Migrate more material tests to NNBD (#67674)

This migrates more material tests to NNBD.

packages/flutter/test/material/about_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';
@@ -733,7 +731,7 @@ class LicensePageObserver extends NavigatorObserver {
   int licensePageCount = 0;
 
   @override
-  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+  void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) {
     if (route is MaterialPageRoute<dynamic>) {
       licensePageCount++;
     }
@@ -745,7 +743,7 @@ class AboutDialogObserver extends NavigatorObserver {
   int dialogCount = 0;
 
   @override
-  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+  void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) {
     if (route.toString().contains('_DialogRoute')) {
       dialogCount++;
     }

packages/flutter/test/material/animated_icons_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 show pi;
 
 import 'package:flutter/material.dart';
@@ -13,8 +11,8 @@ import '../flutter_test_alternative.dart' show Fake;
 import '../widgets/semantics_tester.dart';
 
 class MockCanvas extends Fake implements Canvas {
-  Path capturedPath;
-  Paint capturedPaint;
+  late Path capturedPath;
+  late Paint capturedPaint;
 
   @override
   void drawPath(Path path, Paint paint) {
@@ -22,13 +20,13 @@ class MockCanvas extends Fake implements Canvas {
     capturedPaint = paint;
   }
 
-  double capturedSx;
-  double capturedSy;
+  late double capturedSx;
+  late double capturedSy;
 
   @override
-  void scale(double sx, [double sy]) {
+  void scale(double sx, [double? sy]) {
     capturedSx = sx;
-    capturedSy = sy;
+    capturedSy = sy!;
   }
 
   final List<RecordedCanvasCall> invocations = <RecordedCanvasCall>[];
@@ -96,7 +94,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.capturedPaint, hasColor(0xFF666666));
   });
 
@@ -118,7 +116,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.capturedPaint, hasColor(0x80666666));
   });
 
@@ -140,7 +138,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.capturedPaint, hasColor(0xFF0000FF));
   });
 
@@ -162,7 +160,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(12.0, 12.0));
+    customPaint.painter!.paint(canvas, const Size(12.0, 12.0));
     // arrow_menu default size is 48x48 so we expect it to be scaled by 0.25.
     expect(canvas.capturedSx, 0.25);
     expect(canvas.capturedSy, 0.25);
@@ -187,7 +185,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(12.0, 12.0));
+    customPaint.painter!.paint(canvas, const Size(12.0, 12.0));
     // arrow_menu default size is 48x48 so we expect it to be scaled by 2.
     expect(canvas.capturedSx, 2);
     expect(canvas.capturedSy, 2);
@@ -230,7 +228,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.invocations, const <RecordedCanvasCall>[
       RecordedRotate(math.pi),
       RecordedTranslate(-48, -48),
@@ -254,7 +252,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.invocations, isEmpty);
   });
 
@@ -276,7 +274,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.invocations, const <RecordedCanvasCall>[
       RecordedRotate(math.pi),
       RecordedTranslate(-48, -48),

packages/flutter/test/material/app_bar_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';
@@ -14,10 +12,10 @@ import '../rendering/mock_canvas.dart';
 import '../widgets/semantics_tester.dart';
 
 Widget buildSliverAppBarApp({
-  bool floating,
-  bool pinned,
-  double collapsedHeight,
-  double expandedHeight,
+  bool floating = false,
+  bool pinned = false,
+  double? collapsedHeight,
+  double? expandedHeight,
   bool snap = false,
   double toolbarHeight = kToolbarHeight,
 }) {
@@ -65,7 +63,7 @@ Widget buildSliverAppBarApp({
 }
 
 ScrollController primaryScrollController(WidgetTester tester) {
-  return PrimaryScrollController.of(tester.element(find.byType(CustomScrollView)));
+  return PrimaryScrollController.of(tester.element(find.byType(CustomScrollView)))!;
 }
 
 double appBarHeight(WidgetTester tester) => tester.getSize(find.byType(AppBar, skipOffstage: false)).height;
@@ -303,7 +301,7 @@ void main() {
 
     final Key titleKey = UniqueKey();
     Widget leading = Container();
-    List<Widget> actions;
+    List<Widget> actions = <Widget>[];
 
     Widget buildApp() {
       return MaterialApp(
@@ -360,8 +358,8 @@ void main() {
 
     final Key titleKey = UniqueKey();
     double titleWidth = 700.0;
-    Widget leading = Container();
-    List<Widget> actions;
+    Widget? leading = Container();
+    List<Widget> actions = <Widget>[];
 
     Widget buildApp() {
       return MaterialApp(
@@ -412,8 +410,8 @@ void main() {
 
     final Key titleKey = UniqueKey();
     double titleWidth = 700.0;
-    Widget leading = Container();
-    List<Widget> actions;
+    Widget? leading = Container();
+    List<Widget> actions = <Widget>[];
 
     Widget buildApp() {
       return MaterialApp(
@@ -1952,14 +1950,14 @@ void main() {
   });
 
   testWidgets('AppBars title has upper limit on text scaling, textScaleFactor = 1, 1.34, 2', (WidgetTester tester) async {
-    double textScaleFactor;
+    late double textScaleFactor;
 
     Widget buildFrame() {
       return MaterialApp(
         home: Builder(
           builder: (BuildContext context) {
             return MediaQuery(
-              data: MediaQuery.of(context).copyWith(textScaleFactor: textScaleFactor),
+              data: MediaQuery.of(context)!.copyWith(textScaleFactor: textScaleFactor),
               child: Scaffold(
                 appBar: AppBar(
                   centerTitle: false,
@@ -1988,9 +1986,9 @@ void main() {
   });
 
   testWidgets('AppBars with jumbo titles, textScaleFactor = 3, 3.5, 4', (WidgetTester tester) async {
-    double textScaleFactor;
-    TextDirection textDirection;
-    bool centerTitle;
+    double textScaleFactor = 1.0;
+    TextDirection textDirection = TextDirection.ltr;
+    bool centerTitle = false;
 
     Widget buildFrame() {
       return MaterialApp(
@@ -2004,7 +2002,7 @@ void main() {
                     appBar: AppBar(
                       centerTitle: centerTitle,
                       title: MediaQuery(
-                        data: MediaQuery.of(context).copyWith(textScaleFactor: textScaleFactor),
+                        data: MediaQuery.of(context)!.copyWith(textScaleFactor: textScaleFactor),
                         child: const Text('Jumbo'),
                       ),
                     ),
@@ -2023,10 +2021,8 @@ void main() {
     // Overall screen size is 800x600
     // Left or right justified title is padded by 16 on the "start" side.
     // Toolbar height is 56.
+    // "Jumbo" title is 100x20.
 
