[NNBD] Migrating some Material tests (#67689)

packages/flutter/test/material/dialog_theme_test.dart

@@ -2,13 +2,11 @@
 // 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';
 
-MaterialApp _appWithDialog(WidgetTester tester, Widget dialog, { ThemeData theme }) {
+MaterialApp _appWithDialog(WidgetTester tester, Widget dialog, { ThemeData? theme }) {
   return MaterialApp(
     theme: theme,
     home: Material(
@@ -40,7 +38,7 @@ Material _getMaterialFromDialog(WidgetTester tester) {
 }
 
 RenderParagraph _getTextRenderObject(WidgetTester tester, String text) {
-  return tester.element<StatelessElement>(find.text(text)).renderObject as RenderParagraph;
+  return tester.element<StatelessElement>(find.text(text)).renderObject! as RenderParagraph;
 }
 
 void main() {
@@ -184,7 +182,7 @@ void main() {
     await tester.pumpAndSettle();
 
     final RenderParagraph title = _getTextRenderObject(tester, titleText);
-    expect(title.text.style.color, titleTextStyle.color);
+    expect(title.text.style!.color, titleTextStyle.color);
   });
 
   testWidgets('Simple Dialog - Custom Title Text Style - Constructor Param', (WidgetTester tester) async {
@@ -232,7 +230,7 @@ void main() {
     await tester.pumpAndSettle();
 
     final RenderParagraph title = _getTextRenderObject(tester, titleText);
-    expect(title.text.style.color, titleTextStyle.color);
+    expect(title.text.style!.color, titleTextStyle.color);
   });
 
   testWidgets('Custom Content Text Style - Constructor Param', (WidgetTester tester) async {
@@ -283,6 +281,6 @@ void main() {
     await tester.pumpAndSettle();
 
     final RenderParagraph content = _getTextRenderObject(tester, contentText);
-    expect(content.text.style.color, contentTextStyle.color);
+    expect(content.text.style!.color, contentTextStyle.color);
   });
 }

packages/flutter/test/material/divider_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';
 import 'package:flutter/painting.dart';
@@ -22,8 +20,8 @@ void main() {
     final RenderBox box = tester.firstRenderObject(find.byType(Divider));
     expect(box.size.height, 16.0);
     final Container container = tester.widget(find.byType(Container));
-    final BoxDecoration decoration = container.decoration as BoxDecoration;
-    expect(decoration.border.bottom.width, 0.0);
+    final BoxDecoration decoration = container.decoration! as BoxDecoration;
+    expect(decoration.border!.bottom.width, 0.0);
   });
 
   testWidgets('Divider custom thickness', (WidgetTester tester) async {
@@ -38,8 +36,8 @@ void main() {
       ),
     );
     final Container container = tester.widget(find.byType(Container));
-    final BoxDecoration decoration = container.decoration as BoxDecoration;
-    expect(decoration.border.bottom.width, 5.0);
+    final BoxDecoration decoration = container.decoration! as BoxDecoration;
+    expect(decoration.border!.bottom.width, 5.0);
   });
 
   testWidgets('Horizontal divider custom indentation', (WidgetTester tester) async {
@@ -107,8 +105,8 @@ void main() {
     final RenderBox box = tester.firstRenderObject(find.byType(VerticalDivider));
     expect(box.size.width, 16.0);
     final Container container = tester.widget(find.byType(Container));
-    final BoxDecoration decoration = container.decoration as BoxDecoration;
-    final Border border = decoration.border as Border;
+    final BoxDecoration decoration = container.decoration! as BoxDecoration;
+    final Border border = decoration.border! as Border;
     expect(border.left.width, 0.0);
   });
 
@@ -124,8 +122,8 @@ void main() {
       ),
     );
     final Container container = tester.widget(find.byType(Container));
-    final BoxDecoration decoration = container.decoration as BoxDecoration;
-    final Border border = decoration.border as Border;
+    final BoxDecoration decoration = container.decoration! as BoxDecoration;
+    final Border border = decoration.border! as Border;
     expect(border.left.width, 5.0);
   });
 

packages/flutter/test/material/divider_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';
@@ -71,11 +69,11 @@ void main() {
       expect(box.size.height, 16.0);
 
       final Container container = tester.widget(find.byType(Container));
-      final BoxDecoration decoration = container.decoration as BoxDecoration;
-      expect(decoration.border.bottom.width, 0.0);
+      final BoxDecoration decoration = container.decoration! as BoxDecoration;
+      expect(decoration.border!.bottom.width, 0.0);
 
