[NNBD] Migrate some Material tests to NNBD (flutter#67887)

Migrates the following files to NNBD: 
* input_decorator_test.dart
* list_tile_test.dart
* localizations_test.dart
* material_button_test.dart
* material_state_property_test.dart
* material_test.dart
* mergeable_material_test.dart

Author: Shi-Hao Hong

packages/flutter/test/material/input_decorator_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/material.dart';
@@ -14,15 +12,15 @@ import '../rendering/mock_canvas.dart';
 
 Widget buildInputDecorator({
   InputDecoration decoration = const InputDecoration(),
-  InputDecorationTheme inputDecorationTheme,
+  InputDecorationTheme? inputDecorationTheme,
   TextDirection textDirection = TextDirection.ltr,
   bool expands = false,
   bool isEmpty = false,
   bool isFocused = false,
   bool isHovering = false,
-  TextStyle baseStyle,
-  TextAlignVertical textAlignVertical,
-  VisualDensity visualDensity,
+  TextStyle? baseStyle,
+  TextAlignVertical? textAlignVertical,
+  VisualDensity? visualDensity,
   bool fixTextFieldOutlineLabel = false,
   Widget child = const Text(
     'text',
@@ -34,7 +32,7 @@ Widget buildInputDecorator({
       child: Builder(
         builder: (BuildContext context) {
           return Theme(
-            data: Theme.of(context).copyWith(
+            data: Theme.of(context)!.copyWith(
               inputDecorationTheme: inputDecorationTheme,
               visualDensity: visualDensity,
               fixTextFieldOutlineLabel: fixTextFieldOutlineLabel,
@@ -70,7 +68,7 @@ Finder findBorderPainter() {
 }
 
 double getBorderBottom(WidgetTester tester) {
-  final RenderBox box = InputDecorator.containerOf(tester.element(findBorderPainter()));
+  final RenderBox box = InputDecorator.containerOf(tester.element(findBorderPainter()))!;
   return box.size.height;
 }
 
@@ -85,7 +83,7 @@ Rect getLabelRect(WidgetTester tester) {
   return tester.getRect(findLabel());
 }
 
-InputBorder getBorder(WidgetTester tester) {
+InputBorder? getBorder(WidgetTester tester) {
   if (!tester.any(findBorderPainter()))
     return null;
   final CustomPaint customPaint = tester.widget(findBorderPainter());
@@ -96,21 +94,21 @@ InputBorder getBorder(WidgetTester tester) {
   return border;
 }
 
-BorderSide getBorderSide(WidgetTester tester) {
-  return getBorder(tester)?.borderSide;
+BorderSide? getBorderSide(WidgetTester tester) {
+  return getBorder(tester)!.borderSide;
 }
 
-BorderRadius getBorderRadius(WidgetTester tester) {
-  final InputBorder border = getBorder(tester);
+BorderRadius? getBorderRadius(WidgetTester tester) {
+  final InputBorder border = getBorder(tester)!;
   if (border is UnderlineInputBorder) {
     return border.borderRadius;
   }
   return null;
 }
 
-double getBorderWeight(WidgetTester tester) => getBorderSide(tester)?.width;
+double getBorderWeight(WidgetTester tester) => getBorderSide(tester)!.width;
 
-Color getBorderColor(WidgetTester tester) => getBorderSide(tester)?.color;
+Color getBorderColor(WidgetTester tester) => getBorderSide(tester)!.color;
 
 Color getContainerColor(WidgetTester tester) {
   final CustomPaint customPaint = tester.widget(findBorderPainter());
@@ -925,10 +923,10 @@ void main() {
 
   testWidgets('InputDecorator counter text, widget, and null', (WidgetTester tester) async {
     Widget buildFrame({
-      InputCounterWidgetBuilder buildCounter,
-      String counterText,
-      Widget counter,
-      int maxLength,
+      InputCounterWidgetBuilder? buildCounter,
+      String? counterText,
+      Widget? counter,
+      int? maxLength,
     }) {
       return MaterialApp(
         home: Scaffold(
@@ -953,7 +951,7 @@ void main() {
 
     // When counter, counterText, and buildCounter are null, defaults to showing
     // the built-in counter.
-    int maxLength = 10;
+    int? maxLength = 10;
     await tester.pumpWidget(buildFrame(maxLength: maxLength));
     Finder counterFinder = find.byType(Text);
     expect(counterFinder, findsOneWidget);
@@ -966,13 +964,18 @@ void main() {
     final Key buildCounterKey = UniqueKey();
     const String counterText = 'I show instead of count';
     final Widget counter = Text('hello', key: counterKey);
-    final InputCounterWidgetBuilder buildCounter =
-      (BuildContext context, { int currentLength, int maxLength, bool isFocused }) {
-        return Text(
-          '${currentLength.toString()} of ${maxLength.toString()}',
-          key: buildCounterKey,
-        );
-      };
+    final InputCounterWidgetBuilder buildCounter = (
+      BuildContext context, {
+      required int currentLength,
+      required int? maxLength,
+      required bool isFocused,
+    }) {
+      return Text(
+        '${currentLength.toString()} of ${maxLength.toString()}',
+        key: buildCounterKey,
+      );
+    };
+
     await tester.pumpWidget(buildFrame(
       counterText: counterText,
       counter: counter,
@@ -3021,10 +3024,10 @@ void main() {
     expect(tester.getTopRight(find.text('counter')), const Offset(800.0, 64.0));
 
