[NNBD] More test migration for Cupertino & Painting (#67323)

packages/flutter/test/cupertino/refresh_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/cupertino.dart';
@@ -13,7 +11,7 @@ import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
-  FakeBuilder mockHelper;
+  late FakeBuilder mockHelper;
 
   setUp(() {
     mockHelper = FakeBuilder();
@@ -1407,10 +1405,10 @@ class RefreshTaskInvocation extends MockHelperInvocation {
 @immutable
 class BuilderInvocation extends MockHelperInvocation {
   const BuilderInvocation({
-    @required this.refreshState,
-    @required this.pulledExtent,
-    @required this.refreshIndicatorExtent,
-    @required this.refreshTriggerPullDistance,
+    required this.refreshState,
+    required this.pulledExtent,
+    required this.refreshIndicatorExtent,
+    required this.refreshTriggerPullDistance,
   });
 
   final RefreshIndicatorMode refreshState;
@@ -1423,10 +1421,10 @@ class BuilderInvocation extends MockHelperInvocation {
 }
 
 Matcher matchesBuilder({
-  @required RefreshIndicatorMode refreshState,
-  @required dynamic pulledExtent,
-  @required dynamic refreshTriggerPullDistance,
-  @required dynamic refreshIndicatorExtent,
+  required RefreshIndicatorMode refreshState,
+  required dynamic pulledExtent,
+  required dynamic refreshTriggerPullDistance,
+  required dynamic refreshIndicatorExtent,
 }) {
   return isA<BuilderInvocation>()
     .having((BuilderInvocation invocation) => invocation.refreshState, 'refreshState', refreshState)

packages/flutter/test/cupertino/route_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
@@ -13,40 +11,12 @@ import 'package:flutter_test/flutter_test.dart';
 import '../widgets/semantics_tester.dart';
 
 void main() {
-  MockNavigatorObserver navigatorObserver;
+  late MockNavigatorObserver navigatorObserver;
 
   setUp(() {
     navigatorObserver = MockNavigatorObserver();
   });
 
-  testWidgets(
-    'Throws FlutterError with correct message when route builder returns null',
-      (WidgetTester tester) async {
-    await tester.pumpWidget(
-      const CupertinoApp(
-        home: Placeholder(),
-      ),
-    );
-
-    tester.state<NavigatorState>(find.byType(Navigator)).push(
-          CupertinoPageRoute<void>(
-            title: 'Route 1',
-            builder: (_) => null,
-          ),
-        );
-
-    await tester.pump();
-    await tester.pump(const Duration(milliseconds: 500));
-
-    final dynamic error = tester.takeException();
-    expect(error, isFlutterError);
-    expect(error.toStringDeep(), equalsIgnoringHashCodes(
-      'FlutterError\n'
-      '   The builder for route "null" returned null.\n'
-      '   Route builders must never return null.\n'
-    ));
-  });
-
   testWidgets('Middle auto-populates with title', (WidgetTester tester) async {
     await tester.pumpWidget(
       const CupertinoApp(
@@ -115,14 +85,14 @@ void main() {
         ..sort((Element a, Element b) {
           final RenderParagraph aParagraph = a.renderObject as RenderParagraph;
           final RenderParagraph bParagraph = b.renderObject as RenderParagraph;
-          return aParagraph.text.style.fontSize.compareTo(
-            bParagraph.text.style.fontSize
+          return aParagraph.text.style!.fontSize!.compareTo(
+            bParagraph.text.style!.fontSize!
           );
         });
 
     final Iterable<double> opacities = titles.map<double>((Element element) {
       final RenderAnimatedOpacity renderOpacity =
-          element.findAncestorRenderObjectOfType<RenderAnimatedOpacity>();
+          element.findAncestorRenderObjectOfType<RenderAnimatedOpacity>()!;
       return renderOpacity.opacity.value;
     });
 
@@ -305,7 +275,7 @@ void main() {
           child: Center(
             child: CupertinoButton(
               onPressed: () {
-                Navigator.push<void>(scaffoldKey.currentContext, CupertinoPageRoute<void>(
+                Navigator.push<void>(scaffoldKey.currentContext!, CupertinoPageRoute<void>(
                   builder: (BuildContext context) {
                     return const CupertinoPageScaffold(
                       child: Center(child: Text('route')),
@@ -383,7 +353,7 @@ void main() {
     // Use the navigator to push a route instead of tapping the 'push' button.
     // The topmost route (the one that's animating away), ignores input while
     // the pop is underway because route.navigator.userGestureInProgress.
-    Navigator.push<void>(scaffoldKey.currentContext, CupertinoPageRoute<void>(
+    Navigator.push<void>(scaffoldKey.currentContext!, CupertinoPageRoute<void>(
       builder: (BuildContext context) {
         return const CupertinoPageScaffold(
           child: Center(child: Text('route')),
@@ -503,7 +473,7 @@ void main() {
     expect(tester.getTopLeft(find.byType(Placeholder)).dy, moreOrLessEquals(600.0, epsilon: 0.1));
   });
 
-  Future<void> testParallax(WidgetTester tester, {@required bool fromFullscreenDialog}) async {
+  Future<void> testParallax(WidgetTester tester, {required bool fromFullscreenDialog}) async {
     await tester.pumpWidget(
       CupertinoApp(
         onGenerateRoute: (RouteSettings settings) => CupertinoPageRoute<void>(
@@ -592,7 +562,7 @@ void main() {
     await testParallax(tester, fromFullscreenDialog: true);
   });
 
-  Future<void> testNoParallax(WidgetTester tester, {@required bool fromFullscreenDialog}) async{
+  Future<void> testNoParallax(WidgetTester tester, {required bool fromFullscreenDialog}) async{
     await tester.pumpWidget(
       CupertinoApp(
         onGenerateRoute: (RouteSettings settings) => CupertinoPageRoute<void>(
@@ -844,7 +814,7 @@ void main() {
       }
     );
 
-    navigatorKey.currentState.push(route2);
+    navigatorKey.currentState!.push(route2);
     await tester.pumpAndSettle();
     expect(navigatorObserver.invocations.removeLast(), NavigatorInvocation.didPush);
 
