Migrate Material framework tests to null safety (#67556)

Migrate Material framework tests to null safety.

packages/flutter/test/material/button_bar_theme_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/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -56,7 +54,7 @@ void main() {
       overflowDirection: VerticalDirection.up,
     );
 
-    final ButtonBarThemeData lerp = ButtonBarThemeData.lerp(barThemePrimary, barThemeAccent, 0.5);
+    final ButtonBarThemeData lerp = ButtonBarThemeData.lerp(barThemePrimary, barThemeAccent, 0.5)!;
     expect(lerp.alignment, equals(MainAxisAlignment.center));
     expect(lerp.mainAxisSize, equals(MainAxisSize.max));
     expect(lerp.buttonTextTheme, equals(ButtonTextTheme.accent));
@@ -114,7 +112,7 @@ void main() {
 
   testWidgets('ButtonBarTheme.of falls back to ThemeData.buttonBarTheme', (WidgetTester tester) async {
     const ButtonBarThemeData buttonBarTheme = ButtonBarThemeData(buttonMinWidth: 42.0);
-    BuildContext capturedContext;
+    late BuildContext capturedContext;
     await tester.pumpWidget(
       MaterialApp(
         theme: ThemeData(buttonBarTheme: buttonBarTheme),
@@ -133,7 +131,7 @@ void main() {
   testWidgets('ButtonBarTheme overrides ThemeData.buttonBarTheme', (WidgetTester tester) async {
     const ButtonBarThemeData defaultBarTheme = ButtonBarThemeData(buttonMinWidth: 42.0);
     const ButtonBarThemeData buttonBarTheme = ButtonBarThemeData(buttonMinWidth: 84.0);
-    BuildContext capturedContext;
+    late BuildContext capturedContext;
     await tester.pumpWidget(
       MaterialApp(
         theme: ThemeData(buttonBarTheme: defaultBarTheme),

packages/flutter/test/material/button_style_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/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/button_theme_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/rendering.dart';
@@ -39,13 +37,13 @@ void main() {
   });
 
   testWidgets('ButtonTheme defaults', (WidgetTester tester) async {
-    ButtonTextTheme textTheme;
-    ButtonBarLayoutBehavior layoutBehavior;
-    BoxConstraints constraints;
-    EdgeInsets padding;
-    ShapeBorder shape;
-    bool alignedDropdown;
-    ColorScheme colorScheme;
+    late ButtonTextTheme textTheme;
+    late ButtonBarLayoutBehavior layoutBehavior;
+    late BoxConstraints constraints;
+    late EdgeInsets padding;
+    late ShapeBorder shape;
+    late bool alignedDropdown;
+    late ColorScheme colorScheme;
 
     await tester.pumpWidget(
       ButtonTheme(
@@ -57,7 +55,7 @@ void main() {
             padding = theme.padding as EdgeInsets;
             shape = theme.shape;
             layoutBehavior = theme.layoutBehavior;
-            colorScheme = theme.colorScheme;
+            colorScheme = theme.colorScheme!;
             alignedDropdown = theme.alignedDropdown;
             return Container(
               alignment: Alignment.topLeft,
@@ -121,10 +119,10 @@ void main() {
 
   testWidgets('Theme buttonTheme defaults', (WidgetTester tester) async {
     final ThemeData lightTheme = ThemeData.light();
-    ButtonTextTheme textTheme;
-    BoxConstraints constraints;
-    EdgeInsets padding;
-    ShapeBorder shape;
+    late ButtonTextTheme textTheme;
+    late BoxConstraints constraints;
+    late EdgeInsets padding;
+    late ShapeBorder shape;
 
     const Color disabledColor = Color(0xFF00FF00);
     await tester.pumpWidget(
@@ -133,7 +131,7 @@ void main() {
           disabledColor: disabledColor, // disabled RaisedButton fill color
           buttonTheme: const ButtonThemeData(disabledColor: disabledColor),
           textTheme: lightTheme.textTheme.copyWith(
-            button: lightTheme.textTheme.button.copyWith(
+            button: lightTheme.textTheme.button!.copyWith(
               // The button's height will match because there's no
               // vertical padding by default
               fontSize: 48.0,
@@ -175,10 +173,10 @@ void main() {
   });
 
   testWidgets('Theme buttonTheme ButtonTheme overrides', (WidgetTester tester) async {
-    ButtonTextTheme textTheme;
-    BoxConstraints constraints;
-    EdgeInsets padding;
-    ShapeBorder shape;
+    late ButtonTextTheme textTheme;
+    late BoxConstraints constraints;
+    late EdgeInsets padding;
+    late ShapeBorder shape;
 
     await tester.pumpWidget(
       Theme(
@@ -228,12 +226,12 @@ void main() {
   testWidgets('ButtonTheme alignedDropdown', (WidgetTester tester) async {
     final Key dropdownKey = UniqueKey();
 
-    Widget buildFrame({ bool alignedDropdown, TextDirection textDirection }) {
+    Widget buildFrame({ required bool alignedDropdown, required TextDirection textDirection }) {
       return MaterialApp(
-        builder: (BuildContext context, Widget child) {
+        builder: (BuildContext context, Widget? child) {
           return Directionality(
             textDirection: textDirection,
-            child: child,
+            child: child!,
           );
         },
         home: ButtonTheme(
@@ -248,7 +246,7 @@ void main() {
                       width: 200.0,
                       child: DropdownButton<String>(
                         key: dropdownKey,
-                        onChanged: (String value) { },
+                        onChanged: (String? value) { },
                         value: 'foo',
                         items: const <DropdownMenuItem<String>>[
                           DropdownMenuItem<String>(
@@ -374,7 +372,7 @@ void main() {
     );
 
     Color textColor() {
-      return tester.renderObject<RenderParagraph>(find.text('FlatButton')).text.style.color;
+      return tester.renderObject<RenderParagraph>(find.text('FlatButton')).text.style!.color!;
     }
 
     // Default, not disabled.

packages/flutter/test/material/card_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/painting.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/material.dart';
@@ -178,7 +176,7 @@ void main() {
 
   testWidgets('Card clipBehavior property defers to theme when null', (WidgetTester tester) async {
     await tester.pumpWidget(Builder(builder: (BuildContext context) {
-      final ThemeData themeData = Theme.of(context);
+      final ThemeData themeData = Theme.of(context)!;
       return Theme(
         data: themeData.copyWith(
           cardTheme: themeData.cardTheme.copyWith(
@@ -223,4 +221,4 @@ void main() {
     expect(_getCardMaterial(tester).shadowColor, _getCard(tester).shadowColor);
     expect(_getCardMaterial(tester).shadowColor, Colors.red);
   });
-}
+}
\ No newline at end of file

packages/flutter/test/material/card_theme_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/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/checkbox_list_tile_test.dart

@@ -2,14 +2,12 @@
 // 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';
 
 import '../rendering/mock_canvas.dart';
 
-Widget wrap({ Widget child }) {
+Widget wrap({ required Widget child }) {
   return MediaQuery(
     data: const MediaQueryData(),
     child: Directionality(
@@ -25,7 +23,7 @@ void main() {
     await tester.pumpWidget(wrap(
       child: CheckboxListTile(
         value: true,
-        onChanged: (bool value) { log.add(value); },
+        onChanged: (bool? value) { log.add(value); },
         title: const Text('Hello'),
       ),
     ));
@@ -36,12 +34,12 @@ void main() {
   });
 
   testWidgets('CheckboxListTile checkColor test', (WidgetTester tester) async {
-    Widget buildFrame(Color color) {
+    Widget buildFrame(Color? color) {
       return wrap(
         child: CheckboxListTile(
           value: true,
           checkColor: color,
-          onChanged: (bool value) {},
+          onChanged: (bool? value) {},
         ),
       );
     }
@@ -52,22 +50,22 @@ void main() {
 
     await tester.pumpWidget(buildFrame(null));
     await tester.pumpAndSettle();
-    expect(getCheckboxListTileRenderer(), paints..path(color: const Color(0xFFFFFFFF))); // paints's color is 0xFFFFFFFF (default color)
+    expect(getCheckboxListTileRenderer(), paints..path(color: const Color(0xFFFFFFFF)));
 
     await tester.pumpWidget(buildFrame(const Color(0xFF000000)));
     await tester.pumpAndSettle();
-    expect(getCheckboxListTileRenderer(), paints..path(color: const Color(0xFF000000))); // paints's color is 0xFF000000 (params)
+    expect(getCheckboxListTileRenderer(), paints..path(color: const Color(0xFF000000)));
   });
 
