Dark mode for CupertinoSwitch and CupertinoScrollbar, Fidelity updates (#40636)

bin/internal/goldens.version

-ae7615ce466a548b41a0f7b9860ec453646f73e9
+0728c1b6e968602e173d0153a88d9cfb932d8c9b

packages/flutter/lib/src/cupertino/colors.dart

@@ -1014,14 +1014,14 @@ const CupertinoSystemColorsData _kSystemColorsFallback = CupertinoSystemColorsDa
     darkHighContrastElevatedColor: Color.fromARGB(112, 120, 120, 128),
   ),
   secondarySystemFill: CupertinoDynamicColor(
-    color: Color.fromARGB(153, 60, 60, 67),
-    darkColor: Color.fromARGB(153, 235, 235, 245),
-    highContrastColor: Color.fromARGB(173, 60, 60, 67),
-    darkHighContrastColor: Color.fromARGB(173, 235, 235, 245),
-    elevatedColor: Color.fromARGB(153, 60, 60, 67),
-    darkElevatedColor: Color.fromARGB(153, 235, 235, 245),
-    highContrastElevatedColor: Color.fromARGB(173, 60, 60, 67),
-    darkHighContrastElevatedColor: Color.fromARGB(173, 235, 235, 245),
+    color: Color.fromARGB(40, 120, 120, 128),
+    darkColor: Color.fromARGB(81, 120, 120, 128),
+    highContrastColor: Color.fromARGB(61, 120, 120, 128),
+    darkHighContrastColor: Color.fromARGB(102, 120, 120, 128),
+    elevatedColor: Color.fromARGB(40, 120, 120, 128),
+    darkElevatedColor: Color.fromARGB(81, 120, 120, 128),
+    highContrastElevatedColor: Color.fromARGB(61, 120, 120, 128),
+    darkHighContrastElevatedColor: Color.fromARGB(102, 120, 120, 128),
   ),
   tertiarySystemFill: CupertinoDynamicColor(
     color: Color.fromARGB(30, 118, 118, 128),

packages/flutter/lib/src/cupertino/scrollbar.dart

@@ -8,19 +8,25 @@ import 'package:flutter/gestures.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
+import 'colors.dart';
+
 // All values eyeballed.
-const Color _kScrollbarColor = Color(0x99777777);
 const double _kScrollbarMinLength = 36.0;
 const double _kScrollbarMinOverscrollLength = 8.0;
-const Radius _kScrollbarRadius = Radius.circular(1.5);
-const Radius _kScrollbarRadiusDragging = Radius.circular(4.0);
 const Duration _kScrollbarTimeToFade = Duration(milliseconds: 1200);
 const Duration _kScrollbarFadeDuration = Duration(milliseconds: 250);
 const Duration _kScrollbarResizeDuration = Duration(milliseconds: 150);
 
-// These values are measured using screenshots from an iPhone XR 13.0 simulator.
-const double _kScrollbarThickness = 2.5;
+// Extracted from iOS 13.1 beta using Debug View Hierarchy.
+const Color _kScrollbarColor = CupertinoDynamicColor.withBrightness(
+  color: Color(0x59000000),
+  darkColor: Color(0x80FFFFFF),
+);
+const double _kScrollbarThickness = 3;
 const double _kScrollbarThicknessDragging = 8.0;
+const Radius _kScrollbarRadius = Radius.circular(1.5);
+const Radius _kScrollbarRadiusDragging = Radius.circular(4.0);
+
 // This is the amount of space from the top of a vertical scrollbar to the
 // top edge of the scrollable, measured when the vertical scrollbar overscrolls
 // to the top.
@@ -101,7 +107,6 @@ class CupertinoScrollbar extends StatefulWidget {
 class _CupertinoScrollbarState extends State<CupertinoScrollbar> with TickerProviderStateMixin {
   final GlobalKey _customPaintKey = GlobalKey();
   ScrollbarPainter _painter;
-  TextDirection _textDirection;
 
   AnimationController _fadeoutAnimationController;
   Animation<double> _fadeoutOpacityAnimation;
@@ -141,15 +146,22 @@ class _CupertinoScrollbarState extends State<CupertinoScrollbar> with TickerProv
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
-    _textDirection = Directionality.of(context);
-    _painter = _buildCupertinoScrollbarPainter();
+    if (_painter == null) {
+      _painter = _buildCupertinoScrollbarPainter(context);
+    }
+    else {
+      _painter
+        ..textDirection = Directionality.of(context)
+        ..color = CupertinoDynamicColor.resolve(_kScrollbarColor, context)
+        ..padding = MediaQuery.of(context).padding;
+    }
   }
 