-    textScaleFactor = 1; // "Jumbo" title is 100x20.
-    textDirection = TextDirection.ltr;
-    centerTitle = false;
     await tester.pumpWidget(buildFrame());
     expect(tester.getRect(appBarTitle), const Rect.fromLTRB(16, 18, 116, 38));
     expect(tester.getCenter(appBarTitle).dy, tester.getCenter(toolbar).dy);
@@ -2058,7 +2054,7 @@ void main() {
   });
 
   testWidgets('SliverAppBar configures the delegate properly', (WidgetTester tester) async {
-    Future<void> buildAndVerifyDelegate({ bool pinned, bool floating, bool snap }) async {
+    Future<void> buildAndVerifyDelegate({ required bool pinned, required bool floating, required bool snap }) async {
       await tester.pumpWidget(
         MaterialApp(
           home: CustomScrollView(
@@ -2150,17 +2146,6 @@ void main() {
     expect(appBarHeight(tester), collapsedHeight + initialTabBarHeight);
   });
 
-  test('SliverApp toolbarHeight cannot be null', () {
-    try{
-       SliverAppBar(
-        toolbarHeight: null,
-      );
-    } on AssertionError catch (error) {
-      expect(error.toString(), contains('toolbarHeight != null'));
-      expect(error.toString(), contains('is not true'));
-    }
-  });
-
   testWidgets('AppBar respects leadingWidth', (WidgetTester tester) async {
     const Key key = Key('leading');
     await tester.pumpWidget(MaterialApp(

packages/flutter/test/material/app_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/services.dart';
@@ -31,14 +29,14 @@ void main() {
     final RichText actionIconText = _getAppBarIconRichText(tester);
     final DefaultTextStyle text = _getAppBarText(tester);
 
-    expect(SystemChrome.latestStyle.statusBarBrightness, Brightness.dark);
+    expect(SystemChrome.latestStyle!.statusBarBrightness, Brightness.dark);
     expect(widget.color, Colors.blue);
     expect(widget.elevation, 4.0);
     expect(widget.shadowColor, Colors.black);
     expect(iconTheme.data, const IconThemeData(color: Colors.white));
     expect(actionsIconTheme.data, const IconThemeData(color: Colors.white));
-    expect(actionIconText.text.style.color, Colors.white);
-    expect(text.style, Typography.material2014().englishLike.bodyText2.merge(Typography.material2014().white.bodyText2));
+    expect(actionIconText.text.style!.color, Colors.white);
+    expect(text.style, Typography.material2014().englishLike.bodyText2!.merge(Typography.material2014().white.bodyText2));
   });
 
   testWidgets('AppBar uses values from AppBarTheme', (WidgetTester tester) async {
@@ -60,14 +58,14 @@ void main() {
     final RichText actionIconText = _getAppBarIconRichText(tester);
     final DefaultTextStyle text = _getAppBarText(tester);
 
-    expect(SystemChrome.latestStyle.statusBarBrightness, appBarTheme.brightness);
+    expect(SystemChrome.latestStyle!.statusBarBrightness, appBarTheme.brightness);
     expect(widget.color, appBarTheme.color);
     expect(widget.elevation, appBarTheme.elevation);
     expect(widget.shadowColor, appBarTheme.shadowColor);
     expect(iconTheme.data, appBarTheme.iconTheme);
     expect(actionsIconTheme.data, appBarTheme.actionsIconTheme);
-    expect(actionIconText.text.style.color, appBarTheme.actionsIconTheme.color);
-    expect(text.style, appBarTheme.textTheme.bodyText2);
+    expect(actionIconText.text.style!.color, appBarTheme.actionsIconTheme!.color);
+    expect(text.style, appBarTheme.textTheme!.bodyText2);
   });
 
   testWidgets('AppBar widget properties take priority over theme', (WidgetTester tester) async {
@@ -103,13 +101,13 @@ void main() {
     final RichText actionIconText = _getAppBarIconRichText(tester);
     final DefaultTextStyle text = _getAppBarText(tester);
 
-    expect(SystemChrome.latestStyle.statusBarBrightness, brightness);
+    expect(SystemChrome.latestStyle!.statusBarBrightness, brightness);
     expect(widget.color, color);
     expect(widget.elevation, elevation);
     expect(widget.shadowColor, shadowColor);
     expect(iconTheme.data, iconThemeData);
     expect(actionsIconTheme.data, actionsIconThemeData);
-    expect(actionIconText.text.style.color, actionsIconThemeData.color);
+    expect(actionIconText.text.style!.color, actionsIconThemeData.color);
     expect(text.style, textTheme.bodyText2);
   });
 
@@ -132,7 +130,7 @@ void main() {
     ));
 
     final RichText actionIconText = _getAppBarIconRichText(tester);
-    expect(actionIconText.text.style.color, color);
+    expect(actionIconText.text.style!.color, color);
   });
 
   testWidgets('AppBarTheme properties take priority over ThemeData properties', (WidgetTester tester) async {
@@ -154,14 +152,14 @@ void main() {
     final RichText actionIconText = _getAppBarIconRichText(tester);
     final DefaultTextStyle text = _getAppBarText(tester);
 