       final ThemeData theme = ThemeData();
-      expect(decoration.border.bottom.color, theme.dividerColor);
+      expect(decoration.border!.bottom.color, theme.dividerColor);
 
       final Rect dividerRect = tester.getRect(find.byType(Divider));
       final Rect lineRect = tester.getRect(find.byType(DecoratedBox));
@@ -96,14 +94,14 @@ void main() {
       expect(box.size.height, dividerTheme.space);
 
       final Container container = tester.widget(find.byType(Container));
-      final BoxDecoration decoration = container.decoration as BoxDecoration;
-      expect(decoration.border.bottom.width, dividerTheme.thickness);
-      expect(decoration.border.bottom.color, dividerTheme.color);
+      final BoxDecoration decoration = container.decoration! as BoxDecoration;
+      expect(decoration.border!.bottom.width, dividerTheme.thickness);
+      expect(decoration.border!.bottom.color, dividerTheme.color);
 
       final Rect dividerRect = tester.getRect(find.byType(Divider));
       final Rect lineRect = tester.getRect(find.byType(DecoratedBox));
-      expect(lineRect.left, dividerRect.left + dividerTheme.indent);
-      expect(lineRect.right, dividerRect.right - dividerTheme.endIndent);
+      expect(lineRect.left, dividerRect.left + dividerTheme.indent!);
+      expect(lineRect.right, dividerRect.right - dividerTheme.endIndent!);
     });
 
     testWidgets('Widget properties take priority over theme', (WidgetTester tester) async {
@@ -131,9 +129,9 @@ void main() {
       expect(box.size.height, height);
 
       final Container container = tester.widget(find.byType(Container));
-      final BoxDecoration decoration = container.decoration as BoxDecoration;
-      expect(decoration.border.bottom.width, thickness);
-      expect(decoration.border.bottom.color, color);
+      final BoxDecoration decoration = container.decoration! as BoxDecoration;
+      expect(decoration.border!.bottom.width, thickness);
+      expect(decoration.border!.bottom.color, color);
 
       final Rect dividerRect = tester.getRect(find.byType(Divider));
       final Rect lineRect = tester.getRect(find.byType(DecoratedBox));
@@ -154,8 +152,8 @@ void main() {
       expect(box.size.width, 16.0);
 
       final Container container = tester.widget(find.byType(Container));
-      final BoxDecoration decoration = container.decoration as BoxDecoration;
-      final Border border = decoration.border as Border;
+      final BoxDecoration decoration = container.decoration! as BoxDecoration;
+      final Border border = decoration.border! as Border;
       expect(border.left.width, 0.0);
 
       final ThemeData theme = ThemeData();
@@ -180,15 +178,15 @@ void main() {
       expect(box.size.width, dividerTheme.space);
 
       final Container container = tester.widget(find.byType(Container));
-      final BoxDecoration decoration = container.decoration as BoxDecoration;
-      final Border border = decoration.border as Border;
+      final BoxDecoration decoration = container.decoration! as BoxDecoration;
+      final Border border = decoration.border! as Border;
       expect(border.left.width, dividerTheme.thickness);
       expect(border.left.color, dividerTheme.color);
 
       final Rect dividerRect = tester.getRect(find.byType(VerticalDivider));
       final Rect lineRect = tester.getRect(find.byType(DecoratedBox));
-      expect(lineRect.top, dividerRect.top + dividerTheme.indent);
-      expect(lineRect.bottom, dividerRect.bottom - dividerTheme.endIndent);
+      expect(lineRect.top, dividerRect.top + dividerTheme.indent!);
+      expect(lineRect.bottom, dividerRect.bottom - dividerTheme.endIndent!);
     });
 
     testWidgets('Widget properties take priority over theme', (WidgetTester tester) async {
@@ -216,8 +214,8 @@ void main() {
       expect(box.size.width, width);
 
       final Container container = tester.widget(find.byType(Container));
-      final BoxDecoration decoration = container.decoration as BoxDecoration;
-      final Border border = decoration.border as Border;
+      final BoxDecoration decoration = container.decoration! as BoxDecoration;
+      final Border border = decoration.border! as Border;
       expect(border.left.width, thickness);
       expect(border.left.color, color);
 

packages/flutter/test/material/drawer_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/rendering.dart';
 import 'package:flutter/material.dart';
@@ -126,7 +124,7 @@ void main() {
     }
 