@@ -852,14 +822,14 @@ void main() {
     expect(navigatorObserver.invocations.removeLast(), NavigatorInvocation.didStartUserGesture);
     await tester.pump();
     expect(tester.getTopLeft(find.text('2')).dx, moreOrLessEquals(100));
-    expect(navigatorKey.currentState.userGestureInProgress, true);
+    expect(navigatorKey.currentState!.userGestureInProgress, true);
 
     // Didn't drag far enough to snap into dismissing this route.
     // Each 100px distance takes 100ms to snap back.
     await tester.pump(const Duration(milliseconds: 101));
     // Back to the page covering the whole screen.
     expect(tester.getTopLeft(find.text('2')).dx, moreOrLessEquals(0));
-    expect(navigatorKey.currentState.userGestureInProgress, false);
+    expect(navigatorKey.currentState!.userGestureInProgress, false);
 
     expect(navigatorObserver.invocations.removeLast(), NavigatorInvocation.didStopUserGesture);
     expect(navigatorObserver.invocations.removeLast(), isNot(NavigatorInvocation.didPop));
@@ -867,7 +837,7 @@ void main() {
     await tester.dragFrom(const Offset(5, 100), const Offset(500, 0));
     await tester.pump();
     expect(tester.getTopLeft(find.text('2')).dx, moreOrLessEquals(500));
-    expect(navigatorKey.currentState.userGestureInProgress, true);
+    expect(navigatorKey.currentState!.userGestureInProgress, true);
     expect(navigatorObserver.invocations.removeLast(), NavigatorInvocation.didPop);
 
     // Did go far enough to snap out of this route.
@@ -876,7 +846,7 @@ void main() {
     expect(find.text('2'), findsNothing);
     // First route covers the whole screen.
     expect(tester.getTopLeft(find.text('1')).dx, moreOrLessEquals(0));
-    expect(navigatorKey.currentState.userGestureInProgress, false);
+    expect(navigatorKey.currentState!.userGestureInProgress, false);
   });
 
   /// Regression test for https://github.com/flutter/flutter/issues/29596.
@@ -967,7 +937,7 @@ void main() {
   });
 
   testWidgets('ModalPopup overlay dark mode', (WidgetTester tester) async {
-    StateSetter stateSetter;
+    late StateSetter stateSetter;
     Brightness brightness = Brightness.light;
 
     await tester.pumpWidget(
@@ -998,7 +968,7 @@ void main() {
     await tester.pumpAndSettle();
 
     expect(
-      tester.widget<ModalBarrier>(find.byType(ModalBarrier).last).color.value,
+      tester.widget<ModalBarrier>(find.byType(ModalBarrier).last).color!.value,
       0x33000000,
     );
 
@@ -1007,7 +977,7 @@ void main() {
 
     // TODO(LongCatIsLooong): The background overlay SHOULD switch to dark color.
     expect(
-      tester.widget<ModalBarrier>(find.byType(ModalBarrier).last).color.value,
+      tester.widget<ModalBarrier>(find.byType(ModalBarrier).last).color!.value,
       0x33000000,
     );
 
@@ -1034,7 +1004,7 @@ void main() {
     await tester.pumpAndSettle();
 
     expect(
-      tester.widget<ModalBarrier>(find.byType(ModalBarrier).last).color.value,
+      tester.widget<ModalBarrier>(find.byType(ModalBarrier).last).color!.value,
       0x7A000000,
     );
   });
@@ -1064,7 +1034,7 @@ void main() {
     expect(homeTapCount, 1);
     expect(pageTapCount, 0);
 
-    Navigator.push<void>(homeScaffoldKey.currentContext, CupertinoPageRoute<void>(
+    Navigator.push<void>(homeScaffoldKey.currentContext!, CupertinoPageRoute<void>(
       builder: (BuildContext context) {
         return CupertinoPageScaffold(
           key: pageScaffoldKey,
@@ -1172,7 +1142,7 @@ void main() {
     RenderBox box = tester.renderObject(find.byKey(container)) as RenderBox;
     final double initialPosition = box.localToGlobal(Offset.zero).dx;
 
-    navigator.currentState.pushNamed('/page2');
+    navigator.currentState!.pushNamed('/page2');
     await tester.pumpAndSettle();
     box = tester.renderObject(find.byKey(container)) as RenderBox;
     final double finalPosition = box.localToGlobal(Offset.zero).dx;
@@ -1522,7 +1492,10 @@ void main() {
     await tester.pumpWidget(
       buildNavigator(
         pages: myPages,
-        onPopPage: (Route<dynamic> route, dynamic result) => null,
+        onPopPage: (Route<dynamic> route, dynamic result) {
+          assert(false); // The test shouldn't call this.
+          return true;
+        },
         transitionDelegate: detector,
       )
     );
@@ -1545,7 +1518,10 @@ void main() {
     await tester.pumpWidget(
       buildNavigator(
         pages: myPages,
-        onPopPage: (Route<dynamic> route, dynamic result) => null,
+        onPopPage: (Route<dynamic> route, dynamic result) {
+          assert(false); // The test shouldn't call this.
+          return true;
+        },
         transitionDelegate: detector,
       )
     );
@@ -1570,7 +1546,10 @@ void main() {
     await tester.pumpWidget(
       buildNavigator(
         pages: myPages,
-        onPopPage: (Route<dynamic> route, dynamic result) => null,
+        onPopPage: (Route<dynamic> route, dynamic result) {
+          assert(false); // The test shouldn't call this.
+          return true;
+        },
         transitionDelegate: detector,
       )
     );
@@ -1588,7 +1567,10 @@ void main() {
     await tester.pumpWidget(
       buildNavigator(
         pages: myPages,
-        onPopPage: (Route<dynamic> route, dynamic result) => null,
+        onPopPage: (Route<dynamic> route, dynamic result) {
+          assert(false); // The test shouldn't call this.
+          return true;
+        },
         transitionDelegate: detector,
       )
     );
@@ -1624,17 +1606,17 @@ class MockNavigatorObserver extends NavigatorObserver {
   final List<NavigatorInvocation> invocations = <NavigatorInvocation>[];
 