-    expect(SystemChrome.latestStyle.statusBarBrightness, appBarTheme.brightness);
+    expect(SystemChrome.latestStyle!.statusBarBrightness, appBarTheme.brightness);
     expect(widget.color, appBarTheme.color);
     expect(widget.elevation, appBarTheme.elevation);
     expect(widget.shadowColor, appBarTheme.shadowColor);
     expect(iconTheme.data, appBarTheme.iconTheme);
     expect(actionsIconTheme.data, appBarTheme.actionsIconTheme);
-    expect(actionIconText.text.style.color, appBarTheme.actionsIconTheme.color);
-    expect(text.style, appBarTheme.textTheme.bodyText2);
+    expect(actionIconText.text.style!.color, appBarTheme.actionsIconTheme!.color);
+    expect(text.style, appBarTheme.textTheme!.bodyText2);
   });
 
   testWidgets('ThemeData properties are used when no AppBarTheme is set', (WidgetTester tester) async {
@@ -182,15 +180,15 @@ void main() {
     final RichText actionIconText = _getAppBarIconRichText(tester);
     final DefaultTextStyle text = _getAppBarText(tester);
 
-    expect(SystemChrome.latestStyle.statusBarBrightness, themeData.brightness);
+    expect(SystemChrome.latestStyle!.statusBarBrightness, themeData.brightness);
     expect(widget.color, themeData.primaryColor);
     expect(widget.elevation, 4.0);
     expect(widget.shadowColor, Colors.black);
     expect(iconTheme.data, themeData.primaryIconTheme);
     expect(actionsIconTheme.data, themeData.primaryIconTheme);
-    expect(actionIconText.text.style.color, themeData.primaryIconTheme.color);
+    expect(actionIconText.text.style!.color, themeData.primaryIconTheme.color);
     // Default value for ThemeData.typography is Typography.material2014()
-    expect(text.style, Typography.material2014().englishLike.bodyText2.merge(Typography.material2014().white.bodyText2).merge(themeData.primaryTextTheme.bodyText2));
+    expect(text.style, Typography.material2014().englishLike.bodyText2!.merge(Typography.material2014().white.bodyText2).merge(themeData.primaryTextTheme.bodyText2));
   });
 
   testWidgets('AppBar uses AppBarTheme.centerTitle when centerTitle is null', (WidgetTester tester) async {

packages/flutter/test/material/app_builder_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 
@@ -15,9 +13,9 @@ void main() {
         primarySwatch: Colors.green,
       ),
       home: const Placeholder(),
-      builder: (BuildContext context, Widget child) {
+      builder: (BuildContext context, Widget? child) {
         log.add('build');
-        expect(Theme.of(context).primaryColor, Colors.green);
+        expect(Theme.of(context)!.primaryColor, Colors.green);
         expect(Directionality.of(context), TextDirection.ltr);
         expect(child, isA<Navigator>());
         return const Placeholder();
@@ -49,15 +47,15 @@ void main() {
         home: Builder(
           builder: (BuildContext context) {
             log.add('build');
-            expect(Theme.of(context).primaryColor, Colors.yellow);
+            expect(Theme.of(context)!.primaryColor, Colors.yellow);
             expect(Directionality.of(context), TextDirection.rtl);
             return const Placeholder();
           },
         ),
-        builder: (BuildContext context, Widget child) {
+        builder: (BuildContext context, Widget? child) {
           return Directionality(
             textDirection: TextDirection.rtl,
-            child: child,
+            child: child!,
           );
         },
       ),

packages/flutter/test/material/app_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/semantics.dart';
 import 'package:flutter/services.dart';
@@ -12,21 +10,21 @@ import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 
 class StateMarker extends StatefulWidget {
-  const StateMarker({ Key key, this.child }) : super(key: key);
+  const StateMarker({ Key? key, this.child }) : super(key: key);
 
-  final Widget child;
+  final Widget? child;
 
   @override
   StateMarkerState createState() => StateMarkerState();
 }
 
 class StateMarkerState extends State<StateMarker> {
-  String marker;
+  late String marker;
 
   @override
   Widget build(BuildContext context) {
     if (widget.child != null)
-      return widget.child;
+      return widget.child!;
     return Container();
   }
 }
@@ -102,7 +100,7 @@ void main() {
             return Material(
               child: ElevatedButton(
                 child: const Text('X'),
-                onPressed: () { Navigator.of(context).pushNamed('/next'); },
+                onPressed: () { Navigator.of(context)!.pushNamed('/next'); },
               ),
             );
           }
@@ -251,7 +249,7 @@ void main() {
   });
 
   testWidgets('Return value from pop is correct', (WidgetTester tester) async {
-    Future<Object> result;
+    late Future<Object> result;
     await tester.pumpWidget(
         MaterialApp(
           home: Builder(
@@ -260,7 +258,7 @@ void main() {
                   child: ElevatedButton(
                       child: const Text('X'),
                       onPressed: () async {
-                        result = Navigator.of(context).pushNamed('/a');
+                        result = Navigator.of(context)!.pushNamed('/a');
                       },
                   ),
                 );
@@ -272,7 +270,7 @@ void main() {
                 child: ElevatedButton(
                   child: const Text('Y'),
                   onPressed: () {
-                    Navigator.of(context).pop('all done');
+                    Navigator.of(context)!.pop('all done');
                   },
                 ),
               );
@@ -394,7 +392,7 @@ void main() {
     // Regression test for https://github.com/flutter/flutter/issues/18904
     await tester.pumpWidget(
       MaterialApp(
-        builder: (BuildContext context, Widget child) {
+        builder: (BuildContext context, Widget? child) {
           return const SizedBox();
         },
       ),
@@ -463,10 +461,10 @@ void main() {
   });
 
