[testing_app] Migrate to null safety (#800)

testing_app/integration_test/perf_test.dart

@@ -28,7 +28,7 @@ void main() {
       await binding.watchPerformance(
         () async {
           // Quickly scroll all the way down.
-          await scroller.animateTo(
+          await scroller!.animateTo(
             7000,
             duration: const Duration(seconds: 1),
             curve: Curves.linear,

testing_app/integration_test/state_mgmt_test.dart

@@ -9,7 +9,7 @@ import 'package:provider/provider.dart';
 import 'package:testing_app/models/favorites.dart';
 import 'package:testing_app/screens/favorites.dart';
 
-Favorites favoritesList;
+late Favorites favoritesList;
 
 Widget createFavoritesScreen() => ChangeNotifierProvider<Favorites>(
       create: (context) {

testing_app/pubspec.lock

@@ -105,7 +105,7 @@ packages:
       name: cupertino_icons
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.0"
+    version: "1.0.3"
   fake_async:
     dependency: transitive
     description:
@@ -163,11 +163,9 @@ packages:
     version: "4.0.0"
   integration_test:
     dependency: "direct dev"
-    description:
-      name: integration_test
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.0.2+3"
+    description: flutter
+    source: sdk
+    version: "0.0.0"
   io:
     dependency: transitive
     description:
@@ -216,7 +214,7 @@ packages:
       name: nested
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.4"
+    version: "1.0.0"
   node_preamble:
     dependency: transitive
     description:
@@ -272,7 +270,7 @@ packages:
       name: provider
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "4.3.3"
+    version: "5.0.0"
   pub_semver:
     dependency: transitive
     description:
@@ -286,7 +284,7 @@ packages:
       name: shelf
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.1"
+    version: "1.1.4"
   shelf_packages_handler:
     dependency: transitive
     description:
@@ -424,7 +422,7 @@ packages:
       name: web_socket_channel
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.1.0"
   webdriver:
     dependency: transitive
     description:

testing_app/pubspec.yaml

@@ -4,21 +4,22 @@ description: A sample that shows testing in Flutter.
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.10.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter:
     sdk: flutter
 
-  cupertino_icons: ^1.0.0
-  provider: ^4.1.3
+  cupertino_icons: ^1.0.3
+  provider: ^5.0.0
 
 dev_dependencies:
-  integration_test: ^1.0.1
+  integration_test:
+    sdk: flutter
   flutter_test:
     sdk: flutter
-  test: ^1.14.4
-  pedantic: ^1.9.0
+  test: ^1.16.8
+  pedantic: ^1.11.0
 
 flutter:
   uses-material-design: true

testing_app/test/favorites_test.dart

@@ -8,7 +8,7 @@ import 'package:provider/provider.dart';
 import 'package:testing_app/models/favorites.dart';
 import 'package:testing_app/screens/favorites.dart';
 
-Favorites favoritesList;
+late Favorites favoritesList;
 
 Widget createFavoritesScreen() => ChangeNotifierProvider<Favorites>(
       create: (context) {