     final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
-    Widget buildFrame({ Color drawerScrimColor }) {
+    Widget buildFrame({ Color? drawerScrimColor }) {
       return MaterialApp(
         home: Scaffold(
           key: scaffoldKey,
@@ -147,7 +145,7 @@ void main() {
     // Default drawerScrimColor
 
     await tester.pumpWidget(buildFrame(drawerScrimColor: null));
-    scaffoldKey.currentState.openDrawer();
+    scaffoldKey.currentState!.openDrawer();
     await tester.pumpAndSettle();
 
     expect(getScrim().color, Colors.black54);
@@ -159,7 +157,7 @@ void main() {
     // Specific drawerScrimColor
 
     await tester.pumpWidget(buildFrame(drawerScrimColor: const Color(0xFF323232)));
-    scaffoldKey.currentState.openDrawer();
+    scaffoldKey.currentState!.openDrawer();
     await tester.pumpAndSettle();
 
     expect(getScrim().color, const Color(0xFF323232));

packages/flutter/test/material/dropdown_form_field_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 'dart:ui' show window;
 
@@ -14,7 +12,7 @@ import 'package:flutter/rendering.dart';
 import '../rendering/mock_canvas.dart';
 
 const List<String> menuItems = <String>['one', 'two', 'three', 'four'];
-final ValueChanged<String> onChanged = (_) { };
+final ValueChanged<String?> onChanged = (_) { };
 final Type dropdownButtonType = DropdownButton<String>(
   onChanged: (_) { },
   items: const <DropdownMenuItem<String>>[],
@@ -28,22 +26,22 @@ Finder _iconRichText(Key iconKey) {
 }
 
 Widget buildFormFrame({
-  Key buttonKey,
+  Key? buttonKey,
   AutovalidateMode autovalidateMode = AutovalidateMode.disabled,
   int elevation = 8,
-  String value = 'two',
-  ValueChanged<String> onChanged,
-  VoidCallback onTap,
-  Widget icon,
-  Color iconDisabledColor,
-  Color iconEnabledColor,
+  String? value = 'two',
+  ValueChanged<String?>? onChanged,
+  VoidCallback? onTap,
+  Widget? icon,
+  Color? iconDisabledColor,
+  Color? iconEnabledColor,
   double iconSize = 24.0,
   bool isDense = true,
   bool isExpanded = false,
-  Widget hint,
-  Widget disabledHint,
-  Widget underline,
-  List<String> items = menuItems,
+  Widget? hint,
+  Widget? disabledHint,
+  Widget? underline,
+  List<String>? items = menuItems,
   Alignment alignment = Alignment.center,
   TextDirection textDirection = TextDirection.ltr,
 }) {
@@ -112,15 +110,15 @@ class _TestAppState extends State<TestApp> {
 
 class TestApp extends StatefulWidget {
   const TestApp({
-    Key key,
-    this.textDirection,
-    this.child,
+    Key? key,
+    required this.textDirection,
+    required this.child,
     this.mediaSize,
   }) : super(key: key);
 
   final TextDirection textDirection;
   final Widget child;
-  final Size mediaSize;
+  final Size? mediaSize;
 
   @override
   _TestAppState createState() => _TestAppState();
@@ -129,7 +127,7 @@ class TestApp extends StatefulWidget {
 void verifyPaintedShadow(Finder customPaint, int elevation) {
   const Rect originalRectangle = Rect.fromLTRB(0.0, 0.0, 800, 208.0);
 
-  final List<BoxShadow> boxShadows = List<BoxShadow>.generate(3, (int index) => kElevationToShadow[elevation][index]);
+  final List<BoxShadow> boxShadows = List<BoxShadow>.generate(3, (int index) => kElevationToShadow[elevation]![index]);
   final List<RRect> rrects = List<RRect>.generate(3, (int index) {
     return RRect.fromRectAndRadius(
       originalRectangle.shift(
@@ -151,7 +149,7 @@ void verifyPaintedShadow(Finder customPaint, int elevation) {
 
 void main() {
   testWidgets('DropdownButtonFormField with autovalidation test', (WidgetTester tester) async {
-    String value = 'one';
+    String? value = 'one';
     int _validateCalled = 0;
 
     await tester.pumpWidget(
@@ -171,12 +169,12 @@ void main() {
                     child: Text(value),
                   );
                 }).toList(),
-                onChanged: (String newValue) {
+                onChanged: (String? newValue) {
                   setState(() {
                     value = newValue;
                   });
                 },
-                validator: (String currentValue) {
+                validator: (String? currentValue) {
                   _validateCalled++;
                   return currentValue == null ? 'Must select value' : null;
                 },
@@ -340,14 +338,14 @@ void main() {
       ),
     );
 
