Remove reference to MaterialApp and showCupertinoModalPopup from …

…`CupertinoAlertDialog` (flutter#150725)

This PR removes the usage of Material widgets from unit tests of `CupertinoAlertDialog`. Other than it being just wrong, it also introduces bad behavior, such as the scroll view can't be overscrolled so that the overscroll behavior can't be tested.
* Since there are no longer M2 or M3 variants of tests, I straight up rewrote the unit tests for "default look" with similar tests as those of `CupertinoActionSheet` ([here](https://github.com/flutter/flutter/blob/master/packages/flutter/test/cupertino/action_sheet_test.dart#L21))

This PR also replaces `showCupertinoModalPopup` with `showCupertinoDialog` in `CupertinoAlertDialog`'s example code. The former should only be used by `CupertinoActionSheet`, which has a different animation from the correct `showCupertinoDialog`.

examples/api/lib/cupertino/dialog/cupertino_alert_dialog.0.dart

@@ -23,9 +23,8 @@ class AlertDialogApp extends StatelessWidget {
 class AlertDialogExample extends StatelessWidget {
   const AlertDialogExample({super.key});
 
-  // This shows a CupertinoModalPopup which hosts a CupertinoAlertDialog.
   void _showAlertDialog(BuildContext context) {
-    showCupertinoModalPopup<void>(
+    showCupertinoDialog<void>(
       context: context,
       builder: (BuildContext context) => CupertinoAlertDialog(
         title: const Text('Alert'),

packages/flutter/test/cupertino/dialog_test.dart

@@ -19,6 +19,69 @@ import 'package:flutter_test/flutter_test.dart';
 import '../widgets/semantics_tester.dart';
 
 void main() {
+  testWidgets('Overall appearance is correct for the light theme', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      TestScaffoldApp(
+        theme: const CupertinoThemeData(brightness: Brightness.light),
+        dialog: CupertinoAlertDialog(
+          content: const Text('The content'),
+          actions: <Widget>[
+            CupertinoDialogAction(child: const Text('One'), onPressed: () {}),
+            CupertinoDialogAction(child: const Text('Two'), onPressed: () {}),
+          ],
+        ),
+      ),
+    );
+
+    await tester.tap(find.text('Go'));
+    await tester.pumpAndSettle();
+
+    final TestGesture gesture = await tester.startGesture(tester.getCenter(find.text('One')));
+    await tester.pumpAndSettle();
+    // This golden file also verifies the structure of an alert dialog that
+    // has a content, no title, and no overscroll for any sections (in contrast
+    // to cupertinoAlertDialog.dark-theme.png).
+    await expectLater(
+      find.byType(CupertinoApp),
+      matchesGoldenFile('cupertinoAlertDialog.overall-light-theme.png'),
+    );
+
+    await gesture.up();
+  });
+
+  testWidgets('Overall appearance is correct for the dark theme', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      TestScaffoldApp(
+        theme: const CupertinoThemeData(brightness: Brightness.dark),
+        dialog: CupertinoAlertDialog(
+          title: const Text('The title'),
+          content: const Text('The content'),
+          actions: List<Widget>.generate(20, (int i) =>
+            CupertinoDialogAction(
+              onPressed: () {},
+              child: Text('Button $i'),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    await tester.tap(find.text('Go'));
+    await tester.pumpAndSettle();
+
+    final TestGesture gesture = await tester.startGesture(tester.getCenter(find.text('Button 0')));
+    await tester.pumpAndSettle();
+    // This golden file also verifies the structure of an action sheet that
+    // has both a message and a title, and an overscrolled action section (in
+    // contrast to cupertinoAlertDialog.light-theme.png).
+    await expectLater(
+      find.byType(CupertinoApp),
+      matchesGoldenFile('cupertinoAlertDialog.overall-dark-theme.png'),
+    );
+
+    await gesture.up();
+  });
+
   testWidgets('Alert dialog control test', (WidgetTester tester) async {
     bool didDelete = false;
 