   @override
-  void didStartUserGesture(Route<Object> route, Route<Object> previousRoute) {
+  void didStartUserGesture(Route<dynamic> route, Route<dynamic>? previousRoute) {
     invocations.add(NavigatorInvocation.didStartUserGesture);
   }
 
   @override
-  void didPop(Route<Object> route, Route<Object> previousRoute) {
+  void didPop(Route<dynamic> route, Route<dynamic>? previousRoute) {
     invocations.add(NavigatorInvocation.didPop);
   }
 
   @override
-  void didPush(Route<Object> route, Route<Object> previousRoute) {
+  void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) {
     invocations.add(NavigatorInvocation.didPush);
   }
 
@@ -1655,7 +1637,7 @@ class PopupObserver extends NavigatorObserver {
   int popupCount = 0;
 
   @override
-  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+  void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) {
     if (route.toString().contains('_CupertinoModalPopupRoute')) {
       popupCount++;
     }
@@ -1667,7 +1649,7 @@ class DialogObserver 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++;
     }
@@ -1679,9 +1661,9 @@ class TransitionDetector extends DefaultTransitionDelegate<void> {
   bool hasTransition = false;
   @override
   Iterable<RouteTransitionRecord> resolve({
-    List<RouteTransitionRecord> newPageRouteHistory,
-    Map<RouteTransitionRecord, RouteTransitionRecord> locationToExitingPageRoute,
-    Map<RouteTransitionRecord, List<RouteTransitionRecord>> pageRouteToPagelessRoutes
+    required List<RouteTransitionRecord> newPageRouteHistory,
+    required Map<RouteTransitionRecord?, RouteTransitionRecord> locationToExitingPageRoute,
+    required Map<RouteTransitionRecord?, List<RouteTransitionRecord>> pageRouteToPagelessRoutes,
   }) {
     hasTransition = true;
     return super.resolve(
@@ -1693,13 +1675,13 @@ class TransitionDetector extends DefaultTransitionDelegate<void> {
 }
 
 Widget buildNavigator({
-  List<Page<dynamic>> pages,
-  PopPageCallback onPopPage,
-  GlobalKey<NavigatorState> key,
-  TransitionDelegate<dynamic> transitionDelegate
+  required List<Page<dynamic>> pages,
+  PopPageCallback? onPopPage,
+  GlobalKey<NavigatorState>? key,
+  TransitionDelegate<dynamic>? transitionDelegate
 }) {
   return MediaQuery(
-    data: MediaQueryData.fromWindow(WidgetsBinding.instance.window),
+    data: MediaQueryData.fromWindow(WidgetsBinding.instance!.window),
     child: Localizations(
       locale: const Locale('en', 'US'),
       delegates: const <LocalizationsDelegate<dynamic>>[

packages/flutter/test/cupertino/scaffold_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:typed_data';
 
 import 'package:flutter/cupertino.dart';
@@ -31,7 +29,7 @@ void main() {
   });
 
   testWidgets('Opaque bar pushes contents down', (WidgetTester tester) async {
-    BuildContext childContext;
+    late BuildContext childContext;
     await tester.pumpWidget(Directionality(
       textDirection: TextDirection.ltr,
       child: MediaQuery(
@@ -51,7 +49,7 @@ void main() {
       ),
     ));
 
-    expect(MediaQuery.of(childContext).padding.top, 0);
+    expect(MediaQuery.of(childContext)!.padding.top, 0);
     // The top of the [Container] is 44 px from the top of the screen because
     // it's pushed down by the opaque navigation bar whose height is 44 px,
     // and the 20 px [MediaQuery] top padding is fully absorbed by the navigation bar.
@@ -69,7 +67,7 @@ void main() {
       darkColor: Color(0xFF000000),
     );
 
-    BuildContext childContext;
+    late BuildContext childContext;
     Widget scaffoldWithBrightness(Brightness brightness) {
       return Directionality(
         textDirection: TextDirection.ltr,
@@ -96,12 +94,12 @@ void main() {
     }
     await tester.pumpWidget(scaffoldWithBrightness(Brightness.light));
 
-    expect(MediaQuery.of(childContext).padding.top, 0);
+    expect(MediaQuery.of(childContext)!.padding.top, 0);
     expect(find.byType(CupertinoPageScaffold), paints..rect(color: backgroundColor.color));
 
     await tester.pumpWidget(scaffoldWithBrightness(Brightness.dark));
 
-    expect(MediaQuery.of(childContext).padding.top, greaterThan(0));
+    expect(MediaQuery.of(childContext)!.padding.top, greaterThan(0));
     expect(find.byType(CupertinoPageScaffold), paints..rect(color: backgroundColor.darkColor));
   });
 
@@ -122,7 +120,7 @@ void main() {
 
     expect(tester.getSize(find.byType(Container)).height, 600.0 - 44.0 - 100.0);
 
-    BuildContext childContext;
+    late BuildContext childContext;
     await tester.pumpWidget(Directionality(
       textDirection: TextDirection.ltr,
       child: MediaQuery(
@@ -144,7 +142,7 @@ void main() {
     expect(tester.getSize(find.byType(Container)).height, 600.0 - 100.0);
     // The shouldn't see a media query view inset because it was consumed by
     // the scaffold.
-    expect(MediaQuery.of(childContext).viewInsets.bottom, 0);
+    expect(MediaQuery.of(childContext)!.viewInsets.bottom, 0);
 