-    expect(richText.text.style.color, Colors.amber);
-    expect(richText.text.style.fontSize, 20.0);
+    expect(richText.text.style!.color, Colors.amber);
+    expect(richText.text.style!.fontSize, 20.0);
   });
 
   testWidgets('DropdownButtonFormField - disabledHint displays when the items list is empty, when items is null', (WidgetTester tester) async {
     final Key buttonKey = UniqueKey();
 
-    Widget build({ List<String> items }){
+    Widget build({ List<String>? items }){
       return buildFormFrame(
         items: items,
         buttonKey: buttonKey,
@@ -373,7 +371,7 @@ void main() {
     (WidgetTester tester) async {
       final Key buttonKey = UniqueKey();
 
-      Widget build({ List<String> items }){
+      Widget build({ List<String>? items }){
         return buildFormFrame(
           items: items,
           buttonKey: buttonKey,
@@ -395,7 +393,7 @@ void main() {
   testWidgets('DropdownButtonFormField - disabledHint is null by default', (WidgetTester tester) async {
     final Key buttonKey = UniqueKey();
 
-    Widget build({ List<String> items }){
+    Widget build({ List<String>? items }){
       return buildFormFrame(
         items: items,
         buttonKey: buttonKey,
@@ -415,7 +413,7 @@ void main() {
   testWidgets('DropdownButtonFormField - disabledHint is null by default', (WidgetTester tester) async {
     final Key buttonKey = UniqueKey();
 
-    Widget build({ List<String> items }){
+    Widget build({ List<String>? items }){
       return buildFormFrame(
         items: items,
         buttonKey: buttonKey,
@@ -435,7 +433,7 @@ void main() {
   testWidgets('DropdownButtonFormField - disabledHint displays when onChanged is null', (WidgetTester tester) async {
     final Key buttonKey = UniqueKey();
 
-    Widget build({ List<String> items, ValueChanged<String> onChanged }){
+    Widget build({ List<String>? items, ValueChanged<String?>? onChanged }){
       return buildFormFrame(
         items: items,
         buttonKey: buttonKey,
@@ -453,7 +451,7 @@ void main() {
   testWidgets('DropdownButtonFormField - disabled hint should be of same size as enabled hint', (WidgetTester tester) async {
     final Key buttonKey = UniqueKey();
 
-    Widget build({ List<String> items}){
+    Widget build({ List<String>? items}){
       return buildFormFrame(
         items: items,
         buttonKey: buttonKey,
@@ -493,7 +491,7 @@ void main() {
 
     // test for enabled color
     final RichText enabledRichText = tester.widget<RichText>(_iconRichText(iconKey));
-    expect(enabledRichText.text.style.color, Colors.pink);
+    expect(enabledRichText.text.style!.color, Colors.pink);
 
     // test for disabled color
     await tester.pumpWidget(buildFormFrame(
@@ -505,7 +503,7 @@ void main() {
     ));
 
     final RichText disabledRichText = tester.widget<RichText>(_iconRichText(iconKey));
-    expect(disabledRichText.text.style.color, Colors.orange);
+    expect(disabledRichText.text.style!.color, Colors.orange);
   });
 
   testWidgets('DropdownButtonFormField - default elevation', (WidgetTester tester) async {
@@ -583,7 +581,7 @@ void main() {
           home: Scaffold(
             body: DropdownButtonFormField<String>(
               value: 'c',
-              onChanged: (String newValue) {},
+              onChanged: (String? newValue) {},
               items: itemsWithDuplicateValues,
             ),
           ),
@@ -614,7 +612,7 @@ void main() {
           home: Scaffold(
             body: DropdownButton<String>(
               value: 'e',
-              onChanged: (String newValue) {},
+              onChanged: (String? newValue) {},
               items: itemsWithDuplicateValues,
             ),
           ),
@@ -636,7 +634,7 @@ void main() {
       'Two',
       'Three',
     ];
-    String selectedItem = items[0];
+    String? selectedItem = items[0];
 