@@ -181,16 +244,16 @@ void main() {
 
   testWidgets('Has semantic annotations', (WidgetTester tester) async {
     final SemanticsTester semantics = SemanticsTester(tester);
-    await tester.pumpWidget(const MaterialApp(home: Material(
-      child: CupertinoAlertDialog(
+    await tester.pumpWidget(const CupertinoApp(
+      home: CupertinoAlertDialog(
         title: Text('The Title'),
         content: Text('Content'),
         actions: <Widget>[
           CupertinoDialogAction(child: Text('Cancel')),
           CupertinoDialogAction(child: Text('OK')),
         ],
       ),
-    )));
+    ));
 
     expect(
       semantics,
@@ -506,7 +569,7 @@ void main() {
 
     // Check that the title/message section is not displayed
     expect(actionScrollController.offset, 0.0);
-    expect(tester.getTopLeft(find.widgetWithText(CupertinoDialogAction, 'One')).dy, equals(277.5));
+    expect(tester.getTopLeft(find.widgetWithText(CupertinoDialogAction, 'One')).dy, equals(270.75));
 
     // Check that the button's vertical size is the same.
     expect(
@@ -1160,7 +1223,7 @@ void main() {
 
   testWidgets('Dialog widget insets by MediaQuery viewInsets', (WidgetTester tester) async {
     await tester.pumpWidget(
-      const MaterialApp(
+      const CupertinoApp(
         home: MediaQuery(
           data: MediaQueryData(),
           child: CupertinoAlertDialog(content: Placeholder(fallbackHeight: 200.0)),
@@ -1171,7 +1234,7 @@ void main() {
     final Rect placeholderRectWithoutInsets = tester.getRect(find.byType(Placeholder));
 
     await tester.pumpWidget(
-      const MaterialApp(
+      const CupertinoApp(
         home: MediaQuery(
           data: MediaQueryData(viewInsets: EdgeInsets.fromLTRB(40.0, 30.0, 20.0, 10.0)),
           child: CupertinoAlertDialog(content: Placeholder(fallbackHeight: 200.0)),
@@ -1188,70 +1251,6 @@ void main() {
     expect(tester.getRect(find.byType(Placeholder)), placeholderRectWithoutInsets.translate(10, 10));
   });
 
-  testWidgets('Material2 - Default cupertino dialog golden', (WidgetTester tester) async {
-    await tester.pumpWidget(
-      createAppWithButtonThatLaunchesDialog(
-        useMaterial3: false,
-        dialogBuilder: (BuildContext context) {
-          return MediaQuery.withClampedTextScaling(
-            minScaleFactor: 3.0,
-            maxScaleFactor: 3.0,
-            child: const RepaintBoundary(
-              child: CupertinoAlertDialog(
-                title: Text('Title'),
-                content: Text('text'),
-                actions: <Widget>[
-                  CupertinoDialogAction(child: Text('No')),
-                  CupertinoDialogAction(child: Text('OK')),
-                ],
-              ),
-            ),
-          );
-        },
-      ),
-    );
-
-    await tester.tap(find.text('Go'));
-    await tester.pumpAndSettle();
-
-    await expectLater(
-      find.byType(CupertinoAlertDialog),
-      matchesGoldenFile('m2_dialog_test.cupertino.default.png'),
-    );
-  });
-
-  testWidgets('Material3 - Default cupertino dialog golden', (WidgetTester tester) async {
-    await tester.pumpWidget(
-      createAppWithButtonThatLaunchesDialog(
-        useMaterial3: true,
-        dialogBuilder: (BuildContext context) {
-          return MediaQuery.withClampedTextScaling(
-            minScaleFactor: 3.0,
-            maxScaleFactor: 3.0,
-            child: const RepaintBoundary(
-              child: CupertinoAlertDialog(
-                title: Text('Title'),
-                content: Text('text'),
-                actions: <Widget>[
-                  CupertinoDialogAction(child: Text('No')),
-                  CupertinoDialogAction(child: Text('OK')),
-                ],
-              ),
-            ),
-          );
-        },
-      ),
-    );
-
-    await tester.tap(find.text('Go'));
-    await tester.pumpAndSettle();
-
-    await expectLater(
-      find.byType(CupertinoAlertDialog),
-      matchesGoldenFile('m3_dialog_test.cupertino.default.png'),
-    );
-  });
-
   testWidgets('showCupertinoDialog - custom barrierLabel', (WidgetTester tester) async {
     final SemanticsTester semantics = SemanticsTester(tester);
 