   testWidgets('CheckboxListTile activeColor test', (WidgetTester tester) async {
-    Widget buildFrame(Color themeColor, Color activeColor) {
+    Widget buildFrame(Color? themeColor, Color? activeColor) {
       return wrap(
         child: Theme(
           data: ThemeData(toggleableActiveColor: themeColor),
           child: CheckboxListTile(
             value: true,
             activeColor: activeColor,
-            onChanged: (bool value) {},
+            onChanged: (bool? value) {},
           ),
         ),
       );
@@ -78,11 +76,11 @@ void main() {
 
     await tester.pumpWidget(buildFrame(const Color(0xFF000000), null));
     await tester.pumpAndSettle();
-    expect(getCheckboxListTileRenderer(), paints..rrect(color: const Color(0xFF000000))); // paints's color is 0xFF000000 (theme)
+    expect(getCheckboxListTileRenderer(), paints..rrect(color: const Color(0xFF000000)));
 
     await tester.pumpWidget(buildFrame(const Color(0xFF000000), const Color(0xFFFFFFFF)));
     await tester.pumpAndSettle();
-    expect(getCheckboxListTileRenderer(), paints..rrect(color: const Color(0xFFFFFFFF))); // paints's color is 0xFFFFFFFF (params)
+    expect(getCheckboxListTileRenderer(), paints..rrect(color: const Color(0xFFFFFFFF)));
   });
 
   testWidgets('CheckboxListTile can autofocus unless disabled.', (WidgetTester tester) async {
@@ -100,7 +98,7 @@ void main() {
     );
 
     await tester.pump();
-    expect(Focus.of(childKey.currentContext, nullOk: true).hasPrimaryFocus, isTrue);
+    expect(Focus.of(childKey.currentContext!, nullOk: true)!.hasPrimaryFocus, isTrue);
 
     await tester.pumpWidget(
       wrap(
@@ -114,7 +112,7 @@ void main() {
     );
 
     await tester.pump();
-    expect(Focus.of(childKey.currentContext, nullOk: true).hasPrimaryFocus, isFalse);
+    expect(Focus.of(childKey.currentContext!, nullOk: true)!.hasPrimaryFocus, isFalse);
   });
 
   testWidgets('CheckboxListTile contentPadding test', (WidgetTester tester) async {
@@ -148,7 +146,7 @@ void main() {
   });
 
   testWidgets('CheckboxListTile tristate test', (WidgetTester tester) async {
-    bool _value = false;
+    bool? _value = false;
     bool _tristate = false;
 
     await tester.pumpWidget(
@@ -160,7 +158,7 @@ void main() {
                 title: const Text('Title'),
                 tristate: _tristate,
                 value: _value,
-                onChanged: (bool value) {
+                onChanged: (bool? value) {
                   setState(() {
                     _value = value;
                   });

packages/flutter/test/material/checkbox_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';
@@ -30,7 +28,7 @@ void main() {
             child: Center(
               child: Checkbox(
                 value: true,
-                onChanged: (bool newValue) { },
+                onChanged: (bool? newValue) { },
               ),
             ),
           ),
@@ -49,7 +47,7 @@ void main() {
             child: Center(
               child: Checkbox(
                 value: true,
-                onChanged: (bool newValue) { },
+                onChanged: (bool? newValue) { },
               ),
             ),
           ),
@@ -66,7 +64,7 @@ void main() {
     await tester.pumpWidget(Material(
       child: Checkbox(
         value: false,
-        onChanged: (bool b) { },
+        onChanged: (bool? b) { },
       ),
     ));
 
@@ -81,7 +79,7 @@ void main() {
     await tester.pumpWidget(Material(
       child: Checkbox(
         value: true,
-        onChanged: (bool b) { },
+        onChanged: (bool? b) { },
       ),
     ));
 
@@ -139,7 +137,7 @@ void main() {
         textDirection: TextDirection.ltr,
         child: Checkbox(
           value: false,
-          onChanged: (bool b) { },
+          onChanged: (bool? b) { },
         ),
       ),
     ));
@@ -157,7 +155,7 @@ void main() {
   });
 
   testWidgets('CheckBox tristate: true', (WidgetTester tester) async {
-    bool checkBoxValue;
+    bool? checkBoxValue;
 
     await tester.pumpWidget(
       Material(
@@ -166,7 +164,7 @@ void main() {
             return Checkbox(
               tristate: true,
               value: checkBoxValue,
-              onChanged: (bool value) {
+              onChanged: (bool? value) {
                 setState(() {
                   checkBoxValue = value;
                 });
@@ -207,7 +205,7 @@ void main() {
         child: Checkbox(
           tristate: true,
           value: null,
-          onChanged: (bool newValue) { },
+          onChanged: (bool? newValue) { },
         ),
       ),
     );
@@ -227,7 +225,7 @@ void main() {
         child: Checkbox(
           tristate: true,
           value: true,
-          onChanged: (bool newValue) { },
+          onChanged: (bool? newValue) { },
         ),
       ),
     );
@@ -248,7 +246,7 @@ void main() {
         child: Checkbox(
           tristate: true,
           value: false,
-          onChanged: (bool newValue) { },
+          onChanged: (bool? newValue) { },
         ),
       ),
     );
@@ -268,7 +266,7 @@ void main() {
 
   testWidgets('has semantic events', (WidgetTester tester) async {
     dynamic semanticEvent;
-    bool checkboxValue = false;
+    bool? checkboxValue = false;
     SystemChannels.accessibility.setMockMessageHandler((dynamic message) async {
       semanticEvent = message;
     });
@@ -280,7 +278,7 @@ void main() {
           builder: (BuildContext context, StateSetter setState) {
             return Checkbox(
               value: checkboxValue,
-              onChanged: (bool value) {
+              onChanged: (bool? value) {
                 setState(() {
                   checkboxValue = value;
                 });
@@ -297,24 +295,24 @@ void main() {
     expect(checkboxValue, true);
     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);
 
     SystemChannels.accessibility.setMockMessageHandler(null);
     semanticsTester.dispose();
   });
 
   testWidgets('CheckBox tristate rendering, programmatic transitions', (WidgetTester tester) async {
-    Widget buildFrame(bool checkboxValue) {
+    Widget buildFrame(bool? checkboxValue) {
       return Material(
         child: StatefulBuilder(
           builder: (BuildContext context, StateSetter setState) {
             return Checkbox(
               tristate: true,
               value: checkboxValue,
-              onChanged: (bool value) { },
+              onChanged: (bool? value) { },
             );
           },
         ),
@@ -357,7 +355,7 @@ void main() {
   });
 
   testWidgets('CheckBox color rendering', (WidgetTester tester) async {
-    Widget buildFrame({Color activeColor, Color checkColor, ThemeData themeData}) {
+    Widget buildFrame({Color? activeColor, Color? checkColor, ThemeData? themeData}) {
       return Material(
         child: Theme(
           data: themeData ?? ThemeData(),
@@ -367,7 +365,7 @@ void main() {
                 value: true,
                 activeColor: activeColor,
                 checkColor: checkColor,
-                onChanged: (bool value) { },
+                onChanged: (bool? value) { },
               );
             },
           ),
@@ -401,7 +399,7 @@ void main() {
   testWidgets('Checkbox is focusable and has correct focus color', (WidgetTester tester) async {
     final FocusNode focusNode = FocusNode(debugLabel: 'Checkbox');
     tester.binding.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
-    bool value = true;
+    bool? value = true;
     Widget buildApp({bool enabled = true}) {
       return MaterialApp(
         home: Material(
@@ -409,7 +407,7 @@ void main() {
             child: StatefulBuilder(builder: (BuildContext context, StateSetter setState) {
               return Checkbox(
                 value: value,
-                onChanged: enabled ? (bool newValue) {
+                onChanged: enabled ? (bool? newValue) {
                   setState(() {
                     value = newValue;
                   });
@@ -474,7 +472,7 @@ void main() {
 
   testWidgets('Checkbox can be hovered and has correct hover color', (WidgetTester tester) async {
     tester.binding.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
-    bool value = true;
+    bool? value = true;
     Widget buildApp({bool enabled = true}) {
       return MaterialApp(
         home: Material(
@@ -482,7 +480,7 @@ void main() {
             child: StatefulBuilder(builder: (BuildContext context, StateSetter setState) {
               return Checkbox(
                 value: value,
-                onChanged: enabled ? (bool newValue) {
+                onChanged: enabled ? (bool? newValue) {
                   setState(() {
                     value = newValue;
                   });
@@ -539,7 +537,7 @@ void main() {
 
   testWidgets('Checkbox can be toggled by keyboard shortcuts', (WidgetTester tester) async {
     tester.binding.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
-    bool value = true;
+    bool? value = true;
     Widget buildApp({bool enabled = true}) {
       return MaterialApp(
         home: Material(
@@ -547,7 +545,7 @@ void main() {
             child: StatefulBuilder(builder: (BuildContext context, StateSetter setState) {
               return Checkbox(
                 value: value,
-                onChanged: enabled ? (bool newValue) {
+                onChanged: enabled ? (bool? newValue) {
                   setState(() {
                     value = newValue;
                   });
@@ -587,7 +585,7 @@ void main() {
               child: Checkbox(
                 visualDensity: visualDensity,
                 key: key,
-                onChanged: (bool value) {},
+                onChanged: (bool? value) {},
                 value: true,
               ),
             ),
@@ -616,7 +614,7 @@ void main() {
 
   testWidgets('Checkbox stops hover animation when removed from the tree.', (WidgetTester tester) async {
     const Key checkboxKey = Key('checkbox');
-    bool checkboxVal = true;
+    bool? checkboxVal = true;
 
     await tester.pumpWidget(
       Theme(
@@ -629,7 +627,7 @@ void main() {
                 builder: (_, StateSetter setState) => Checkbox(
                   key: checkboxKey,
                   value: checkboxVal,
-                  onChanged: (bool newValue) => setState(() {checkboxVal = newValue;}),
+                  onChanged: (bool? newValue) => setState(() {checkboxVal = newValue;}),
                 ),
               ),
             ),
@@ -696,7 +694,7 @@ 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(
@@ -718,7 +716,7 @@ 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(
@@ -740,7 +738,7 @@ void main() {
       ),
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.basic);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.basic);
 