   /// Returns a [ScrollbarPainter] visually styled like the iOS scrollbar.
-  ScrollbarPainter _buildCupertinoScrollbarPainter() {
+  ScrollbarPainter _buildCupertinoScrollbarPainter(BuildContext context) {
     return ScrollbarPainter(
-      color: _kScrollbarColor,
-      textDirection: _textDirection,
+      color: CupertinoDynamicColor.resolve(_kScrollbarColor, context),
+      textDirection: Directionality.of(context),
       thickness: _thickness,
       fadeoutOpacityAnimation: _fadeoutOpacityAnimation,
       mainAxisMargin: _kScrollbarMainAxisMargin,
@@ -353,9 +365,7 @@ class _CupertinoScrollbarState extends State<CupertinoScrollbar> with TickerProv
           child: CustomPaint(
             key: _customPaintKey,
             foregroundPainter: _painter,
-            child: RepaintBoundary(
-              child: widget.child,
-            ),
+            child: RepaintBoundary(child: widget.child),
           ),
         ),
       ),

packages/flutter/lib/src/cupertino/slider.dart

@@ -474,8 +474,6 @@ class _RenderCupertinoSlider extends RenderConstrainedBox {
       _drag.addPointer(event);
   }
 
-  final CupertinoThumbPainter _thumbPainter = CupertinoThumbPainter();
-
   @override
   void paint(PaintingContext context, Offset offset) {
     double visualPosition;
@@ -514,7 +512,7 @@ class _RenderCupertinoSlider extends RenderConstrainedBox {
     }
 
     final Offset thumbCenter = Offset(trackActive, trackCenter);
-    _thumbPainter.paint(canvas, Rect.fromCircle(center: thumbCenter, radius: CupertinoThumbPainter.radius));
+    const CupertinoThumbPainter().paint(canvas, Rect.fromCircle(center: thumbCenter, radius: CupertinoThumbPainter.radius));
   }
 
   @override

packages/flutter/lib/src/cupertino/switch.dart

@@ -96,8 +96,8 @@ class CupertinoSwitch extends StatefulWidget {
 
   /// The color to use when this switch is on.
   ///
-  /// Defaults to [CupertinoColors.activeGreen] when null and ignores the
-  /// [CupertinoTheme] in accordance to native iOS behavior.
+  /// Defaults to [CupertinoSystemColorsData.systemGreen] when null and ignores
+  /// the [CupertinoTheme] in accordance to native iOS behavior.
   final Color activeColor;
 
   /// {@template flutter.cupertino.switch.dragStartBehavior}
@@ -140,7 +140,10 @@ class _CupertinoSwitchState extends State<CupertinoSwitch> with TickerProviderSt
       opacity: widget.onChanged == null ? _kCupertinoSwitchDisabledOpacity : 1.0,
       child: _CupertinoSwitchRenderObjectWidget(
         value: widget.value,
-        activeColor: widget.activeColor ?? CupertinoColors.activeGreen,
+        activeColor: CupertinoDynamicColor.resolve(
+          widget.activeColor ?? CupertinoSystemColors.of(context).systemGreen,
+          context,
+        ),
         onChanged: widget.onChanged,
         vsync: this,
         dragStartBehavior: widget.dragStartBehavior,
@@ -170,6 +173,7 @@ class _CupertinoSwitchRenderObjectWidget extends LeafRenderObjectWidget {
     return _RenderCupertinoSwitch(
       value: value,
       activeColor: activeColor,
+      trackColor: CupertinoDynamicColor.resolve(CupertinoSystemColors.of(context).secondarySystemFill, context),
       onChanged: onChanged,
       textDirection: Directionality.of(context),
       vsync: vsync,
@@ -182,6 +186,7 @@ class _CupertinoSwitchRenderObjectWidget extends LeafRenderObjectWidget {
     renderObject
       ..value = value
       ..activeColor = activeColor
+      ..trackColor = CupertinoDynamicColor.resolve(CupertinoSystemColors.of(context).secondarySystemFill, context)
       ..onChanged = onChanged
       ..textDirection = Directionality.of(context)
       ..vsync = vsync
@@ -200,7 +205,6 @@ const double _kSwitchHeight = 39.0;
 // Opacity of a disabled switch, as eye-balled from iOS Simulator on Mac.
 const double _kCupertinoSwitchDisabledOpacity = 0.5;
 