   testWidgets('Can get text scale from media query', (WidgetTester tester) async {
-    double textScaleFactor;
+    double? textScaleFactor;
     await tester.pumpWidget(MaterialApp(
       home: Builder(builder:(BuildContext context) {
-        textScaleFactor = MediaQuery.of(context).textScaleFactor;
+        textScaleFactor = MediaQuery.of(context)!.textScaleFactor;
         return Container();
       }),
     ));
@@ -502,8 +500,8 @@ void main() {
           builder: (BuildContext context) {
             return Column(
               children: <Widget>[
-                Text(MaterialLocalizations.of(context).selectAllButtonLabel),
-                Text(CupertinoLocalizations.of(context).selectAllButtonLabel),
+                Text(MaterialLocalizations.of(context)!.selectAllButtonLabel),
+                Text(CupertinoLocalizations.of(context)!.selectAllButtonLabel),
               ],
             );
           },
@@ -521,7 +519,7 @@ void main() {
     // Mock the Window to explicitly report a light platformBrightness.
     tester.binding.window.platformBrightnessTestValue = Brightness.light;
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
     await tester.pumpWidget(
       MaterialApp(
         theme: ThemeData(
@@ -533,7 +531,7 @@ void main() {
         themeMode: ThemeMode.light,
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -554,7 +552,7 @@ void main() {
         themeMode: ThemeMode.light,
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -567,7 +565,7 @@ void main() {
     // Mock the Window to explicitly report a light platformBrightness.
     tester.binding.window.platformBrightnessTestValue = Brightness.light;
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
     await tester.pumpWidget(
       MaterialApp(
         theme: ThemeData(
@@ -579,7 +577,7 @@ void main() {
         themeMode: ThemeMode.dark,
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -600,7 +598,7 @@ void main() {
         themeMode: ThemeMode.dark,
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -614,7 +612,7 @@ void main() {
     final TestWidgetsFlutterBinding binding = tester.binding;
     binding.window.platformBrightnessTestValue = Brightness.light;
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -627,7 +625,7 @@ void main() {
         themeMode: ThemeMode.system,
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -641,7 +639,7 @@ void main() {
     // Mock the Window to explicitly report a dark platformBrightness.
     tester.binding.window.platformBrightnessTestValue = Brightness.dark;
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
     await tester.pumpWidget(
       MaterialApp(
         theme: ThemeData(
@@ -653,7 +651,7 @@ void main() {
         themeMode: ThemeMode.system,
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -667,7 +665,7 @@ void main() {
     final TestWidgetsFlutterBinding binding = tester.binding;
     binding.window.platformBrightnessTestValue = Brightness.dark;
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -676,7 +674,7 @@ void main() {
         ),
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -691,13 +689,13 @@ void main() {
     final TestWidgetsFlutterBinding binding = tester.binding;
     binding.window.platformBrightnessTestValue = Brightness.dark;
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
 
     await tester.pumpWidget(
       MaterialApp(
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -712,7 +710,7 @@ void main() {
     final TestWidgetsFlutterBinding binding = tester.binding;
     binding.window.platformBrightnessTestValue = Brightness.light;
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -721,7 +719,7 @@ void main() {
         ),
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -736,7 +734,7 @@ void main() {
     final TestWidgetsFlutterBinding binding = tester.binding;
     binding.window.platformBrightnessTestValue = Brightness.dark;
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -748,7 +746,7 @@ void main() {
         ),
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -762,7 +760,7 @@ void main() {
     tester.binding.window.platformBrightnessTestValue = Brightness.light;
     tester.binding.window.accessibilityFeaturesTestValue = MockAccessibilityFeature();
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -774,7 +772,7 @@ void main() {
         ),
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -789,7 +787,7 @@ void main() {
     tester.binding.window.platformBrightnessTestValue = Brightness.dark;
     tester.binding.window.accessibilityFeaturesTestValue = MockAccessibilityFeature();
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -807,7 +805,7 @@ void main() {
         ),
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -822,7 +820,7 @@ void main() {
     tester.binding.window.platformBrightnessTestValue = Brightness.dark;
     tester.binding.window.accessibilityFeaturesTestValue = MockAccessibilityFeature();
 
-    ThemeData appliedTheme;
+    late ThemeData appliedTheme;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -834,7 +832,7 @@ void main() {
         ),
         home: Builder(
           builder: (BuildContext context) {
-            appliedTheme = Theme.of(context);
+            appliedTheme = Theme.of(context)!;
             return const SizedBox();
           },
         ),
@@ -851,8 +849,8 @@ void main() {
     final TestWidgetsFlutterBinding binding = tester.binding;
     binding.window.platformBrightnessTestValue = Brightness.light;
 
-    ThemeData themeBeforeBrightnessChange;
-    ThemeData themeAfterBrightnessChange;
+    ThemeData? themeBeforeBrightnessChange;
+    ThemeData? themeAfterBrightnessChange;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -880,8 +878,8 @@ void main() {
     binding.window.platformBrightnessTestValue = Brightness.dark;
     await tester.pumpAndSettle();
 
-    expect(themeBeforeBrightnessChange.brightness, Brightness.light);
-    expect(themeAfterBrightnessChange.brightness, Brightness.dark);
+    expect(themeBeforeBrightnessChange!.brightness, Brightness.light);
+    expect(themeAfterBrightnessChange!.brightness, Brightness.dark);
   });
 
   testWidgets('MaterialApp can customize initial routes', (WidgetTester tester) async {
@@ -921,7 +919,7 @@ void main() {
     expect(find.text('non-regular page one'), findsNothing);
     expect(find.text('regular page one'), findsNothing);
     expect(find.text('regular page two'), findsNothing);
-    navigatorKey.currentState.pop();
+    navigatorKey.currentState!.pop();
     await tester.pumpAndSettle();
     expect(find.text('non-regular page two'), findsNothing);
     expect(find.text('non-regular page one'), findsOneWidget);
@@ -931,7 +929,7 @@ void main() {
 
   testWidgets('MaterialApp does create HeroController with the MaterialRectArcTween', (WidgetTester tester) async {
     final HeroController controller = MaterialApp.createMaterialHeroController();
-    final Tween<Rect> tween = controller.createRectTween(
+    final Tween<Rect?> tween = controller.createRectTween!(
       const Rect.fromLTRB(0.0, 0.0, 10.0, 10.0),
       const Rect.fromLTRB(0.0, 0.0, 20.0, 20.0)
     );
@@ -962,7 +960,7 @@ void main() {
     );
     final SimpleNavigatorRouterDelegate delegate = SimpleNavigatorRouterDelegate(
       builder: (BuildContext context, RouteInformation information) {
-        return Text(information.location);
+        return Text(information.location!);
       },
       onPopPage: (Route<void> route, void result, SimpleNavigatorRouterDelegate delegate) {
         delegate.routeInformation = const RouteInformation(
@@ -980,15 +978,15 @@ void main() {
 