     // Test cursor when tristate
     await tester.pumpWidget(
@@ -764,7 +762,7 @@ void main() {
       ),
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.grab);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.grab);
 
     await tester.pumpAndSettle();
   });

packages/flutter/test/material/chip_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' show window;
 
 import 'package:flutter/gestures.dart';
@@ -73,7 +71,7 @@ double getEnableProgress(WidgetTester tester) => getRenderChip(tester)?.enableAn
 
 /// Adds the basic requirements for a Chip.
 Widget _wrapForChip({
-  Widget child,
+  required Widget child,
   TextDirection textDirection = TextDirection.ltr,
   double textScaleFactor = 1.0,
   Brightness brightness = Brightness.light,
@@ -96,8 +94,8 @@ Widget _wrapForChip({
 /// cause the chip or label to exceed its constrained height.
 Future<void> _testConstrainedLabel(
   WidgetTester tester, {
-  CircleAvatar avatar,
-  VoidCallback onDeleted,
+  CircleAvatar? avatar,
+  VoidCallback? onDeleted,
 }) async {
   const double labelWidth = 100.0;
   const double labelHeight = 50.0;
@@ -134,7 +132,7 @@ Future<void> _testConstrainedLabel(
   expect(chipSize.height, chipParentHeight);
 }
 
-Widget _selectedInputChip({ Color checkmarkColor }) {
+Widget _selectedInputChip({ Color? checkmarkColor }) {
   return InputChip(
     label: const Text('InputChip'),
     selected: true,
@@ -143,7 +141,7 @@ Widget _selectedInputChip({ Color checkmarkColor }) {
   );
 }
 
-Widget _selectedFilterChip({ Color checkmarkColor }) {
+Widget _selectedFilterChip({ Color? checkmarkColor }) {
   return FilterChip(
     label: const Text('InputChip'),
     selected: true,
@@ -155,8 +153,8 @@ Widget _selectedFilterChip({ Color checkmarkColor }) {
 
 Future<void> _pumpCheckmarkChip(
   WidgetTester tester, {
-  @required Widget chip,
-  Color themeColor,
+  required Widget chip,
+  Color? themeColor,
   Brightness brightness = Brightness.light,
 }) async {
   await tester.pumpWidget(
@@ -191,9 +189,9 @@ void _expectCheckmarkColor(Finder finder, Color color) {
 }
 
 Widget _chipWithOptionalDeleteButton({
-  UniqueKey deleteButtonKey,
-  UniqueKey labelKey,
-  bool deletable,
+  UniqueKey? deleteButtonKey,
+  UniqueKey? labelKey,
+  required bool deletable,
   TextDirection textDirection = TextDirection.ltr,
 }){
   return _wrapForChip(
@@ -394,7 +392,7 @@ void main() {
     'the chip when it exceeds the available space',
     (WidgetTester tester) async {
       // Regression test for https://github.com/flutter/flutter/issues/11523
-      Widget chipBuilder (String text, {Widget avatar, VoidCallback onDeleted}) {
+      Widget chipBuilder (String text, {Widget? avatar, VoidCallback? onDeleted}) {
         return MaterialApp(
           home: Scaffold(
             body: Container(
@@ -770,7 +768,7 @@ void main() {
 
   testWidgets('Avatar drawer works as expected on RawChip', (WidgetTester tester) async {
     final GlobalKey labelKey = GlobalKey();
-    Future<void> pushChip({ Widget avatar }) async {
+    Future<void> pushChip({ Widget? avatar }) async {
       return tester.pumpWidget(
         _wrapForChip(
           child: Wrap(
@@ -1195,7 +1193,7 @@ void main() {
   testWidgets('Selection with avatar works as expected on RawChip', (WidgetTester tester) async {
     bool selected = false;
     final UniqueKey labelKey = UniqueKey();
-    Future<void> pushChip({ Widget avatar, bool selectable = false }) async {
+    Future<void> pushChip({ Widget? avatar, bool selectable = false }) async {
       return tester.pumpWidget(
         _wrapForChip(
           child: Wrap(
@@ -1241,7 +1239,7 @@ void main() {
     // Simulate a tap on the label to select the chip.
     await tester.tap(find.byKey(labelKey));
     expect(selected, equals(true));
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(2));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(2));
     await tester.pump();
     await tester.pump(const Duration(milliseconds: 50));
     expect(getSelectProgress(tester), moreOrLessEquals(0.002, epsilon: 0.01));
@@ -1259,7 +1257,7 @@ void main() {
     // Simulate another tap on the label to deselect the chip.
     await tester.tap(find.byKey(labelKey));
     expect(selected, equals(false));
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(2));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(2));
     await tester.pump();
     await tester.pump(const Duration(milliseconds: 20));
     expect(getSelectProgress(tester), moreOrLessEquals(0.875, epsilon: 0.01));
@@ -1317,7 +1315,7 @@ void main() {
     // Simulate a tap on the label to select the chip.
     await tester.tap(find.byKey(labelKey));
     expect(selected, equals(true));
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(2));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(2));
     await tester.pump();
     await tester.pump(const Duration(milliseconds: 50));
     expect(getSelectProgress(tester), moreOrLessEquals(0.002, epsilon: 0.01));
@@ -1335,7 +1333,7 @@ void main() {
     // Simulate another tap on the label to deselect the chip.
     await tester.tap(find.byKey(labelKey));
     expect(selected, equals(false));
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(2));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(2));
     await tester.pump();
     await tester.pump(const Duration(milliseconds: 20));
     expect(getSelectProgress(tester), moreOrLessEquals(0.875, epsilon: 0.01));
@@ -1354,7 +1352,7 @@ void main() {
   testWidgets('Activation works as expected on RawChip', (WidgetTester tester) async {
     bool selected = false;
     final UniqueKey labelKey = UniqueKey();
-    Future<void> pushChip({ Widget avatar, bool selectable = false }) async {
+    Future<void> pushChip({ Widget? avatar, bool selectable = false }) async {
       return tester.pumpWidget(
         _wrapForChip(
           child: Wrap(
@@ -1392,7 +1390,7 @@ void main() {
 
     await tester.tap(find.byKey(labelKey));
     expect(selected, equals(true));
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(2));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(2));
     await tester.pump();
     await tester.pump(const Duration(milliseconds: 50));
     expect(getSelectProgress(tester), moreOrLessEquals(0.002, epsilon: 0.01));
@@ -1484,9 +1482,9 @@ void main() {
     final ChipThemeData defaultChipTheme = themeData.chipTheme;
     bool value = false;
     Widget buildApp({
-      ChipThemeData chipTheme,
-      Widget avatar,
-      Widget deleteIcon,
+      ChipThemeData? chipTheme,
+      Widget? avatar,
+      Widget? deleteIcon,
       bool isSelectable = true,
       bool isPressable = false,
       bool isDeletable = true,
@@ -1506,7 +1504,7 @@ void main() {
                 avatar: avatar,
                 deleteIcon: deleteIcon,
                 isEnabled: isSelectable || isPressable,
-                shape: chipTheme.shape,
+                shape: chipTheme?.shape,
                 selected: isSelectable && value,
                 label: Text('$value'),
                 onSelected: isSelectable
@@ -2296,20 +2294,6 @@ void main() {
     expect(find.byType(InkWell), findsOneWidget);
   });
 
-  testWidgets('RawChip.selected can not be null', (WidgetTester tester) async {
-    expect(() async {
-      MaterialApp(
-        home: Material(
-          child: RawChip(
-            onPressed: () { },
-            selected: null,
-            label: const Text('Chip'),
-          ),
-        ),
-      );
-    }, throwsAssertionError);
-  });
-
   testWidgets('Chip uses stateful color for text color in different states', (WidgetTester tester) async {
     final FocusNode focusNode = FocusNode();
 
