLayer root = layer;
-      Layer child = root.firstChild;
+      Layer? child = root.firstChild;
       while (child != null) {
         yield* _walkLayers(child);
         child = child.nextSibling;
@@ -253,12 +253,12 @@ abstract class WidgetController {
   ///
   /// If the center of the widget is not exposed, this might send events to
   /// another object.
-  Future<void> tap(Finder finder, {int pointer, int buttons = kPrimaryButton}) {
+  Future<void> tap(Finder finder, {int? pointer, int buttons = kPrimaryButton}) {
     return tapAt(getCenter(finder), pointer: pointer, buttons: buttons);
   }
 
   /// Dispatch a pointer down / pointer up sequence at the given location.
-  Future<void> tapAt(Offset location, {int pointer, int buttons = kPrimaryButton}) {
+  Future<void> tapAt(Offset location, {int? pointer, int buttons = kPrimaryButton}) {
     return TestAsyncUtils.guard<void>(() async {
       final TestGesture gesture = await startGesture(location, pointer: pointer, buttons: buttons);
       await gesture.up();
@@ -270,7 +270,7 @@ abstract class WidgetController {
   ///
   /// If the center of the widget is not exposed, this might send events to
   /// another object.
-  Future<TestGesture> press(Finder finder, {int pointer, int buttons = kPrimaryButton}) {
+  Future<TestGesture> press(Finder finder, {int? pointer, int buttons = kPrimaryButton}) {
     return TestAsyncUtils.guard<TestGesture>(() {
       return startGesture(getCenter(finder), pointer: pointer, buttons: buttons);
     });
@@ -282,13 +282,13 @@ abstract class WidgetController {
   ///
   /// If the center of the widget is not exposed, this might send events to
   /// another object.
-  Future<void> longPress(Finder finder, {int pointer, int buttons = kPrimaryButton}) {
+  Future<void> longPress(Finder finder, {int? pointer, int buttons = kPrimaryButton}) {
     return longPressAt(getCenter(finder), pointer: pointer, buttons: buttons);
   }
 
   /// Dispatch a pointer down / pointer up sequence at the given location with
   /// a delay of [kLongPressTimeout] + [kPressTimeout] between the two events.
-  Future<void> longPressAt(Offset location, {int pointer, int buttons = kPrimaryButton}) {
+  Future<void> longPressAt(Offset location, {int? pointer, int buttons = kPrimaryButton}) {
     return TestAsyncUtils.guard<void>(() async {
       final TestGesture gesture = await startGesture(location, pointer: pointer, buttons: buttons);
       await pump(kLongPressTimeout + kPressTimeout);
@@ -337,7 +337,7 @@ abstract class WidgetController {
     Finder finder,
     Offset offset,
     double speed, {
-    int pointer,
+    int? pointer,
     int buttons = kPrimaryButton,
     Duration frameInterval = const Duration(milliseconds: 16),
     Offset initialOffset = Offset.zero,
@@ -366,7 +366,7 @@ abstract class WidgetController {
     Offset startLocation,
     Offset offset,
     double speed, {
-    int pointer,
+    int? pointer,
     int buttons = kPrimaryButton,
     Duration frameInterval = const Duration(milliseconds: 16),
     Offset initialOffset = Offset.zero,
@@ -387,7 +387,7 @@ abstract class WidgetController {
         await pump(initialOffsetDelay);
       }
       for (int i = 0; i <= kMoveCount; i += 1) {
-        final Offset location = startLocation + initialOffset + Offset.lerp(Offset.zero, offset, i / kMoveCount);
+        final Offset location = startLocation + initialOffset + Offset.lerp(Offset.zero, offset, i / kMoveCount)!;
         await sendEventToBinding(testPointer.move(location, timeStamp: Duration(microseconds: timeStamp.round())));
         timeStamp += timeStampDelta;
         if (timeStamp - lastTimeStamp > frameInterval.inMicroseconds) {
@@ -496,7 +496,7 @@ abstract class WidgetController {
   Future<void> drag(
     Finder finder,
     Offset offset, {
-    int pointer,
+    int? pointer,
     int buttons = kPrimaryButton,
     double touchSlopX = kDragSlopDefault,
     double touchSlopY = kDragSlopDefault,
@@ -525,7 +525,7 @@ abstract class WidgetController {
   Future<void> dragFrom(
     Offset startLocation,
     Offset offset, {
-    int pointer,
+    int? pointer,
     int buttons = kPrimaryButton,
     double touchSlopX = kDragSlopDefault,
     double touchSlopY = kDragSlopDefault,
@@ -626,7 +626,7 @@ abstract class WidgetController {
     Finder finder,
     Offset offset,
     Duration duration, {
-    int pointer,
+    int? pointer,
     int buttons = kPrimaryButton,
     double frequency = 60.0,
   }) {
@@ -652,7 +652,7 @@ abstract class WidgetController {
     Offset startLocation,
     Offset offset,
     Duration duration, {
-    int pointer,
+    int? pointer,
     int buttons = kPrimaryButton,
     double frequency = 60.0,
   }) {
@@ -707,7 +707,7 @@ abstract class WidgetController {
       ]),
     ];
     return TestAsyncUtils.guard<void>(() async {
-      return handlePointerEventRecord(records);
+      await handlePointerEventRecord(records);
     });
   }
 
@@ -731,7 +731,7 @@ abstract class WidgetController {
   /// You can use [startGesture] instead if your gesture begins with a down
   /// event.
   Future<TestGesture> createGesture({
-    int pointer,
+    int? pointer,
     PointerDeviceKind kind = PointerDeviceKind.touch,
     int buttons = kPrimaryButton,
   }) async {
@@ -751,7 +751,7 @@ abstract class WidgetController {
   /// down gesture.
   Future<TestGesture> startGesture(
     Offset downLocation, {
-    int pointer,
+    int? pointer,
     PointerDeviceKind kind = PointerDeviceKind.touch,
     int buttons = kPrimaryButton,
   }) async {
@@ -924,10 +924,10 @@ abstract class WidgetController {
       throw StateError('Finder returned more than one element.');
     }
     final Element element = candidates.single;
-    RenderObject renderObject = element.findRenderObject();
-    SemanticsNode result = renderObject.debugSemantics;
+    RenderObject? renderObject = element.findRenderObject();
+    SemanticsNode? result = renderObject?.debugSemantics;
     while (renderObject != null && (result == null || result.isMergedIntoParent)) {
-      renderObject = renderObject?.parent as RenderObject;
+      renderObject = renderObject.parent as RenderObject?;
       result = renderObject?.debugSemantics;
     }
     if (result == null)
@@ -978,7 +978,7 @@ abstract class WidgetController {
   Future<void> scrollUntilVisible(
     Finder finder,
     double delta, {
-      Finder scrollable,
+      Finder? scrollable,
       int maxScrolls = 50,
       Duration duration = const Duration(milliseconds: 50),
     }
@@ -987,7 +987,7 @@ abstract class WidgetController {
     scrollable ??= find.byType(Scrollable);
     return TestAsyncUtils.guard<void>(() async {
       Offset moveStep;
-      switch(widget<Scrollable>(scrollable).axisDirection) {
+      switch (widget<Scrollable>(scrollable!).axisDirection) {
         case AxisDirection.up:
           moveStep = Offset(0, delta);
           break;
@@ -1043,7 +1043,7 @@ class LiveWidgetController extends WidgetController {
   LiveWidgetController(WidgetsBinding binding) : super(binding);
 