     // Simulate android back button intent.
     final ByteData message = const JSONMethodCodec().encodeMethodCall(const MethodCall('popRoute'));
-    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
+    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
     expect(find.text('popped'), findsOneWidget);
   });
 
   testWidgets('MaterialApp.builder can build app without a Navigator', (WidgetTester tester) async {
-    Widget builderChild;
+    Widget? builderChild;
     await tester.pumpWidget(MaterialApp(
-      builder: (BuildContext context, Widget child) {
+      builder: (BuildContext context, Widget? child) {
         builderChild = child;
         return Container();
       },
@@ -1036,15 +1034,15 @@ class SimpleRouteInformationParser extends RouteInformationParser<RouteInformati
 
 class SimpleNavigatorRouterDelegate extends RouterDelegate<RouteInformation> with PopNavigatorRouterDelegateMixin<RouteInformation>, ChangeNotifier {
   SimpleNavigatorRouterDelegate({
-    @required this.builder,
-    this.onPopPage,
+    required this.builder,
+    required this.onPopPage,
   });
 
   @override
   GlobalKey<NavigatorState> navigatorKey = GlobalKey<NavigatorState>();
 
   RouteInformation get routeInformation => _routeInformation;
-  RouteInformation _routeInformation;
+  late RouteInformation _routeInformation;
   set routeInformation(RouteInformation newValue) {
     _routeInformation = newValue;
     notifyListeners();
@@ -1075,7 +1073,7 @@ class SimpleNavigatorRouterDelegate extends RouterDelegate<RouteInformation> wit
           child: Text('base'),
         ),
         MaterialPage<void>(
-          key: ValueKey<String>(routeInformation?.location),
+          key: ValueKey<String>(routeInformation.location!),
           child: builder(context, routeInformation),
         )
       ],

packages/flutter/test/material/arc_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/back_button_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -132,7 +130,7 @@ void main() {
         of: find.byType(BackButton),
         matching: find.byType(RichText)
     ));
-    expect(iconText.text.style.color, Colors.blue);
+    expect(iconText.text.style!.color, Colors.blue);
   });
 
   testWidgets('BackButton semantics', (WidgetTester tester) async {
@@ -182,7 +180,7 @@ void main() {
         of: find.byType(CloseButton),
         matching: find.byType(RichText)
     ));
-    expect(iconText.text.style.color, Colors.red);
+    expect(iconText.text.style!.color, Colors.red);
   });
 
   testWidgets('CloseButton onPressed overrides default pop behavior', (WidgetTester tester) async {

packages/flutter/test/material/banner_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';
@@ -260,5 +258,5 @@ Container _getContainerFromBanner(WidgetTester tester) {
 }
 
 RenderParagraph _getTextRenderObjectFromDialog(WidgetTester tester, String text) {
-  return tester.element<StatelessElement>(find.descendant(of: find.byType(MaterialBanner), matching: find.text(text))).renderObject as RenderParagraph;
+  return tester.element<StatelessElement>(find.descendant(of: find.byType(MaterialBanner), matching: find.text(text))).renderObject! as RenderParagraph;
 }

packages/flutter/test/material/banner_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';
@@ -70,7 +68,7 @@ void main() {
     final RenderParagraph content = _getTextRenderObjectFromDialog(tester, contentText);
     expect(container.color, const Color(0xffffffff));
     // Default value for ThemeData.typography is Typography.material2014()
-    expect(content.text.style, Typography.material2014().englishLike.bodyText2.merge(Typography.material2014().black.bodyText2));
+    expect(content.text.style, Typography.material2014().englishLike.bodyText2!.merge(Typography.material2014().black.bodyText2));
   });
 
   testWidgets('MaterialBanner uses values from MaterialBannerThemeData', (WidgetTester tester) async {
@@ -185,7 +183,7 @@ Finder _containerFinder() {
 }
 
 RenderParagraph _getTextRenderObjectFromDialog(WidgetTester tester, String text) {
-  return tester.element<StatelessElement>(_textFinder(text)).renderObject as RenderParagraph;
+  return tester.element<StatelessElement>(_textFinder(text)).renderObject! as RenderParagraph;
 }
 
 Finder _textFinder(String text) {

packages/flutter/test/material/bottom_app_bar_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
@@ -90,7 +88,7 @@ void main() {
         home: Builder(
           builder: (BuildContext context) {
             return Theme(
-              data: Theme.of(context).copyWith(bottomAppBarColor: const Color(0xffffff00)),
+              data: Theme.of(context)!.copyWith(bottomAppBarColor: const Color(0xffffff00)),
               child: const Scaffold(
                 floatingActionButton: FloatingActionButton(
                   onPressed: null,
@@ -115,7 +113,7 @@ void main() {
         home: Builder(
           builder: (BuildContext context) {
             return Theme(
-              data: Theme.of(context).copyWith(bottomAppBarColor: const Color(0xffffff00)),
+              data: Theme.of(context)!.copyWith(bottomAppBarColor: const Color(0xffffff00)),
               child: const Scaffold(
                 floatingActionButton: FloatingActionButton(
                   onPressed: null,
@@ -392,19 +390,19 @@ void main() {
 class ClipCachePainter extends CustomPainter {
   ClipCachePainter(this.context);
 
-  Path value;
+  late Path value;
   BuildContext context;
 
   @override
   void paint(Canvas canvas, Size size) {
-    final RenderPhysicalShape physicalShape = findPhysicalShapeChild(context);
-    value = physicalShape.clipper.getClip(size);
+    final RenderPhysicalShape physicalShape = findPhysicalShapeChild(context)!;
+    value = physicalShape.clipper!.getClip(size);
   }
 
-  RenderPhysicalShape findPhysicalShapeChild(BuildContext context) {
-    RenderPhysicalShape result;
+  RenderPhysicalShape? findPhysicalShapeChild(BuildContext context) {
+    RenderPhysicalShape? result;
     context.visitChildElements((Element e) {
-      final RenderObject renderObject = e.findRenderObject();
+      final RenderObject renderObject = e.findRenderObject()!;
       if (renderObject.runtimeType == RenderPhysicalShape) {
         assert(result == null);
         result = renderObject as RenderPhysicalShape;
@@ -422,7 +420,7 @@ class ClipCachePainter extends CustomPainter {
 }
 
 class ShapeListener extends StatefulWidget {
-  const ShapeListener(this.child, { Key key }) : super(key: key);
+  const ShapeListener(this.child, { Key? key }) : super(key: key);
 
   final Widget child;
 