@@ -1363,7 +1362,7 @@ void main() {
   testWidgets('CupertinoAlertDialog scrollbars controllers should be different', (WidgetTester tester) async {
     // https://github.com/flutter/flutter/pull/81278
     await tester.pumpWidget(
-      const MaterialApp(
+      const CupertinoApp(
         home: MediaQuery(
           data: MediaQueryData(),
           child: CupertinoAlertDialog(
@@ -1565,24 +1564,20 @@ RenderBox findScrollableActionsSectionRenderBox(WidgetTester tester) {
 
 Widget createAppWithButtonThatLaunchesDialog({
   required WidgetBuilder dialogBuilder,
-  bool? useMaterial3,
 }) {
-  return MaterialApp(
-    theme: ThemeData(useMaterial3: useMaterial3),
-    home: Material(
-      child: Center(
-        child: Builder(builder: (BuildContext context) {
-          return ElevatedButton(
-            onPressed: () {
-              showDialog<void>(
-                context: context,
-                builder: dialogBuilder,
-              );
-            },
-            child: const Text('Go'),
-          );
-        }),
-      ),
+  return CupertinoApp(
+    home: Center(
+      child: Builder(builder: (BuildContext context) {
+        return CupertinoButton(
+          onPressed: () {
+            showCupertinoDialog<void>(
+              context: context,
+              builder: dialogBuilder,
+            );
+          },
+          child: const Text('Go'),
+        );
+      }),
     ),
   );
 }
@@ -1595,13 +1590,11 @@ Widget boilerplate(Widget child) {
 }
 
 Widget createAppWithCenteredButton(Widget child) {
-  return MaterialApp(
-    home: Material(
-      child: Center(
-        child: ElevatedButton(
-          onPressed: null,
-          child: child,
-        ),
+  return CupertinoApp(
+    home: Center(
+      child: CupertinoButton(
+        onPressed: null,
+        child: child,
       ),
     ),
   );
@@ -1643,3 +1636,52 @@ class _RestorableDialogTestWidget extends StatelessWidget {
     );
   }
 }
+
+// Shows an app that has a button with text "Go", and clicking this button
+// displays the `dialog` and hides the button.
+//
+// The `theme` will be applied to the app and determines the background.
+class TestScaffoldApp extends StatefulWidget {
+  const TestScaffoldApp({super.key, required this.theme, required this.dialog});
+  final CupertinoThemeData theme;
+  final Widget dialog;
+
+  @override
+  TestScaffoldAppState createState() => TestScaffoldAppState();
+}
+
+class TestScaffoldAppState extends State<TestScaffoldApp> {
+  bool _pressedButton = false;
+
+  @override
+  Widget build(BuildContext context) {
+    return CupertinoApp(
+      // Hide the debug banner. Because this CupertinoApp is captured in golden
+      // test as a whole. The debug banner contains tilted text, whose
+      // anti-alias might cause false negative result.
+      // https://github.com/flutter/flutter/pull/150442
+      debugShowCheckedModeBanner: false,
+      theme: widget.theme,
+      home: Builder(builder: (BuildContext context) =>
+        CupertinoPageScaffold(
+          child: Center(
+            child: _pressedButton ? Container() : CupertinoButton(
+              onPressed: () {
+                setState(() {
+                  _pressedButton = true;
+                });
+                showCupertinoDialog<void>(
+                  context: context,
+                  builder: (BuildContext context) {
+                    return widget.dialog;
+                  },
+                );
+              },
+              child: const Text('Go'),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}