Migrate More Material Tests (#67482)

packages/flutter/lib/src/material/radio.dart

@@ -129,7 +129,7 @@ class Radio<T> extends StatefulWidget {
   ///
   /// This radio button is considered selected if its [value] matches the
   /// [groupValue].
-  final T groupValue;
+  final T? groupValue;
 
   /// Called when the user selects this radio button.
   ///

packages/flutter/lib/src/material/radio_list_tile.dart

@@ -335,7 +335,7 @@ class RadioListTile<T> extends StatelessWidget {
   ///
   /// This radio button is considered selected if its [value] matches the
   /// [groupValue].
-  final T groupValue;
+  final T? groupValue;
 
   /// Called when the user selects this radio button.
   ///

packages/flutter/lib/src/material/refresh_indicator.dart

@@ -175,7 +175,7 @@ class RefreshIndicatorState extends State<RefreshIndicator> with TickerProviderS
   late Animation<Color?> _valueColor;
 
   _RefreshIndicatorMode? _mode;
-  Future<void>? _pendingRefreshFuture;
+  late Future<void> _pendingRefreshFuture;
   bool? _isIndicatorAtTop;
   double? _dragOffset;
 
@@ -406,7 +406,7 @@ class RefreshIndicatorState extends State<RefreshIndicator> with TickerProviderS
   /// When initiated in this manner, the refresh indicator is independent of any
   /// actual scroll view. It defaults to showing the indicator at the top. To
   /// show it at the bottom, set `atTop` to false.
-  Future<void>? show({ bool atTop = true }) {
+  Future<void> show({ bool atTop = true }) {
     if (_mode != _RefreshIndicatorMode.refresh &&
         _mode != _RefreshIndicatorMode.snap) {
       if (_mode == null)

packages/flutter/test/material/progress_indicator_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/material.dart';
@@ -298,8 +296,8 @@ void main() {
   });
 
   testWidgets('Determinate CircularProgressIndicator stops the animator', (WidgetTester tester) async {
-    double progressValue;
-    StateSetter setState;
+    double? progressValue;
+    late StateSetter setState;
     await tester.pumpWidget(
       Directionality(
         textDirection: TextDirection.ltr,

packages/flutter/test/material/radio_list_tile_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';
@@ -14,7 +12,7 @@ import 'package:flutter/material.dart';
 
 import '../widgets/semantics_tester.dart';
 
-Widget wrap({Widget child}) {
+Widget wrap({Widget? child}) {
   return MediaQuery(
     data: const MediaQueryData(),
     child: Directionality(
@@ -28,7 +26,7 @@ void main() {
   testWidgets('RadioListTile should initialize according to groupValue',
       (WidgetTester tester) async {
     final List<int> values = <int>[0, 1, 2];
-    int selectedValue;
+    int? selectedValue;
     // Constructor parameters are required for [RadioListTile], but they are
     // irrelevant when searching with [find.byType].
     final Type radioListTileType = const RadioListTile<int>(
@@ -53,7 +51,7 @@ void main() {
               body: ListView.builder(
                 itemCount: values.length,
                 itemBuilder: (BuildContext context, int index) => RadioListTile<int>(
-                  onChanged: (int value) {
+                  onChanged: (int? value) {
                     setState(() {
                       selectedValue = value;
                     });
@@ -89,7 +87,7 @@ void main() {
   testWidgets('RadioListTile simple control test', (WidgetTester tester) async {
     final Key key = UniqueKey();
     final Key titleKey = UniqueKey();
-    final List<int> log = <int>[];
+    final List<int?> log = <int?>[];
 
     await tester.pumpWidget(
       wrap(
@@ -160,7 +158,7 @@ void main() {
 
   testWidgets('RadioListTile control tests', (WidgetTester tester) async {
     final List<int> values = <int>[0, 1, 2];
-    int selectedValue;
+    int? selectedValue;
     // Constructor parameters are required for [Radio], but they are irrelevant
     // when searching with [find.byType].
     final Type radioType = const Radio<int>(
@@ -178,7 +176,7 @@ void main() {
               body: ListView.builder(
                 itemCount: values.length,
                 itemBuilder: (BuildContext context, int index) => RadioListTile<int>(
-                  onChanged: (int value) {
+                  onChanged: (int? value) {
                     log.add(value);
                     setState(() {
                       selectedValue = value;
@@ -228,7 +226,7 @@ void main() {
   testWidgets('Selected RadioListTile should not trigger onChanged', (WidgetTester tester) async {
     // Regression test for https://github.com/flutter/flutter/issues/30311
     final List<int> values = <int>[0, 1, 2];
-    int selectedValue;
+    int? selectedValue;
     // Constructor parameters are required for [Radio], but they are irrelevant
     // when searching with [find.byType].
     final Type radioType = const Radio<int>(
@@ -246,7 +244,7 @@ void main() {
               body: ListView.builder(
                 itemCount: values.length,
                 itemBuilder: (BuildContext context, int index) => RadioListTile<int>(
-                  onChanged: (int value) {
+                  onChanged: (int? value) {
                     log.add(value);
                     setState(() {
                       selectedValue = value;
@@ -280,7 +278,7 @@ void main() {
   testWidgets('Selected RadioListTile should trigger onChanged when toggleable',
       (WidgetTester tester) async {
     final List<int> values = <int>[0, 1, 2];
-    int selectedValue;
+    int? selectedValue;
     // Constructor parameters are required for [Radio], but they are irrelevant
     // when searching with [find.byType].
     final Type radioType = const Radio<int>(
@@ -299,7 +297,7 @@ void main() {
                 itemCount: values.length,
                 itemBuilder: (BuildContext context, int index) {
                   return RadioListTile<int>(
-                    onChanged: (int value) {
+                    onChanged: (int? value) {
                       log.add(value);
                       setState(() {
                         selectedValue = value;
@@ -325,16 +323,16 @@ void main() {
 