@@ -440,7 +438,7 @@ class ShapeListenerState extends State<ShapeListener> {
     );
   }
 
-  ClipCachePainter cache;
+  late ClipCachePainter cache;
 
   @override
   void didChangeDependencies() {
@@ -454,7 +452,7 @@ class RectangularNotch extends NotchedShape {
   const RectangularNotch();
 
   @override
-  Path getOuterPath(Rect host, Rect guest) {
+  Path getOuterPath(Rect host, Rect? guest) {
     if (guest == null)
       return Path()..addRect(host);
     return Path()

packages/flutter/test/material/bottom_app_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';

packages/flutter/test/material/bottom_navigation_bar_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/material.dart';
@@ -15,7 +13,7 @@ import '../rendering/mock_canvas.dart';
 
 void main() {
   testWidgets('BottomNavigationBar callback test', (WidgetTester tester) async {
-    int mutatedIndex;
+    late int mutatedIndex;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -100,8 +98,8 @@ void main() {
 
     const double selectedFontSize = 14.0;
     const double unselectedFontSize = 12.0;
-    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style;
-    final TextStyle unselectedFontStyle = tester.renderObject<RenderParagraph>(find.text('Alarm')).text.style;
+    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style!;
+    final TextStyle unselectedFontStyle = tester.renderObject<RenderParagraph>(find.text('Alarm')).text.style!;
     final TextStyle selectedIcon = _iconStyle(tester, Icons.ac_unit);
     final TextStyle unselectedIcon = _iconStyle(tester, Icons.access_alarm);
     expect(selectedFontStyle.color, equals(primaryColor));
@@ -161,13 +159,13 @@ void main() {
         ),
     );
 
-    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style;
-    final TextStyle unselectedFontStyle = tester.renderObject<RenderParagraph>(find.text('Alarm')).text.style;
+    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style!;
+    final TextStyle unselectedFontStyle = tester.renderObject<RenderParagraph>(find.text('Alarm')).text.style!;
     expect(selectedFontStyle.fontSize, equals(selectedTextStyle.fontSize));
     expect(selectedFontStyle.fontWeight, equals(selectedTextStyle.fontWeight));
     expect(
       tester.firstWidget<Transform>(find.ancestor(of: find.text('Alarm'), matching: find.byType(Transform))).transform,
-      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize / selectedTextStyle.fontSize))),
+      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize! / selectedTextStyle.fontSize!))),
     );
     expect(unselectedFontStyle.fontWeight, equals(unselectedTextStyle.fontWeight));
   });
@@ -202,11 +200,11 @@ void main() {
         ),
     );
 
-    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style;
+    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style!;
     expect(selectedFontStyle.fontSize, equals(selectedTextStyle.fontSize));
     expect(
       tester.firstWidget<Transform>(find.ancestor(of: find.text('Alarm'), matching: find.byType(Transform))).transform,
-      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize / selectedTextStyle.fontSize))),
+      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize! / selectedTextStyle.fontSize!))),
     );
   });
 
@@ -274,8 +272,8 @@ void main() {
       ),
     );
 
-    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style;
-    final TextStyle unselectedFontStyle = tester.renderObject<RenderParagraph>(find.text('Alarm')).text.style;
+    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style!;
+    final TextStyle unselectedFontStyle = tester.renderObject<RenderParagraph>(find.text('Alarm')).text.style!;
     final TextStyle selectedIcon = _iconStyle(tester, Icons.ac_unit);
     final TextStyle unselectedIcon = _iconStyle(tester, Icons.access_alarm);
     expect(selectedIcon.color, equals(selectedIconTheme.color));
@@ -433,8 +431,8 @@ void main() {
     );
 
     const double selectedFontSize = 14.0;
-    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style.fontSize, selectedFontSize);
-    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style.color, equals(Colors.white));
+    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style!.fontSize, selectedFontSize);
+    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style!.color, equals(Colors.white));
     expect(_getOpacity(tester, 'Alarm'), equals(0.0));
     expect(_getMaterial(tester).elevation, equals(8.0));
   });
@@ -475,15 +473,15 @@ void main() {
       ),
     );
 
-    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style.fontSize, selectedFontSize);
+    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style!.fontSize, selectedFontSize);
     // Unselected label has a font size of 18 but is scaled down to be font size 14.
-    expect(tester.renderObject<RenderParagraph>(find.text('Alarm')).text.style.fontSize, selectedFontSize);
+    expect(tester.renderObject<RenderParagraph>(find.text('Alarm')).text.style!.fontSize, selectedFontSize);
     expect(
       tester.firstWidget<Transform>(find.ancestor(of: find.text('Alarm'), matching: find.byType(Transform))).transform,
       equals(Matrix4.diagonal3(Vector3.all(unselectedFontSize / selectedFontSize))),
     );
-    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style.color, equals(selectedColor));
-    expect(tester.renderObject<RenderParagraph>(find.text('Alarm')).text.style.color, equals(unselectedColor));
+    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style!.color, equals(selectedColor));
+    expect(tester.renderObject<RenderParagraph>(find.text('Alarm')).text.style!.color, equals(unselectedColor));
     // There should not be any [Opacity] or [FadeTransition] widgets
     // since showUnselectedLabels and showSelectedLabels are true.
     final Finder findOpacity = find.descendant(
@@ -535,8 +533,8 @@ void main() {
       ),
     );
 
-    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style.fontSize, selectedFontSize);
-    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style.color, equals(selectedColor));
+    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style!.fontSize, selectedFontSize);
+    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style!.color, equals(selectedColor));
     expect(_getOpacity(tester, 'Alarm'), equals(0.0));
   });
 
@@ -668,7 +666,7 @@ void main() {
       ),
     );
 
