MediaQuery.of shouldn't give a default return value (#9596)

examples/flutter_gallery/test/calculator/smoke_test.dart

@@ -14,7 +14,7 @@ void main() {
   // We press the "1" and the "2" buttons and check that the display
   // reads "12".
   testWidgets('Flutter calculator app smoke test', (WidgetTester tester)  async {
-    await tester.pumpWidget(const CalculatorDemo());
+    await tester.pumpWidget(new MaterialApp(home: const CalculatorDemo()));
 
     final Finder oneButton = find.widgetWithText(InkResponse, '1');
     expect(oneButton, findsOneWidget);

packages/flutter/lib/src/material/app_bar.dart

@@ -341,6 +341,7 @@ class _AppBarState extends State<AppBar> {
 
   @override
   Widget build(BuildContext context) {
+    assert(!widget.primary || debugCheckHasMediaQuery(context));
     final ThemeData themeData = Theme.of(context);
 
     IconThemeData appBarIconTheme = widget.iconTheme ?? themeData.primaryIconTheme;
@@ -906,6 +907,7 @@ class _SliverAppBarState extends State<SliverAppBar> with TickerProviderStateMix
 
   @override
   Widget build(BuildContext context) {
+    assert(!widget.primary || debugCheckHasMediaQuery(context));
     final double topPadding = widget.primary ? MediaQuery.of(context).padding.top : 0.0;
     final double collapsedHeight = (widget.pinned && widget.floating && widget.bottom != null)
       ? widget.bottom.preferredSize.height + topPadding : null;

packages/flutter/lib/src/material/drawer_header.dart

@@ -72,6 +72,7 @@ class DrawerHeader extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
+    assert(debugCheckHasMediaQuery(context));
     final ThemeData theme = Theme.of(context);
     final double statusBarHeight = MediaQuery.of(context).padding.top;
     return new Container(

packages/flutter/lib/src/material/scaffold.dart

@@ -769,6 +769,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasMediaQuery(context));
     EdgeInsets padding = MediaQuery.of(context).padding;
     final ThemeData themeData = Theme.of(context);
     if (!widget.resizeToAvoidBottomPadding)

packages/flutter/lib/src/material/text_selection.dart

@@ -151,6 +151,7 @@ class _MaterialTextSelectionControls extends TextSelectionControls {
   @override
   Widget buildToolbar(
       BuildContext context, Offset position, TextSelectionDelegate delegate) {
+    assert(debugCheckHasMediaQuery(context));
     final Size screenSize = MediaQuery.of(context).size;
     return new ConstrainedBox(
       constraints: new BoxConstraints.loose(screenSize),

packages/flutter/lib/src/widgets/debug.dart

@@ -5,7 +5,9 @@
 import 'dart:collection';
 
 import 'package:flutter/foundation.dart';
+
 import 'framework.dart';
+import 'media_query.dart';
 import 'table.dart';
 
 // Any changes to this file should be reflected in the debugAssertAllWidgetVarsUnset()
@@ -153,6 +155,39 @@ bool debugCheckHasTable(BuildContext context) {
   return true;
 }
 
+/// Asserts that the given context has a [MediaQuery] ancestor.
+///
+/// Used by various widgets to make sure that they are only used in an
+/// appropriate context.
+///
+/// To invoke this function, use the following pattern, typically in the
+/// relevant Widget's [build] method:
+///
+/// ```dart
+/// assert(debugCheckHasMediaQuery(context));
+/// ```
+///
+/// Does nothing if asserts are disabled. Always returns true.
+bool debugCheckHasMediaQuery(BuildContext context) {
+  assert(() {
+    if (context.widget is! MediaQuery && context.ancestorWidgetOfExactType(MediaQuery) == null) {
+      final Element element = context;
+      throw new FlutterError(
+        'No MediaQuery widget found.\n'
+        '${context.widget.runtimeType} widgets require a MediaQuery widget ancestor.\n'
+        'The specific widget that could not find a MediaQuery ancestor was:\n'
+        '  ${context.widget}\n'
+        'The ownership chain for the affected widget is:\n'
+        '  ${element.debugGetCreatorChain(10)}\n'
+        'Typically, the MediaQuery widget is introduced by the MaterialApp or '
+        'WidgetsApp widget at the top of your application widget tree.'
+      );
+    }
+    return true;
+  });
+  return true;
+}
+
 /// Asserts that the `built` widget is not null.
 ///
 /// Used when the given `widget` calls a builder function to check that the