@@ -2355,7 +2339,7 @@ void main() {
       );
     }
     Color textColor() {
-      return tester.renderObject<RenderParagraph>(find.text('Chip')).text.style.color;
+      return tester.renderObject<RenderParagraph>(find.text('Chip')).text.style!.color!;
     }
 
     // Default, not disabled.

packages/flutter/test/material/chip_theme_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' show window;
 
 import 'package:flutter/gestures.dart';
@@ -171,7 +169,7 @@ void main() {
   testWidgets('ChipThemeData generates correct opacities for defaults', (WidgetTester tester) async {
     const Color customColor1 = Color(0xcafefeed);
     const Color customColor2 = Color(0xdeadbeef);
-    final TextStyle customStyle = ThemeData.fallback().textTheme.bodyText1.copyWith(color: customColor2);
+    final TextStyle customStyle = ThemeData.fallback().textTheme.bodyText1!.copyWith(color: customColor2);
 
     final ChipThemeData lightTheme = ChipThemeData.fromDefaults(
       secondaryColor: customColor1,
@@ -232,7 +230,7 @@ void main() {
     final ChipThemeData chipThemeBlack = ChipThemeData.fromDefaults(
       secondaryColor: Colors.black,
       brightness: Brightness.dark,
-      labelStyle: ThemeData.fallback().textTheme.bodyText1.copyWith(color: Colors.black),
+      labelStyle: ThemeData.fallback().textTheme.bodyText1!.copyWith(color: Colors.black),
     ).copyWith(
       elevation: 1.0,
       labelPadding: const EdgeInsets.symmetric(horizontal: 8.0),
@@ -244,7 +242,7 @@ void main() {
     final ChipThemeData chipThemeWhite = ChipThemeData.fromDefaults(
       secondaryColor: Colors.white,
       brightness: Brightness.light,
-      labelStyle: ThemeData.fallback().textTheme.bodyText1.copyWith(color: Colors.white),
+      labelStyle: ThemeData.fallback().textTheme.bodyText1!.copyWith(color: Colors.white),
     ).copyWith(
       padding: const EdgeInsets.all(2.0),
       labelPadding: const EdgeInsets.only(top: 8.0, bottom: 8.0),
@@ -255,7 +253,7 @@ void main() {
       checkmarkColor: Colors.white,
     );
 
-    final ChipThemeData lerp = ChipThemeData.lerp(chipThemeBlack, chipThemeWhite, 0.5);
+    final ChipThemeData lerp = ChipThemeData.lerp(chipThemeBlack, chipThemeWhite, 0.5)!;
     const Color middleGrey = Color(0xff7f7f7f);
     expect(lerp.backgroundColor, equals(middleGrey.withAlpha(0x1f)));
     expect(lerp.deleteIconColor, equals(middleGrey.withAlpha(0xde)));
@@ -276,7 +274,7 @@ void main() {
 
     expect(ChipThemeData.lerp(null, null, 0.25), isNull);
 
-    final ChipThemeData lerpANull25 = ChipThemeData.lerp(null, chipThemeWhite, 0.25);
+    final ChipThemeData lerpANull25 = ChipThemeData.lerp(null, chipThemeWhite, 0.25)!;
     expect(lerpANull25.backgroundColor, equals(Colors.black.withAlpha(0x08)));
     expect(lerpANull25.deleteIconColor, equals(Colors.black.withAlpha(0x38)));
     expect(lerpANull25.disabledColor, equals(Colors.black.withAlpha(0x03)));
@@ -294,7 +292,7 @@ void main() {
     expect(lerpANull25.pressElevation, 2.5);
     expect(lerpANull25.checkmarkColor, equals(Colors.white.withAlpha(0x40)));
 
-    final ChipThemeData lerpANull75 = ChipThemeData.lerp(null, chipThemeWhite, 0.75);
+    final ChipThemeData lerpANull75 = ChipThemeData.lerp(null, chipThemeWhite, 0.75)!;
     expect(lerpANull75.backgroundColor, equals(Colors.black.withAlpha(0x17)));
     expect(lerpANull75.deleteIconColor, equals(Colors.black.withAlpha(0xa7)));
     expect(lerpANull75.disabledColor, equals(Colors.black.withAlpha(0x09)));
@@ -312,7 +310,7 @@ void main() {
     expect(lerpANull75.pressElevation, 7.5);
     expect(lerpANull75.checkmarkColor, equals(Colors.white.withAlpha(0xbf)));
 
-    final ChipThemeData lerpBNull25 = ChipThemeData.lerp(chipThemeBlack, null, 0.25);
+    final ChipThemeData lerpBNull25 = ChipThemeData.lerp(chipThemeBlack, null, 0.25)!;
     expect(lerpBNull25.backgroundColor, equals(Colors.white.withAlpha(0x17)));
     expect(lerpBNull25.deleteIconColor, equals(Colors.white.withAlpha(0xa7)));
     expect(lerpBNull25.disabledColor, equals(Colors.white.withAlpha(0x09)));
@@ -330,7 +328,7 @@ void main() {
     expect(lerpBNull25.pressElevation, 3.0);
     expect(lerpBNull25.checkmarkColor, equals(Colors.black.withAlpha(0xbf)));
 
-    final ChipThemeData lerpBNull75 = ChipThemeData.lerp(chipThemeBlack, null, 0.75);
+    final ChipThemeData lerpBNull75 = ChipThemeData.lerp(chipThemeBlack, null, 0.75)!;
     expect(lerpBNull75.backgroundColor, equals(Colors.white.withAlpha(0x08)));
     expect(lerpBNull75.deleteIconColor, equals(Colors.white.withAlpha(0x38)));
     expect(lerpBNull75.disabledColor, equals(Colors.white.withAlpha(0x03)));
@@ -402,7 +400,7 @@ void main() {
       );
     }
     Color textColor() {
-      return tester.renderObject<RenderParagraph>(find.text('Chip')).text.style.color;
+      return tester.renderObject<RenderParagraph>(find.text('Chip')).text.style!.color!;
     }
 
     // Default, not disabled.

packages/flutter/test/material/circle_avatar_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:typed_data';
 
 import 'package:flutter/material.dart';
@@ -32,7 +30,7 @@ void main() {
     expect(decoration.color, equals(backgroundColor));
 
     final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
-    expect(paragraph.text.style.color, equals(ThemeData.fallback().primaryColorLight));
+    expect(paragraph.text.style!.color, equals(ThemeData.fallback().primaryColorLight));
   });
 
   testWidgets('CircleAvatar with light background color', (WidgetTester tester) async {
@@ -54,7 +52,7 @@ void main() {
     expect(decoration.color, equals(backgroundColor));
 
     final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
-    expect(paragraph.text.style.color, equals(ThemeData.fallback().primaryColorDark));
+    expect(paragraph.text.style!.color, equals(ThemeData.fallback().primaryColorDark));
   });
 
   testWidgets('CircleAvatar with image background', (WidgetTester tester) async {
@@ -71,7 +69,7 @@ void main() {
     expect(box.size, equals(const Size(100.0, 100.0)));
     final RenderDecoratedBox child = box.child as RenderDecoratedBox;
     final BoxDecoration decoration = child.decoration as BoxDecoration;
-    expect(decoration.image.fit, equals(BoxFit.cover));
+    expect(decoration.image!.fit, equals(BoxFit.cover));
   });
 
   testWidgets('CircleAvatar with foreground color', (WidgetTester tester) async {
@@ -94,7 +92,7 @@ void main() {
     expect(decoration.color, equals(fallback.primaryColorDark));
 
     final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
-    expect(paragraph.text.style.color, equals(foregroundColor));
+    expect(paragraph.text.style!.color, equals(foregroundColor));
   });
 
   testWidgets('CircleAvatar with light theme', (WidgetTester tester) async {
@@ -119,7 +117,7 @@ void main() {
     expect(decoration.color, equals(theme.primaryColorLight));
 
     final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
-    expect(paragraph.text.style.color, equals(theme.primaryTextTheme.headline6.color));
+    expect(paragraph.text.style!.color, equals(theme.primaryTextTheme.headline6!.color));
   });
 
   testWidgets('CircleAvatar with dark theme', (WidgetTester tester) async {
@@ -144,7 +142,7 @@ void main() {
     expect(decoration.color, equals(theme.primaryColorDark));
 
     final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
-    expect(paragraph.text.style.color, equals(theme.primaryTextTheme.headline6.color));
+    expect(paragraph.text.style!.color, equals(theme.primaryTextTheme.headline6!.color));
   });
 
   testWidgets('CircleAvatar text does not expand with textScaleFactor', (WidgetTester tester) async {
@@ -171,7 +169,7 @@ void main() {
           child: CircleAvatar(
             child: Builder(
               builder: (BuildContext context) {
-                final MediaQueryData data = MediaQuery.of(context);
+                final MediaQueryData data = MediaQuery.of(context)!;
 