-    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style.color, equals(fixedColor));
+    expect(tester.renderObject<RenderParagraph>(find.text('AC')).text.style!.color, equals(fixedColor));
   });
 
   testWidgets('setting selectedFontSize to zero hides all labels', (WidgetTester tester) async {
@@ -875,7 +873,7 @@ void main() {
 
     await tester.tap(find.text('Alarm'));
     await tester.pump(const Duration(seconds: 1));
-    expect(Theme.of(tester.element(find.text('Alarm'))).brightness, equals(Brightness.dark));
+    expect(Theme.of(tester.element(find.text('Alarm')))!.brightness, equals(Brightness.dark));
   });
 
   testWidgets('BottomNavigationBar inherits shadowed app theme for fixed navbar', (WidgetTester tester) async {
@@ -913,11 +911,11 @@ void main() {
 
     await tester.tap(find.text('Alarm'));
     await tester.pump(const Duration(seconds: 1));
-    expect(Theme.of(tester.element(find.text('Alarm'))).brightness, equals(Brightness.dark));
+    expect(Theme.of(tester.element(find.text('Alarm')))!.brightness, equals(Brightness.dark));
   });
 
   testWidgets('BottomNavigationBar iconSize test', (WidgetTester tester) async {
-    double builderIconSize;
+    late double builderIconSize;
     await tester.pumpWidget(
       MaterialApp(
         home: Scaffold(
@@ -932,7 +930,7 @@ void main() {
                 label: 'B',
                 icon: Builder(
                   builder: (BuildContext context) {
-                    builderIconSize = IconTheme.of(context).size;
+                    builderIconSize = IconTheme.of(context).size!;
                     return SizedBox(
                       width: builderIconSize,
                       height: builderIconSize,
@@ -1101,7 +1099,7 @@ void main() {
   testWidgets('BottomNavigationBar shows tool tips with text scaling on long press when labels are provided', (WidgetTester tester) async {
     const String label = 'Foo';
 
-    Widget buildApp({ double textScaleFactor }) {
+    Widget buildApp({ required double textScaleFactor }) {
       return MediaQuery(
         data: MediaQueryData(textScaleFactor: textScaleFactor),
         child: Localizations(
@@ -1178,9 +1176,9 @@ void main() {
     final RenderBox box = tester.renderObject(find.byType(BottomNavigationBar));
     expect(box.size.height, equals(kBottomNavigationBarHeight));
 
-    final RenderBox itemBoxA = tester.renderObject(find.text(longTextA.data));
+    final RenderBox itemBoxA = tester.renderObject(find.text(longTextA.data!));
     expect(itemBoxA.size, equals(const Size(400.0, 14.0)));
-    final RenderBox itemBoxB = tester.renderObject(find.text(longTextB.data));
+    final RenderBox itemBoxB = tester.renderObject(find.text(longTextB.data!));
     expect(itemBoxB.size, equals(const Size(400.0, 14.0)));
   });
 
@@ -1767,7 +1765,7 @@ void main() {
 
     await tester.pumpAndSettle();
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
 
     // Test default cursor
     await tester.pumpWidget(
@@ -1786,11 +1784,11 @@ void main() {
       ),
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.click);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.click);
   });
 }
 
-Widget boilerplate({ Widget bottomNavigationBar, @required TextDirection textDirection }) {
+Widget boilerplate({ Widget? bottomNavigationBar, required TextDirection textDirection }) {
   assert(textDirection != null);
   return MaterialApp(
     home: Localizations(
@@ -1834,7 +1832,7 @@ TextStyle _iconStyle(WidgetTester tester, IconData icon) {
   final RichText iconRichText = tester.widget<RichText>(
       find.descendant(of: find.byIcon(icon), matching: find.byType(RichText)),
   );
-  return iconRichText.text.style;
+  return iconRichText.text.style!;
 }
 
 EdgeInsets _itemPadding(WidgetTester tester, IconData icon) {

packages/flutter/test/material/bottom_navigation_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';
@@ -139,14 +137,14 @@ void main() {
       ),
     );
 
-    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style;
+    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style!;
     final TextStyle selectedIcon = _iconStyle(tester, Icons.ac_unit);
     final TextStyle unselectedIcon = _iconStyle(tester, Icons.access_alarm);
     expect(selectedFontStyle.fontSize, selectedFontStyle.fontSize);
     // Unselected label has a font size of 22 but is scaled down to be font size 21.
     expect(
       tester.firstWidget<Transform>(find.ancestor(of: find.text('Alarm'), matching: find.byType(Transform))).transform,
-      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize / selectedTextStyle.fontSize))),
+      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize! / selectedTextStyle.fontSize!))),
     );
     expect(selectedIcon.color, equals(selectedItemColor));
     expect(selectedIcon.fontSize, equals(selectedIconTheme.size));
@@ -232,14 +230,14 @@ void main() {
       ),
     );
 
-    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style;
+    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style!;
     final TextStyle selectedIcon = _iconStyle(tester, Icons.ac_unit);
     final TextStyle unselectedIcon = _iconStyle(tester, Icons.access_alarm);
     expect(selectedFontStyle.fontSize, selectedFontStyle.fontSize);
     // Unselected label has a font size of 22 but is scaled down to be font size 21.
     expect(
       tester.firstWidget<Transform>(find.ancestor(of: find.text('Alarm'), matching: find.byType(Transform))).transform,
-      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize / selectedTextStyle.fontSize))),
+      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize! / selectedTextStyle.fontSize!))),
     );
     expect(selectedIcon.color, equals(selectedItemColor));
     expect(selectedIcon.fontSize, equals(selectedIconTheme.size));
@@ -266,7 +264,7 @@ TextStyle _iconStyle(WidgetTester tester, IconData icon) {
   final RichText iconRichText = tester.widget<RichText>(
     find.descendant(of: find.byIcon(icon), matching: find.byType(RichText)),
   );
-  return iconRichText.text.style;
+  return iconRichText.text.style!;
 }
 