packages/flutter/lib/src/widgets/editable_text.dart

@@ -463,7 +463,7 @@ class EditableTextState extends State<EditableText> implements TextInputClient {
           showCursor: _showCursor,
           maxLines: widget.maxLines,
           selectionColor: widget.selectionColor,
-          textScaleFactor: widget.textScaleFactor ?? MediaQuery.of(context).textScaleFactor,
+          textScaleFactor: widget.textScaleFactor ?? MediaQuery.of(context, nullOk: true)?.textScaleFactor ?? 1.0,
           textAlign: widget.textAlign,
           obscureText: widget.obscureText,
           offset: offset,

packages/flutter/lib/src/widgets/image.dart

@@ -27,10 +27,10 @@ export 'package:flutter/services.dart' show
 ImageConfiguration createLocalImageConfiguration(BuildContext context, { Size size }) {
   return new ImageConfiguration(
     bundle: DefaultAssetBundle.of(context),
-    devicePixelRatio: MediaQuery.of(context).devicePixelRatio,
+    devicePixelRatio: MediaQuery.of(context, nullOk: true)?.devicePixelRatio ?? 1.0,
     // TODO(ianh): provide the locale
     size: size,
-    platform: Platform.operatingSystem
+    platform: Platform.operatingSystem,
   );
 }
 

packages/flutter/lib/src/widgets/media_query.dart

@@ -26,6 +26,10 @@ enum Orientation {
 /// To obtain the current [MediaQueryData] for a given [BuildContext], use the
 /// [MediaQuery.of] function. For example, to obtain the size of the current
 /// window, use `MediaQuery.of(context).size`.
+///
+/// If no [MediaQuery] is in scope then the [MediaQuery.of] method will throw an
+/// exception, unless the `nullOk` argument is set to true, in which case it
+/// returns null.
 @immutable
 class MediaQueryData {
   /// Creates data for a media query with explicit values.
@@ -40,6 +44,11 @@ class MediaQueryData {
   });
 
   /// Creates data for a media query based on the given window.
+  ///
+  /// If you use this, you should ensure that you also register for
+  /// notifications so that you can update your [MediaQueryData] when the
+  /// window's metrics change. For example, see
+  /// [WidgetsBindingObserver.didChangeMetrics] or [ui.window.onMetricsChanged].
   MediaQueryData.fromWindow(ui.Window window)
     : size = window.physicalSize / window.devicePixelRatio,
       devicePixelRatio = window.devicePixelRatio,
@@ -117,6 +126,16 @@ class MediaQueryData {
 /// Querying the current media using [MediaQuery.of] will cause your widget to
 /// rebuild automatically whenever the [MediaQueryData] changes (e.g., if the
 /// user rotates their device).
+///
+/// If no [MediaQuery] is in scope then the [MediaQuery.of] method will throw an
+/// exception, unless the `nullOk` argument is set to true, in which case it
+/// returns null.
+///
+/// See also:
+///
+///  * [WidgetsApp] and [MaterialApp], which introduce a [MediaQuery] and keep
+///    it up to date with the current screen metrics as they change.
+///  * [MediaQueryData], the data structure that represents the metrics.
 class MediaQuery extends InheritedWidget {
   /// Creates a widget that provides [MediaQueryData] to its descendants.
   ///
@@ -135,7 +154,8 @@ class MediaQuery extends InheritedWidget {
   /// height of the current window.
   final MediaQueryData data;
 
-  /// The data from the closest instance of this class that encloses the given context.
+  /// The data from the closest instance of this class that encloses the given
+  /// context.
   ///
   /// You can use this function to query the size an orientation of the screen.
   /// When that information changes, your widget will be scheduled to be rebuilt,
@@ -146,9 +166,27 @@ class MediaQuery extends InheritedWidget {
   /// ```dart
   /// MediaQueryData media = MediaQuery.of(context);
   /// ```
-  static MediaQueryData of(BuildContext context) {
+  ///
+  /// If there is no [MediaQuery] in scope, then this will throw an exception.
+  /// To return null if there is no [MediaQuery], then pass `nullOk: true`.
+  ///
+  /// If you use this from a widget (e.g. in its build function), consider
+  /// calling [debugCheckHasMediaQuery].
+  static MediaQueryData of(BuildContext context, { bool nullOk: false }) {
     final MediaQuery query = context.inheritFromWidgetOfExactType(MediaQuery);
-    return query?.data ?? new MediaQueryData.fromWindow(ui.window);
+    if (query != null)
+      return query.data;
+    if (nullOk)
+      return null;
+    throw new FlutterError(
+      'MediaQuery.of() called with a context that does not contain a MediaQuery.\n'
+      'No MediaQuery ancestor could be found starting from the context that was passed '
+      'to MediaQuery.of(). This can happen because you do not have a WidgetsApp or '
+      'MaterialApp widget (those widgets introduce a MediaQuery), or it can happen '
+      'if the context you use comes from a widget above those widgets.\n'
+      'The context used was:\n'
+      '  $context'
+    );
   }
 