   @override
-  Future<void> pump([Duration duration]) async {
+  Future<void> pump([Duration? duration]) async {
     if (duration != null)
       await Future<void>.delayed(duration);
     binding.scheduleFrame();
@@ -1075,7 +1075,7 @@ class LiveWidgetController extends WidgetController {
       // used as state for all pointers which are currently down.
       final Map<int, HitTestResult> hitTestHistory = <int, HitTestResult>{};
       final List<Duration> handleTimeStampDiff = <Duration>[];
-      DateTime startTime;
+      DateTime? startTime;
       for (final PointerEventRecord record in records) {
         final DateTime now = clock.now();
         startTime ??= now;

packages/flutter_test/lib/src/event_simulation.dart

@@ -47,8 +47,7 @@ class KeyEventSimulator {
 
   static int _getScanCode(PhysicalKeyboardKey key, String platform) {
     assert(_osIsSupported(platform), 'Platform $platform not supported for key simulation');
-    int scanCode;
-    Map<int, PhysicalKeyboardKey> map;
+    late Map<int, PhysicalKeyboardKey> map;
     switch (platform) {
       case 'android':
         map = kAndroidToPhysicalKey;
@@ -66,22 +65,23 @@ class KeyEventSimulator {
         map = kWindowsToPhysicalKey;
         break;
       case 'web':
-      // web doesn't have int type code
-        return null;
+        // web doesn't have int type code
+        return -1;
     }
+    int? scanCode;
     for (final int code in map.keys) {
-      if (key.usbHidUsage == map[code].usbHidUsage) {
+      if (key.usbHidUsage == map[code]!.usbHidUsage) {
         scanCode = code;
         break;
       }
     }
-    return scanCode;
+    assert(scanCode != null, 'Physical key for $key not found in $platform scanCode map');
+    return scanCode!;
   }
 
   static int _getKeyCode(LogicalKeyboardKey key, String platform) {
     assert(_osIsSupported(platform), 'Platform $platform not supported for key simulation');
-    int keyCode;
-    Map<int, LogicalKeyboardKey> map;
+    late Map<int, LogicalKeyboardKey> map;
     switch (platform) {
       case 'android':
         map = kAndroidToLogicalKey;
@@ -90,11 +90,11 @@ class KeyEventSimulator {
         map = kFuchsiaToLogicalKey;
         break;
       case 'macos':
-      // macOS doesn't do key codes, just scan codes.
-        return null;
+        // macOS doesn't do key codes, just scan codes.
+        return -1;
       case 'web':
-      // web doesn't have int type code
-        return null;
+        // web doesn't have int type code
+        return -1;
       case 'linux':
         map = kGlfwToLogicalKey;
         break;
@@ -102,26 +102,31 @@ class KeyEventSimulator {
         map = kWindowsToLogicalKey;
         break;
     }
+    int? keyCode;
     for (final int code in map.keys) {
-      if (key.keyId == map[code].keyId) {
+      if (key.keyId == map[code]!.keyId) {
         keyCode = code;
         break;
       }
     }
-    return keyCode;
+    assert(keyCode != null, 'Key $key not found in $platform keyCode map');
+    return keyCode!;
   }
   static String _getWebKeyCode(LogicalKeyboardKey key) {
+    String? result;
     for (final String code in kWebToLogicalKey.keys) {
-      if (key.keyId == kWebToLogicalKey[code].keyId) {
-        return code;
+      if (key.keyId == kWebToLogicalKey[code]!.keyId) {
+        result = code;
+        break;
       }
     }
-    return null;
+    assert(result != null, 'Key $key not found in web keyCode map');
+    return result!;
   }
 
   static PhysicalKeyboardKey _findPhysicalKey(LogicalKeyboardKey key, String platform) {
     assert(_osIsSupported(platform), 'Platform $platform not supported for key simulation');
-    Map<dynamic, PhysicalKeyboardKey> map;
+    late Map<dynamic, PhysicalKeyboardKey> map;
     switch (platform) {
       case 'android':
         map = kAndroidToPhysicalKey;
@@ -142,20 +147,23 @@ class KeyEventSimulator {
         map = kWindowsToPhysicalKey;
         break;
     }
+    PhysicalKeyboardKey? result;
     for (final PhysicalKeyboardKey physicalKey in map.values) {
       if (key.debugName == physicalKey.debugName) {
-        return physicalKey;
+        result = physicalKey;
+        break;
       }
     }
-    return null;
+    assert(result != null, 'Physical key for $key not found in $platform physical key map');
+    return result!;
   }
 
   /// Get a raw key data map given a [LogicalKeyboardKey] and a platform.
   static Map<String, dynamic> getKeyData(
     LogicalKeyboardKey key, {
-    String platform,
+    required String platform,
     bool isDown = true,
-    PhysicalKeyboardKey physicalKey,
+    PhysicalKeyboardKey? physicalKey,
   }) {
     assert(_osIsSupported(platform), 'Platform $platform not supported for key simulation');
 
@@ -165,10 +173,8 @@ class KeyEventSimulator {
     physicalKey ??= _findPhysicalKey(key, platform);
 
     assert(key.debugName != null);
-    final int keyCode = platform == 'macos' || platform == 'web' ? -1 : _getKeyCode(key, platform);
-    assert(platform == 'macos' || platform == 'web' || keyCode != null, 'Key $key not found in $platform keyCode map');
-    final int scanCode = platform == 'web' ? -1 : _getScanCode(physicalKey, platform);
-    assert(platform == 'web' || scanCode != null, 'Physical key for $key not found in $platform scanCode map');
+    final int keyCode = _getKeyCode(key, platform);
+    final int scanCode = _getScanCode(physicalKey, platform);
 
     final Map<String, dynamic> result = <String, dynamic>{
       'type': isDown ? 'keydown' : 'keyup',
@@ -186,7 +192,7 @@ class KeyEventSimulator {
         result['metaState'] = _getAndroidModifierFlags(key, isDown);
         break;
       case 'fuchsia':
-        result['hidUsage'] = physicalKey?.usbHidUsage ?? (key.keyId & LogicalKeyboardKey.hidPlane != 0 ? key.keyId & LogicalKeyboardKey.valueMask : null);
+        result['hidUsage'] = physicalKey.usbHidUsage;
         if (key.keyLabel.isNotEmpty) {
           result['codePoint'] = key.keyLabel.codeUnitAt(0);
         }
@@ -513,16 +519,16 @@ class KeyEventSimulator {
   /// See also:
   ///
   ///  - [simulateKeyUpEvent] to simulate the corresponding key up event.
-  static Future<void> simulateKeyDownEvent(LogicalKeyboardKey key, {String platform, PhysicalKeyboardKey physicalKey}) async {
+  static Future<void> simulateKeyDownEvent(LogicalKeyboardKey key, {String? platform, PhysicalKeyboardKey? physicalKey}) async {
     return TestAsyncUtils.guard<void>(() async {
       platform ??= Platform.operatingSystem;
-      assert(_osIsSupported(platform), 'Platform $platform not supported for key simulation');
+      assert(_osIsSupported(platform!), 'Platform $platform not supported for key simulation');
 