     await tester.pumpWidget(
       StatefulBuilder(
@@ -645,7 +643,7 @@ void main() {
             home: Scaffold(
               body: DropdownButtonFormField<String>(
                 value: selectedItem,
-                onChanged: (String string) => setState(() => selectedItem = string),
+                onChanged: (String? string) => setState(() => selectedItem = string),
                 selectedItemBuilder: (BuildContext context) {
                   int index = 0;
                   return items.map((String string) {
@@ -676,8 +674,10 @@ void main() {
 
   testWidgets('DropdownButton onTap callback is called when defined', (WidgetTester tester) async {
     int dropdownButtonTapCounter = 0;
-    String value = 'one';
-    void onChanged(String newValue) { value = newValue; }
+    String? value = 'one';
+    void onChanged(String? newValue) {
+      value = newValue;
+    }
     void onTap() { dropdownButtonTapCounter += 1; }
 
     Widget build() => buildFormFrame(
@@ -780,7 +780,7 @@ void main() {
                 );
               }).toList(),
               onChanged: onChanged,
-              validator: (String value) {
+              validator: (String? value) {
                 _validateCalled++;
                 return null;
               },

packages/flutter/test/material/elevated_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/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -37,10 +35,10 @@ void main() {
     expect(material.elevation, 2);
     expect(material.shadowColor, const Color(0xff000000));
     expect(material.shape, RoundedRectangleBorder(borderRadius: BorderRadius.circular(4.0)));
-    expect(material.textStyle.color, colorScheme.onPrimary);
-    expect(material.textStyle.fontFamily, 'Roboto');
-    expect(material.textStyle.fontSize, 14);
-    expect(material.textStyle.fontWeight, FontWeight.w500);
+    expect(material.textStyle!.color, colorScheme.onPrimary);
+    expect(material.textStyle!.fontFamily, 'Roboto');
+    expect(material.textStyle!.fontSize, 14);
+    expect(material.textStyle!.fontWeight, FontWeight.w500);
   });
 
   group('[Theme, TextTheme, ElevatedButton style overrides]', () {
@@ -78,7 +76,7 @@ void main() {
       enableFeedback: enableFeedback,
     );
 
-    Widget buildFrame({ ButtonStyle buttonStyle, ButtonStyle themeStyle, ButtonStyle overallStyle }) {
+    Widget buildFrame({ ButtonStyle? buttonStyle, ButtonStyle? themeStyle, ButtonStyle? overallStyle }) {
       final Widget child = Builder(
         builder: (BuildContext context) {
           return ElevatedButton(
@@ -124,16 +122,16 @@ void main() {
     void checkButton(WidgetTester tester) {
       final Material material = tester.widget<Material>(findMaterial);
       final InkWell inkWell = tester.widget<InkWell>(findInkWell);
-      expect(material.textStyle.color, onPrimaryColor);
-      expect(material.textStyle.fontSize, 12);
+      expect(material.textStyle!.color, onPrimaryColor);
+      expect(material.textStyle!.fontSize, 12);
       expect(material.color, primaryColor);
       expect(material.shadowColor, shadowColor);
       expect(material.elevation, elevation);
-      expect(MaterialStateProperty.resolveAs<MouseCursor>(inkWell.mouseCursor, enabled), enabledMouseCursor);
-      expect(MaterialStateProperty.resolveAs<MouseCursor>(inkWell.mouseCursor, disabled), disabledMouseCursor);
-      expect(inkWell.overlayColor.resolve(hovered), onPrimaryColor.withOpacity(0.08));
-      expect(inkWell.overlayColor.resolve(focused), onPrimaryColor.withOpacity(0.24));
-      expect(inkWell.overlayColor.resolve(pressed), onPrimaryColor.withOpacity(0.24));
+      expect(MaterialStateProperty.resolveAs<MouseCursor>(inkWell.mouseCursor!, enabled), enabledMouseCursor);
+      expect(MaterialStateProperty.resolveAs<MouseCursor>(inkWell.mouseCursor!, disabled), disabledMouseCursor);
+      expect(inkWell.overlayColor!.resolve(hovered), onPrimaryColor.withOpacity(0.08));
+      expect(inkWell.overlayColor!.resolve(focused), onPrimaryColor.withOpacity(0.24));
+      expect(inkWell.overlayColor!.resolve(pressed), onPrimaryColor.withOpacity(0.24));
       expect(inkWell.enableFeedback, enableFeedback);
       expect(material.borderRadius, null);
       expect(material.shape, shape);
@@ -185,7 +183,7 @@ void main() {
     const Color shadowColor = Color(0xff000001);
     const Color overiddenColor = Color(0xff000002);
 