-const Color _kTrackColor = CupertinoColors.lightBackgroundGray;
 const Duration _kReactionDuration = Duration(milliseconds: 300);
 const Duration _kToggleDuration = Duration(milliseconds: 200);
 
@@ -208,6 +212,7 @@ class _RenderCupertinoSwitch extends RenderConstrainedBox {
   _RenderCupertinoSwitch({
     @required bool value,
     @required Color activeColor,
+    @required Color trackColor,
     ValueChanged<bool> onChanged,
     @required TextDirection textDirection,
     @required TickerProvider vsync,
@@ -217,6 +222,7 @@ class _RenderCupertinoSwitch extends RenderConstrainedBox {
        assert(vsync != null),
        _value = value,
        _activeColor = activeColor,
+       _trackColor = trackColor,
        _onChanged = onChanged,
        _textDirection = textDirection,
        _vsync = vsync,
@@ -295,6 +301,16 @@ class _RenderCupertinoSwitch extends RenderConstrainedBox {
     markNeedsPaint();
   }
 
+  Color get trackColor => _trackColor;
+  Color _trackColor;
+  set trackColor(Color value) {
+    assert(value != null);
+    if (value == _trackColor)
+      return;
+    _trackColor = value;
+    markNeedsPaint();
+  }
+
   ValueChanged<bool> get onChanged => _onChanged;
   ValueChanged<bool> _onChanged;
   set onChanged(ValueChanged<bool> value) {
@@ -458,8 +474,6 @@ class _RenderCupertinoSwitch extends RenderConstrainedBox {
     config.isToggled = _value;
   }
 
-  final CupertinoThumbPainter _thumbPainter = CupertinoThumbPainter();
-
   @override
   void paint(PaintingContext context, Offset offset) {
     final Canvas canvas = context.canvas;
@@ -478,7 +492,7 @@ class _RenderCupertinoSwitch extends RenderConstrainedBox {
     }
 
     final Paint paint = Paint()
-      ..color = Color.lerp(_kTrackColor, activeColor, currentValue);
+      ..color = Color.lerp(trackColor, activeColor, currentValue);
 
     final Rect trackRect = Rect.fromLTWH(
         offset.dx + (size.width - _kTrackWidth) / 2.0,
@@ -509,7 +523,7 @@ class _RenderCupertinoSwitch extends RenderConstrainedBox {
     );
 
     context.pushClipRRect(needsCompositing, Offset.zero, thumbBounds, trackRRect, (PaintingContext innerContext, Offset offset) {
-      _thumbPainter.paint(innerContext.canvas, thumbBounds);
+      const CupertinoThumbPainter.switchThumb().paint(innerContext.canvas, thumbBounds);
     });
   }
 

packages/flutter/lib/src/cupertino/thumb_painter.dart

@@ -6,27 +6,62 @@ import 'package:flutter/painting.dart';
 
 import 'colors.dart';
 
-/// Paints an iOS-style slider thumb.
+const Color _kThumbBorderColor = Color(0x0A000000);
+
+const List<BoxShadow> _kSwitchBoxShadows = <BoxShadow> [
+  BoxShadow(
+    color: Color(0x26000000),
+    offset: Offset(0, 3),
+    blurRadius: 8.0,
+  ),
+  BoxShadow(
+    color: Color(0x0F000000),
+    offset: Offset(0, 3),
+    blurRadius: 1.0,
+  ),
+];
+
+const List<BoxShadow> _kSliderBoxShadows = <BoxShadow> [
+  BoxShadow(
+    color: Color(0x26000000),
+    offset: Offset(0, 3),
+    blurRadius: 8.0,
+  ),
+  BoxShadow(
+    color: Color(0x29000000),
+    offset: Offset(0, 1),
+    blurRadius: 1.0,
+  ),
+  BoxShadow(
+    color: Color(0x1A000000),
+    offset: Offset(0, 3),
+    blurRadius: 1.0,
+  ),
+];
+
+/// Paints an iOS-style slider thumb or switch thumb.
 ///
 /// Used by [CupertinoSwitch] and [CupertinoSlider].
 class CupertinoThumbPainter {
   /// Creates an object that paints an iOS-style slider thumb.
-  CupertinoThumbPainter({
+  const CupertinoThumbPainter({
     this.color = CupertinoColors.white,
-    this.shadowColor = const Color(0x2C000000),
-  }) : _shadowPaint = BoxShadow(
-         color: shadowColor,
-         blurRadius: 1.0,
-       ).toPaint();
+    this.shadows = _kSliderBoxShadows,
+  }) : assert(shadows != null);
+
+  /// Creates an object that paints an iOS-style switch thumb.
+  const CupertinoThumbPainter.switchThumb({
+    Color color = CupertinoColors.white,
+    List<BoxShadow> shadows = _kSwitchBoxShadows,
+  }) : this(color: color, shadows: shadows);
 