     await tester.tap(find.text('0'));
     await tester.pump();
-    expect(log, equals(<int>[0, null]));
+    expect(log, equals(<int?>[0, null]));
 
     await tester.tap(find.byType(radioType).at(0));
     await tester.pump();
-    expect(log, equals(<int>[0, null, 0]));
+    expect(log, equals(<int?>[0, null, 0]));
   });
 
   testWidgets('RadioListTile can be toggled when toggleable is set', (WidgetTester tester) async {
     final Key key = UniqueKey();
-    final List<int> log = <int>[];
+    final List<int?> log = <int?>[];
 
     await tester.pumpWidget(Material(
       child: Center(
@@ -367,7 +365,7 @@ void main() {
 
     await tester.tap(find.byKey(key));
 
-    expect(log, equals(<int>[null]));
+    expect(log, equals(<int?>[null]));
     log.clear();
 
     await tester.pumpWidget(Material(
@@ -395,7 +393,7 @@ void main() {
         child: RadioListTile<int>(
           value: 1,
           groupValue: 2,
-          onChanged: (int i) {},
+          onChanged: (int? i) {},
           title: const Text('Title'),
         ),
       ),
@@ -431,7 +429,7 @@ void main() {
         child: RadioListTile<int>(
           value: 2,
           groupValue: 2,
-          onChanged: (int i) {},
+          onChanged: (int? i) {},
           title: const Text('Title'),
         ),
       ),
@@ -540,7 +538,7 @@ void main() {
     final SemanticsTester semantics = SemanticsTester(tester);
     final Key key = UniqueKey();
     dynamic semanticEvent;
-    int radioValue = 2;
+    int? radioValue = 2;
     SystemChannels.accessibility.setMockMessageHandler((dynamic message) async {
       semanticEvent = message;
     });
@@ -551,7 +549,7 @@ void main() {
           key: key,
           value: 1,
           groupValue: radioValue,
-          onChanged: (int i) {
+          onChanged: (int? i) {
             radioValue = i;
           },
           title: const Text('Title'),
@@ -566,10 +564,10 @@ void main() {
     expect(radioValue, 1);
     expect(semanticEvent, <String, dynamic>{
       'type': 'tap',
-      'nodeId': object.debugSemantics.id,
+      'nodeId': object.debugSemantics!.id,
       'data': <String, dynamic>{},
     });
-    expect(object.debugSemantics.getSemanticsData().hasAction(SemanticsAction.tap), true);
+    expect(object.debugSemantics!.getSemanticsData().hasAction(SemanticsAction.tap), true);
 
     semantics.dispose();
     SystemChannels.accessibility.setMockMessageHandler(null);
@@ -591,7 +589,7 @@ void main() {
     );
 
     await tester.pump();
-    expect(Focus.of(childKey.currentContext, nullOk: true).hasPrimaryFocus, isTrue);
+    expect(Focus.of(childKey.currentContext!)!.hasPrimaryFocus, isTrue);
 
     await tester.pumpWidget(
       wrap(
@@ -606,6 +604,6 @@ void main() {
     );
 
     await tester.pump();
-    expect(Focus.of(childKey.currentContext, nullOk: true).hasPrimaryFocus, isFalse);
+    expect(Focus.of(childKey.currentContext!)!.hasPrimaryFocus, isFalse);
   });
 }

packages/flutter/test/material/radio_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';
@@ -18,7 +16,7 @@ import '../widgets/semantics_tester.dart';
 void main() {
   testWidgets('Radio control test', (WidgetTester tester) async {
     final Key key = UniqueKey();
-    final List<int> log = <int>[];
+    final List<int?> log = <int?>[];
 
     await tester.pumpWidget(Material(
       child: Center(
@@ -70,7 +68,7 @@ void main() {
 
   testWidgets('Radio can be toggled when toggleable is set', (WidgetTester tester) async {
     final Key key = UniqueKey();
-    final List<int> log = <int>[];
+    final List<int?> log = <int?>[];
 
     await tester.pumpWidget(Material(
       child: Center(
@@ -103,7 +101,7 @@ void main() {
 
     await tester.tap(find.byKey(key));
 
-    expect(log, equals(<int>[null]));
+    expect(log, equals(<int?>[null]));
     log.clear();
 
     await tester.pumpWidget(Material(
@@ -136,7 +134,7 @@ void main() {
                 key: key1,
                 groupValue: true,
                 value: true,
-                onChanged: (bool newValue) { },
+                onChanged: (bool? newValue) { },
               ),
             ),
           ),
@@ -158,7 +156,7 @@ void main() {
                 key: key2,
                 groupValue: true,
                 value: true,
-                onChanged: (bool newValue) { },
+                onChanged: (bool? newValue) { },
               ),
             ),
           ),
@@ -177,7 +175,7 @@ void main() {
       child: Radio<int>(
         value: 1,
         groupValue: 2,
-        onChanged: (int i) { },
+        onChanged: (int? i) { },
       ),
     ));
 