     await tester.pumpWidget(Directionality(
       textDirection: TextDirection.ltr,
@@ -324,7 +322,7 @@ void main() {
                     child: CupertinoButton(
                       child: const Text('Next'),
                       onPressed: () {
-                        Navigator.of(context).push(
+                        Navigator.of(context)!.push(
                           CupertinoPageRoute<void>(
                             builder: (BuildContext context) {
                               return CupertinoPageScaffold(
@@ -335,7 +333,7 @@ void main() {
                                   child: CupertinoButton(
                                     child: const Text('Back'),
                                     onPressed: () {
-                                      Navigator.of(context).pop();
+                                      Navigator.of(context)!.pop();
                                     },
                                   ),
                                 ),
@@ -438,11 +436,11 @@ void main() {
   testWidgets('Lists in CupertinoPageScaffold scroll to the top when status bar tapped', (WidgetTester tester) async {
     await tester.pumpWidget(
       CupertinoApp(
-        builder: (BuildContext context, Widget child) {
+        builder: (BuildContext context, Widget? child) {
           // Acts as a 20px status bar at the root of the app.
           return MediaQuery(
-            data: MediaQuery.of(context).copyWith(padding: const EdgeInsets.only(top: 20)),
-            child: child,
+            data: MediaQuery.of(context)!.copyWith(padding: const EdgeInsets.only(top: 20)),
+            child: child!,
           );
         },
         home: CupertinoPageScaffold(
@@ -539,7 +537,7 @@ void main() {
       CupertinoApp(
         home: Builder(builder: (BuildContext context) {
           return MediaQuery(
-            data: MediaQuery.of(context).copyWith(textScaleFactor: 99),
+            data: MediaQuery.of(context)!.copyWith(textScaleFactor: 99),
             child: const CupertinoPageScaffold(
               navigationBar: CupertinoNavigationBar(
                 middle: Text('middle'),

packages/flutter/test/cupertino/scrollbar_paint_test.dart

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

packages/flutter/test/cupertino/scrollbar_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
@@ -62,7 +60,7 @@ void main() {
 
   testWidgets('Scrollbar dark mode', (WidgetTester tester) async {
     Brightness brightness = Brightness.light;
-    StateSetter setState;
+    late StateSetter setState;
     await tester.pumpWidget(
       Directionality(
         textDirection: TextDirection.ltr,

packages/flutter/test/cupertino/segmented_control_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/widgets.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -41,7 +39,7 @@ StatefulBuilder setupSimpleSegmentedControl() {
   );
 }
 
-Widget boilerplate({ Widget child }) {
+Widget boilerplate({ required Widget child }) {
   return Directionality(
     textDirection: TextDirection.ltr,
     child: Center(child: child),
@@ -132,18 +130,18 @@ void main() {
       child: Text('Child 2'),
     ) ;
 
-    Future<void> verifyPadding({ EdgeInsets padding }) async {
+    Future<void> verifyPadding({ EdgeInsets? padding }) async {
       final EdgeInsets effectivePadding = padding ?? const EdgeInsets.symmetric(horizontal: 16);
       final Rect segmentedControlRect = tester.getRect(find.byKey(key));
       expect(
-          tester.getTopLeft(find.byWidget(children[0])),
+          tester.getTopLeft(find.byWidget(children[0]!)),
           segmentedControlRect.topLeft.translate(
             effectivePadding.topLeft.dx,
             effectivePadding.topLeft.dy,
           ),
       );
       expect(
-        tester.getBottomLeft(find.byWidget(children[0])),
+        tester.getBottomLeft(find.byWidget(children[0]!)),
         segmentedControlRect.bottomLeft.translate(
           effectivePadding.bottomLeft.dx,
           effectivePadding.bottomLeft.dy,
@@ -151,14 +149,14 @@ void main() {
       );
 
       expect(
-        tester.getTopRight(find.byWidget(children[1])),
+        tester.getTopRight(find.byWidget(children[1]!)),
         segmentedControlRect.topRight.translate(
           effectivePadding.topRight.dx,
           effectivePadding.topRight.dy,
         ),
       );
       expect(
-        tester.getBottomRight(find.byWidget(children[1])),
+        tester.getBottomRight(find.byWidget(children[1]!)),
         segmentedControlRect.bottomRight.translate(
           effectivePadding.bottomRight.dx,
           effectivePadding.bottomRight.dy,
@@ -228,40 +226,6 @@ void main() {
     }
   });
 
-  testWidgets('Children and onValueChanged arguments can not be null', (WidgetTester tester) async {
-    try {
-      await tester.pumpWidget(
-        boilerplate(
-          child: CupertinoSegmentedControl<int>(
-            children: null,
-            onValueChanged: (int newValue) { },
-          ),
-        ),
-      );
-      fail('Should not be possible to create segmented control with null children');
-    } on AssertionError catch (e) {
-      expect(e.toString(), contains('children'));
-    }
-
-    final Map<int, Widget> children = <int, Widget>{};
-    children[0] = const Text('Child 1');
-    children[1] = const Text('Child 2');
-
-    try {
-      await tester.pumpWidget(
-        boilerplate(
-          child: CupertinoSegmentedControl<int>(
-            children: children,
-            onValueChanged: null,
-          ),
-        ),
-      );
-      fail('Should not be possible to create segmented control with null onValueChanged');
-    } on AssertionError catch (e) {
-      expect(e.toString(), contains('onValueChanged'));
-    }
-  });
-
   testWidgets('Widgets have correct default text/icon styles, change correctly on selection', (WidgetTester tester) async {
     final Map<int, Widget> children = <int, Widget>{};
     children[0] = const Text('Child 1');
@@ -292,7 +256,7 @@ void main() {
     DefaultTextStyle textStyle = tester.widget(find.widgetWithText(DefaultTextStyle, 'Child 1'));
     IconTheme iconTheme = tester.widget(find.widgetWithIcon(IconTheme, const IconData(1)));
 
-    expect(textStyle.style.color, isSameColorAs(CupertinoColors.white));
+    expect(textStyle.style!.color, isSameColorAs(CupertinoColors.white));
     expect(iconTheme.data.color, CupertinoColors.activeBlue);
 
     await tester.tap(find.widgetWithIcon(IconTheme, const IconData(1)));
@@ -301,7 +265,7 @@ void main() {
     textStyle = tester.widget(find.widgetWithText(DefaultTextStyle, 'Child 1'));
     iconTheme = tester.widget(find.widgetWithIcon(IconTheme, const IconData(1)));
 
-    expect(textStyle.style.color, CupertinoColors.activeBlue);
+    expect(textStyle.style!.color, CupertinoColors.activeBlue);
     expect(iconTheme.data.color, isSameColorAs(CupertinoColors.white));
   });
 