-    Widget buildFrame({ Color overallShadowColor, Color themeShadowColor, Color shadowColor }) {
+    Widget buildFrame({ Color? overallShadowColor, Color? themeShadowColor, Color? shadowColor }) {
       return MaterialApp(
         theme: ThemeData.from(colorScheme: colorScheme).copyWith(
           shadowColor: overallShadowColor,

packages/flutter/test/material/expand_icon_test.dart

@@ -2,12 +2,10 @@
 // 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';
 
-Widget wrap({ Widget child, ThemeData theme }) {
+Widget wrap({ required Widget child, ThemeData? theme }) {
   return MaterialApp(
     theme: theme,
     home: Center(

packages/flutter/test/material/expansion_panel_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/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 class SimpleExpansionPanelListTestWidget extends StatefulWidget {
   const SimpleExpansionPanelListTestWidget({
-    Key key,
+    Key? key,
     this.firstPanelKey,
     this.secondPanelKey,
     this.canTapOnHeader = false,
@@ -18,14 +16,14 @@ class SimpleExpansionPanelListTestWidget extends StatefulWidget {
     this.elevation = 2,
   }) : super(key: key);
 
-  final Key firstPanelKey;
-  final Key secondPanelKey;
+  final Key? firstPanelKey;
+  final Key? secondPanelKey;
   final bool canTapOnHeader;
-  final Color dividerColor;
+  final Color? dividerColor;
   final int elevation;
 
   /// If null, the default [ExpansionPanelList]'s expanded header padding value is applied via [defaultExpandedHeaderPadding]
-  final EdgeInsets expandedHeaderPadding;
+  final EdgeInsets? expandedHeaderPadding;
 
   /// Mirrors the default expanded header padding as its source constants are private.
   static EdgeInsets defaultExpandedHeaderPadding()
@@ -74,7 +72,7 @@ class _SimpleExpansionPanelListTestWidgetState extends State<SimpleExpansionPane
 }
 
 class ExpansionPanelListSemanticsTest extends StatefulWidget {
-  const ExpansionPanelListSemanticsTest({ Key key, this.headerKey }) : super(key: key);
+  const ExpansionPanelListSemanticsTest({ Key? key, required this.headerKey }) : super(key: key);
 
   final Key headerKey;
 
@@ -118,8 +116,8 @@ class ExpansionPanelListSemanticsTestState extends State<ExpansionPanelListSeman
 
 void main() {
   testWidgets('ExpansionPanelList test', (WidgetTester tester) async {
-    int index;
-    bool isExpanded;
+    late int index;
+    late bool isExpanded;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -1364,7 +1362,7 @@ void main() {
     final BoxDecoration decoration = decoratedBox.decoration as BoxDecoration;
 
     // For the last DecoratedBox, we will have a Border.top with the provided dividerColor.
-    expect(decoration.border.top.color, dividerColor);
+    expect(decoration.border!.top.color, dividerColor);
   });
 
   testWidgets('ExpansionPanelList.radio respects DividerColor', (WidgetTester tester) async {
@@ -1397,7 +1395,7 @@ void main() {
     final BoxDecoration boxDecoration = decoratedBox.decoration as BoxDecoration;
 
     // For the last DecoratedBox, we will have a Border.top with the provided dividerColor.
-    expect(boxDecoration.border.top.color, dividerColor);
+    expect(boxDecoration.border!.top.color, dividerColor);
   });
 
   testWidgets('elevation is propagated properly to MergeableMaterial', (WidgetTester tester) async {

packages/flutter/test/material/expansion_tile_test.dart

@@ -2,21 +2,19 @@
 // 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/widgets.dart';
 import 'package:flutter/material.dart';
 
 class TestIcon extends StatefulWidget {
-  const TestIcon({Key key}) : super(key: key);
+  const TestIcon({Key? key}) : super(key: key);
 
   @override
   TestIconState createState() => TestIconState();
 }
 
 class TestIconState extends State<TestIcon> {
-  IconThemeData iconTheme;
+  late IconThemeData iconTheme;
 
   @override
   Widget build(BuildContext context) {
@@ -26,7 +24,7 @@ class TestIconState extends State<TestIcon> {
 }
 
 class TestText extends StatefulWidget {
-  const TestText(this.text, {Key key}) : super(key: key);
+  const TestText(this.text, {Key? key}) : super(key: key);
 
   final String text;
 