     // Verify that the styles were passed along
-    expect(tester.widget<Text>(find.text('prefix')).style.color, prefixStyle.color);
-    expect(tester.widget<Text>(find.text('suffix')).style.color, suffixStyle.color);
-    expect(tester.widget<Text>(find.text('helper')).style.color, helperStyle.color);
-    expect(tester.widget<Text>(find.text('counter')).style.color, counterStyle.color);
+    expect(tester.widget<Text>(find.text('prefix')).style!.color, prefixStyle.color);
+    expect(tester.widget<Text>(find.text('suffix')).style!.color, suffixStyle.color);
+    expect(tester.widget<Text>(find.text('helper')).style!.color, helperStyle.color);
+    expect(tester.widget<Text>(find.text('counter')).style!.color, counterStyle.color);
 
     TextStyle getLabelStyle() {
       return tester.firstWidget<AnimatedDefaultTextStyle>(
@@ -3073,7 +3076,7 @@ void main() {
 
     final RenderObject renderer = tester.renderObject(find.byType(InputDecorator));
     final Iterable<String> nodeNames = renderer.debugDescribeChildren()
-      .map((DiagnosticsNode node) => node.name);
+      .map((DiagnosticsNode node) => node.name!);
     expect(nodeNames, unorderedEquals(<String>[
       'container',
       'counter',
@@ -3089,7 +3092,7 @@ void main() {
     ]));
 
     final Set<Object> nodeValues = Set<Object>.from(
-      renderer.debugDescribeChildren().map<Object>((DiagnosticsNode node) => node.value)
+      renderer.debugDescribeChildren().map<Object>((DiagnosticsNode node) => node.value!)
     );
     expect(nodeValues.length, 11);
   });
@@ -3347,7 +3350,11 @@ void main() {
     const Color disabledColor = Color(0x05000000);
     const Color enabledBorderColor = Color(0x61000000);
 
-    Future<void> pumpDecorator({bool hovering, bool enabled = true, bool filled = true}) async {
+    Future<void> pumpDecorator({
+      required bool hovering,
+      bool enabled = true,
+      bool filled = true,
+    }) async {
       return await tester.pumpWidget(
         buildInputDecorator(
           isHovering: hovering,
@@ -3422,7 +3429,11 @@ void main() {
     const Color disabledColor = Color(0x05000000);
     const Color enabledBorderColor = Color(0x61000000);
 
-    Future<void> pumpDecorator({bool focused, bool enabled = true, bool filled = true}) async {
+    Future<void> pumpDecorator({
+      required bool focused,
+      bool enabled = true,
+      bool filled = true,
+    }) async {
       return await tester.pumpWidget(
         buildInputDecorator(
           isFocused: focused,
@@ -3467,7 +3478,13 @@ void main() {
   });
 
   testWidgets('InputDecorator withdraws label when not empty or focused', (WidgetTester tester) async {
-    Future<void> pumpDecorator({bool focused, bool enabled = true, bool filled = false, bool empty = true, bool directional = false}) async {
+    Future<void> pumpDecorator({
+      required bool focused,
+      bool enabled = true,
+      bool filled = false,
+      bool empty = true,
+      bool directional = false,
+    }) async {
       return await tester.pumpWidget(
         buildInputDecorator(
           isEmpty: empty,
@@ -4140,8 +4157,8 @@ void main() {
   testWidgets('textAlignVertical can be updated', (WidgetTester tester) async {
     // Regression test for https://github.com/flutter/flutter/issues/56933
     const String hintText = 'hint';
-    TextAlignVertical alignment = TextAlignVertical.top;
-    StateSetter setState;
+    TextAlignVertical? alignment = TextAlignVertical.top;
+    late StateSetter setState;
     await tester.pumpWidget(
       MaterialApp(
         home: StatefulBuilder(
@@ -4187,7 +4204,7 @@ void main() {
           child: Builder(
             builder: (BuildContext context) {
               return Theme(
-                data: Theme.of(context),
+                data: Theme.of(context)!,
                 child: Align(
                   alignment: Alignment.topLeft,
                   child: TextField(
@@ -4247,7 +4264,7 @@ void main() {
           child: Builder(
             builder: (BuildContext context) {
               return Theme(
-                data: Theme.of(context).copyWith(visualDensity: visualDensity),
+                data: Theme.of(context)!.copyWith(visualDensity: visualDensity),
                 child: Center(
                   child: Row(
                     children: <Widget>[
@@ -4320,7 +4337,7 @@ void main() {
         child: Builder(
           builder: (BuildContext context) {
             return Theme(
-              data: Theme.of(context).copyWith(visualDensity: VisualDensity.compact),
+              data: Theme.of(context)!.copyWith(visualDensity: VisualDensity.compact),
               child: Center(
                 child: Row(
                   children: <Widget>[