@@ -203,7 +201,7 @@ void main() {
       child: Radio<int>(
         value: 2,
         groupValue: 2,
-        onChanged: (int i) { },
+        onChanged: (int? i) { },
       ),
     ));
 
@@ -293,7 +291,7 @@ void main() {
     final SemanticsTester semantics = SemanticsTester(tester);
     final Key key = UniqueKey();
     dynamic semanticEvent;
-    int radioValue = 2;
+    int? radioValue = 2;
     SystemChannels.accessibility.setMockMessageHandler((dynamic message) async {
       semanticEvent = message;
     });
@@ -303,7 +301,7 @@ void main() {
         key: key,
         value: 1,
         groupValue: radioValue,
-        onChanged: (int i) {
+        onChanged: (int? i) {
           radioValue = i;
         },
       ),
@@ -315,10 +313,10 @@ void main() {
     expect(radioValue, 1);
     expect(semanticEvent, <String, dynamic>{
       'type': 'tap',
-      'nodeId': object.debugSemantics.id,
+      'nodeId': object.debugSemantics!.id,
       'data': <String, dynamic>{},
     });
-    expect(object.debugSemantics.getSemanticsData().hasAction(SemanticsAction.tap), true);
+    expect(object.debugSemantics!.getSemanticsData().hasAction(SemanticsAction.tap), true);
 
     semantics.dispose();
     SystemChannels.accessibility.setMockMessageHandler(null);
@@ -342,7 +340,7 @@ void main() {
                 key: radioKey,
                 value: 1,
                 groupValue: 1,
-                onChanged: (int value) { },
+                onChanged: (int? value) { },
               ),
             ),
           ),
@@ -361,7 +359,7 @@ void main() {
   testWidgets('Radio is focusable and has correct focus color', (WidgetTester tester) async {
     final FocusNode focusNode = FocusNode(debugLabel: 'Radio');
     tester.binding.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
-    int groupValue = 0;
+    int? groupValue = 0;
     const Key radioKey = Key('radio');
     Widget buildApp({bool enabled = true}) {
       return MaterialApp(
@@ -375,7 +373,7 @@ void main() {
                 child: Radio<int>(
                   key: radioKey,
                   value: 0,
-                  onChanged: enabled ? (int newValue) {
+                  onChanged: enabled ? (int? newValue) {
                     setState(() {
                       groupValue = newValue;
                     });
@@ -439,7 +437,7 @@ void main() {
 
   testWidgets('Radio can be hovered and has correct hover color', (WidgetTester tester) async {
     tester.binding.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
-    int groupValue = 0;
+    int? groupValue = 0;
     const Key radioKey = Key('radio');
     Widget buildApp({bool enabled = true}) {
       return MaterialApp(
@@ -453,7 +451,7 @@ void main() {
                 child: Radio<int>(
                   key: radioKey,
                   value: 0,
-                  onChanged: enabled ? (int newValue) {
+                  onChanged: enabled ? (int? newValue) {
                     setState(() {
                       groupValue = newValue;
                     });
@@ -519,7 +517,7 @@ void main() {
 
   testWidgets('Radio can be controlled by keyboard shortcuts', (WidgetTester tester) async {
     tester.binding.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
-    int groupValue = 1;
+    int? groupValue = 1;
     const Key radioKey0 = Key('radio0');
     const Key radioKey1 = Key('radio1');
     const Key radioKey2 = Key('radio2');
@@ -538,7 +536,7 @@ void main() {
                     Radio<int>(
                       key: radioKey0,
                       value: 0,
-                      onChanged: enabled ? (int newValue) {
+                      onChanged: enabled ? (int? newValue) {
                         setState(() {
                           groupValue = newValue;
                         });
@@ -550,7 +548,7 @@ void main() {
                     Radio<int>(
                       key: radioKey1,
                       value: 1,
-                      onChanged: enabled ? (int newValue) {
+                      onChanged: enabled ? (int? newValue) {
                         setState(() {
                           groupValue = newValue;
                         });
@@ -561,7 +559,7 @@ void main() {
                     Radio<int>(
                       key: radioKey2,
                       value: 2,
-                      onChanged: enabled ? (int newValue) {
+                      onChanged: enabled ? (int? newValue) {
                         setState(() {
                           groupValue = newValue;
                         });
@@ -605,7 +603,7 @@ void main() {
               child: Radio<int>(
                 visualDensity: visualDensity,
                 key: key,
-                onChanged: (int value) {},
+                onChanged: (int? value) {},
                 value: 0,
                 groupValue: 0,
               ),
@@ -648,7 +646,7 @@ void main() {
                   key: key,
                   mouseCursor: SystemMouseCursors.text,
                   value: 1,
-                  onChanged: (int v) {},
+                  onChanged: (int? v) {},
                   groupValue: 2,
                 ),
               ),
@@ -664,7 +662,7 @@ void main() {
 
     await tester.pump();
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
 
 
     // Test default cursor
@@ -678,7 +676,7 @@ void main() {
                 cursor: SystemMouseCursors.forbidden,
                 child: Radio<int>(
                   value: 1,
-                  onChanged: (int v) {},
+                  onChanged: (int? v) {},
                   groupValue: 2,
                 ),
               ),
@@ -688,7 +686,7 @@ void main() {
       ),
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.click);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.click);
 