@@ -336,7 +300,7 @@ void main() {
       DefaultTextStyle textStyle = tester.widget(find.widgetWithText(DefaultTextStyle, 'Child 1').first);
       IconThemeData iconTheme = IconTheme.of(tester.element(find.byIcon(const IconData(1))));
 
-      expect(textStyle.style.color, isSameColorAs(CupertinoColors.black));
+      expect(textStyle.style!.color, isSameColorAs(CupertinoColors.black));
       expect(iconTheme.color, isSameColorAs(CupertinoColors.systemBlue.darkColor));
 
       await tester.tap(find.byIcon(const IconData(1)));
@@ -346,7 +310,7 @@ void main() {
       textStyle = tester.widget(find.widgetWithText(DefaultTextStyle, 'Child 1').first);
       iconTheme = IconTheme.of(tester.element(find.byIcon(const IconData(1))));
 
-      expect(textStyle.style.color, isSameColorAs(CupertinoColors.systemBlue.darkColor));
+      expect(textStyle.style!.color, isSameColorAs(CupertinoColors.systemBlue.darkColor));
       expect(iconTheme.color, isSameColorAs(CupertinoColors.black));
     },
   );
@@ -384,7 +348,7 @@ void main() {
     IconTheme iconTheme = tester.widget(find.widgetWithIcon(IconTheme, const IconData(1)));
 
     expect(getRenderSegmentedControl(tester).borderColor, CupertinoColors.black);
-    expect(textStyle.style.color, CupertinoColors.lightBackgroundGray);
+    expect(textStyle.style!.color, CupertinoColors.lightBackgroundGray);
     expect(iconTheme.data.color, CupertinoColors.activeGreen.color);
     expect(getBackgroundColor(tester, 0), CupertinoColors.activeGreen.color);
     expect(getBackgroundColor(tester, 1), CupertinoColors.lightBackgroundGray);
@@ -395,7 +359,7 @@ void main() {
     textStyle = tester.widget(find.widgetWithText(DefaultTextStyle, 'Child 1'));
     iconTheme = tester.widget(find.widgetWithIcon(IconTheme, const IconData(1)));
 
-    expect(textStyle.style.color, CupertinoColors.activeGreen.color);
+    expect(textStyle.style!.color, CupertinoColors.activeGreen.color);
     expect(iconTheme.data.color, CupertinoColors.lightBackgroundGray);
     expect(getBackgroundColor(tester, 0), CupertinoColors.lightBackgroundGray);
     expect(getBackgroundColor(tester, 1), CupertinoColors.activeGreen.color);
@@ -562,7 +526,7 @@ void main() {
     children[0] = const Text('Child 1');
     children[1] = const Text('Child 2');
 
-    int sharedValue;
+    int? sharedValue;
 
     await tester.pumpWidget(
       StatefulBuilder(
@@ -930,7 +894,7 @@ void main() {
 
   testWidgets('Hit-tests report accurate local position in segments', (WidgetTester tester) async {
     final Map<int, Widget> children = <int, Widget>{};
-    TapDownDetails tapDownDetails;
+    late TapDownDetails tapDownDetails;
     children[0] = GestureDetector(
       behavior: HitTestBehavior.opaque,
       onTapDown: (TapDownDetails details) { tapDownDetails = details; },
@@ -961,7 +925,7 @@ void main() {
 
     expect(sharedValue, 1);
 
-    final Offset segment0GlobalOffset = tester.getTopLeft(find.byWidget(children[0]));
+    final Offset segment0GlobalOffset = tester.getTopLeft(find.byWidget(children[0]!));
     await tester.tapAt(segment0GlobalOffset + const Offset(7, 11));
 
     expect(tapDownDetails.localPosition, const Offset(7, 11));
@@ -998,7 +962,7 @@ void main() {
 
       expect(sharedValue, 0);
 
-      final Offset centerOfTwo = tester.getCenter(find.byWidget(children[1]));
+      final Offset centerOfTwo = tester.getCenter(find.byWidget(children[1]!));
       // Tap within the bounds of children[1], but not at the center.
       // children[1] is a SizedBox thus not hittable by itself.
       await tester.tapAt(centerOfTwo + const Offset(10, 0));
@@ -1418,7 +1382,7 @@ void main() {
     children[0] = const Text('A');
     children[1] = const Text('B');
     children[2] = const Text('C');
-    int sharedValue = 0;
+    int? sharedValue = 0;
 
     await tester.pumpWidget(
       StatefulBuilder(

packages/flutter/test/cupertino/slider_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
@@ -66,7 +64,7 @@ void main() {
     await tester.pump(); // No animation should start.
     // Check the transientCallbackCount before tearing down the widget to ensure
     // that no animation is running.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
   });
 
   testWidgets('Slider does not move when tapped (RTL)', (WidgetTester tester) async {
@@ -102,7 +100,7 @@ void main() {
     await tester.pump(); // No animation should start.
     // Check the transientCallbackCount before tearing down the widget to ensure
     // that no animation is running.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
   });
 
   testWidgets('Slider calls onChangeStart once when interaction begins', (WidgetTester tester) async {
@@ -143,7 +141,7 @@ void main() {
     await tester.pump(); // No animation should start.
     // Check the transientCallbackCount before tearing down the widget to ensure
     // that no animation is running.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
   });
 
   testWidgets('Slider calls onChangeEnd once after interaction has ended', (WidgetTester tester) async {
@@ -184,14 +182,14 @@ void main() {
     await tester.pump(); // No animation should start.
     // Check the transientCallbackCount before tearing down the widget to ensure
     // that no animation is running.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
   });
 
   testWidgets('Slider moves when dragged (LTR)', (WidgetTester tester) async {
     final Key sliderKey = UniqueKey();
     double value = 0.0;
-    double startValue;
-    double endValue;
+    late double startValue;
+    late double endValue;
 
     await tester.pumpWidget(
       CupertinoApp(
@@ -238,14 +236,14 @@ void main() {
     await tester.pump(); // No animation should start.
     // Check the transientCallbackCount before tearing down the widget to ensure
     // that no animation is running.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
   });
 
   testWidgets('Slider moves when dragged (RTL)', (WidgetTester tester) async {
     final Key sliderKey = UniqueKey();
     double value = 0.0;
-    double startValue;
-    double endValue;
+    late double startValue;
+    late double endValue;
 