                 // These should not change.
                 expect(data.size, equals(const Size(111.0, 111.0)));
@@ -211,7 +209,7 @@ void main() {
     expect(decoration.color, equals(backgroundColor));
 
     final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
-    expect(paragraph.text.style.color, equals(ThemeData.fallback().primaryColorLight));
+    expect(paragraph.text.style!.color, equals(ThemeData.fallback().primaryColorLight));
   });
 
   testWidgets('CircleAvatar respects maxRadius', (WidgetTester tester) async {
@@ -233,7 +231,7 @@ void main() {
     expect(decoration.color, equals(backgroundColor));
 
     final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
-    expect(paragraph.text.style.color, equals(ThemeData.fallback().primaryColorLight));
+    expect(paragraph.text.style!.color, equals(ThemeData.fallback().primaryColorLight));
   });
 
   testWidgets('CircleAvatar respects setting both minRadius and maxRadius', (WidgetTester tester) async {
@@ -256,11 +254,11 @@ void main() {
     expect(decoration.color, equals(backgroundColor));
 
     final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
-    expect(paragraph.text.style.color, equals(ThemeData.fallback().primaryColorLight));
+    expect(paragraph.text.style!.color, equals(ThemeData.fallback().primaryColorLight));
   });
 }
 
-Widget wrap({ Widget child }) {
+Widget wrap({ required Widget child }) {
   return Directionality(
     textDirection: TextDirection.ltr,
     child: MediaQuery(

packages/flutter/test/material/color_scheme_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/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/colors_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/material.dart';
 
 import '../flutter_test_alternative.dart';
@@ -31,16 +29,16 @@ void main() {
 
     expect(color.value, 500);
 
-    expect(color[50].value, 0x00000050);
-    expect(color[100].value, 0x00000100);
-    expect(color[200].value, 0x00000200);
-    expect(color[300].value, 0x00000300);
-    expect(color[400].value, 0x00000400);
-    expect(color[500].value, 0x00000500);
-    expect(color[600].value, 0x00000600);
-    expect(color[700].value, 0x00000700);
-    expect(color[800].value, 0x00000800);
-    expect(color[900].value, 0x00000900);
+    expect(color[50]!.value, 0x00000050);
+    expect(color[100]!.value, 0x00000100);
+    expect(color[200]!.value, 0x00000200);
+    expect(color[300]!.value, 0x00000300);
+    expect(color[400]!.value, 0x00000400);
+    expect(color[500]!.value, 0x00000500);
+    expect(color[600]!.value, 0x00000600);
+    expect(color[700]!.value, 0x00000700);
+    expect(color[800]!.value, 0x00000800);
+    expect(color[900]!.value, 0x00000900);
 
     expect(color.shade50.value, 0x00000050);
     expect(color.shade100.value, 0x00000100);
@@ -56,31 +54,31 @@ void main() {
 
   test('Colors swatches do not contain duplicates', () {
     for (final MaterialColor color in Colors.primaries)
-      expect(primaryKeys.map<Color>((int key) => color[key]).toSet().length, primaryKeys.length);
+      expect(primaryKeys.map<Color>((int key) => color[key]!).toSet().length, primaryKeys.length);
 
-    expect(primaryKeys.map<Color>((int key) => Colors.grey[key]).toSet().length, primaryKeys.length);
+    expect(primaryKeys.map<Color>((int key) => Colors.grey[key]!).toSet().length, primaryKeys.length);
 
     for (final MaterialAccentColor color in Colors.accents)
-      expect(accentKeys.map<Color>((int key) => color[key]).toSet().length, accentKeys.length);
+      expect(accentKeys.map<Color>((int key) => color[key]!).toSet().length, accentKeys.length);
   });
 
   test('All color swatch colors are opaque and equal their primary color', () {
     for (final MaterialColor color in Colors.primaries) {
       expect(color.value, color.shade500.value);
       for (final int key in primaryKeys) {
-        expect(color[key].alpha, 0xFF);
+        expect(color[key]!.alpha, 0xFF);
       }
     }
 
     expect(Colors.grey.value, Colors.grey.shade500.value);
     for (final int key in primaryKeys) {
-      expect(Colors.grey[key].alpha, 0xFF);
+      expect(Colors.grey[key]!.alpha, 0xFF);
     }
 
     for (final MaterialAccentColor color in Colors.accents) {
       expect(color.value, color.shade200.value);
       for (final int key in accentKeys) {
-        expect(color[key].alpha, 0xFF);
+        expect(color[key]!.alpha, 0xFF);
       }
     }
   });

packages/flutter/test/material/data_table_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:math' as math;
 
 import 'package:flutter/gestures.dart';
@@ -18,11 +16,11 @@ void main() {
   testWidgets('DataTable control test', (WidgetTester tester) async {
     final List<String> log = <String>[];
 
-    Widget buildTable({ int sortColumnIndex, bool sortAscending = true }) {
+    Widget buildTable({ int? sortColumnIndex, bool sortAscending = true }) {
       return DataTable(
         sortColumnIndex: sortColumnIndex,
         sortAscending: sortAscending,
-        onSelectAll: (bool value) {
+        onSelectAll: (bool? value) {
           log.add('select-all: $value');
         },
         columns: <DataColumn>[
@@ -42,7 +40,7 @@ void main() {
         rows: kDesserts.map<DataRow>((Dessert dessert) {
           return DataRow(
             key: ValueKey<String>(dessert.name),
-            onSelectChanged: (bool selected) {
+            onSelectChanged: (bool? selected) {
               log.add('row-selected: ${dessert.name}');
             },
             cells: <DataCell>[
@@ -112,7 +110,7 @@ void main() {
     Widget buildTable({ bool checkboxes = false }) {
       return DataTable(
         showCheckboxColumn: checkboxes,
-        onSelectAll: (bool value) {
+        onSelectAll: (bool? value) {
           log.add('select-all: $value');
         },
         columns: const <DataColumn>[
@@ -129,7 +127,7 @@ void main() {
         rows: kDesserts.map<DataRow>((Dessert dessert) {
           return DataRow(
             key: ValueKey<String>(dessert.name),
-            onSelectChanged: (bool selected) {
+            onSelectChanged: (bool? selected) {
               log.add('row-selected: ${dessert.name}');
             },
             cells: <DataCell>[
@@ -395,7 +393,7 @@ void main() {
 
   testWidgets('DataTable custom row height', (WidgetTester tester) async {
     Widget buildCustomTable({
-      int sortColumnIndex,
+      int? sortColumnIndex,
       bool sortAscending = true,
       double dataRowHeight = 48.0,
       double headingRowHeight = 56.0,
@@ -403,7 +401,7 @@ void main() {
       return DataTable(
         sortColumnIndex: sortColumnIndex,
         sortAscending: sortAscending,
-        onSelectAll: (bool value) {},
+        onSelectAll: (bool? value) {},
         dataRowHeight: dataRowHeight,
         headingRowHeight: headingRowHeight,
         columns: <DataColumn>[
@@ -421,7 +419,7 @@ void main() {
         rows: kDesserts.map<DataRow>((Dessert dessert) {
           return DataRow(
             key: ValueKey<String>(dessert.name),
-            onSelectChanged: (bool selected) {},
+            onSelectChanged: (bool? selected) {},
             cells: <DataCell>[
               DataCell(
                 Text(dessert.name),
@@ -441,7 +439,7 @@ void main() {
     await tester.pumpWidget(MaterialApp(
       home: Material(
         child: DataTable(
-          onSelectAll: (bool value) {},
+          onSelectAll: (bool? value) {},
           columns: <DataColumn>[
             const DataColumn(
               label: Text('Name'),
@@ -457,7 +455,7 @@ void main() {
           rows: kDesserts.map<DataRow>((Dessert dessert) {
             return DataRow(
               key: ValueKey<String>(dessert.name),
-              onSelectChanged: (bool selected) {},
+              onSelectChanged: (bool? selected) {},
               cells: <DataCell>[
                 DataCell(
                   Text(dessert.name),
@@ -520,13 +518,13 @@ void main() {
     Finder padding;
 
     Widget buildDefaultTable({
-      int sortColumnIndex,
+      int? sortColumnIndex,
       bool sortAscending = true,
     }) {
       return DataTable(
         sortColumnIndex: sortColumnIndex,
         sortAscending: sortAscending,
-        onSelectAll: (bool value) {},
+        onSelectAll: (bool? value) {},
         columns: <DataColumn>[
           const DataColumn(
             label: Text('Name'),
@@ -548,7 +546,7 @@ void main() {
         rows: kDesserts.map<DataRow>((Dessert dessert) {
           return DataRow(
             key: ValueKey<String>(dessert.name),
-            onSelectChanged: (bool selected) {},
+            onSelectChanged: (bool? selected) {},
             cells: <DataCell>[
               DataCell(
                 Text(dessert.name),
@@ -623,15 +621,15 @@ void main() {
     );
 