-      final Map<String, dynamic> data = getKeyData(key, platform: platform, isDown: true, physicalKey: physicalKey);
-      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+      final Map<String, dynamic> data = getKeyData(key, platform: platform!, isDown: true, physicalKey: physicalKey);
+      await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
         SystemChannels.keyEvent.name,
         SystemChannels.keyEvent.codec.encodeMessage(data),
-            (ByteData data) {},
+            (ByteData? data) { },
       );
     });
   }
@@ -540,16 +546,16 @@ class KeyEventSimulator {
   /// See also:
   ///
   ///  - [simulateKeyDownEvent] to simulate the corresponding key down event.
-  static Future<void> simulateKeyUpEvent(LogicalKeyboardKey key, {String platform, PhysicalKeyboardKey physicalKey}) async {
+  static Future<void> simulateKeyUpEvent(LogicalKeyboardKey key, {String? platform, PhysicalKeyboardKey? physicalKey}) async {
     return TestAsyncUtils.guard<void>(() async {
       platform ??= Platform.operatingSystem;
-      assert(_osIsSupported(platform), 'Platform $platform not supported for key simulation');
+      assert(_osIsSupported(platform!), 'Platform $platform not supported for key simulation');
 
-      final Map<String, dynamic> data = getKeyData(key, platform: platform, isDown: false, physicalKey: physicalKey);
-      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+      final Map<String, dynamic> data = getKeyData(key, platform: platform!, isDown: false, physicalKey: physicalKey);
+      await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
         SystemChannels.keyEvent.name,
         SystemChannels.keyEvent.codec.encodeMessage(data),
-            (ByteData data) {},
+            (ByteData? data) { },
       );
     });
   }
@@ -573,7 +579,7 @@ class KeyEventSimulator {
 /// See also:
 ///
 ///  - [simulateKeyUpEvent] to simulate the corresponding key up event.
-Future<void> simulateKeyDownEvent(LogicalKeyboardKey key, {String platform, PhysicalKeyboardKey physicalKey}) {
+Future<void> simulateKeyDownEvent(LogicalKeyboardKey key, {String? platform, PhysicalKeyboardKey? physicalKey}) {
   return KeyEventSimulator.simulateKeyDownEvent(key, platform: platform, physicalKey: physicalKey);
 }
 
@@ -593,6 +599,6 @@ Future<void> simulateKeyDownEvent(LogicalKeyboardKey key, {String platform, Phys
 /// See also:
 ///
 ///  - [simulateKeyDownEvent] to simulate the corresponding key down event.
-Future<void> simulateKeyUpEvent(LogicalKeyboardKey key, {String platform, PhysicalKeyboardKey physicalKey}) {
+Future<void> simulateKeyUpEvent(LogicalKeyboardKey key, {String? platform, PhysicalKeyboardKey? physicalKey}) {
   return KeyEventSimulator.simulateKeyUpEvent(key, platform: platform, physicalKey: physicalKey);
 }

packages/flutter_test/lib/src/finders.dart

@@ -3,7 +3,8 @@
 // found in the LICENSE file.
 
 import 'package:flutter/gestures.dart';
-import 'package:flutter/material.dart';
+import 'package:flutter/material.dart' show Tooltip;
+import 'package:flutter/widgets.dart';
 import 'package:meta/meta.dart';
 
 import 'all_elements.dart';
@@ -196,7 +197,7 @@ class CommonFinders {
   ///
   /// If the `skipOffstage` argument is true (the default), then this skips
   /// nodes that are [Offstage] or that are from inactive [Route]s.
-  Finder byWidgetPredicate(WidgetPredicate predicate, { String description, bool skipOffstage = true }) {
+  Finder byWidgetPredicate(WidgetPredicate predicate, { String? description, bool skipOffstage = true }) {
     return _WidgetPredicateFinder(predicate, description: description, skipOffstage: skipOffstage);
   }
 
@@ -238,7 +239,7 @@ class CommonFinders {
   ///
   /// If the `skipOffstage` argument is true (the default), then this skips
   /// nodes that are [Offstage] or that are from inactive [Route]s.
-  Finder byElementPredicate(ElementPredicate predicate, { String description, bool skipOffstage = true }) {
+  Finder byElementPredicate(ElementPredicate predicate, { String? description, bool skipOffstage = true }) {
     return _ElementPredicateFinder(predicate, description: description, skipOffstage: skipOffstage);
   }
 
@@ -259,8 +260,8 @@ class CommonFinders {
   /// If the [skipOffstage] argument is true (the default), then nodes that are
   /// [Offstage] or that are from inactive [Route]s are skipped.
   Finder descendant({
-    @required Finder of,
-    @required Finder matching,
+    required Finder of,
+    required Finder matching,
     bool matchRoot = false,
     bool skipOffstage = true,
   }) {
@@ -289,8 +290,8 @@ class CommonFinders {
   /// If the [matchRoot] argument is true then the widget(s) specified by [of]
   /// will be matched along with the ancestors.
   Finder ancestor({
-    @required Finder of,
-    @required Finder matching,
+    required Finder of,
+    required Finder matching,
     bool matchRoot = false,
   }) {
     return _AncestorFinder(of, matching, matchRoot: matchRoot);
@@ -318,7 +319,7 @@ class CommonFinders {
   /// If the `skipOffstage` argument is true (the default), then this skips
   /// nodes that are [Offstage] or that are from inactive [Route]s.
   Finder bySemanticsLabel(Pattern label, { bool skipOffstage = true }) {
-    if (WidgetsBinding.instance.pipelineOwner.semanticsOwner == null)
+    if (WidgetsBinding.instance!.pipelineOwner.semanticsOwner == null)
       throw StateError('Semantics are not enabled. '
                        'Make sure to call tester.ensureSemantics() before using '
                        'this finder, and call dispose on its return value after.');
@@ -329,7 +330,7 @@ class CommonFinders {
         if (element is! RenderObjectElement) {
           return false;
         }
-        final String semanticsLabel = element.renderObject?.debugSemantics?.label;
+        final String? semanticsLabel = element.renderObject.debugSemantics?.label;
         if (semanticsLabel == null) {
           return false;
         }
@@ -375,12 +376,12 @@ abstract class Finder {
   @protected
   Iterable<Element> get allCandidates {
     return collectAllElementsFrom(
-      WidgetsBinding.instance.renderViewElement,
+      WidgetsBinding.instance!.renderViewElement!,
       skipOffstage: skipOffstage,
     );
   }
 