     await tester.pumpWidget(
       CupertinoApp(
@@ -292,7 +290,7 @@ void main() {
     await tester.pump(); // No animation should start.
     // Check the transientCallbackCount before tearing down the widget to ensure
     // that no animation is running.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
   });
 
   testWidgets('Slider Semantics', (WidgetTester tester) async {

packages/flutter/test/cupertino/sliding_segmented_control_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:collection';
 
 import 'package:flutter/gestures.dart';
@@ -28,7 +26,7 @@ Rect currentUnscaledThumbRect(WidgetTester tester, { bool useGlobalCoordinate =
     return local;
 
   final RenderBox segmentedControl = renderSegmentedControl as RenderBox;
-  return local?.shift(segmentedControl.localToGlobal(Offset.zero));
+  return local.shift(segmentedControl.localToGlobal(Offset.zero));
 }
 
 double currentThumbScale(WidgetTester tester) => getRenderSegmentedControl(tester).currentThumbScale as double;
@@ -50,13 +48,13 @@ Widget setupSimpleSegmentedControl() {
   );
 }
 
-StateSetter setState;
-int groupValue = 0;
-void defaultCallback(int newValue) {
-  setState(() { groupValue = newValue; });
+StateSetter? setState;
+int? groupValue = 0;
+void defaultCallback(int? newValue) {
+  setState!(() { groupValue = newValue; });
 }
 
-Widget boilerplate({ WidgetBuilder builder }) {
+Widget boilerplate({ required WidgetBuilder builder }) {
   return Directionality(
     textDirection: TextDirection.ltr,
     child: Center(
@@ -75,54 +73,6 @@ void main() {
     groupValue = 0;
   });
 
-  testWidgets('Children and onValueChanged and padding arguments can not be null', (WidgetTester tester) async {
-    groupValue = null;
-    try {
-      await tester.pumpWidget(
-        CupertinoSlidingSegmentedControl<int>(
-          children: null,
-          groupValue: groupValue,
-          onValueChanged: defaultCallback,
-        ),
-      );
-      fail('Should not be possible to create segmented control with null children');
-    } on AssertionError catch (e) {
-      expect(e.toString(), contains('children'));
-    }
-
-    const Map<int, Widget> children = <int, Widget>{
-      0: Text('Child 1'),
-      1: Text('Child 2'),
-    };
-
-    try {
-      await tester.pumpWidget(
-        CupertinoSlidingSegmentedControl<int>(
-          children: children,
-          groupValue: groupValue,
-          onValueChanged: null,
-        ),
-      );
-      fail('Should not be possible to create segmented control without an onValueChanged');
-    } on AssertionError catch (e) {
-      expect(e.toString(), contains('onValueChanged'));
-    }
-
-    try {
-      await tester.pumpWidget(
-        CupertinoSlidingSegmentedControl<int>(
-          children: children,
-          groupValue: groupValue,
-          onValueChanged: defaultCallback,
-          padding: null,
-        ),
-      );
-      fail('Should not be possible to create segmented control with null padding');
-    } on AssertionError catch (e) {
-      expect(e.toString(), contains('padding'));
-    }
-  });
-
   testWidgets('Need at least 2 children', (WidgetTester tester) async {
     final Map<int, Widget> children = <int, Widget>{};
     groupValue = null;
@@ -178,25 +128,25 @@ void main() {
       1: Text('Child 2'),
     };
 
-    Future<void> verifyPadding({ EdgeInsets padding }) async {
+    Future<void> verifyPadding({ EdgeInsets? padding }) async {
       final EdgeInsets effectivePadding = padding ?? const EdgeInsets.symmetric(vertical: 2, horizontal: 3);
       final Rect segmentedControlRect = tester.getRect(find.byKey(key));
 
       expect(
-          tester.getTopLeft(find.ancestor(of: find.byWidget(children[0]), matching: find.byType(Opacity))),
+          tester.getTopLeft(find.ancestor(of: find.byWidget(children[0]!), matching: find.byType(Opacity))),
           segmentedControlRect.topLeft + effectivePadding.topLeft,
       );
       expect(
-        tester.getBottomLeft(find.ancestor(of: find.byWidget(children[0]), matching: find.byType(Opacity))),
+        tester.getBottomLeft(find.ancestor(of: find.byWidget(children[0]!), matching: find.byType(Opacity))),
         segmentedControlRect.bottomLeft + effectivePadding.bottomLeft,
       );
 
       expect(
-        tester.getTopRight(find.ancestor(of: find.byWidget(children[1]), matching: find.byType(Opacity))),
+        tester.getTopRight(find.ancestor(of: find.byWidget(children[1]!), matching: find.byType(Opacity))),
         segmentedControlRect.topRight + effectivePadding.topRight,
       );
       expect(
-        tester.getBottomRight(find.ancestor(of: find.byWidget(children[1]), matching: find.byType(Opacity))),
+        tester.getBottomRight(find.ancestor(of: find.byWidget(children[1]!), matching: find.byType(Opacity))),
         segmentedControlRect.bottomRight + effectivePadding.bottomRight,
       );
     }
@@ -304,7 +254,7 @@ void main() {
 
       DefaultTextStyle textStyle = tester.widget(find.widgetWithText(DefaultTextStyle, 'Child 1').first);
 
-      expect(textStyle.style.fontWeight, FontWeight.w500);
+      expect(textStyle.style!.fontWeight, FontWeight.w500);
 
       await tester.tap(find.byIcon(const IconData(1)));
       await tester.pump();
@@ -313,7 +263,7 @@ void main() {
       textStyle = tester.widget(find.widgetWithText(DefaultTextStyle, 'Child 1').first);
 
       expect(groupValue, 1);
-      expect(textStyle.style.fontWeight, FontWeight.normal);
+      expect(textStyle.style!.fontWeight, FontWeight.normal);
     },
   );
 
@@ -324,7 +274,7 @@ void main() {
     };
 