 Material _material(WidgetTester tester) {

packages/flutter/test/material/bottom_sheet_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
@@ -28,7 +26,7 @@ void main() {
   }
 
   testWidgets('Tapping on a modal BottomSheet should not dismiss it', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -64,7 +62,7 @@ void main() {
   });
 
   testWidgets('Tapping outside a modal BottomSheet should dismiss it by default', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -98,7 +96,7 @@ void main() {
   });
 
   testWidgets('Tapping outside a modal BottomSheet should dismiss it when isDismissible=true', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -133,7 +131,7 @@ void main() {
   });
 
   testWidgets('Verify that the BottomSheet animates non-linearly', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -165,7 +163,7 @@ void main() {
   });
 
   testWidgets('Tapping outside a modal BottomSheet should not dismiss it when isDismissible=false', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -202,7 +200,7 @@ void main() {
   });
 
   testWidgets('Swiping down a modal BottomSheet should dismiss it by default', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -237,7 +235,7 @@ void main() {
   });
 
   testWidgets('Swiping down a modal BottomSheet should not dismiss it when enableDrag is false', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -273,7 +271,7 @@ void main() {
   });
 
   testWidgets('Swiping down a modal BottomSheet should dismiss it when enableDrag is true', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -309,7 +307,7 @@ void main() {
   });
 
   testWidgets('Modal BottomSheet builder should only be called once', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -354,7 +352,7 @@ void main() {
     expect(showBottomSheetThenCalled, isFalse);
     expect(find.text('BottomSheet'), findsNothing);
 
-    scaffoldKey.currentState.showBottomSheet<void>((BuildContext context) {
+    scaffoldKey.currentState!.showBottomSheet<void>((BuildContext context) {
       return Container(
         margin: const EdgeInsets.all(40.0),
         child: const Text('BottomSheet'),
@@ -408,7 +406,7 @@ void main() {
       ),
     ));
 
-    scaffoldKey.currentState.showBottomSheet<void>((BuildContext context) {
+    scaffoldKey.currentState!.showBottomSheet<void>((BuildContext context) {
       return Container(
         margin: const EdgeInsets.all(40.0),
         child: const Text('BottomSheet'),
@@ -428,8 +426,8 @@ void main() {
   });
 
   testWidgets('modal BottomSheet has no top MediaQuery', (WidgetTester tester) async {
-    BuildContext outerContext;
-    BuildContext innerContext;
+    late BuildContext outerContext;
+    late BuildContext innerContext;
 
     await tester.pumpWidget(Localizations(
       locale: const Locale('en', 'US'),
@@ -469,11 +467,11 @@ void main() {
     await tester.pump(const Duration(seconds: 1));
 
     expect(
-      MediaQuery.of(outerContext).padding,
+      MediaQuery.of(outerContext)!.padding,
       const EdgeInsets.all(50.0),
     );
     expect(
-      MediaQuery.of(innerContext).padding,
+      MediaQuery.of(innerContext)!.padding,
       const EdgeInsets.only(left: 50.0, right: 50.0, bottom: 50.0),
     );
   });
@@ -490,7 +488,7 @@ void main() {
     ));
 
 
-    showModalBottomSheet<void>(context: scaffoldKey.currentContext, builder: (BuildContext context) {
+    showModalBottomSheet<void>(context: scaffoldKey.currentContext!, builder: (BuildContext context) {
       return Container(
         child: const Text('BottomSheet'),
       );
@@ -545,7 +543,7 @@ void main() {
     ));
 
     showModalBottomSheet<void>(
-      context: scaffoldKey.currentContext,
+      context: scaffoldKey.currentContext!,
       backgroundColor: color,
       barrierColor: barrierColor,
       elevation: elevation,
@@ -584,7 +582,7 @@ void main() {
 
 
     showModalBottomSheet<void>(
-      context: scaffoldKey.currentContext,
+      context: scaffoldKey.currentContext!,
       builder: (BuildContext context) {
         return DraggableScrollableSheet(
           expand: false,
@@ -710,13 +708,13 @@ void main() {
       ),
     ));
 
-    RouteSettings retrievedRouteSettings;
+    late RouteSettings retrievedRouteSettings;
 
     showModalBottomSheet<void>(
-      context: scaffoldKey.currentContext,
+      context: scaffoldKey.currentContext!,
       routeSettings: routeSettings,
       builder: (BuildContext context) {
-        retrievedRouteSettings = ModalRoute.of(context).settings;
+        retrievedRouteSettings = ModalRoute.of(context)!.settings;
         return Container(
           child: const Text('BottomSheet'),
         );
@@ -731,9 +729,9 @@ void main() {
 }
 
 class _TestPage extends StatelessWidget {
-  const _TestPage({Key key, this.useRootNavigator}) : super(key: key);
+  const _TestPage({Key? key, this.useRootNavigator}) : super(key: key);
 
-  final bool useRootNavigator;
+  final bool? useRootNavigator;
 
   @override
   Widget build(BuildContext context) {
@@ -743,7 +741,7 @@ class _TestPage extends StatelessWidget {
         onPressed: () {
           if (useRootNavigator != null) {
             showModalBottomSheet<void>(
-              useRootNavigator: useRootNavigator,
+              useRootNavigator: useRootNavigator!,
               context: context,
               builder: (_) => const Text('Modal bottom sheet'),
             );

packages/flutter/test/material/bottom_sheet_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/services.dart';

packages/flutter/test/material/button_bar_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';
 
@@ -243,7 +241,7 @@ void main() {
   group('button properties override ButtonTheme', () {
 
     testWidgets('default button properties override ButtonTheme properties', (WidgetTester tester) async {
-      BuildContext capturedContext;
+      late BuildContext capturedContext;
       await tester.pumpWidget(
         MaterialApp(
           home: ButtonBar(
@@ -266,7 +264,7 @@ void main() {
     });
 
     testWidgets('ButtonBarTheme button properties override defaults and ButtonTheme properties', (WidgetTester tester) async {
-      BuildContext capturedContext;
+      late BuildContext capturedContext;
       await tester.pumpWidget(
         MaterialApp(
           home: ButtonBarTheme(
@@ -299,7 +297,7 @@ void main() {
     });
 
     testWidgets('ButtonBar button properties override ButtonBarTheme, defaults and ButtonTheme properties', (WidgetTester tester) async {
-      BuildContext capturedContext;
+      late BuildContext capturedContext;
       await tester.pumpWidget(
         MaterialApp(
           home: ButtonBarTheme(