-  Iterable<Element> _cachedResult;
+  Iterable<Element>? _cachedResult;
 
   /// Returns the current result. If [precache] was called and returned true, this will
   /// cheaply return the result that was computed then. Otherwise, it creates a new
@@ -519,7 +520,7 @@ class _HitTestableFinder extends ChainedFinder {
       assert(box != null);
       final Offset absoluteOffset = box.localToGlobal(alignment.alongSize(box.size));
       final HitTestResult hitResult = HitTestResult();
-      WidgetsBinding.instance.hitTest(hitResult, absoluteOffset);
+      WidgetsBinding.instance!.hitTest(hitResult, absoluteOffset);
       for (final HitTestEntry entry in hitResult.path) {
         if (entry.target == candidate.renderObject) {
           yield candidate;
@@ -562,7 +563,8 @@ class _TextFinder extends MatchFinder {
     if (widget is Text) {
       if (widget.data != null)
         return widget.data == text;
-      return widget.textSpan.toPlainText() == text;
+      assert(widget.textSpan != null);
+      return widget.textSpan!.toPlainText() == text;
     } else if (widget is EditableText) {
       return widget.controller.text == text;
     }
@@ -584,8 +586,9 @@ class _TextContainingFinder extends MatchFinder {
     final Widget widget = candidate.widget;
     if (widget is Text) {
       if (widget.data != null)
-        return widget.data.contains(pattern);
-      return widget.textSpan.toPlainText().contains(pattern);
+        return widget.data!.contains(pattern);
+      assert(widget.textSpan != null);
+      return widget.textSpan!.toPlainText().contains(pattern);
     } else if (widget is EditableText) {
       return widget.controller.text.contains(pattern);
     }
@@ -665,12 +668,12 @@ class _WidgetFinder extends MatchFinder {
 }
 
 class _WidgetPredicateFinder extends MatchFinder {
-  _WidgetPredicateFinder(this.predicate, { String description, bool skipOffstage = true })
+  _WidgetPredicateFinder(this.predicate, { String? description, bool skipOffstage = true })
     : _description = description,
       super(skipOffstage: skipOffstage);
 
   final WidgetPredicate predicate;
-  final String _description;
+  final String? _description;
 
   @override
   String get description => _description ?? 'widget matching predicate ($predicate)';
@@ -682,12 +685,12 @@ class _WidgetPredicateFinder extends MatchFinder {
 }
 
 class _ElementPredicateFinder extends MatchFinder {
-  _ElementPredicateFinder(this.predicate, { String description, bool skipOffstage = true })
+  _ElementPredicateFinder(this.predicate, { String? description, bool skipOffstage = true })
     : _description = description,
       super(skipOffstage: skipOffstage);
 
   final ElementPredicate predicate;
-  final String _description;
+  final String? _description;
 
   @override
   String get description => _description ?? 'element matching predicate ($predicate)';

packages/flutter_test/lib/src/frame_timing_summarizer.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'dart:ui';
-import 'package:meta/meta.dart';
 
 /// The maximum amount of time considered safe to spend for a frame's build
 /// phase. Anything past that is in the danger of missing the frame as 60FPS.
@@ -64,23 +63,23 @@ class FrameTimingSummarizer {
   }
 
   const FrameTimingSummarizer._({
-    @required this.frameBuildTime,
-    @required this.frameRasterizerTime,
-    @required this.averageFrameBuildTime,
-    @required this.p90FrameBuildTime,
-    @required this.p99FrameBuildTime,
-    @required this.worstFrameBuildTime,
-    @required this.missedFrameBuildBudget,
-    @required this.averageFrameRasterizerTime,
-    @required this.p90FrameRasterizerTime,
-    @required this.p99FrameRasterizerTime,
-    @required this.worstFrameRasterizerTime,
-    @required this.missedFrameRasterizerBudget,
-    @required this.vsyncOverhead,
-    @required this.averageVsyncOverhead,
-    @required this.p90VsyncOverhead,
-    @required this.p99VsyncOverhead,
-    @required this.worstVsyncOverhead,
+    required this.frameBuildTime,
+    required this.frameRasterizerTime,
+    required this.averageFrameBuildTime,
+    required this.p90FrameBuildTime,
+    required this.p99FrameBuildTime,
+    required this.worstFrameBuildTime,
+    required this.missedFrameBuildBudget,
+    required this.averageFrameRasterizerTime,
+    required this.p90FrameRasterizerTime,
+    required this.p99FrameRasterizerTime,
+    required this.worstFrameRasterizerTime,
+    required this.missedFrameRasterizerBudget,
+    required this.vsyncOverhead,
+    required this.averageVsyncOverhead,
+    required this.p90VsyncOverhead,
+    required this.p99VsyncOverhead,
+    required this.worstVsyncOverhead,
   });
 
   /// List of frame build time in microseconds

packages/flutter_test/lib/src/goldens.dart

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.10
 import 'dart:typed_data';
 
 import 'package:path/path.dart' as path;

packages/flutter_test/lib/src/image.dart

@@ -38,7 +38,7 @@ Future<ui.Image> createTestImage({
 
   final int cacheKey = hashValues(width, height);
   if (cache && _cache.containsKey(cacheKey)) {
-    return _cache[cacheKey];
+    return _cache[cacheKey]!;
   }
 
   final ui.Image image = await _createImage(width, height);
@@ -74,8 +74,8 @@ Future<ui.Image> _createImage(int width, int height) async {
 // TODO(dnfield): Remove this when https://github.com/flutter/flutter/issues/49244
 // is resolved.
 Future<ui.Image> _webCreateTestImage({
-  int width,
-  int height,
+  required int width,
+  required int height,
 }) async {
   // See https://en.wikipedia.org/wiki/BMP_file_format for format examples.
   final int bufferSize = 0x36 + (width * height);

packages/flutter_test/lib/src/restoration.dart

@@ -20,7 +20,7 @@ class TestRestorationManager extends RestorationManager {
   }
 
   @override
-  Future<RestorationBucket> get rootBucket {
+  Future<RestorationBucket?> get rootBucket {
     _debugRootBucketAccessed = true;
     return super.rootBucket;
   }
@@ -35,7 +35,7 @@ class TestRestorationManager extends RestorationManager {
   ///  * [WidgetTester.getRestorationData], which makes this data available
   ///    in a widget test.
   TestRestorationData get restorationData => _restorationData;
-  TestRestorationData _restorationData;
+  late TestRestorationData _restorationData;
 
   /// Whether the [rootBucket] has been obtained.
   bool get debugRootBucketAccessed => _debugRootBucketAccessed;
@@ -59,7 +59,7 @@ class TestRestorationManager extends RestorationManager {
   ///
   /// To turn restoration back on call [restoreFrom].
   void disableRestoration() {
-    _restorationData = null;
+    _restorationData = TestRestorationData.empty;
     handleRestorationUpdateFromEngine(enabled: false, data: null);
   }
 