     // Test default cursor when disabled
     await tester.pumpWidget(
@@ -711,6 +709,6 @@ void main() {
       ),
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.basic);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.basic);
   });
 }

packages/flutter/test/material/raised_button_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -38,10 +36,10 @@ void main() {
     expect(material.elevation, 2.0);
     expect(material.shadowColor, null);
     expect(material.shape, RoundedRectangleBorder(borderRadius: BorderRadius.circular(2.0)));
-    expect(material.textStyle.color, const Color(0xdd000000));
-    expect(material.textStyle.fontFamily, 'Roboto');
-    expect(material.textStyle.fontSize, 14);
-    expect(material.textStyle.fontWeight, FontWeight.w500);
+    expect(material.textStyle!.color, const Color(0xdd000000));
+    expect(material.textStyle!.fontFamily, 'Roboto');
+    expect(material.textStyle!.fontSize, 14);
+    expect(material.textStyle!.fontWeight, FontWeight.w500);
     expect(material.type, MaterialType.button);
 
     final Offset center = tester.getCenter(find.byType(RaisedButton));
@@ -58,10 +56,10 @@ void main() {
     expect(material.elevation, 8.0);
     expect(material.shadowColor, null);
     expect(material.shape, RoundedRectangleBorder(borderRadius: BorderRadius.circular(2.0)));
-    expect(material.textStyle.color, const Color(0xdd000000));
-    expect(material.textStyle.fontFamily, 'Roboto');
-    expect(material.textStyle.fontSize, 14);
-    expect(material.textStyle.fontWeight, FontWeight.w500);
+    expect(material.textStyle!.color, const Color(0xdd000000));
+    expect(material.textStyle!.fontFamily, 'Roboto');
+    expect(material.textStyle!.fontSize, 14);
+    expect(material.textStyle!.fontWeight, FontWeight.w500);
     expect(material.type, MaterialType.button);
 
     // Disabled RaisedButton
@@ -83,10 +81,10 @@ void main() {
     expect(material.elevation, 0.0);
     expect(material.shadowColor, null);
     expect(material.shape, RoundedRectangleBorder(borderRadius: BorderRadius.circular(2.0)));
-    expect(material.textStyle.color, const Color(0x61000000));
-    expect(material.textStyle.fontFamily, 'Roboto');
-    expect(material.textStyle.fontSize, 14);
-    expect(material.textStyle.fontWeight, FontWeight.w500);
+    expect(material.textStyle!.color, const Color(0x61000000));
+    expect(material.textStyle!.fontFamily, 'Roboto');
+    expect(material.textStyle!.fontSize, 14);
+    expect(material.textStyle!.fontWeight, FontWeight.w500);
     expect(material.type, MaterialType.button);
   });
 
@@ -198,7 +196,7 @@ void main() {
     );
 
     Color textColor() {
-      return tester.renderObject<RenderParagraph>(find.text('RaisedButton')).text.style.color;
+      return tester.renderObject<RenderParagraph>(find.text('RaisedButton')).text.style!.color!;
     }
 
     // Default, not disabled.
@@ -267,7 +265,7 @@ void main() {
       ),
     );
 
-    Color iconColor() => _iconStyle(tester, Icons.add).color;
+    Color iconColor() => _iconStyle(tester, Icons.add).color!;
     // Default, not disabled.
     expect(iconColor(), equals(defaultColor));
 
@@ -325,7 +323,7 @@ void main() {
     );
 
     Color textColor() {
-      return tester.renderObject<RenderParagraph>(find.text('RaisedButton')).text.style.color;
+      return tester.renderObject<RenderParagraph>(find.text('RaisedButton')).text.style!.color!;
     }
 
     // Disabled.
@@ -338,7 +336,7 @@ void main() {
     bool wasPressed;
     Finder raisedButton;
 
-    Widget buildFrame({ VoidCallback onPressed, VoidCallback onLongPress }) {
+    Widget buildFrame({ VoidCallback? onPressed, VoidCallback? onLongPress }) {
       return Directionality(
         textDirection: TextDirection.ltr,
         child: RaisedButton(
@@ -454,7 +452,7 @@ void main() {
     addTearDown(gesture.removePointer);
 
     await tester.pump();
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
 
     await tester.pumpWidget(
       Directionality(
@@ -469,7 +467,7 @@ void main() {
       ),
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
 
     // Test default cursor
     await tester.pumpWidget(
@@ -484,7 +482,7 @@ void main() {
       ),
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.click);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.click);
 
     // Test default cursor when disabled
     await tester.pumpWidget(
@@ -499,7 +497,7 @@ void main() {
       ),
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.basic);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.basic);
   });
 