   @override

packages/flutter/lib/src/widgets/text.dart

@@ -203,7 +203,7 @@ class Text extends StatelessWidget {
       textAlign: textAlign ?? defaultTextStyle.textAlign,
       softWrap: softWrap ?? defaultTextStyle.softWrap,
       overflow: overflow ?? defaultTextStyle.overflow,
-      textScaleFactor: textScaleFactor ?? MediaQuery.of(context).textScaleFactor,
+      textScaleFactor: textScaleFactor ?? MediaQuery.of(context, nullOk: true)?.textScaleFactor ?? 1.0,
       maxLines: maxLines ?? defaultTextStyle.maxLines,
       text: new TextSpan(
         style: effectiveTextStyle,

packages/flutter/test/material/about_test.dart

@@ -89,9 +89,13 @@ void main() {
       ]);
     });
 
-    await tester.pumpWidget(const Center(
-      child: const LicensePage()
-    ));
+    await tester.pumpWidget(
+      new MaterialApp(
+        home: const Center(
+          child: const LicensePage()
+        ),
+      ),
+    );
 
     expect(licenseFuture, isNotNull);
     await licenseFuture;

packages/flutter/test/material/app_bar_test.dart

@@ -8,29 +8,32 @@ import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 Widget buildSliverAppBarApp({ bool floating, bool pinned, double expandedHeight, bool snap: false }) {
-  return new Scaffold(
-    body: new DefaultTabController(
-      length: 3,
-      child: new CustomScrollView(
-        primary: true,
-        slivers: <Widget>[
-          new SliverAppBar(
-            title: const Text('AppBar Title'),
-            floating: floating,
-            pinned: pinned,
-            expandedHeight: expandedHeight,
-            snap: snap,
-            bottom: new TabBar(
-              tabs: <String>['A','B','C'].map((String t) => new Tab(text: 'TAB $t')).toList(),
+  return new MediaQuery(
+    data: const MediaQueryData(),
+    child: new Scaffold(
+      body: new DefaultTabController(
+        length: 3,
+        child: new CustomScrollView(
+          primary: true,
+          slivers: <Widget>[
+            new SliverAppBar(
+              title: const Text('AppBar Title'),
+              floating: floating,
+              pinned: pinned,
+              expandedHeight: expandedHeight,
+              snap: snap,
+              bottom: new TabBar(
+                tabs: <String>['A','B','C'].map((String t) => new Tab(text: 'TAB $t')).toList(),
+              ),
             ),
-          ),
-          new SliverToBoxAdapter(
-            child: new Container(
-              height: 1200.0,
-              color: Colors.orange[400],
+            new SliverToBoxAdapter(
+              child: new Container(
+                height: 1200.0,
+                color: Colors.orange[400],
+              ),
             ),
-          ),
-        ],
+          ],
+        ),
       ),
     ),
   );
@@ -246,12 +249,14 @@ void main() {
 
   testWidgets('AppBar with no Scaffold', (WidgetTester tester) async {
     await tester.pumpWidget(
-      new SizedBox(
-        height: kToolbarHeight,
-        child: new AppBar(
-          leading: const Text('L'),
-          title: const Text('No Scaffold'),
-          actions: <Widget>[const Text('A1'), const Text('A2')],
+      new MaterialApp(
+        home: new SizedBox(
+          height: kToolbarHeight,
+          child: new AppBar(
+            leading: const Text('L'),
+            title: const Text('No Scaffold'),
+            actions: <Widget>[const Text('A1'), const Text('A2')],
+          ),
         ),
       ),
     );
@@ -265,13 +270,15 @@ void main() {
 