@@ -89,5 +89,5 @@ class TestRestorationData {
   ///
   /// Should only be accessed by the test framework.
   @protected
-  final Uint8List binary;
+  final Uint8List? binary;
 }

packages/flutter_test/lib/src/stack_manipulation.dart

@@ -25,7 +25,7 @@ int reportExpectCall(StackTrace stack, List<DiagnosticsNode> information) {
       line1.firstMatch(stackLines[1]) != null &&
       line2.firstMatch(stackLines[2]) != null &&
       line3.firstMatch(stackLines[3]) != null) {
-    final Match expectMatch = line4.firstMatch(stackLines[4]);
+    final Match expectMatch = line4.firstMatch(stackLines[4])!;
     assert(expectMatch != null);
     assert(expectMatch.groupCount == 2);
     information.add(DiagnosticsStackTrace.singleFrame(

packages/flutter_test/lib/src/test_async_utils.dart

@@ -70,8 +70,8 @@ class TestAsyncUtils {
     final _AsyncScope scope = _AsyncScope(StackTrace.current, zone);
     _scopeStack.add(scope);
     final Future<T> result = scope.zone.run<Future<T>>(body);
-    T resultValue; // This is set when the body of work completes with a result value.
-    Future<T> completionHandler(dynamic error, StackTrace stack) {
+    late T resultValue; // This is set when the body of work completes with a result value.
+    Future<T> completionHandler(dynamic error, StackTrace? stack) {
       assert(_scopeStack.isNotEmpty);
       assert(_scopeStack.contains(scope));
       bool leaked = false;
@@ -86,7 +86,7 @@ class TestAsyncUtils {
           information.add(ErrorHint('You must use "await" with all Future-returning test APIs.'));
           leaked = true;
         }
-        final _StackEntry originalGuarder = _findResponsibleMethod(closedScope.creationStack, 'guard', information);
+        final _StackEntry? originalGuarder = _findResponsibleMethod(closedScope.creationStack, 'guard', information);
         if (originalGuarder != null) {
           information.add(ErrorDescription(
             'The test API method "${originalGuarder.methodName}" '
@@ -109,7 +109,7 @@ class TestAsyncUtils {
         throw FlutterError.fromParts(information);
       }
       if (error != null)
-        return Future<T>.error(error, stack);
+        return Future<T>.error(error! as Object, stack);
       return Future<T>.value(resultValue);
     }
     return result.then<T>(
@@ -121,8 +121,8 @@ class TestAsyncUtils {
     );
   }
 
-  static Zone get _currentScopeZone {
-    Zone zone = Zone.current;
+  static Zone? get _currentScopeZone {
+    Zone? zone = Zone.current;
     while (zone != null) {
       if (zone[_scopeStack] == true)
         return zone;
@@ -142,7 +142,7 @@ class TestAsyncUtils {
       return;
     }
     // Find the current TestAsyncUtils scope zone so we can see if it's the one we expect.
-    final Zone zone = _currentScopeZone;
+    final Zone? zone = _currentScopeZone;
     if (zone == _scopeStack.last.zone) {
       // We're still in the current scope zone. All good.
       return;
@@ -192,8 +192,8 @@ class TestAsyncUtils {
       ErrorSummary('Guarded function conflict.'),
       ErrorHint('You must use "await" with all Future-returning test APIs.'),
     ];
-    final _StackEntry originalGuarder = _findResponsibleMethod(scope.creationStack, 'guard', information);
-    final _StackEntry collidingGuarder = _findResponsibleMethod(StackTrace.current, 'guardSync', information);
+    final _StackEntry? originalGuarder = _findResponsibleMethod(scope.creationStack, 'guard', information);
+    final _StackEntry? collidingGuarder = _findResponsibleMethod(StackTrace.current, 'guardSync', information);
     if (originalGuarder != null && collidingGuarder != null) {
       final String originalKind = originalGuarder.className == null ? 'function' : 'method';
       String originalName;
@@ -278,7 +278,7 @@ class TestAsyncUtils {
         ErrorHint('You must use "await" with all Future-returning test APIs.')
       ];
       for (final _AsyncScope scope in _scopeStack) {
-        final _StackEntry guarder = _findResponsibleMethod(scope.creationStack, 'guard', information);
+        final _StackEntry? guarder = _findResponsibleMethod(scope.creationStack, 'guard', information);
         if (guarder != null) {
           information.add(ErrorDescription(
             'The guarded method "${guarder.methodName}" '
@@ -297,29 +297,29 @@ class TestAsyncUtils {
     return line != '<asynchronous suspension>';
   }
 
-  static _StackEntry _findResponsibleMethod(StackTrace rawStack, String method, List<DiagnosticsNode> information) {
+  static _StackEntry? _findResponsibleMethod(StackTrace rawStack, String method, List<DiagnosticsNode> information) {
     assert(method == 'guard' || method == 'guardSync');
     final List<String> stack = rawStack.toString().split('\n').where(_stripAsynchronousSuspensions).toList();
     assert(stack.last == '');
     stack.removeLast();
     final RegExp getClassPattern = RegExp(r'^#[0-9]+ +([^. ]+)');
-    Match lineMatch;
+    Match? lineMatch;
     int index = -1;
     do { // skip past frames that are from this class
       index += 1;
       assert(index < stack.length);
-      lineMatch = getClassPattern.matchAsPrefix(stack[index]);
+      lineMatch = getClassPattern.matchAsPrefix(stack[index])!;
       assert(lineMatch != null);
       assert(lineMatch.groupCount == 1);
     } while (lineMatch.group(1) == _className);
     // try to parse the stack to find the interesting frame
     if (index < stack.length) {
       final RegExp guardPattern = RegExp(r'^#[0-9]+ +(?:([^. ]+)\.)?([^. ]+)');
-      final Match guardMatch = guardPattern.matchAsPrefix(stack[index]); // find the class that called us
+      final Match? guardMatch = guardPattern.matchAsPrefix(stack[index]); // find the class that called us
       if (guardMatch != null) {
         assert(guardMatch.groupCount == 2);
-        final String guardClass = guardMatch.group(1); // might be null
-        final String guardMethod = guardMatch.group(2);
+        final String? guardClass = guardMatch.group(1); // might be null
+        final String? guardMethod = guardMatch.group(2);
         while (index < stack.length) { // find the last stack frame that called the class that called us
           lineMatch = getClassPattern.matchAsPrefix(stack[index]);
           if (lineMatch != null) {
@@ -333,11 +333,11 @@ class TestAsyncUtils {
         }
         if (index < stack.length) {
           final RegExp callerPattern = RegExp(r'^#[0-9]+ .* \((.+?):([0-9]+)(?::[0-9]+)?\)$');
-          final Match callerMatch = callerPattern.matchAsPrefix(stack[index]); // extract the caller's info
+          final Match? callerMatch = callerPattern.matchAsPrefix(stack[index]); // extract the caller's info
           if (callerMatch != null) {
             assert(callerMatch.groupCount == 2);
-            final String callerFile = callerMatch.group(1);
-            final String callerLine = callerMatch.group(2);
+            final String? callerFile = callerMatch.group(1);
+            final String? callerLine = callerMatch.group(2);
             return _StackEntry(guardClass, guardMethod, callerFile, callerLine);
           } else {
             // One reason you might get here is if the guarding method was called directly from
@@ -362,8 +362,8 @@ class TestAsyncUtils {
 