     Widget buildCustomTable({
-      int sortColumnIndex,
+      int? sortColumnIndex,
       bool sortAscending = true,
-      double horizontalMargin,
-      double columnSpacing,
+      double? horizontalMargin,
+      double? columnSpacing,
     }) {
       return DataTable(
         sortColumnIndex: sortColumnIndex,
         sortAscending: sortAscending,
-        onSelectAll: (bool value) {},
+        onSelectAll: (bool? value) {},
         horizontalMargin: horizontalMargin,
         columnSpacing: columnSpacing,
         columns: <DataColumn>[
@@ -655,7 +653,7 @@ void main() {
         rows: kDesserts.map<DataRow>((Dessert dessert) {
           return DataRow(
             key: ValueKey<String>(dessert.name),
-            onSelectChanged: (bool selected) {},
+            onSelectChanged: (bool? selected) {},
             cells: <DataCell>[
               DataCell(
                 Text(dessert.name),
@@ -742,7 +740,7 @@ void main() {
     Finder padding;
 
     Widget buildDefaultTable({
-      int sortColumnIndex,
+      int? sortColumnIndex,
       bool sortAscending = true,
     }) {
       return DataTable(
@@ -831,10 +829,10 @@ void main() {
     );
 
     Widget buildCustomTable({
-      int sortColumnIndex,
+      int? sortColumnIndex,
       bool sortAscending = true,
-      double horizontalMargin,
-      double columnSpacing,
+      double? horizontalMargin,
+      double? columnSpacing,
     }) {
       return DataTable(
         sortColumnIndex: sortColumnIndex,
@@ -959,7 +957,7 @@ void main() {
     Table table = tester.widget(find.byType(Table));
     TableRow tableRow = table.children.last;
     BoxDecoration boxDecoration = tableRow.decoration as BoxDecoration;
-    expect(boxDecoration.border.top.width, 1.0);
+    expect(boxDecoration.border!.top.width, 1.0);
 
     const double thickness =  4.2;
     await tester.pumpWidget(
@@ -976,7 +974,7 @@ void main() {
     table = tester.widget(find.byType(Table));
     tableRow = table.children.last;
     boxDecoration = tableRow.decoration as BoxDecoration;
-    expect(boxDecoration.border.top.width, thickness);
+    expect(boxDecoration.border!.top.width, thickness);
   });
 
   testWidgets('DataTable set show bottom border', (WidgetTester tester) async {
@@ -1010,7 +1008,7 @@ void main() {
     Table table = tester.widget(find.byType(Table));
     TableRow tableRow = table.children.last;
     BoxDecoration boxDecoration = tableRow.decoration as BoxDecoration;
-    expect(boxDecoration.border.bottom.width, 1.0);
+    expect(boxDecoration.border!.bottom.width, 1.0);
 
     await tester.pumpWidget(
       MaterialApp(
@@ -1025,11 +1023,11 @@ void main() {
     table = tester.widget(find.byType(Table));
     tableRow = table.children.last;
     boxDecoration = tableRow.decoration as BoxDecoration;
-    expect(boxDecoration.border.bottom.width, 0.0);
+    expect(boxDecoration.border!.bottom.width, 0.0);
   });
 
   testWidgets('DataTable column heading cell - with and without sorting', (WidgetTester tester) async {
-    Widget buildTable({ int sortColumnIndex, bool sortEnabled = true }) {
+    Widget buildTable({ int? sortColumnIndex, bool sortEnabled = true }) {
       return DataTable(
         sortColumnIndex: sortColumnIndex,
         columns: <DataColumn>[
@@ -1098,7 +1096,7 @@ void main() {
     // Regression test for a bug described in
     // https://github.com/flutter/flutter/pull/43735#issuecomment-589459947
     // Filed at https://github.com/flutter/flutter/issues/51152
-    Widget buildTable({ int sortColumnIndex }) {
+    Widget buildTable({ int? sortColumnIndex }) {
       return DataTable(
         sortColumnIndex: sortColumnIndex,
         columns: <DataColumn>[
@@ -1208,7 +1206,7 @@ void main() {
               cells: const <DataCell>[
                 DataCell(Text('Content1')),
               ],
-              onSelectChanged: (bool value) {},
+              onSelectChanged: (bool? value) {},
             ),
             DataRow(
               color: MaterialStateProperty.resolveWith<Color>(
@@ -1221,7 +1219,7 @@ void main() {
               cells: const <DataCell>[
                 DataCell(Text('Content2')),
               ],
-              onSelectChanged: disabled ? null : (bool value) {},
+              onSelectChanged: disabled ? null : (bool? value) {},
             ),
           ],
         ),
@@ -1263,7 +1261,7 @@ void main() {
                 return Colors.transparent;
               },
             ),
-            onSelectChanged: (bool value) {},
+            onSelectChanged: (bool? value) {},
             cells: const <DataCell>[
               DataCell(Text('Content1')),
             ],

packages/flutter/test/material/data_table_theme_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/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -135,15 +133,15 @@ void main() {
       ),
     );
 
-    final TextStyle dataRowTextStyle = tester.renderObject<RenderParagraph>(find.text('Data')).text.style;
+    final TextStyle dataRowTextStyle = tester.renderObject<RenderParagraph>(find.text('Data')).text.style!;
     expect(dataRowTextStyle.fontSize, dataTextStyle.fontSize);
     expect(_tableRowBoxDecoration(tester: tester, index: 1).color, dataRowColor.resolve(<MaterialState>{}));
-    expect(_tableRowBoxDecoration(tester: tester, index: 1).border.top.width, dividerThickness);
+    expect(_tableRowBoxDecoration(tester: tester, index: 1).border!.top.width, dividerThickness);
 
     final Finder dataRowContainer = find.ancestor(of: find.text('Data'), matching: find.byType(Container));
     expect(tester.getSize(dataRowContainer).height, dataRowHeight);
 
-    final TextStyle headingRowTextStyle = tester.renderObject<RenderParagraph>(find.text('A')).text.style;
+    final TextStyle headingRowTextStyle = tester.renderObject<RenderParagraph>(find.text('A')).text.style!;
     expect(headingRowTextStyle.fontSize, headingTextStyle.fontSize);
     expect(_tableRowBoxDecoration(tester: tester, index: 0).color, headingRowColor.resolve(<MaterialState>{}));
 
@@ -226,15 +224,15 @@ void main() {
       ),
     );
 
-    final TextStyle dataRowTextStyle = tester.renderObject<RenderParagraph>(find.text('Data')).text.style;
+    final TextStyle dataRowTextStyle = tester.renderObject<RenderParagraph>(find.text('Data')).text.style!;
     expect(dataRowTextStyle.fontSize, dataTextStyle.fontSize);
     expect(_tableRowBoxDecoration(tester: tester, index: 1).color, dataRowColor.resolve(<MaterialState>{}));
-    expect(_tableRowBoxDecoration(tester: tester, index: 1).border.top.width, dividerThickness);
+    expect(_tableRowBoxDecoration(tester: tester, index: 1).border!.top.width, dividerThickness);
 
     final Finder dataRowContainer = find.ancestor(of: find.text('Data'), matching: find.byType(Container));
     expect(tester.getSize(dataRowContainer).height, dataRowHeight);
 
-    final TextStyle headingRowTextStyle = tester.renderObject<RenderParagraph>(find.text('A')).text.style;
+    final TextStyle headingRowTextStyle = tester.renderObject<RenderParagraph>(find.text('A')).text.style!;
     expect(headingRowTextStyle.fontSize, headingTextStyle.fontSize);
     expect(_tableRowBoxDecoration(tester: tester, index: 0).color, headingRowColor.resolve(<MaterialState>{}));
 
@@ -245,7 +243,7 @@ void main() {
   });
 }
 
-BoxDecoration _tableRowBoxDecoration({WidgetTester tester, int index}) {
+BoxDecoration _tableRowBoxDecoration({required WidgetTester tester, required int index}) {
   final Table table = tester.widget(find.byType(Table));
   final TableRow tableRow = table.children[index];
   return tableRow.decoration as BoxDecoration;

packages/flutter/test/material/date_picker_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/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -12,7 +10,7 @@ import '../rendering/mock_canvas.dart';
 import 'feedback_tester.dart';
 
 class MockClipboard {
-  Object _clipboardData = <String, dynamic>{
+  dynamic _clipboardData = <String, dynamic>{
     'text': null,
   };
 
@@ -31,21 +29,21 @@ void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
   final MockClipboard mockClipboard = MockClipboard();
 