     Brightness brightness = Brightness.light;
-    StateSetter setState;
+    late StateSetter setState;
 
     await tester.pumpWidget(
       StatefulBuilder(
@@ -354,7 +304,7 @@ void main() {
     )).decoration as BoxDecoration;
 
     expect(getRenderSegmentedControl(tester).thumbColor.value, CupertinoColors.systemGreen.color.value);
-    expect(decoration.color.value, CupertinoColors.systemRed.color.value);
+    expect(decoration.color!.value, CupertinoColors.systemRed.color.value);
 
     setState(() { brightness = Brightness.dark; });
     await tester.pump();
@@ -366,7 +316,7 @@ void main() {
 
 
     expect(getRenderSegmentedControl(tester).thumbColor.value, CupertinoColors.systemGreen.darkColor.value);
-    expect(decorationDark.color.value, CupertinoColors.systemRed.darkColor.value);
+    expect(decorationDark.color!.value, CupertinoColors.systemRed.darkColor.value);
   });
 
   testWidgets(
@@ -777,7 +727,7 @@ void main() {
 
     expect(groupValue, 0);
 
-    final Offset centerOfTwo = tester.getCenter(find.byWidget(children[1]));
+    final Offset centerOfTwo = tester.getCenter(find.byWidget(children[1]!));
     // Tap within the bounds of children[1], but not at the center.
     // children[1] is a SizedBox thus not hittable by itself.
     await tester.tapAt(centerOfTwo + const Offset(10, 0));
@@ -787,7 +737,7 @@ void main() {
 
   testWidgets('Hit-tests report accurate local position in segments', (WidgetTester tester) async {
     final Map<int, Widget> children = <int, Widget>{};
-    TapDownDetails tapDownDetails;
+    late TapDownDetails tapDownDetails;
     children[0] = GestureDetector(
       behavior: HitTestBehavior.opaque,
       onTapDown: (TapDownDetails details) { tapDownDetails = details; },
@@ -810,7 +760,7 @@ void main() {
 
     expect(groupValue, 0);
 
-    final Offset segment0GlobalOffset = tester.getTopLeft(find.byWidget(children[0]));
+    final Offset segment0GlobalOffset = tester.getTopLeft(find.byWidget(children[0]!));
     await tester.tapAt(segment0GlobalOffset + const Offset(7, 11));
 
     expect(tapDownDetails.localPosition, const Offset(7, 11));

packages/flutter/test/cupertino/switch_test.dart

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

packages/flutter/test/cupertino/tab_scaffold_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:typed_data';
 
 import 'package:flutter/cupertino.dart';
@@ -12,10 +10,10 @@ import 'package:flutter_test/flutter_test.dart';
 import '../image_data.dart';
 import '../rendering/rendering_tester.dart';
 
-List<int> selectedTabs;
+late List<int> selectedTabs;
 
 class MockCupertinoTabController extends CupertinoTabController {
-  MockCupertinoTabController({ int initialIndex }): super(initialIndex: initialIndex);
+  MockCupertinoTabController({ required int initialIndex }): super(initialIndex: initialIndex);
 
   bool isDisposed = false;
   int numOfListeners = 0;
@@ -75,12 +73,12 @@ void main() {
       of: find.text('Tab 1'),
       matching: find.byType(RichText),
     ));
-    expect(tab1.text.style.color, CupertinoColors.activeBlue);
+    expect(tab1.text.style!.color, CupertinoColors.activeBlue);
     RichText tab2 = tester.widget(find.descendant(
       of: find.text('Tab 2'),
       matching: find.byType(RichText),
     ));
-    expect(tab2.text.style.color.value, 0xFF999999);
+    expect(tab2.text.style!.color!.value, 0xFF999999);
 
     await tester.tap(find.text('Tab 2'));
     await tester.pump();
@@ -90,12 +88,12 @@ void main() {
       of: find.text('Tab 1'),
       matching: find.byType(RichText),
     ));
-    expect(tab1.text.style.color.value, 0xFF999999);
+    expect(tab1.text.style!.color!.value, 0xFF999999);
     tab2 = tester.widget(find.descendant(
       of: find.text('Tab 2'),
       matching: find.byType(RichText),
     ));
-    expect(tab2.text.style.color, CupertinoColors.activeBlue);
+    expect(tab2.text.style!.color, CupertinoColors.activeBlue);
 
     await tester.tap(find.text('Tab 1'));
     await tester.pump();
@@ -377,16 +375,16 @@ void main() {
       matching: find.byType(RichText),
     ));
     // Tab 2 should still be selected after changing theme.
-    expect(tab1.text.style.color.value, 0xFF757575);
+    expect(tab1.text.style!.color!.value, 0xFF757575);
     final RichText tab2 = tester.widget(find.descendant(
       of: find.text('Tab 2'),
       matching: find.byType(RichText),
     ));
-    expect(tab2.text.style.color, isSameColorAs(CupertinoColors.systemRed.darkColor));
+    expect(tab2.text.style!.color, isSameColorAs(CupertinoColors.systemRed.darkColor));
   });
 
   testWidgets('Tab contents are padded when there are view insets', (WidgetTester tester) async {
-    BuildContext innerContext;
+    late BuildContext innerContext;
 
     await tester.pumpWidget(
       CupertinoApp(
@@ -408,11 +406,11 @@ void main() {
     expect(tester.getRect(find.byType(Placeholder)), const Rect.fromLTWH(0, 0, 800, 400));
     // Don't generate more media query padding from the translucent bottom
     // tab since the tab is behind the keyboard now.
-    expect(MediaQuery.of(innerContext).padding.bottom, 0);
+    expect(MediaQuery.of(innerContext)!.padding.bottom, 0);
   });
 
   testWidgets('Tab contents are not inset when resizeToAvoidBottomInset overridden', (WidgetTester tester) async {
-    BuildContext innerContext;
+    late BuildContext innerContext;
 
     await tester.pumpWidget(
       CupertinoApp(
@@ -435,7 +433,7 @@ void main() {
     expect(tester.getRect(find.byType(Placeholder)), const Rect.fromLTWH(0, 0, 800, 600));
     // Media query padding shows up in the inner content because it wasn't masked
     // by the view inset.
-    expect(MediaQuery.of(innerContext).padding.bottom, 50);
+    expect(MediaQuery.of(innerContext)!.padding.bottom, 50);
   });
 