 class _StackEntry {
   const _StackEntry(this.className, this.methodName, this.callerFile, this.callerLine);
-  final String className;
-  final String methodName;
-  final String callerFile;
-  final String callerLine;
+  final String? className;
+  final String? methodName;
+  final String? callerFile;
+  final String? callerLine;
 }

packages/flutter_test/lib/src/test_compat.dart

@@ -21,9 +21,9 @@ import 'package:test_api/src/backend/state.dart'; // ignore: implementation_impo
 // ignore: deprecated_member_use
 import 'package:test_api/test_api.dart';
 
-Declarer _localDeclarer;
+Declarer? _localDeclarer;
 Declarer get _declarer {
-  final Declarer declarer = Zone.current[#test.declarer] as Declarer;
+  final Declarer? declarer = Zone.current[#test.declarer] as Declarer?;
   if (declarer != null) {
     return declarer;
   }
@@ -40,7 +40,7 @@ Declarer get _declarer {
       });
     });
   }
-  return _localDeclarer;
+  return _localDeclarer!;
 }
 
 Future<void> _runGroup(Suite suiteConfig, Group group, List<Group> parents, _Reporter reporter) async {
@@ -49,7 +49,7 @@ Future<void> _runGroup(Suite suiteConfig, Group group, List<Group> parents, _Rep
     final bool skipGroup = group.metadata.skip;
     bool setUpAllSucceeded = true;
     if (!skipGroup && group.setUpAll != null) {
-      final LiveTest liveTest = group.setUpAll.load(suiteConfig, groups: parents);
+      final LiveTest liveTest = group.setUpAll!.load(suiteConfig, groups: parents);
       await _runLiveTest(suiteConfig, liveTest, reporter, countSuccess: false);
       setUpAllSucceeded = liveTest.state.result.isPassing;
     }
@@ -68,7 +68,7 @@ Future<void> _runGroup(Suite suiteConfig, Group group, List<Group> parents, _Rep
     // Even if we're closed or setUpAll failed, we want to run all the
     // teardowns to ensure that any state is properly cleaned up.
     if (!skipGroup && group.tearDownAll != null) {
-      final LiveTest liveTest = group.tearDownAll.load(suiteConfig, groups: parents);
+      final LiveTest liveTest = group.tearDownAll!.load(suiteConfig, groups: parents);
       await _runLiveTest(suiteConfig, liveTest, reporter, countSuccess: false);
     }
   } finally {
@@ -155,12 +155,12 @@ Future<void> _runSkippedTest(Suite suiteConfig, Test test, List<Group> parents,
 void test(
   Object description,
   dynamic Function() body, {
-  String testOn,
-  Timeout timeout,
+  String? testOn,
+  Timeout? timeout,
   dynamic skip,
   dynamic tags,
-  Map<String, dynamic> onPlatform,
-  int retry,
+  Map<String, dynamic>? onPlatform,
+  int? retry,
 }) {
   _declarer.test(
     description.toString(),
@@ -300,21 +300,21 @@ class _Reporter {
 
   /// The size of `_engine.passed` last time a progress notification was
   /// printed.
-  int _lastProgressPassed;
+  int? _lastProgressPassed;
 
   /// The size of `_engine.skipped` last time a progress notification was
   /// printed.
-  int _lastProgressSkipped;
+  int? _lastProgressSkipped;
 
   /// The size of `_engine.failed` last time a progress notification was
   /// printed.
-  int _lastProgressFailed;
+  int? _lastProgressFailed;
 
   /// The message printed for the last progress notification.
-  String _lastProgressMessage;
+  String? _lastProgressMessage;
 
   /// The suffix added to the last progress notification.
-  String _lastProgressSuffix;
+  String? _lastProgressSuffix;
 
   /// The set of all subscriptions to various streams.
   final Set<StreamSubscription<void>> _subscriptions = <StreamSubscription<void>>{};
@@ -355,14 +355,8 @@ class _Reporter {
   }
 
   /// A callback called when the engine is finished running tests.
-  ///
-  /// [success] will be `true` if all tests passed, `false` if some tests
-  /// failed, and `null` if the engine was closed prematurely.
   void _onDone() {
     final bool success = failed.isEmpty;
-    if (success == null) {
-      return;
-    }
     if (!success) {
       _progressLine('Some tests failed.', color: _red);
     } else if (passed.isEmpty) {
@@ -377,7 +371,7 @@ class _Reporter {
   /// [message] goes after the progress report. If [color] is passed, it's used
   /// as the color for [message]. If [suffix] is passed, it's added to the end
   /// of [message].
-  void _progressLine(String message, { String color, String suffix }) {
+  void _progressLine(String message, { String? color, String? suffix }) {
     // Print nothing if nothing has changed since the last progress line.
     if (passed.length == _lastProgressPassed &&
         skipped.length == _lastProgressSkipped &&
@@ -449,15 +443,15 @@ class _Reporter {
   }
 }
 
-String _indent(String string, { int size, String first }) {
+String _indent(String string, { int? size, String? first }) {
   size ??= first == null ? 2 : first.length;
   return _prefixLines(string, ' ' * size, first: first);
 }
 
-String _prefixLines(String text, String prefix, { String first, String last, String single }) {
+String _prefixLines(String text, String prefix, { String? first, String? last, String? single }) {
   first ??= prefix;
   last ??= prefix;
-  single ??= first ?? last ?? prefix;
+  single ??= first;
   final List<String> lines = text.split('\n');
   if (lines.length == 1) {
     return '$single$text';

packages/flutter_test/lib/src/test_pointer.dart

@@ -23,7 +23,7 @@ class TestPointer {
   TestPointer([
     this.pointer = 1,
     this.kind = PointerDeviceKind.touch,
-    this._device,
+    int? device,
     int buttons = kPrimaryButton,
   ])
       : assert(kind != null),
@@ -32,13 +32,13 @@ class TestPointer {
         _buttons = buttons {
     switch (kind) {
       case PointerDeviceKind.mouse:
-        _device ??= 1;
+        _device = device ?? 1;
         break;
       case PointerDeviceKind.stylus:
       case PointerDeviceKind.invertedStylus:
       case PointerDeviceKind.touch:
       case PointerDeviceKind.unknown:
-        _device ??= 0;
+        _device = device ?? 0;
         break;
     }
   }
@@ -48,7 +48,7 @@ class TestPointer {
   /// Set when the object is constructed. Defaults to 1 if the [kind] is
   /// [PointerDeviceKind.mouse], and 0 otherwise.
   int get device => _device;
-  int _device;
+  late int _device;
 