-  DateTime firstDate;
-  DateTime lastDate;
-  DateTime initialDate;
-  DateTime today;
-  SelectableDayPredicate selectableDayPredicate;
-  DatePickerEntryMode initialEntryMode;
-  DatePickerMode initialCalendarMode;
-
-  String cancelText;
-  String confirmText;
-  String errorFormatText;
-  String errorInvalidText;
-  String fieldHintText;
-  String fieldLabelText;
-  String helpText;
+  late DateTime firstDate;
+  late DateTime lastDate;
+  late DateTime initialDate;
+  late DateTime today;
+  late SelectableDayPredicate? selectableDayPredicate;
+  late DatePickerEntryMode initialEntryMode;
+  late DatePickerMode initialCalendarMode;
+
+  String? cancelText;
+  String? confirmText;
+  String? errorFormatText;
+  String? errorInvalidText;
+  String? fieldHintText;
+  String? fieldLabelText;
+  String? helpText;
 
   final Finder nextMonthIcon = find.byWidgetPredicate((Widget w) => w is IconButton && (w.tooltip?.startsWith('Next month') ?? false));
   final Finder previousMonthIcon = find.byWidgetPredicate((Widget w) => w is IconButton && (w.tooltip?.startsWith('Previous month') ?? false));
@@ -88,7 +86,7 @@ void main() {
     Future<void> callback(Future<DateTime> date),
     { TextDirection textDirection = TextDirection.ltr }
   ) async {
-    BuildContext buttonContext;
+    late BuildContext buttonContext;
     await tester.pumpWidget(MaterialApp(
       home: Material(
         child: Builder(
@@ -123,10 +121,10 @@ void main() {
       fieldHintText: fieldHintText,
       fieldLabelText: fieldLabelText,
       helpText: helpText,
-      builder: (BuildContext context, Widget child) {
+      builder: (BuildContext context, Widget? child) {
         return Directionality(
           textDirection: textDirection,
-          child: child,
+          child: child ?? const SizedBox(),
         );
       },
     );
@@ -141,9 +139,9 @@ void main() {
       confirmText = 'yep';
       helpText = 'help';
       await prepareDatePicker(tester, (Future<DateTime> date) async {
-        expect(find.text(cancelText), findsOneWidget);
-        expect(find.text(confirmText), findsOneWidget);
-        expect(find.text(helpText), findsOneWidget);
+        expect(find.text(cancelText!), findsOneWidget);
+        expect(find.text(confirmText!), findsOneWidget);
+        expect(find.text(helpText!), findsOneWidget);
       });
     });
 
@@ -219,10 +217,10 @@ void main() {
                         initialDate: DateTime.now(),
                         firstDate: DateTime(2018),
                         lastDate: DateTime(2030),
-                        builder: (BuildContext context, Widget child) {
+                        builder: (BuildContext context, Widget? child) {
                           return Directionality(
                             textDirection: textDirection,
-                            child: child,
+                            child: child ?? const SizedBox(),
                           );
                         },
                       );
@@ -273,7 +271,7 @@ void main() {
                       initialDate: DateTime.now(),
                       firstDate: DateTime(2018),
                       lastDate: DateTime(2030),
-                      builder: (BuildContext context, Widget child) => const SizedBox(),
+                      builder: (BuildContext context, Widget? child) => const SizedBox(),
                     );
                   },
                   child: const Text('Show Date Picker'),
@@ -377,10 +375,10 @@ void main() {
                          initialDate: DateTime(2016, DateTime.january, 15),
                          firstDate:DateTime(2001, DateTime.january, 1),
                          lastDate: DateTime(2031, DateTime.december, 31),
-                         builder: (BuildContext context, Widget child) {
+                         builder: (BuildContext context, Widget? child) {
                            return Directionality(
                              textDirection: textDirection,
-                             child: child,
+                             child: child ?? const SizedBox(),
                            );
                          },
                        );
@@ -670,11 +668,11 @@ void main() {
       fieldLabelText = 'label';
       helpText = 'help';
       await prepareDatePicker(tester, (Future<DateTime> date) async {
-        expect(find.text(cancelText), findsOneWidget);
-        expect(find.text(confirmText), findsOneWidget);
-        expect(find.text(fieldHintText), findsOneWidget);
-        expect(find.text(fieldLabelText), findsOneWidget);
-        expect(find.text(helpText), findsOneWidget);
+        expect(find.text(cancelText!), findsOneWidget);
+        expect(find.text(confirmText!), findsOneWidget);
+        expect(find.text(fieldHintText!), findsOneWidget);
+        expect(find.text(fieldLabelText!), findsOneWidget);
+        expect(find.text(helpText!), findsOneWidget);
       });
     });
 
@@ -697,7 +695,7 @@ void main() {
     testWidgets('Toggle to calendar mode keeps selected date', (WidgetTester tester) async {
       await prepareDatePicker(tester, (Future<DateTime> date) async {
         final TextField field = textField(tester);
-        field.controller.clear();
+        field.controller!.clear();
 
         await tester.enterText(find.byType(TextField), '12/25/2016');
         await tester.tap(find.byIcon(Icons.calendar_today));
@@ -710,7 +708,7 @@ void main() {
     testWidgets('Entered text returns date', (WidgetTester tester) async {
       await prepareDatePicker(tester, (Future<DateTime> date) async {
         final TextField field = textField(tester);
-        field.controller.clear();
+        field.controller!.clear();
 
         await tester.enterText(find.byType(TextField), '12/25/2016');
         await tester.tap(find.text('OK'));
@@ -722,15 +720,15 @@ void main() {
       errorFormatText = 'oops';
       await prepareDatePicker(tester, (Future<DateTime> date) async {
         final TextField field = textField(tester);
-        field.controller.clear();
+        field.controller!.clear();
 
         await tester.pumpAndSettle();
         await tester.enterText(find.byType(TextField), '1225');
-        expect(find.text(errorFormatText), findsNothing);
+        expect(find.text(errorFormatText!), findsNothing);
 
         await tester.tap(find.text('OK'));
         await tester.pumpAndSettle();
-        expect(find.text(errorFormatText), findsOneWidget);
+        expect(find.text(errorFormatText!), findsOneWidget);
       });
     });
 
@@ -738,16 +736,16 @@ void main() {
       errorFormatText = 'oops';
       await prepareDatePicker(tester, (Future<DateTime> date) async {
         final TextField field = textField(tester);
-        field.controller.clear();
+        field.controller!.clear();
 
         await tester.pumpAndSettle();
         await tester.enterText(find.byType(TextField), '20 days, 3 months, 2003');
         expect(find.text('20 days, 3 months, 2003'), findsOneWidget);
-        expect(find.text(errorFormatText), findsNothing);
+        expect(find.text(errorFormatText!), findsNothing);
 
         await tester.tap(find.text('OK'));
         await tester.pumpAndSettle();
-        expect(find.text(errorFormatText), findsOneWidget);
+        expect(find.text(errorFormatText!), findsOneWidget);
       });
     });
 
@@ -755,20 +753,20 @@ void main() {
       errorInvalidText = 'oops';
       await prepareDatePicker(tester, (Future<DateTime> date) async {
         final TextField field = textField(tester);
-        field.controller.clear();
+        field.controller!.clear();
 
         await tester.pumpAndSettle();
         await tester.enterText(find.byType(TextField), '08/10/1969');
-        expect(find.text(errorInvalidText), findsNothing);
+        expect(find.text(errorInvalidText!), findsNothing);
 
         await tester.tap(find.text('OK'));
         await tester.pumpAndSettle();
-        expect(find.text(errorInvalidText), findsOneWidget);
+        expect(find.text(errorInvalidText!), findsOneWidget);
       });
     });
 
     testWidgets('InputDecorationTheme is honored', (WidgetTester tester) async {
-      BuildContext buttonContext;
+      late BuildContext buttonContext;
       const InputBorder border = InputBorder.none;
       await tester.pumpWidget(MaterialApp(
         theme: ThemeData.light().copyWith(
@@ -883,7 +881,7 @@ void main() {
 
   group('Haptic feedback', () {
     const Duration hapticFeedbackInterval = Duration(milliseconds: 10);
-    FeedbackTester feedback;
+    late FeedbackTester feedback;
 
     setUp(() {
       feedback = FeedbackTester();
@@ -895,7 +893,7 @@ void main() {
     });
 
     tearDown(() {
-      feedback?.dispose();
+      feedback.dispose();
     });
 
     testWidgets('Selecting date vibrates', (WidgetTester tester) async {
@@ -1523,7 +1521,7 @@ class _DatePickerObserver extends NavigatorObserver {
   int datePickerCount = 0;
 
