diff --git a/packages/flutter/lib/src/rendering/proxy_box.dart b/packages/flutter/lib/src/rendering/proxy_box.dart
index 7ac99b271c..c4aa4a1a27 100644
--- a/packages/flutter/lib/src/rendering/proxy_box.dart
+++ b/packages/flutter/lib/src/rendering/proxy_box.dart
@@ -3177,6 +3177,8 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
     bool button,
     String label,
     String value,
+    String increasedValue,
+    String decreasedValue,
     String hint,
     TextDirection textDirection,
     VoidCallback onTap,
@@ -3195,6 +3197,8 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
        _button = button,
        _label = label,
        _value = value,
+       _increasedValue = increasedValue,
+       _decreasedValue = decreasedValue,
        _hint = hint,
        _textDirection = textDirection,
        _onTap = onTap,
@@ -3283,7 +3287,7 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
 
   /// If non-null, sets the [SemanticsNode.label] semantic to the given value.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   String get label => _label;
   String _label;
   set label(String value) {
@@ -3296,7 +3300,7 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
 
   /// If non-null, sets the [SemanticsNode.value] semantic to the given value.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   String get value => _value;
   String _value;
   set value(String value) {
@@ -3307,9 +3311,37 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
     markNeedsSemanticsUpdate(onlyLocalUpdates: (value != null) == hadValue);
   }
 
+  /// If non-null, sets the [SemanticsNode.increasedValue] semantic to the given
+  /// value.
+  ///
+  /// The reading direction is given by [textDirection].
+  String get increasedValue => _increasedValue;
+  String _increasedValue;
+  set increasedValue(String value) {
+    if (_increasedValue == value)
+      return;
+    final bool hadValue = _increasedValue != null;
+    _increasedValue = value;
+    markNeedsSemanticsUpdate(onlyLocalUpdates: (value != null) == hadValue);
+  }
+
+  /// If non-null, sets the [SemanticsNode.decreasedValue] semantic to the given
+  /// value.
+  ///
+  /// The reading direction is given by [textDirection].
+  String get decreasedValue => _decreasedValue;
+  String _decreasedValue;
+  set decreasedValue(String value) {
+    if (_decreasedValue == value)
+      return;
+    final bool hadValue = _decreasedValue != null;
+    _decreasedValue = value;
+    markNeedsSemanticsUpdate(onlyLocalUpdates: (value != null) == hadValue);
+  }
+
   /// If non-null, sets the [SemanticsNode.hint] semantic to the given value.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   String get hint => _hint;
   String _hint;
   set hint(String value) {
@@ -3322,7 +3354,8 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
 
   /// If non-null, sets the [SemanticsNode.textDirection] semantic to the given value.
   ///
-  /// This must not be null if [label], [hint], or [value] is not null.
+  /// This must not be null if [label], [hint], [value], [increasedValue], or
+  /// [decreasedValue] are not null.
   TextDirection get textDirection => _textDirection;
   TextDirection _textDirection;
   set textDirection(TextDirection value) {
@@ -3499,6 +3532,15 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
 
   @override
   void describeSemanticsConfiguration(SemanticsConfiguration config) {
+    assert(
+      onIncrease == null || (value == null) == (increasedValue == null),
+      'If "onIncrease" is set either both "value" and "increasedValue" or neither have to be set.',
+    );
+    assert(
+      onDecrease == null || (value == null) == (decreasedValue == null),
+      'If "onDecrease" is set either both "value" and "decreasedValue" or neither have to be set.',
+    );
+
     config.isSemanticBoundary = container;
     config.explicitChildNodes = explicitChildNodes;
 