   testWidgets('Tab contents bottom padding are not consumed by viewInsets when resizeToAvoidBottomInset overridden', (WidgetTester tester) async {
@@ -492,7 +490,7 @@ void main() {
     (WidgetTester tester) async {
       // Regression test for https://github.com/flutter/flutter/issues/43581.
       Future<EdgeInsets> getContentPaddingWithTabBarColor(Color color) async {
-        EdgeInsets contentPadding;
+        late EdgeInsets contentPadding;
 
         await tester.pumpWidget(
           CupertinoApp(
@@ -504,7 +502,7 @@ void main() {
                   items: List<BottomNavigationBarItem>.generate(2, tabGenerator),
                 ),
                 tabBuilder: (BuildContext context, int index) {
-                  contentPadding = MediaQuery.of(context).padding;
+                  contentPadding = MediaQuery.of(context)!.padding;
                   return const Placeholder();
                 }
               ),
@@ -519,7 +517,7 @@ void main() {
   });
 
   testWidgets('Tab and page scaffolds do not double stack view insets', (WidgetTester tester) async {
-    BuildContext innerContext;
+    late BuildContext innerContext;
 
     await tester.pumpWidget(
       CupertinoApp(
@@ -545,7 +543,7 @@ void main() {
     );
 
     expect(tester.getRect(find.byType(Placeholder)), const Rect.fromLTWH(0, 0, 800, 400));
-    expect(MediaQuery.of(innerContext).padding.bottom, 0);
+    expect(MediaQuery.of(innerContext)!.padding.bottom, 0);
   });
 
   testWidgets('Deleting tabs after selecting them should switch to the last available tab', (WidgetTester tester) async {
@@ -965,7 +963,7 @@ void main() {
   testWidgets("Don't replace focus nodes for existing tabs when changing tab count", (WidgetTester tester) async {
     final CupertinoTabController controller = CupertinoTabController(initialIndex: 2);
 
-    final List<FocusScopeNode> scopes = List<FocusScopeNode>(5);
+    final List<FocusScopeNode> scopes = List<FocusScopeNode>.filled(5, FocusScopeNode());
     await tester.pumpWidget(
         CupertinoApp(
           home: CupertinoTabScaffold(
@@ -987,7 +985,7 @@ void main() {
     }
     await tester.pump();
 
-    final List<FocusScopeNode> newScopes = List<FocusScopeNode>(5);
+    final List<FocusScopeNode> newScopes = <FocusScopeNode>[];
     await tester.pumpWidget(
         CupertinoApp(
           home: CupertinoTabScaffold(
@@ -996,7 +994,7 @@ void main() {
             ),
             controller: controller,
             tabBuilder: (BuildContext context, int index) {
-              newScopes[index] = FocusScope.of(context);
+              newScopes.add(FocusScope.of(context));
               return Container();
             },
           ),
@@ -1021,12 +1019,10 @@ void main() {
     }
 
     expectAssertionError(() => CupertinoTabController(initialIndex: -1), '>= 0');
-    expectAssertionError(() => CupertinoTabController(initialIndex: null), '!= null');
 
     final CupertinoTabController controller = CupertinoTabController();
 
     expectAssertionError(() => controller.index = -1, '>= 0');
-    expectAssertionError(() => controller.index = null, '!= null');
   });
 
   testWidgets('Does not lose state when focusing on text input', (WidgetTester tester) async {
@@ -1078,7 +1074,7 @@ void main() {
       CupertinoApp(
         home: Builder(builder: (BuildContext context) {
           return MediaQuery(
-            data: MediaQuery.of(context).copyWith(textScaleFactor: 99),
+            data: MediaQuery.of(context)!.copyWith(textScaleFactor: 99),
             child: CupertinoTabScaffold(
               tabBar: CupertinoTabBar(
                 items: List<BottomNavigationBarItem>.generate(

packages/flutter/test/cupertino/tab_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -42,7 +40,7 @@ void main() {
             return CupertinoButton(
               child: const Text('go to second page'),
               onPressed: () {
-                Navigator.of(context).pushNamed('/2');
+                Navigator.of(context)!.pushNamed('/2');
               },
             );
           },
@@ -83,12 +81,12 @@ void main() {
   });
 
   testWidgets('Use onUnknownRoute', (WidgetTester tester) async {
-    String unknownForRouteCalled;
+    late String unknownForRouteCalled;
     await tester.pumpWidget(
       CupertinoApp(
         home: CupertinoTabView(
           onUnknownRoute: (RouteSettings settings) {
-            unknownForRouteCalled = settings.name;
+            unknownForRouteCalled = settings.name!;
             return null;
           },
         ),
@@ -117,7 +115,7 @@ void main() {
       ),
     );
 
-    key.currentState.pushNamed('/2');
+    key.currentState!.pushNamed('/2');
 
     await tester.pump();
     await tester.pump(const Duration(milliseconds: 300));
@@ -133,7 +131,7 @@ void main() {
             return CupertinoButton(
               child: const Text('go to second page'),
               onPressed: () {
-                Navigator.of(context).pushNamed('/2');
+                Navigator.of(context)!.pushNamed('/2');
               },
             );
           },
@@ -158,7 +156,7 @@ void main() {
             return CupertinoButton(
               child: const Text('go to second page'),
               onPressed: () {
-                Navigator.of(context).pushNamed('/2');
+                Navigator.of(context)!.pushNamed('/2');
               },
             );
           },
@@ -186,9 +184,9 @@ void main() {
         ),
       ),
     );
-    FlutterError error;
+    late FlutterError error;
     try {
-      key.currentState.pushNamed('/2');
+      key.currentState!.pushNamed('/2');
     } on FlutterError catch (e) {
       error = e;
     }
@@ -222,9 +220,9 @@ void main() {
         ),
       ),
     );
-    FlutterError error;
+    late FlutterError error;
     try {
-      key.currentState.pushNamed('/2');
+      key.currentState!.pushNamed('/2');
     } on FlutterError catch (e) {
       error = e;
     }