   testWidgets('AppBar render at zero size', (WidgetTester tester) async {
     await tester.pumpWidget(
-      new Center(
-        child: new Container(
-          height: 0.0,
-          width: 0.0,
-          child: new Scaffold(
-            appBar: new AppBar(
-              title: const Text('X'),
+      new MaterialApp(
+        home: new Center(
+          child: new Container(
+            height: 0.0,
+            width: 0.0,
+            child: new Scaffold(
+              appBar: new AppBar(
+                title: const Text('X'),
+              ),
             ),
           ),
         ),

packages/flutter/test/material/drawer_test.dart

@@ -10,24 +10,26 @@ void main() {
     final Key containerKey = const Key('container');
 
     await tester.pumpWidget(
-      new Scaffold(
-        drawer: new Drawer(
-          child: new ListView(
-            children: <Widget>[
-              new DrawerHeader(
-                child: new Container(
-                  key: containerKey,
-                  child: const Text('header')
-                )
-              ),
-              const ListTile(
-                leading: const Icon(Icons.archive),
-                title: const Text('Archive')
-              )
-            ]
-          )
-        )
-      )
+      new MaterialApp(
+        home: new Scaffold(
+          drawer: new Drawer(
+            child: new ListView(
+              children: <Widget>[
+                new DrawerHeader(
+                  child: new Container(
+                    key: containerKey,
+                    child: const Text('header'),
+                  ),
+                ),
+                const ListTile(
+                  leading: const Icon(Icons.archive),
+                  title: const Text('Archive'),
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
     );
 
     expect(find.text('Archive'), findsNothing);

packages/flutter/test/material/icon_button_test.dart

@@ -172,15 +172,17 @@ void main() {
 
   testWidgets('IconButton AppBar size', (WidgetTester tester) async {
     await tester.pumpWidget(
-      new Scaffold(
-        appBar: new AppBar(
-          actions: <Widget>[
-            new IconButton(
-              padding: EdgeInsets.zero,
-              onPressed: mockOnPressedFunction,
-              icon: const Icon(Icons.ac_unit),
-            ),
-          ],
+      new MaterialApp(
+        home: new Scaffold(
+          appBar: new AppBar(
+            actions: <Widget>[
+              new IconButton(
+                padding: EdgeInsets.zero,
+                onPressed: mockOnPressedFunction,
+                icon: const Icon(Icons.ac_unit),
+              ),
+            ],
+          ),
         ),
       ),
     );

packages/flutter/test/material/scaffold_test.dart

@@ -11,9 +11,16 @@ void main() {
     final Key bodyKey = new UniqueKey();
     await tester.pumpWidget(new Scaffold(
       appBar: new AppBar(title: const Text('Title')),
-      body: new Container(key: bodyKey)
+      body: new Container(key: bodyKey),
     ));
+    expect(tester.takeException(), isFlutterError);
 
+    await tester.pumpWidget(new MaterialApp(
+      home: new Scaffold(
+        appBar: new AppBar(title: const Text('Title')),
+        body: new Container(key: bodyKey),
+      ),
+    ));
     RenderBox bodyBox = tester.renderObject(find.byKey(bodyKey));
     expect(bodyBox.size, equals(const Size(800.0, 544.0)));
 
@@ -82,37 +89,37 @@ void main() {
   });
 
   testWidgets('Floating action animation', (WidgetTester tester) async {
-    await tester.pumpWidget(const Scaffold(
+    await tester.pumpWidget(new MaterialApp(home: const Scaffold(
       floatingActionButton: const FloatingActionButton(
         key: const Key('one'),
         onPressed: null,
         child: const Text("1")
       )
-    ));
+    )));
 
     expect(tester.binding.transientCallbackCount, 0);
 
-    await tester.pumpWidget(const Scaffold(
+    await tester.pumpWidget(new MaterialApp(home: const Scaffold(
       floatingActionButton: const FloatingActionButton(
         key: const Key('two'),
         onPressed: null,
         child: const Text("2")
       )
-    ));
+    )));
 
     expect(tester.binding.transientCallbackCount, greaterThan(0));
     await tester.pumpWidget(new Container());
     expect(tester.binding.transientCallbackCount, 0);
-    await tester.pumpWidget(const Scaffold());
+    await tester.pumpWidget(new MaterialApp(home: const Scaffold()));
     expect(tester.binding.transientCallbackCount, 0);
 