   /// The color of the interior of the thumb.
   final Color color;
 
-  /// The color of the shadow case by the thumb.
-  final Color shadowColor;
-
-  /// The paint used to draw the shadow case by the thumb.
-  final Paint _shadowPaint;
+  /// The list of [BoxShadow] to paint below the thumb.
+  ///
+  /// Must not be null.
+  final List<BoxShadow> shadows;
 
   /// Half the default diameter of the thumb.
   static const double radius = 14.0;
@@ -44,8 +79,13 @@ class CupertinoThumbPainter {
       Radius.circular(rect.shortestSide / 2.0),
     );
 
-    canvas.drawRRect(rrect, _shadowPaint);
-    canvas.drawRRect(rrect.shift(const Offset(0.0, 3.0)), _shadowPaint);
+    for (BoxShadow shadow in shadows)
+      canvas.drawRRect(rrect.shift(shadow.offset), shadow.toPaint());
+
+    canvas.drawRRect(
+      rrect.inflate(0.5),
+      Paint()..color = _kThumbBorderColor,
+    );
     canvas.drawRRect(rrect, Paint()..color = color);
   }
 }

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

@@ -44,11 +44,11 @@ const double _kMinInteractiveSize = 48.0;
 class ScrollbarPainter extends ChangeNotifier implements CustomPainter {
   /// Creates a scrollbar with customizations given by construction arguments.
   ScrollbarPainter({
-    @required this.color,
-    @required this.textDirection,
+    @required Color color,
+    @required TextDirection textDirection,
     @required this.thickness,
     @required this.fadeoutOpacityAnimation,
-    this.padding = EdgeInsets.zero,
+    EdgeInsets padding = EdgeInsets.zero,
     this.mainAxisMargin = 0.0,
     this.crossAxisMargin = 0.0,
     this.radius,
@@ -66,16 +66,37 @@ class ScrollbarPainter extends ChangeNotifier implements CustomPainter {
        assert(minOverscrollLength == null || minOverscrollLength >= 0),
        assert(padding != null),
        assert(padding.isNonNegative),
+       _color = color,
+       _textDirection = textDirection,
+       _padding = padding,
        minOverscrollLength = minOverscrollLength ?? minLength {
     fadeoutOpacityAnimation.addListener(notifyListeners);
   }
 
   /// [Color] of the thumb. Mustn't be null.
-  final Color color;
+  Color get color => _color;
+  Color _color;
+  set color(Color value) {
+    assert(value != null);
+    if (color == value)
+      return;
+
+    _color = value;
+    notifyListeners();
+  }
 
   /// [TextDirection] of the [BuildContext] which dictates the side of the
   /// screen the scrollbar appears in (the trailing side). Mustn't be null.
-  final TextDirection textDirection;
+  TextDirection get textDirection => _textDirection;
+  TextDirection _textDirection;
+  set textDirection(TextDirection value) {
+    assert(value != null);
+    if (textDirection == value)
+      return;
+
+    _textDirection = value;
+    notifyListeners();
+  }
 
   /// Thickness of the scrollbar in its cross-axis in logical pixels. Mustn't be null.
   double thickness;
@@ -110,7 +131,17 @@ class ScrollbarPainter extends ChangeNotifier implements CustomPainter {
   ///
   /// Defaults to [EdgeInsets.zero]. Must not be null and offsets from all four
   /// directions must be greater than or equal to zero.
-  final EdgeInsets padding;
+  EdgeInsets get padding => _padding;
+  EdgeInsets _padding;
+  set padding(EdgeInsets value) {
+    assert(value != null);
+    if (padding == value)
+      return;
+
+    _padding = value;
+    notifyListeners();
+  }
+
 
   /// The preferred smallest size the scrollbar can shrink to when the total
   /// scrollable extent is large, the current visible viewport is small, and the
@@ -162,8 +193,8 @@ class ScrollbarPainter extends ChangeNotifier implements CustomPainter {
   }
 