   /// The pointer identifier used for events generated by this object.
   ///
@@ -75,15 +75,15 @@ class TestPointer {
   /// The position of the last event sent by this object.
   ///
   /// If no event has ever been sent by this object, returns null.
-  Offset get location => _location;
-  Offset _location;
+  Offset? get location => _location;
+  Offset? _location;
 
   /// If a custom event is created outside of this class, this function is used
   /// to set the [isDown].
   bool setDownInfo(
     PointerEvent event,
     Offset newLocation, {
-    int buttons,
+    int? buttons,
   }) {
     _location = newLocation;
     if (buttons != null)
@@ -114,7 +114,7 @@ class TestPointer {
   PointerDownEvent down(
     Offset newLocation, {
     Duration timeStamp = Duration.zero,
-    int buttons,
+    int? buttons,
   }) {
     assert(!isDown);
     _isDown = true;
@@ -126,7 +126,7 @@ class TestPointer {
       kind: kind,
       device: _device,
       pointer: pointer,
-      position: location,
+      position: location!,
       buttons: _buttons,
     );
   }
@@ -144,14 +144,14 @@ class TestPointer {
   PointerMoveEvent move(
     Offset newLocation, {
     Duration timeStamp = Duration.zero,
-    int buttons,
+    int? buttons,
   }) {
     assert(
         isDown,
         'Move events can only be generated when the pointer is down. To '
         'create a movement event simulating a pointer move when the pointer is '
         'up, use hover() instead.');
-    final Offset delta = newLocation - location;
+    final Offset delta = newLocation - location!;
     _location = newLocation;
     if (buttons != null)
       _buttons = buttons;
@@ -180,7 +180,7 @@ class TestPointer {
       kind: kind,
       device: _device,
       pointer: pointer,
-      position: location,
+      position: location!,
     );
   }
 
@@ -198,7 +198,7 @@ class TestPointer {
       kind: kind,
       device: _device,
       pointer: pointer,
-      position: location,
+      position: location!,
     );
   }
 
@@ -209,7 +209,7 @@ class TestPointer {
   /// specific time stamp by passing the `timeStamp` argument.
   PointerAddedEvent addPointer({
     Duration timeStamp = Duration.zero,
-    Offset location,
+    Offset? location,
   }) {
     assert(timeStamp != null);
     _location = location ?? _location;
@@ -228,7 +228,7 @@ class TestPointer {
   /// specific time stamp by passing the `timeStamp` argument.
   PointerRemovedEvent removePointer({
     Duration timeStamp = Duration.zero,
-    Offset location,
+    Offset? location,
   }) {
     assert(timeStamp != null);
     _location = location ?? _location;
@@ -258,7 +258,7 @@ class TestPointer {
         'Hover events can only be generated when the pointer is up. To '
         'simulate movement when the pointer is down, use move() instead.');
     assert(kind != PointerDeviceKind.touch, "Touch pointers can't generate hover events");
-    final Offset delta = location != null ? newLocation - location : Offset.zero;
+    final Offset delta = location != null ? newLocation - location! : Offset.zero;
     _location = newLocation;
     return PointerHoverEvent(
       timeStamp: timeStamp,
@@ -281,11 +281,12 @@ class TestPointer {
     assert(scrollDelta != null);
     assert(timeStamp != null);
     assert(kind != PointerDeviceKind.touch, "Touch pointers can't generate pointer signal events");
+    assert(location != null);
     return PointerScrollEvent(
       timeStamp: timeStamp,
       kind: kind,
       device: _device,
-      position: location,
+      position: location!,
       scrollDelta: scrollDelta,
     );
   }
@@ -321,10 +322,10 @@ class TestGesture {
   /// None of the arguments may be null. The `dispatcher` and `hitTester`
   /// arguments are required.
   TestGesture({
-    @required EventDispatcher dispatcher,
+    required EventDispatcher dispatcher,
     int pointer = 1,
     PointerDeviceKind kind = PointerDeviceKind.touch,
-    int device,
+    int? device,
     int buttons = kPrimaryButton,
   }) : assert(dispatcher != null),
        assert(pointer != null),
@@ -363,14 +364,14 @@ class TestGesture {
   }
 
   /// In a test, send a pointer add event for this pointer.
-  Future<void> addPointer({ Duration timeStamp = Duration.zero, Offset location }) {
+  Future<void> addPointer({ Duration timeStamp = Duration.zero, Offset? location }) {
     return TestAsyncUtils.guard<void>(() {
       return _dispatcher(_pointer.addPointer(timeStamp: timeStamp, location: location ?? _pointer.location));
     });
   }
 
   /// In a test, send a pointer remove event for this pointer.
-  Future<void> removePointer({ Duration timeStamp = Duration.zero, Offset location }) {
+  Future<void> removePointer({ Duration timeStamp = Duration.zero, Offset? location }) {
     return TestAsyncUtils.guard<void>(() {
       return _dispatcher(_pointer.removePointer(timeStamp: timeStamp, location: location ?? _pointer.location));
     });
@@ -382,7 +383,8 @@ class TestGesture {
   /// up, then a hover event is dispatched. Touch devices are not able to send
   /// hover events.
   Future<void> moveBy(Offset offset, { Duration timeStamp = Duration.zero }) {
-    return moveTo(_pointer.location + offset, timeStamp: timeStamp);
+    assert(_pointer.location != null);
+    return moveTo(_pointer.location! + offset, timeStamp: timeStamp);
   }
 
   /// Send a move event moving the pointer to the given location.

packages/flutter_test/lib/src/test_text_input.dart

@@ -34,10 +34,10 @@ class TestTextInput {
   /// To use the methods on this API that send fake keyboard messages (such as
   /// [updateEditingValue], [enterText], or [receiveAction]), the keyboard must
   /// first be requested, e.g. using [WidgetTester.showKeyboard].
-  final VoidCallback onCleared;
+  final VoidCallback? onCleared;
 
   /// The messenger which sends the bytes for this channel, not null.
-  BinaryMessenger get _binaryMessenger => ServicesBinding.instance.defaultBinaryMessenger;
+  BinaryMessenger get _binaryMessenger => ServicesBinding.instance!.defaultBinaryMessenger;
 
   /// Resets any internal state of this object and calls [register].
   ///
@@ -81,7 +81,7 @@ class TestTextInput {
   int _client = 0;
 
   /// Arguments supplied to the TextInput.setClient method call.
-  Map<String, dynamic> setClientArgs;
+  Map<String, dynamic>? setClientArgs;
 
   /// The last set of arguments that [TextInputConnection.setEditingState] sent
   /// to the embedder.
@@ -89,7 +89,7 @@ class TestTextInput {
   /// This is a map representation of a [TextEditingValue] object. For example,
   /// it will have a `text` entry whose value matches the most recent
   /// [TextEditingValue.text] that was sent to the embedder.
-  Map<String, dynamic> editingState;
+  Map<String, dynamic>? editingState;
 