 
@@ -735,5 +733,5 @@ TextStyle _iconStyle(WidgetTester tester, IconData icon) {
   final RichText iconRichText = tester.widget<RichText>(
     find.descendant(of: find.byIcon(icon), matching: find.byType(RichText)),
   );
-  return iconRichText.text.style;
+  return iconRichText.text.style!;
 }

packages/flutter/test/material/range_slider_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:ui';
 
 import 'package:flutter/cupertino.dart';
@@ -886,8 +884,8 @@ void main() {
 
   testWidgets('Range Slider onChangeEnd and onChangeStart are called on an interaction initiated by tap', (WidgetTester tester) async {
     RangeValues values = const RangeValues(30, 70);
-    RangeValues startValues;
-    RangeValues endValues;
+    RangeValues? startValues;
+    RangeValues? endValues;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -934,18 +932,18 @@ void main() {
     expect(startValues, null);
     expect(endValues, null);
     await tester.dragFrom(leftTarget, (bottomRight - topLeft) * 0.2);
-    expect(startValues.start, moreOrLessEquals(30, epsilon: 1));
-    expect(startValues.end, moreOrLessEquals(70, epsilon: 1));
+    expect(startValues!.start, moreOrLessEquals(30, epsilon: 1));
+    expect(startValues!.end, moreOrLessEquals(70, epsilon: 1));
     expect(values.start, moreOrLessEquals(50, epsilon: 1));
     expect(values.end, moreOrLessEquals(70, epsilon: 1));
-    expect(endValues.start, moreOrLessEquals(50, epsilon: 1));
-    expect(endValues.end, moreOrLessEquals(70, epsilon: 1));
+    expect(endValues!.start, moreOrLessEquals(50, epsilon: 1));
+    expect(endValues!.end, moreOrLessEquals(70, epsilon: 1));
   });
 
   testWidgets('Range Slider onChangeEnd and onChangeStart are called on an interaction initiated by drag', (WidgetTester tester) async {
     RangeValues values = const RangeValues(30, 70);
-    RangeValues startValues;
-    RangeValues endValues;
+    late RangeValues startValues;
+    late RangeValues endValues;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -1029,14 +1027,14 @@ void main() {
   }
 
   Widget _buildThemedApp({
-    ThemeData theme,
-    Color activeColor,
-    Color inactiveColor,
-    int divisions,
+    required ThemeData theme,
+    Color? activeColor,
+    Color? inactiveColor,
+    int? divisions,
     bool enabled = true,
   }) {
     RangeValues values = const RangeValues(0.5, 0.75);
-    final ValueChanged<RangeValues> onChanged = !enabled ? null : (RangeValues newValues) {
+    final ValueChanged<RangeValues>? onChanged = !enabled ? null : (RangeValues newValues) {
       values = newValues;
     };
     return MaterialApp(
@@ -1287,12 +1285,12 @@ void main() {
     RangeValues values = const RangeValues(0.5, 0.75);
 
     Widget buildApp({
-      Color activeColor,
-      Color inactiveColor,
-      int divisions,
+      Color? activeColor,
+      Color? inactiveColor,
+      int? divisions,
       bool enabled = true,
     }) {
-      final ValueChanged<RangeValues> onChanged = !enabled ? null : (RangeValues newValues) {
+      final ValueChanged<RangeValues>? onChanged = !enabled ? null : (RangeValues newValues) {
         values = newValues;
       };
       return MaterialApp(
@@ -1345,9 +1343,9 @@ void main() {
     const Color fillColor = Color(0xf55f5f5f);
 
     Widget buildApp({
-      Color activeColor,
-      Color inactiveColor,
-      int divisions,
+      Color? activeColor,
+      Color? inactiveColor,
+      int? divisions,
       bool enabled = true,
     }) {
       final ValueChanged<RangeValues> onChanged = (RangeValues newValues) {
@@ -1374,12 +1372,12 @@ void main() {
                   ElevatedButton(
                     child: const Text('Next'),
                     onPressed: () {
-                      Navigator.of(context).pushReplacement(
+                      Navigator.of(context)!.pushReplacement(
                         MaterialPageRoute<void>(
                           builder: (BuildContext context) {
                             return ElevatedButton(
                               child: const Text('Inner page'),
-                              onPressed: () { Navigator.of(context).pop(); },
+                              onPressed: () { Navigator.of(context)!.pop(); },
                             );
                           },
                         ),
@@ -1943,7 +1941,7 @@ void main() {
     await tester.pumpWidget(buildFrame(15));
     await tester.pumpAndSettle(); // Finish the animation.
 
-    Rect activeTrackRect;
+    late Rect activeTrackRect;
     expect(renderObject, paints..something((Symbol method, List<dynamic> arguments) {
       if (method != #drawRect)
         return false;

packages/flutter/test/material/raw_material_button_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
@@ -443,7 +441,7 @@ void main() {
     bool wasPressed;
     Finder rawMaterialButton;
 
-    Widget buildFrame({ VoidCallback onPressed, VoidCallback onLongPress }) {
+    Widget buildFrame({ VoidCallback? onPressed, VoidCallback? onLongPress }) {
       return Directionality(
         textDirection: TextDirection.ltr,
         child: RawMaterialButton(
@@ -593,7 +591,7 @@ void main() {
 
     await tester.pump();
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
 
     // Test default cursor
     await tester.pumpWidget(
@@ -608,7 +606,7 @@ void main() {
       ),
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.click);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.click);
 
     // Test default cursor when disabled
     await tester.pumpWidget(
@@ -623,6 +621,6 @@ void main() {
       ),
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.basic);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.basic);
   });
 }

packages/flutter/test/material/refresh_indicator_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';
@@ -360,35 +358,6 @@ void main() {
     expect(completed2, true);
   });
 