   Paint get _paint {
-    return Paint()..color =
-        color.withOpacity(color.opacity * fadeoutOpacityAnimation.value);
+    return Paint()
+      ..color = color.withOpacity(color.opacity * fadeoutOpacityAnimation.value);
   }
 
   void _paintThumbCrossAxis(Canvas canvas, Size size, double thumbOffset, double thumbExtent, AxisDirection direction) {

packages/flutter/test/cupertino/scrollbar_paint_test.dart

@@ -7,7 +7,7 @@ import 'package:flutter_test/flutter_test.dart';
 
 import '../rendering/mock_canvas.dart';
 
-const Color _kScrollbarColor = Color(0x99777777);
+const Color _kScrollbarColor = Color(0x59000000);
 
 // The `y` offset has to be larger than `ScrollDragController._bigThresholdBreakDistance`
 // to prevent [motionStartDistanceThreshold] from affecting the actual drag distance.
@@ -42,9 +42,9 @@ void main() {
       color: _kScrollbarColor,
       rrect: RRect.fromRectAndRadius(
         const Rect.fromLTWH(
-          800.0 - 3 - 2.5, // Screen width - margin - thickness.
+          800.0 - 3 - 3, // Screen width - margin - thickness.
           3.0, // Initial position is the top margin.
-          2.5, // Thickness.
+          3, // Thickness.
           // Fraction in viewport * scrollbar height - top, bottom margin.
           600.0 / 4000.0 * (600.0 - 2 * 3),
         ),
@@ -86,9 +86,9 @@ void main() {
       color: _kScrollbarColor,
       rrect: RRect.fromRectAndRadius(
         const Rect.fromLTWH(
-          800.0 - 3 - 2.5, // Screen width - margin - thickness.
+          800.0 - 3 - 3, // Screen width - margin - thickness.
           44 + 20 + 3.0, // nav bar height + top margin
-          2.5, // Thickness.
+          3, // Thickness.
           // Fraction visible * (viewport size - padding - margin)
           // where Fraction visible = (viewport size - padding) / content size
           (600.0 - 34 - 44 - 20) / 4000.0 * (600.0 - 2 * 3 - 34 - 44 - 20),

packages/flutter/test/cupertino/scrollbar_test.dart

@@ -8,6 +8,11 @@ import 'package:flutter_test/flutter_test.dart';
 
 import '../rendering/mock_canvas.dart';
 
+const CupertinoDynamicColor _kScrollbarColor = CupertinoDynamicColor.withBrightness(
+  color: Color(0x59000000),
+  darkColor:Color(0x80FFFFFF),
+);
+
 void main() {
   const Duration _kScrollbarTimeToFade = Duration(milliseconds: 1200);
   const Duration _kScrollbarFadeDuration = Duration(milliseconds: 250);
@@ -31,14 +36,14 @@ void main() {
     // Scrollbar fully showing
     await tester.pump(const Duration(milliseconds: 500));
     expect(find.byType(CupertinoScrollbar), paints..rrect(
-      color: const Color(0x99777777),
+      color: _kScrollbarColor.color,
     ));
 
     await tester.pump(const Duration(seconds: 3));
     await tester.pump(const Duration(seconds: 3));
     // Still there.
     expect(find.byType(CupertinoScrollbar), paints..rrect(
-      color: const Color(0x99777777),
+      color: _kScrollbarColor.color,
     ));
 
     await gesture.up();
@@ -47,7 +52,44 @@ void main() {
 
     // Opacity going down now.
     expect(find.byType(CupertinoScrollbar), paints..rrect(
-      color: const Color(0x77777777),
+      color: _kScrollbarColor.color.withAlpha(69),
+    ));
+  });
+
+  testWidgets('Scrollbar dark mode', (WidgetTester tester) async {
+    Brightness brightness = Brightness.light;
+    StateSetter setState;
+    await tester.pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: StatefulBuilder(
+          builder: (BuildContext context, StateSetter setter) {
+            setState = setter;
+            return MediaQuery(
+              data: MediaQueryData(platformBrightness: brightness),
+              child: const CupertinoScrollbar(
+                child: SingleChildScrollView(child: SizedBox(width: 4000.0, height: 4000.0)),
+              ),
+            );
+          },
+        ),
+      ),
+    );
+
+    final TestGesture gesture = await tester.startGesture(tester.getCenter(find.byType(SingleChildScrollView)));
+    await gesture.moveBy(const Offset(0.0, 10.0));
+    await tester.pump();
+    // Scrollbar fully showing
+    await tester.pumpAndSettle();
+    expect(find.byType(CupertinoScrollbar), paints..rrect(
+      color: _kScrollbarColor.color,
+    ));
+
+    setState(() { brightness = Brightness.dark; });
+    await tester.pump();
+
+    expect(find.byType(CupertinoScrollbar), paints..rrect(
+      color: _kScrollbarColor.darkColor,
     ));
   });
 