@@ -35,7 +33,7 @@ class TestText extends StatefulWidget {
 }
 
 class TestTextState extends State<TestText> {
-  TextStyle textStyle;
+  late TextStyle textStyle;
 
   @override
   Widget build(BuildContext context) {
@@ -113,15 +111,15 @@ void main() {
     expect(getHeight(topKey), getHeight(collapsedKey) - 2.0);
     expect(getHeight(topKey), getHeight(defaultKey) - 2.0);
 
-    BoxDecoration expandedContainerDecoration = getContainer(expandedKey).decoration as BoxDecoration;
+    BoxDecoration expandedContainerDecoration = getContainer(expandedKey).decoration! as BoxDecoration;
     expect(expandedContainerDecoration.color, Colors.red);
-    expect(expandedContainerDecoration.border.top.color, _dividerColor);
-    expect(expandedContainerDecoration.border.bottom.color, _dividerColor);
+    expect(expandedContainerDecoration.border!.top.color, _dividerColor);
+    expect(expandedContainerDecoration.border!.bottom.color, _dividerColor);
 
-    BoxDecoration collapsedContainerDecoration = getContainer(collapsedKey).decoration as BoxDecoration;
+    BoxDecoration collapsedContainerDecoration = getContainer(collapsedKey).decoration! as BoxDecoration;
     expect(collapsedContainerDecoration.color, Colors.transparent);
-    expect(collapsedContainerDecoration.border.top.color, Colors.transparent);
-    expect(collapsedContainerDecoration.border.bottom.color, Colors.transparent);
+    expect(collapsedContainerDecoration.border!.top.color, Colors.transparent);
+    expect(collapsedContainerDecoration.border!.bottom.color, Colors.transparent);
 
     await tester.tap(find.text('Expanded'));
     await tester.tap(find.text('Collapsed'));
@@ -131,11 +129,11 @@ void main() {
 
     // Pump to the middle of the animation for expansion.
     await tester.pump(const Duration(milliseconds: 100));
-    final BoxDecoration collapsingContainerDecoration = getContainer(collapsedKey).decoration as BoxDecoration;
+    final BoxDecoration collapsingContainerDecoration = getContainer(collapsedKey).decoration! as BoxDecoration;
     expect(collapsingContainerDecoration.color, Colors.transparent);
     // Opacity should change but color component should remain the same.
-    expect(collapsingContainerDecoration.border.top.color, const Color(0x15333333));
-    expect(collapsingContainerDecoration.border.bottom.color, const Color(0x15333333));
+    expect(collapsingContainerDecoration.border!.top.color, const Color(0x15333333));
+    expect(collapsingContainerDecoration.border!.bottom.color, const Color(0x15333333));
 
     // Pump all the way to the end now.
     await tester.pump(const Duration(seconds: 1));
@@ -145,16 +143,16 @@ void main() {
     expect(getHeight(topKey), getHeight(defaultKey) - getHeight(tileKey) - 2.0);
 
     // Expanded should be collapsed now.
-    expandedContainerDecoration = getContainer(expandedKey).decoration as BoxDecoration;
+    expandedContainerDecoration = getContainer(expandedKey).decoration! as BoxDecoration;
     expect(expandedContainerDecoration.color, Colors.transparent);
-    expect(expandedContainerDecoration.border.top.color, Colors.transparent);
-    expect(expandedContainerDecoration.border.bottom.color, Colors.transparent);
+    expect(expandedContainerDecoration.border!.top.color, Colors.transparent);
+    expect(expandedContainerDecoration.border!.bottom.color, Colors.transparent);
 
     // Collapsed should be expanded now.
-    collapsedContainerDecoration = getContainer(collapsedKey).decoration as BoxDecoration;
+    collapsedContainerDecoration = getContainer(collapsedKey).decoration! as BoxDecoration;
     expect(collapsedContainerDecoration.color, Colors.transparent);
-    expect(collapsedContainerDecoration.border.top.color, _dividerColor);
-    expect(collapsedContainerDecoration.border.bottom.color, _dividerColor);
+    expect(collapsedContainerDecoration.border!.top.color, _dividerColor);
+    expect(collapsedContainerDecoration.border!.bottom.color, _dividerColor);
   }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));
 
   testWidgets('ListTileTheme', (WidgetTester tester) async {
@@ -195,8 +193,8 @@ void main() {
       ),
     );
 