-  testWidgets('RefreshIndicator - onRefresh asserts', (WidgetTester tester) async {
-    refreshCalled = false;
-    await tester.pumpWidget(
-      MaterialApp(
-        home: RefreshIndicator(
-          onRefresh: () {
-            refreshCalled = true;
-            return null; // Missing a returned Future value here, should cause framework to throw.
-          },
-          child: ListView(
-            physics: const AlwaysScrollableScrollPhysics(),
-            children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map<Widget>((String item) {
-              return SizedBox(
-                height: 200.0,
-                child: Text(item),
-              );
-            }).toList(),
-          ),
-        ),
-      ),
-    );
-
-    await tester.fling(find.text('A'), const Offset(0.0, 300.0), 1000.0);
-    await tester.pump();
-    await tester.pump(const Duration(seconds: 1)); // finish the scroll animation
-    expect(refreshCalled, true);
-    expect(tester.takeException(), isFlutterError);
-  });
-
   testWidgets('Refresh starts while scroll view moves back to 0.0 after overscroll', (WidgetTester tester) async {
     refreshCalled = false;
     double lastScrollOffset;
@@ -458,31 +427,6 @@ void main() {
     expect(layoutCount, 1);
   });
 
-  testWidgets('strokeWidth cannot be null in RefreshIndicator', (WidgetTester tester) async {
-    try {
-      await tester.pumpWidget(
-          MaterialApp(
-            home: RefreshIndicator(
-              onRefresh: () async {},
-              strokeWidth: null,
-              child: ListView(
-                physics: const AlwaysScrollableScrollPhysics(),
-                children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map<Widget>((String item) {
-                  return SizedBox(
-                    height: 200.0,
-                    child: Text(item),
-                  );
-                }).toList(),
-              ),
-            ),
-          )
-      );
-    } on AssertionError catch(_) {
-      return;
-    }
-    fail('The assertion was not thrown when strokeWidth was null');
-  });
-
   testWidgets('RefreshIndicator responds to strokeWidth', (WidgetTester tester) async {
     await tester.pumpWidget(
         MaterialApp(

packages/flutter/test/material/scaffold_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart' show DragStartBehavior;
 import 'package:flutter/material.dart';
@@ -298,7 +296,7 @@ void main() {
     expect(renderBox.size.height, equals(appBarHeight));
   });
 
-  Widget _buildStatusBarTestApp(TargetPlatform platform) {
+  Widget _buildStatusBarTestApp(TargetPlatform? platform) {
     return MaterialApp(
       theme: ThemeData(platform: platform),
       home: MediaQuery(
@@ -357,7 +355,7 @@ void main() {
             builder: (BuildContext context) {
               return GestureDetector(
                 onTap: () {
-                  Scaffold.of(context).showBottomSheet<void>((BuildContext context) {
+                  Scaffold.of(context)!.showBottomSheet<void>((BuildContext context) {
                     return Container(
                       key: sheetKey,
                       color: Colors.blue[500],
@@ -519,7 +517,7 @@ void main() {
       };
       await tester.pumpWidget(MaterialApp(routes: routes));
 
-      Navigator.pushNamed(rootKey.currentContext, '/scaffold');
+      Navigator.pushNamed(rootKey.currentContext!, '/scaffold');
       await tester.pump();
       await tester.pump(const Duration(seconds: 1));
 
@@ -671,9 +669,9 @@ void main() {
 
     testWidgets('body size with extendBody', (WidgetTester tester) async {
       final Key bodyKey = UniqueKey();
-      double mediaQueryBottom;
+      late double mediaQueryBottom;
 
-      Widget buildFrame({ bool extendBody, bool resizeToAvoidBottomInset, double viewInsetBottom = 0.0 }) {
+      Widget buildFrame({ required bool extendBody, bool? resizeToAvoidBottomInset, double viewInsetBottom = 0.0 }) {
         return Directionality(
           textDirection: TextDirection.ltr,
           child: MediaQuery(
@@ -685,7 +683,7 @@ void main() {
               extendBody: extendBody,
               body: Builder(
                 builder: (BuildContext context) {
-                  mediaQueryBottom = MediaQuery.of(context).padding.bottom;
+                  mediaQueryBottom = MediaQuery.of(context)!.padding.bottom;
                   return Container(key: bodyKey);
                 },
               ),
@@ -732,10 +730,10 @@ void main() {
 
       const double appBarHeight = 100;
       const double windowPaddingTop = 24;
-      bool fixedHeightAppBar;
-      double mediaQueryTop;
+      late bool fixedHeightAppBar;
+      late double mediaQueryTop;
 
-      Widget buildFrame({ bool extendBodyBehindAppBar, bool hasAppBar }) {
+      Widget buildFrame({ required bool extendBodyBehindAppBar, required bool hasAppBar }) {
         return Directionality(
           textDirection: TextDirection.ltr,
           child: MediaQuery(
@@ -758,7 +756,7 @@ void main() {
                   ),
                   body: Builder(
                     builder: (BuildContext context) {
-                      mediaQueryTop = MediaQuery.of(context).padding.top;
+                      mediaQueryTop = MediaQuery.of(context)!.padding.top;
                       return Container(key: bodyKey);
                     }
                   ),
@@ -1224,7 +1222,7 @@ void main() {
       await tester.pump(const Duration(milliseconds: 50));
 