   @override
-  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+  void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) {
     if (route.toString().contains('_DialogRoute')) {
       datePickerCount++;
     }

packages/flutter/test/material/date_range_picker_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/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -11,23 +9,23 @@ import 'package:flutter_test/flutter_test.dart';
 import 'feedback_tester.dart';
 
 void main() {
-  DateTime firstDate;
-  DateTime lastDate;
-  DateTime currentDate;
-  DateTimeRange initialDateRange;
-  DatePickerEntryMode initialEntryMode = DatePickerEntryMode.calendar;
-
-  String cancelText;
-  String confirmText;
-  String errorInvalidRangeText;
-  String errorFormatText;
-  String errorInvalidText;
-  String fieldStartHintText;
-  String fieldEndHintText;
-  String fieldStartLabelText;
-  String fieldEndLabelText;
-  String helpText;
-  String saveText;
+  late DateTime firstDate;
+  late DateTime lastDate;
+  late DateTime? currentDate;
+  late DateTimeRange? initialDateRange;
+  late DatePickerEntryMode initialEntryMode = DatePickerEntryMode.calendar;
+
+  String? cancelText;
+  String? confirmText;
+  String? errorInvalidRangeText;
+  String? errorFormatText;
+  String? errorInvalidText;
+  String? fieldStartHintText;
+  String? fieldEndHintText;
+  String? fieldStartLabelText;
+  String? fieldEndLabelText;
+  String? helpText;
+  String? saveText;
 
   setUp(() {
     firstDate = DateTime(2015, DateTime.january, 1);
@@ -57,7 +55,7 @@ void main() {
     Future<void> callback(Future<DateTimeRange> date),
     { TextDirection textDirection = TextDirection.ltr }
   ) async {
-    BuildContext buttonContext;
+    late BuildContext buttonContext;
     await tester.pumpWidget(MaterialApp(
       home: Material(
         child: Builder(
@@ -94,10 +92,10 @@ void main() {
       fieldEndLabelText: fieldEndLabelText,
       helpText: helpText,
       saveText: saveText,
-      builder: (BuildContext context, Widget child) {
+      builder: (BuildContext context, Widget? child) {
         return Directionality(
           textDirection: textDirection,
-          child: child,
+          child: child ?? const SizedBox(),
         );
       },
     );
@@ -110,8 +108,8 @@ void main() {
     helpText = 'help';
     saveText = 'make it so';
     await preparePicker(tester, (Future<DateTimeRange> range) async {
-      expect(find.text(helpText), findsOneWidget);
-      expect(find.text(saveText), findsOneWidget);
+      expect(find.text(helpText!), findsOneWidget);
+      expect(find.text(saveText!), findsOneWidget);
     });
   });
 
@@ -316,10 +314,10 @@ void main() {
                        context: context,
                        firstDate:DateTime(2001, DateTime.january, 1),
                        lastDate: DateTime(2031, DateTime.december, 31),
-                       builder: (BuildContext context, Widget child) {
+                       builder: (BuildContext context, Widget? child) {
                          return Directionality(
                            textDirection: textDirection,
-                           child: child,
+                           child: child ?? const SizedBox(),
                          );
                        },
                      );
@@ -360,7 +358,7 @@ void main() {
 
   group('Haptic feedback', () {
     const Duration hapticFeedbackInterval = Duration(milliseconds: 10);
-    FeedbackTester feedback;
+    late FeedbackTester feedback;
 
     setUp(() {
       feedback = FeedbackTester();
@@ -373,7 +371,7 @@ void main() {
     });
 
     tearDown(() {
-      feedback?.dispose();
+      feedback.dispose();
     });
 
     testWidgets('Selecting dates vibrates', (WidgetTester tester) async {
@@ -606,13 +604,13 @@ void main() {
       fieldEndLabelText = 'label2';
       helpText = 'help';
       await preparePicker(tester, (Future<DateTimeRange> range) async {
-        expect(find.text(cancelText), findsOneWidget);
-        expect(find.text(confirmText), findsOneWidget);
-        expect(find.text(fieldStartHintText), findsOneWidget);
-        expect(find.text(fieldEndHintText), findsOneWidget);
-        expect(find.text(fieldStartLabelText), findsOneWidget);
-        expect(find.text(fieldEndLabelText), findsOneWidget);
-        expect(find.text(helpText), findsOneWidget);
+        expect(find.text(cancelText!), findsOneWidget);
+        expect(find.text(confirmText!), findsOneWidget);
+        expect(find.text(fieldStartHintText!), findsOneWidget);
+        expect(find.text(fieldEndHintText!), findsOneWidget);
+        expect(find.text(fieldStartLabelText!), findsOneWidget);
+        expect(find.text(fieldEndLabelText!), findsOneWidget);
+        expect(find.text(helpText!), findsOneWidget);
       });
     });
 
@@ -671,11 +669,11 @@ void main() {
       await preparePicker(tester, (Future<DateTimeRange> range) async {
         await tester.enterText(find.byType(TextField).at(0), '12/25');
         await tester.enterText(find.byType(TextField).at(1), '12/25');
-        expect(find.text(errorFormatText), findsNothing);
+        expect(find.text(errorFormatText!), findsNothing);
 
         await tester.tap(find.text('OK'));
         await tester.pumpAndSettle();
-        expect(find.text(errorFormatText), findsNWidgets(2));
+        expect(find.text(errorFormatText!), findsNWidgets(2));
       });
     });
 
@@ -685,11 +683,11 @@ void main() {
       await preparePicker(tester, (Future<DateTimeRange> range) async {
         await tester.enterText(find.byType(TextField).at(0), '20202014');
         await tester.enterText(find.byType(TextField).at(1), '20212014');
-        expect(find.text(errorFormatText), findsNothing);
+        expect(find.text(errorFormatText!), findsNothing);
 
         await tester.tap(find.text('OK'));
         await tester.pumpAndSettle();
-        expect(find.text(errorFormatText), findsNWidgets(2));
+        expect(find.text(errorFormatText!), findsNWidgets(2));
       });
     });
 
@@ -699,11 +697,11 @@ void main() {
       await preparePicker(tester, (Future<DateTimeRange> range) async {
         await tester.enterText(find.byType(TextField).at(0), '08/08/2014');
         await tester.enterText(find.byType(TextField).at(1), '08/08/2014');
-        expect(find.text(errorInvalidText), findsNothing);
+        expect(find.text(errorInvalidText!), findsNothing);
 
         await tester.tap(find.text('OK'));
         await tester.pumpAndSettle();
-        expect(find.text(errorInvalidText), findsNWidgets(2));
+        expect(find.text(errorInvalidText!), findsNWidgets(2));
       });
     });
 
@@ -713,11 +711,11 @@ void main() {
       await preparePicker(tester, (Future<DateTimeRange> range) async {
         await tester.enterText(find.byType(TextField).at(0), '12/27/2016');
         await tester.enterText(find.byType(TextField).at(1), '12/25/2016');
-        expect(find.text(errorInvalidRangeText), findsNothing);
+        expect(find.text(errorInvalidRangeText!), findsNothing);
 
         await tester.tap(find.text('OK'));
         await tester.pumpAndSettle();
-        expect(find.text(errorInvalidRangeText), findsOneWidget);
+        expect(find.text(errorInvalidRangeText!), findsOneWidget);
       });
     });
 
@@ -727,11 +725,11 @@ void main() {
       await preparePicker(tester, (Future<DateTimeRange> range) async {
         await tester.enterText(find.byType(TextField).at(0), '12/27/2016');
         await tester.enterText(find.byType(TextField).at(1), '01/01/2018');
-        expect(find.text(errorInvalidText), findsNothing);
+        expect(find.text(errorInvalidText!), findsNothing);
 
         await tester.tap(find.text('OK'));
         await tester.pumpAndSettle();
-        expect(find.text(errorInvalidText), findsOneWidget);
+        expect(find.text(errorInvalidText!), findsOneWidget);
       });
     });
 
@@ -768,7 +766,7 @@ void main() {
         expect(containerColor, equals(expectedContainerColor));
       }
 
-      BuildContext buttonContext;
+      late BuildContext buttonContext;
       const InputBorder border = InputBorder.none;
       await tester.pumpWidget(MaterialApp(
         theme: ThemeData.light().copyWith(

packages/flutter/test/material/debug_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/material.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -231,12 +229,12 @@ void main() {
       )
     ));
     final List<dynamic> exceptions = <dynamic>[];
-    final FlutterExceptionHandler oldHandler = FlutterError.onError;
+    final FlutterExceptionHandler? oldHandler = FlutterError.onError;
     FlutterError.onError = (FlutterErrorDetails details) {
       exceptions.add(details.exception);
     };
     // ScaffoldMessenger shows SnackBar.
-    _scaffoldMessengerKey.currentState.showSnackBar(snackBar);
+    _scaffoldMessengerKey.currentState!.showSnackBar(snackBar);
     await tester.pumpAndSettle();
 
     // Pump widget to rebuild without ScaffoldMessenger