-    await tester.pumpWidget(const Scaffold(
+    await tester.pumpWidget(new MaterialApp(home: const Scaffold(
       floatingActionButton: const FloatingActionButton(
         key: const Key('one'),
         onPressed: null,
         child: const Text("1")
       )
-    ));
+    )));
 
     expect(tester.binding.transientCallbackCount, greaterThan(0));
   });
@@ -367,7 +374,14 @@ void main() {
     testWidgets('body size with container', (WidgetTester tester) async {
       final Key testKey = new UniqueKey();
       await tester.pumpWidget(
-        new Scaffold(body: new Container(key: testKey))
+        new MediaQuery(
+          data: const MediaQueryData(),
+          child: new Scaffold(
+            body: new Container(
+              key: testKey,
+            ),
+          ),
+        ),
       );
       expect(tester.element(find.byKey(testKey)).size, const Size(800.0, 600.0));
       expect(tester.renderObject<RenderBox>(find.byKey(testKey)).localToGlobal(Offset.zero), const Offset(0.0, 0.0));
@@ -376,7 +390,15 @@ void main() {
     testWidgets('body size with sized container', (WidgetTester tester) async {
       final Key testKey = new UniqueKey();
       await tester.pumpWidget(
-        new Scaffold(body: new Container(key: testKey, height: 100.0))
+        new MediaQuery(
+          data: const MediaQueryData(),
+          child: new Scaffold(
+            body: new Container(
+              key: testKey,
+              height: 100.0,
+            ),
+          ),
+        ),
       );
       expect(tester.element(find.byKey(testKey)).size, const Size(800.0, 100.0));
       expect(tester.renderObject<RenderBox>(find.byKey(testKey)).localToGlobal(Offset.zero), const Offset(0.0, 0.0));
@@ -385,7 +407,16 @@ void main() {
     testWidgets('body size with centered container', (WidgetTester tester) async {
       final Key testKey = new UniqueKey();
       await tester.pumpWidget(
-        new Scaffold(body: new Center(child: new Container(key: testKey)))
+        new MediaQuery(
+          data: const MediaQueryData(),
+          child: new Scaffold(
+            body: new Center(
+              child: new Container(
+                key: testKey,
+              ),
+            ),
+          ),
+        ),
       );
       expect(tester.element(find.byKey(testKey)).size, const Size(800.0, 600.0));
       expect(tester.renderObject<RenderBox>(find.byKey(testKey)).localToGlobal(Offset.zero), const Offset(0.0, 0.0));
@@ -394,7 +425,16 @@ void main() {
     testWidgets('body size with button', (WidgetTester tester) async {
       final Key testKey = new UniqueKey();
       await tester.pumpWidget(
-        new Scaffold(body: new FlatButton(key: testKey, onPressed: () { }, child: const Text('')))
+        new MediaQuery(
+          data: const MediaQueryData(),
+          child: new Scaffold(
+            body: new FlatButton(
+              key: testKey,
+              onPressed: () { },
+              child: const Text(''),
+            ),
+          ),
+        ),
       );
       expect(tester.element(find.byKey(testKey)).size, const Size(88.0, 36.0));
       expect(tester.renderObject<RenderBox>(find.byKey(testKey)).localToGlobal(Offset.zero), const Offset(0.0, 0.0));

packages/flutter/test/material/text_field_test.dart

@@ -26,12 +26,15 @@ class MockClipboard {
 }
 
 Widget overlay(Widget child) {
-  return new Overlay(
-    initialEntries: <OverlayEntry>[
-      new OverlayEntry(
-        builder: (BuildContext context) => child,
-      ),
-    ],
+  return new MediaQuery(
+    data: const MediaQueryData(),
+    child: new Overlay(
+      initialEntries: <OverlayEntry>[
+        new OverlayEntry(
+          builder: (BuildContext context) => child,
+        ),
+      ],
+    ),
   );
 }
 
@@ -229,20 +232,23 @@ void main() {
     final TextEditingController controller = new TextEditingController();
 