       ScaffoldGeometry geometry = listenerState.cache.value;
-      final Rect transitioningFabRect = geometry.floatingActionButtonArea;
+      final Rect transitioningFabRect = geometry.floatingActionButtonArea!;
 
       final double transitioningRotation = tester.widget<RotationTransition>(
         find.byType(RotationTransition),
@@ -1249,17 +1247,17 @@ void main() {
       );
 
       expect(
-        geometry.floatingActionButtonArea.center,
+        geometry.floatingActionButtonArea!.center,
         transitioningFabRect.center,
       );
 
       expect(
-        geometry.floatingActionButtonArea.width,
+        geometry.floatingActionButtonArea!.width,
         greaterThan(transitioningFabRect.width),
       );
 
       expect(
-        geometry.floatingActionButtonArea.height,
+        geometry.floatingActionButtonArea!.height,
         greaterThan(transitioningFabRect.height),
       );
     });
@@ -1672,12 +1670,12 @@ void main() {
   });
 
   testWidgets('End drawer does not open with a drag gesture when it is disabled', (WidgetTester tester) async {
-    double screenWidth;
+    late double screenWidth;
     await tester.pumpWidget(
       MaterialApp(
         home: Builder(
           builder: (BuildContext context) {
-            screenWidth = MediaQuery.of(context).size.width;
+            screenWidth = MediaQuery.of(context)!.size.width;
             return Scaffold(
               endDrawer: const Drawer(
                 child: Text('Drawer'),
@@ -1746,7 +1744,7 @@ void main() {
     // Regression test for https://github.com/flutter/flutter/issues/20295
     final Key bodyKey = UniqueKey();
 
-    Widget buildFrame(bool innerResizeToAvoidBottomInset, bool outerResizeToAvoidBottomInset) {
+    Widget buildFrame(bool? innerResizeToAvoidBottomInset, bool? outerResizeToAvoidBottomInset) {
       return Directionality(
         textDirection: TextDirection.ltr,
         child: MediaQuery(
@@ -1810,10 +1808,10 @@ void main() {
             ),
           ),
         );
-        FlutterError error;
+        late FlutterError error;
         try {
-          key.currentState.showBottomSheet<void>((BuildContext context) {
-            final ThemeData themeData = Theme.of(context);
+          key.currentState!.showBottomSheet<void>((BuildContext context) {
+            final ThemeData themeData = Theme.of(context)!;
             return Container(
               decoration: BoxDecoration(
                 border: Border(top: BorderSide(color: themeData.disabledColor))
@@ -1872,7 +1870,7 @@ void main() {
             ),
           ),
         );
-        key.currentState.showBottomSheet<void>((_) => Container());
+        key.currentState!.showBottomSheet<void>((_) => Container());
         await tester.tap(find.byKey(buttonKey));
         await tester.pump();
         expect(errors, isNotEmpty);
@@ -1902,7 +1900,7 @@ void main() {
         MaterialApp(
           home: Builder(
             builder: (BuildContext context) {
-              Scaffold.of(context).showBottomSheet<void>((BuildContext context) {
+              Scaffold.of(context)!.showBottomSheet<void>((BuildContext context) {
                 return Container();
               });
               return Container();
@@ -1970,7 +1968,7 @@ void main() {
     });
 
     testWidgets('Call to Scaffold.geometryOf() without context', (WidgetTester tester) async {
-      ValueListenable<ScaffoldGeometry> geometry;
+      ValueListenable<ScaffoldGeometry>? geometry;
       await tester.pumpWidget(
         MaterialApp(
           home: Builder(
@@ -2036,7 +2034,7 @@ void main() {
   });
 
   testWidgets('ScaffoldMessenger.of can return null', (WidgetTester tester) async {
-    ScaffoldMessengerState scaffoldMessenger;
+    ScaffoldMessengerState? scaffoldMessenger;
     const Key tapTarget = Key('tap-target');
     await tester.pumpWidget(Directionality(
       textDirection: TextDirection.ltr,
@@ -2070,7 +2068,7 @@ void main() {
     const Key tapTarget = Key('tap-target');
 
     final List<dynamic> exceptions = <dynamic>[];
-    final FlutterExceptionHandler oldHandler = FlutterError.onError;
+    final FlutterExceptionHandler? oldHandler = FlutterError.onError;
     FlutterError.onError = (FlutterErrorDetails details) {
       exceptions.add(details.exception);
     };
@@ -2161,8 +2159,8 @@ class _GeometryListenerState extends State<_GeometryListener> {
   }
 
   int numNotifications = 0;
-  ValueListenable<ScaffoldGeometry> geometryListenable;
-  _GeometryCachePainter cache;
+  ValueListenable<ScaffoldGeometry>? geometryListenable;
+  late _GeometryCachePainter cache;
 