-    Color iconColor(Key key) => tester.state<TestIconState>(find.byKey(key)).iconTheme.color;
-    Color textColor(Key key) => tester.state<TestTextState>(find.byKey(key)).textStyle.color;
+    Color iconColor(Key key) => tester.state<TestIconState>(find.byKey(key)).iconTheme.color!;
+    Color textColor(Key key) => tester.state<TestTextState>(find.byKey(key)).textStyle.color!;
 
     expect(textColor(expandedTitleKey), _accentColor);
     expect(textColor(collapsedTitleKey), _headerColor);

packages/flutter/test/material/feedback_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';
@@ -14,18 +12,18 @@ import 'feedback_tester.dart';
 void main () {
   const Duration kWaitDuration = Duration(seconds: 1);
 
-  FeedbackTester feedback;
+  late FeedbackTester feedback;
 
   setUp(() {
     feedback = FeedbackTester();
   });
 
   tearDown(() {
-    feedback?.dispose();
+    feedback.dispose();
   });
 
   group('Feedback on Android', () {
-    List<Map<String, Object>> semanticEvents;
+    late List<Map<String, Object>> semanticEvents;
 
     setUp(() {
       semanticEvents = <Map<String, Object>>[];
@@ -60,10 +58,10 @@ void main () {
       expect(feedback.clickSoundCount, 1);
       expect(semanticEvents.single, <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);
 
       semanticsTester.dispose();
     });
@@ -78,7 +76,7 @@ void main () {
 
       await tester.pumpWidget(TestWidget(
         tapHandler: (BuildContext context) {
-          return Feedback.wrapForTap(callback, context);
+          return Feedback.wrapForTap(callback, context)!;
         },
       ));
       await tester.pumpAndSettle(kWaitDuration);
@@ -95,10 +93,10 @@ void main () {
       expect(callbackCount, 1);
       expect(semanticEvents.single, <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);
 
       semanticsTester.dispose();
     });
@@ -123,10 +121,10 @@ void main () {
       expect(feedback.clickSoundCount, 0);
       expect(semanticEvents.single, <String, dynamic>{
         'type': 'longPress',
-        'nodeId': object.debugSemantics.id,
+        'nodeId': object.debugSemantics!.id,
         'data': <String, dynamic>{},
       });
-      expect(object.debugSemantics.getSemanticsData().hasAction(SemanticsAction.longPress), true);
+      expect(object.debugSemantics!.getSemanticsData().hasAction(SemanticsAction.longPress), true);
 
       semanticsTester.dispose();
     });
@@ -140,7 +138,7 @@ void main () {
 
       await tester.pumpWidget(TestWidget(
         longPressHandler: (BuildContext context) {
-          return Feedback.wrapForLongPress(callback, context);
+          return Feedback.wrapForLongPress(callback, context)!;
         },
       ));
       await tester.pumpAndSettle(kWaitDuration);
@@ -157,10 +155,10 @@ void main () {
       expect(callbackCount, 1);
       expect(semanticEvents.single, <String, dynamic>{
         'type': 'longPress',
-        'nodeId': object.debugSemantics.id,
+        'nodeId': object.debugSemantics!.id,
         'data': <String, dynamic>{},
       });
-      expect(object.debugSemantics.getSemanticsData().hasAction(SemanticsAction.longPress), true);
+      expect(object.debugSemantics!.getSemanticsData().hasAction(SemanticsAction.longPress), true);
 
       semanticsTester.dispose();
     });
@@ -204,7 +202,7 @@ void main () {
 
 class TestWidget extends StatelessWidget {
   const TestWidget({
-    Key key,
+    Key? key,
     this.tapHandler = nullHandler,
     this.longPressHandler = nullHandler,
   }) : super(key: key);
@@ -212,7 +210,7 @@ class TestWidget extends StatelessWidget {
   final HandlerCreator tapHandler;
   final HandlerCreator longPressHandler;
 
-  static VoidCallback nullHandler(BuildContext context) => null;
+  static VoidCallback? nullHandler(BuildContext context) => null;
 
   @override
   Widget build(BuildContext context) {
@@ -224,4 +222,4 @@ class TestWidget extends StatelessWidget {
   }
 }
 
-typedef HandlerCreator = VoidCallback Function(BuildContext context);
+typedef HandlerCreator = VoidCallback? Function(BuildContext context);