   Future<dynamic> _handleTextInputCall(MethodCall methodCall) async {
     log.add(methodCall);
@@ -105,7 +105,7 @@ class TestTextInput {
         _client = 0;
         _isVisible = false;
         if (onCleared != null)
-          onCleared();
+          onCleared!();
         break;
       case 'TextInput.setEditingState':
         editingState = methodCall.arguments as Map<String, dynamic>;
@@ -141,7 +141,7 @@ class TestTextInput {
           <dynamic>[_client, value.toJSON()],
         ),
       ),
-      (ByteData data) { /* response from framework is discarded */ },
+      (ByteData? data) { /* response from framework is discarded */ },
     );
   }
 
@@ -164,7 +164,7 @@ class TestTextInput {
            <dynamic>[_client,]
         ),
       ),
-      (ByteData data) { /* response from framework is discarded */ },
+      (ByteData? data) { /* response from framework is discarded */ },
     );
   }
 
@@ -198,11 +198,12 @@ class TestTextInput {
             <dynamic>[_client, action.toString()],
           ),
         ),
-        (ByteData data) {
+        (ByteData? data) {
+          assert(data != null);
           try {
             // Decoding throws a PlatformException if the data represents an
             // error, and that's all we care about here.
-            SystemChannels.textInput.codec.decodeEnvelope(data);
+            SystemChannels.textInput.codec.decodeEnvelope(data!);
 
             // No error was found. Complete without issue.
             completer.complete();

packages/flutter_test/pubspec.yaml

@@ -2,7 +2,7 @@ name: flutter_test
 
 environment:
   # The pub client defaults to an <2.0.0 sdk constraint which we need to explicitly overwrite.
-  sdk: ">=2.2.2 <3.0.0"
+  sdk: ">=2.10.0-0.0.dev <3.0.0"
 
 dependencies:
   # To update these, use "flutter update-packages --force-upgrade".

packages/flutter_test/test/accessibility_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.
 
+// @dart = 2.9
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter_test/test/accessibility_window_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.
 
+// @dart = 2.9
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter_test/test/bindings_async_gap_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.
 
+// @dart = 2.9
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';
@@ -38,7 +40,7 @@ Future<void> main() async {
       );
 
       completer.completeError(const CustomException());
-    }, null);
+    }, () { });
 
     final FlutterErrorDetails details = await errorCompleter.future;
     expect(details, isNotNull);
@@ -49,4 +51,4 @@ Future<void> main() async {
 
 class CustomException implements Exception {
   const CustomException();
-}
+}
\ No newline at end of file

packages/flutter_test/test/bindings_environment/flutter_test_variable_is_false_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.
 
+// @dart = 2.9
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/bindings_environment/flutter_test_variable_is_not_true_or_false_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.
 
+// @dart = 2.9
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/bindings_environment/flutter_test_variable_is_null_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.
 
+// @dart = 2.9
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/bindings_environment/flutter_test_variable_is_true_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.
 
+// @dart = 2.9
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/bindings_environment/no_flutter_test_variable_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.
 
+// @dart = 2.9
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/bindings_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.
 
+// @dart = 2.9
+
 import 'dart:io';
 
 import 'package:flutter/material.dart';

packages/flutter_test/test/bindings_test_failure.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.
 
+// @dart = 2.9
+
 import 'dart:io';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/controller_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.
 
+// @dart = 2.9
+
 import 'dart:ui';
 
 import 'package:flutter/semantics.dart';

packages/flutter_test/test/custom_exception_reporter/flutter_test_config.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.
 
+// @dart = 2.9
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter_test/test/custom_exception_reporter/test_exception_reporter_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.
 
+// @dart = 2.9
+
 import 'flutter_test_config.dart' as real_test;
 
 void main() => real_test.runTest();

packages/flutter_test/test/demangle_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.
 
+// @dart = 2.9
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter_test/test/event_simulation_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.
 
+// @dart = 2.9
+
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/finders_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.
 
+// @dart = 2.9
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';

packages/flutter_test/test/frame_timing_summarizer_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.
 
+// @dart = 2.9
+
 import 'dart:ui';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/goldens_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.
 
+// @dart = 2.9
+
 import 'dart:async';
 import 'dart:io' as io;
 import 'dart:typed_data';

packages/flutter_test/test/integration_bindings_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.
 
+// @dart = 2.9
+
 import 'dart:io';
 
 import 'package:flutter/widgets.dart';

packages/flutter_test/test/live_binding_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.
 
+// @dart = 2.9
+
 import 'dart:ui';
 
 import 'package:flutter/material.dart';

packages/flutter_test/test/live_widget_controller_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.
 
+// @dart = 2.9
+
 import 'dart:ui';
 
 import 'package:flutter/material.dart';

packages/flutter_test/test/matchers_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.
 
+// @dart = 2.9
+
 import 'dart:typed_data';
 import 'dart:ui';
 

packages/flutter_test/test/reference_image_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.
 
+// @dart = 2.9
+
 import 'dart:ui' as ui;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/restoration_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.
 
+// @dart = 2.9
+
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/stack_manipulation_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.
 
+// @dart = 2.9
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter_test/test/test_async_utils_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.
 
+// @dart = 2.9
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/test_config/child_directory/config_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.
 
+// @dart = 2.9
+
 import '../config_test_utils.dart';
 
 void main() {

packages/flutter_test/test/test_config/child_directory/grandchild_directory/config_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.
 
+// @dart = 2.9
+
 import '../../config_test_utils.dart';
 
 void main() {

packages/flutter_test/test/test_config/config_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.
 
+// @dart = 2.9
+
 import 'config_test_utils.dart';
 
 void main() {

packages/flutter_test/test/test_config/config_test_utils.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.
 
+// @dart = 2.9
+
 import 'dart:async';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/test_config/flutter_test_config.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.
 
+// @dart = 2.9
+
 import 'dart:async';
 
 Future<void> main(FutureOr<void> testMain()) async {

packages/flutter_test/test/test_config/nested_config/config_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.
 
+// @dart = 2.9
+
 import '../config_test_utils.dart';
 
 void main() {

packages/flutter_test/test/test_config/nested_config/flutter_test_config.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.
 
+// @dart = 2.9
+
 import 'dart:async';
 
 Future<void> main(FutureOr<void> testMain()) async {

packages/flutter_test/test/test_config/project_root/config_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.
 
+// @dart = 2.9
+
 import '../config_test_utils.dart';
 
 void main() {

packages/flutter_test/test/test_text_input_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.
 
+// @dart = 2.9
+
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter_test/test/widget_tester_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.
 
+// @dart = 2.9
+
 import 'dart:async';
 import 'dart:io';
 import 'dart:ui';

packages/flutter_test/test/window_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.
 
+// @dart = 2.9
+
 import 'dart:ui' as ui show window;
 import 'dart:ui' show Size, Locale, WindowPadding, AccessibilityFeatures, Brightness;