   @override
   void didChangeDependencies() {
@@ -2172,11 +2170,11 @@ class _GeometryListenerState extends State<_GeometryListener> {
       return;
 
     if (geometryListenable != null)
-      geometryListenable.removeListener(onGeometryChanged);
+      geometryListenable!.removeListener(onGeometryChanged);
 
     geometryListenable = newListenable;
-    geometryListenable.addListener(onGeometryChanged);
-    cache = _GeometryCachePainter(geometryListenable);
+    geometryListenable!.addListener(onGeometryChanged);
+    cache = _GeometryCachePainter(geometryListenable!);
   }
 
   void onGeometryChanged() {
@@ -2192,7 +2190,7 @@ class _GeometryCachePainter extends CustomPainter {
 
   final ValueListenable<ScaffoldGeometry> geometryListenable;
 
-  ScaffoldGeometry value;
+  late ScaffoldGeometry value;
   @override
   void paint(Canvas canvas, Size size) {
     value = geometryListenable.value;
@@ -2206,7 +2204,7 @@ class _GeometryCachePainter extends CustomPainter {
 
 class _CustomPageRoute<T> extends PageRoute<T> {
   _CustomPageRoute({
-    @required this.builder,
+    required this.builder,
     RouteSettings settings = const RouteSettings(),
     this.maintainState = true,
     bool fullscreenDialog = false,
@@ -2219,10 +2217,10 @@ class _CustomPageRoute<T> extends PageRoute<T> {
   Duration get transitionDuration => const Duration(milliseconds: 300);
 
   @override
-  Color get barrierColor => null;
+  Color? get barrierColor => null;
 
   @override
-  String get barrierLabel => null;
+  String? get barrierLabel => null;
 
   @override
   final bool maintainState;

packages/flutter/test/material/scrollbar_paint_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 
@@ -12,7 +10,7 @@ import '../rendering/mock_canvas.dart';
 Widget _buildSingleChildScrollViewWithScrollbar({
   TextDirection textDirection = TextDirection.ltr,
   EdgeInsets padding = EdgeInsets.zero,
-  Widget child,
+  Widget? child,
 }) {
   return Directionality(
     textDirection: textDirection,

packages/flutter/test/material/scrollbar_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
@@ -13,20 +11,18 @@ import 'package:flutter_test/flutter_test.dart';
 import '../rendering/mock_canvas.dart';
 
 class TestCanvas implements Canvas {
-  TestCanvas([this.invocations]);
-
-  final List<Invocation> invocations;
+  final List<Invocation> invocations = <Invocation>[];
 
   @override
   void noSuchMethod(Invocation invocation) {
-    invocations?.add(invocation);
+    invocations.add(invocation);
   }
 }
 
 Widget _buildBoilerplate({
   TextDirection textDirection = TextDirection.ltr,
   EdgeInsets padding = EdgeInsets.zero,
-  Widget child,
+  required Widget child,
 }) {
   return Directionality(
     textDirection: textDirection,
@@ -67,15 +63,15 @@ void main() {
       ),
     );
 
-    SchedulerBinding.instance.debugAssertNoTransientCallbacks('Building a list with a scrollbar triggered an animation.');
+    SchedulerBinding.instance!.debugAssertNoTransientCallbacks('Building a list with a scrollbar triggered an animation.');
     await tester.tap(find.byType(ListView));
-    SchedulerBinding.instance.debugAssertNoTransientCallbacks('Tapping a block with a scrollbar triggered an animation.');
+    SchedulerBinding.instance!.debugAssertNoTransientCallbacks('Tapping a block with a scrollbar triggered an animation.');
     await tester.pump(const Duration(milliseconds: 200));
     await tester.pump(const Duration(milliseconds: 200));
     await tester.pump(const Duration(milliseconds: 200));
     await tester.pump(const Duration(milliseconds: 200));
     await tester.drag(find.byType(ListView), const Offset(0.0, -10.0));
-    expect(SchedulerBinding.instance.transientCallbackCount, greaterThan(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, greaterThan(0));
     await tester.pump(const Duration(milliseconds: 200));
     await tester.pump(const Duration(milliseconds: 200));
     await tester.pump(const Duration(milliseconds: 200));
@@ -116,12 +112,11 @@ void main() {
     );
     scrollPainter.update(metrics, AxisDirection.down);
 
-    final List<Invocation> invocations = <Invocation>[];
-    final TestCanvas canvas = TestCanvas(invocations);
+    final TestCanvas canvas = TestCanvas();
     scrollPainter.paint(canvas, const Size(10.0, 100.0));
 
     // Scrollbar is not supposed to draw anything if there isn't enough content.
-    expect(invocations.isEmpty, isTrue);
+    expect(canvas.invocations.isEmpty, isTrue);
   });
 
   testWidgets('Adaptive scrollbar', (WidgetTester tester) async {
@@ -174,7 +169,7 @@ void main() {
 
   testWidgets('Scrollbar passes controller to CupertinoScrollbar', (WidgetTester tester) async {
     final ScrollController controller = ScrollController();
-    Widget viewWithScroll(TargetPlatform platform) {
+    Widget viewWithScroll(TargetPlatform? platform) {
       return _buildBoilerplate(
         child: Theme(
           data: ThemeData(
@@ -517,7 +512,7 @@ void main() {
 
   testWidgets('Scrollbar respects thickness and radius', (WidgetTester tester) async {
     final ScrollController controller = ScrollController();
-    Widget viewWithScroll({Radius radius}) {
+    Widget viewWithScroll({Radius? radius}) {
       return _buildBoilerplate(
         child: Theme(
           data: ThemeData(),