     Widget builder() {
-      return new Overlay(
-        initialEntries: <OverlayEntry>[
-          new OverlayEntry(
-            builder: (BuildContext context) {
-              return new Center(
-                child: new Material(
-                  child: new TextField(
-                    controller: controller,
+      return new MediaQuery(
+        data: const MediaQueryData(),
+        child: new Overlay(
+          initialEntries: <OverlayEntry>[
+            new OverlayEntry(
+              builder: (BuildContext context) {
+                return new Center(
+                  child: new Material(
+                    child: new TextField(
+                      controller: controller,
+                    ),
                   ),
-                ),
-              );
-            },
-          ),
-        ],
+                );
+              },
+            ),
+          ],
+        ),
       );
     }
 

packages/flutter/test/material/user_accounts_drawer_header_test.dart

@@ -13,31 +13,33 @@ void main() {
     final Key avatarD = const Key('D');
 
     await tester.pumpWidget(
-      new Material(
-        child: new Center(
-          child: new UserAccountsDrawerHeader(
-            currentAccountPicture: new CircleAvatar(
-              key: avatarA,
-              child: const Text('A'),
-            ),
-            otherAccountsPictures: <Widget>[
-              const CircleAvatar(
-                child: const Text('B'),
-              ),
-              new CircleAvatar(
-                key: avatarC,
-                child: const Text('C'),
-              ),
-              new CircleAvatar(
-                key: avatarD,
-                child: const Text('D'),
+      new MaterialApp(
+        home: new Material(
+          child: new Center(
+            child: new UserAccountsDrawerHeader(
+              currentAccountPicture: new CircleAvatar(
+                key: avatarA,
+                child: const Text('A'),
               ),
-              const CircleAvatar(
-                child: const Text('E'),
-              )
-            ],
-            accountName: const Text("name"),
-            accountEmail: const Text("email"),
+              otherAccountsPictures: <Widget>[
+                const CircleAvatar(
+                  child: const Text('B'),
+                ),
+                new CircleAvatar(
+                  key: avatarC,
+                  child: const Text('C'),
+                ),
+                new CircleAvatar(
+                  key: avatarD,
+                  child: const Text('D'),
+                ),
+                const CircleAvatar(
+                  child: const Text('E'),
+                )
+              ],
+              accountName: const Text("name"),
+              accountEmail: const Text("email"),
+            ),
           ),
         ),
       ),
@@ -87,15 +89,17 @@ void main() {
       VoidCallback onDetailsPressed,
       EdgeInsets margin,
     }) {
-      return new Material(
-        child: new Center(
-          child: new UserAccountsDrawerHeader(
-            currentAccountPicture: currentAccountPicture,
-            otherAccountsPictures: otherAccountsPictures,
-            accountName: accountName,
-            accountEmail: accountEmail,
-            onDetailsPressed: onDetailsPressed,
-            margin: margin,
+      return new MaterialApp(
+        home: new Material(
+          child: new Center(
+            child: new UserAccountsDrawerHeader(
+              currentAccountPicture: currentAccountPicture,
+              otherAccountsPictures: otherAccountsPictures,
+              accountName: accountName,
+              accountEmail: accountEmail,
+              onDetailsPressed: onDetailsPressed,
+              margin: margin,
+            ),
           ),
         ),
       );

packages/flutter/test/widgets/media_query_test.dart

@@ -8,21 +8,40 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 
 void main() {
-  testWidgets('MediaQuery has a default', (WidgetTester tester) async {
-    Size size;
+  testWidgets('MediaQuery does not have a default', (WidgetTester tester) async {
+    bool tested = false;
+    await tester.pumpWidget(
+      new Builder(
+        builder: (BuildContext context) {
+          tested = true;
+          MediaQuery.of(context); // should throw
+          return new Container();
+        }
+      )
+    );
+    expect(tested, isTrue);
+    expect(tester.takeException(), isFlutterError);
+  });
 
+  testWidgets('MediaQuery defaults to null', (WidgetTester tester) async {
+    bool tested = false;
     await tester.pumpWidget(
       new Builder(
         builder: (BuildContext context) {
-          final MediaQueryData data = MediaQuery.of(context);
-          expect(data, hasOneLineDescription);
-          expect(data.hashCode, equals(data.copyWith().hashCode));
-          size = data.size;
+          final MediaQueryData data = MediaQuery.of(context, nullOk: true);
+          expect(data, isNull);
+          tested = true;
           return new Container();
         }
       )
     );
+    expect(tested, isTrue);
+  });
 
-    expect(size, equals(ui.window.physicalSize / ui.window.devicePixelRatio));
+  testWidgets('MediaQueryData is sane', (WidgetTester tester) async {
+    final MediaQueryData data = new MediaQueryData.fromWindow(ui.window);
+    expect(data, hasOneLineDescription);
+    expect(data.hashCode, equals(data.copyWith().hashCode));
+    expect(data.size, equals(ui.window.physicalSize / ui.window.devicePixelRatio));
   });
 }