@@ -81,7 +123,7 @@ void main() {
     // Scrollbar thumb is fully showing and scroll offset has moved by
     // scrollAmount.
     expect(find.byType(CupertinoScrollbar), paints..rrect(
-      color: const Color(0x99777777),
+      color: _kScrollbarColor.color,
     ));
     expect(scrollController.offset, scrollAmount);
     await scrollGesture.up();
@@ -111,7 +153,7 @@ void main() {
     expect(scrollController.offset, greaterThan(scrollAmount * 2));
     // The scrollbar thumb is still fully visible.
     expect(find.byType(CupertinoScrollbar), paints..rrect(
-      color: const Color(0x99777777),
+      color: _kScrollbarColor.color,
     ));
 
     // Let the thumb fade out so all timers have resolved.
@@ -149,7 +191,7 @@ void main() {
     // Scrollbar thumb is fully showing and scroll offset has moved by
     // scrollAmount.
     expect(find.byType(CupertinoScrollbar), paints..rrect(
-      color: const Color(0x99777777),
+      color: _kScrollbarColor.color,
     ));
     expect(scrollController.offset, scrollAmount);
     await scrollGesture.up();
@@ -182,7 +224,7 @@ void main() {
     expect(scrollController.offset, greaterThan(scrollAmount * 2));
     // The scrollbar thumb is still fully visible.
     expect(find.byType(CupertinoScrollbar), paints..rrect(
-      color: const Color(0x99777777),
+      color: _kScrollbarColor.color,
     ));
 
     // Let the thumb fade out so all timers have resolved.

packages/flutter/test/cupertino/switch_test.dart

@@ -532,8 +532,8 @@ void main() {
                       value = newValue;
                     });
                   },
-                )
-              )
+                ),
+              ),
             );
           },
         ),
@@ -544,7 +544,7 @@ void main() {
       find.byKey(switchKey),
       matchesGoldenFile(
         'switch.tap.off.png',
-        version: 0,
+        version: 1,
       ),
     );
 
@@ -558,7 +558,7 @@ void main() {
       find.byKey(switchKey),
       matchesGoldenFile(
         'switch.tap.turningOn.png',
-        version: 0,
+        version: 1,
       ),
     );
 
@@ -567,9 +567,59 @@ void main() {
       find.byKey(switchKey),
       matchesGoldenFile(
         'switch.tap.on.png',
-        version: 0,
+        version: 1,
       ),
     );
   });
 
+  testWidgets('Switch renders correctly in dark mode', (WidgetTester tester) async {
+    final Key switchKey = UniqueKey();
+    bool value = false;
+    await tester.pumpWidget(
+      MediaQuery(
+        data: const MediaQueryData(platformBrightness: Brightness.dark),
+        child: Directionality(
+          textDirection: TextDirection.ltr,
+          child: StatefulBuilder(
+            builder: (BuildContext context, StateSetter setState) {
+              return Center(
+                child: RepaintBoundary(
+                  child: CupertinoSwitch(
+                    key: switchKey,
+                    value: value,
+                    dragStartBehavior: DragStartBehavior.down,
+                    onChanged: (bool newValue) {
+                      setState(() {
+                        value = newValue;
+                      });
+                    },
+                  ),
+                ),
+              );
+            },
+          ),
+        ),
+      ),
+    );
+
+    await expectLater(
+      find.byKey(switchKey),
+      matchesGoldenFile(
+        'switch.tap.off.dark.png',
+        version: 0,
+      ),
+    );
+
+    await tester.tap(find.byKey(switchKey));
+    expect(value, isTrue);
+
+    await tester.pumpAndSettle();
+    await expectLater(
+      find.byKey(switchKey),
+      matchesGoldenFile(
+        'switch.tap.on.dark.png',
+        version: 0,
+      ),
+    );
+  });
 }