@@ -3512,6 +3554,10 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
       config.label = label;
     if (value != null)
       config.value = value;
+    if (increasedValue != null)
+      config.increasedValue = increasedValue;
+    if (decreasedValue != null)
+      config.decreasedValue = decreasedValue;
     if (hint != null)
       config.hint = hint;
     if (textDirection != null)
diff --git a/packages/flutter/lib/src/rendering/semantics.dart b/packages/flutter/lib/src/rendering/semantics.dart
index 347b93306a..edc5939521 100644
--- a/packages/flutter/lib/src/rendering/semantics.dart
+++ b/packages/flutter/lib/src/rendering/semantics.dart
@@ -76,7 +76,9 @@ class SemanticsData extends Diagnosticable {
     @required this.flags,
     @required this.actions,
     @required this.label,
+    @required this.increasedValue,
     @required this.value,
+    @required this.decreasedValue,
     @required this.hint,
     @required this.textDirection,
     @required this.rect,
@@ -85,7 +87,15 @@ class SemanticsData extends Diagnosticable {
   }) : assert(flags != null),
        assert(actions != null),
        assert(label != null),
+       assert(value != null),
+       assert(decreasedValue != null),
+       assert(increasedValue != null),
+       assert(hint != null),
        assert(label == '' || textDirection != null, 'A SemanticsData object with label "$label" had a null textDirection.'),
+       assert(value == '' || textDirection != null, 'A SemanticsData object with value "$value" had a null textDirection.'),
+       assert(hint == '' || textDirection != null, 'A SemanticsData object with hint "$hint" had a null textDirection.'),
+       assert(decreasedValue == '' || textDirection != null, 'A SemanticsData object with decreasedValue "$decreasedValue" had a null textDirection.'),
+       assert(increasedValue == '' || textDirection != null, 'A SemanticsData object with increasedValue "$increasedValue" had a null textDirection.'),
        assert(rect != null);
 
   /// A bit field of [SemanticsFlags] that apply to this node.
@@ -96,20 +106,33 @@ class SemanticsData extends Diagnosticable {
 
   /// A textual description of this node.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   final String label;
 
   /// A textual description for the current value of the node.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   final String value;
 
+  /// The value that [value] will become after performing a
+  /// [SemanticsAction.increase] action.
+  ///
+  /// The reading direction is given by [textDirection].
+  final String increasedValue;
+
+  /// The value that [value] will become after performing a
+  /// [SemanticsAction.decrease] action.
+  ///
+  /// The reading direction is given by [textDirection].
+  final String decreasedValue;
+
   /// A brief description of the result of performing an action on this node.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   final String hint;
 
-  /// The reading direction for the text in [label], [value], and [hint].
+  /// The reading direction for the text in [label], [value], [hint],
+  /// [increasedValue], and [decreasedValue].
   final TextDirection textDirection;
 
   /// The bounding box for this node in its coordinate system.
@@ -153,6 +176,10 @@ class SemanticsData extends Diagnosticable {
     }
     properties.add(new IterableProperty<String>('flags', flagSummary, ifEmpty: null));
     properties.add(new StringProperty('label', label, defaultValue: ''));
+    properties.add(new StringProperty('value', value, defaultValue: ''));
+    properties.add(new StringProperty('increasedValue', increasedValue, defaultValue: ''));
+    properties.add(new StringProperty('decreasedValue', decreasedValue, defaultValue: ''));
+    properties.add(new StringProperty('hint', hint, defaultValue: ''));
     properties.add(new EnumProperty<TextDirection>('textDirection', textDirection, defaultValue: null));
   }
 
@@ -495,7 +522,9 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
   bool _isDifferentFromCurrentSemanticAnnotation(SemanticsConfiguration config) {
     return _label != config.label ||
         _hint != config.hint ||
+        _decreasedValue != config.decreasedValue ||
         _value != config.value ||
+        _increasedValue != config.increasedValue ||
         _flags != config._flags ||
         _textDirection != config.textDirection ||
         _actionsAsBits != config._actionsAsBits ||
@@ -523,23 +552,44 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
 
   /// A textual description of this node.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   String get label => _label;
   String _label = _kEmptyConfig.label;
 
   /// A textual description for the current value of the node.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   String get value => _value;
   String _value = _kEmptyConfig.value;
 
+  /// The value that [value] will have after a [SemanticsAction.decrease] action
+  /// has been performed.
+  ///
+  /// This property is only valid if the [SemanticsAction.decrease] action is
+  /// available on this node.
+  ///
+  /// The reading direction is given by [textDirection].
+  String get decreasedValue => _decreasedValue;
+  String _decreasedValue = _kEmptyConfig.decreasedValue;
+
+  /// The value that [value] will have after a [SemanticsAction.increase] action
+  /// has been performed.
+  ///
+  /// This property is only valid if the [SemanticsAction.increase] action is
+  /// available on this node.
+  ///
+  /// The reading direction is given by [textDirection].
+  String get increasedValue => _increasedValue;
+  String _increasedValue = _kEmptyConfig.increasedValue;
+
   /// A brief description of the result of performing an action on this node.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   String get hint => _hint;
   String _hint = _kEmptyConfig.hint;
 
-  /// The reading direction for [label], [value], and [hint].
+  /// The reading direction for [label], [value], [hint], [increasedValue], and
+  /// [decreasedValue].
   TextDirection get textDirection => _textDirection;
   TextDirection _textDirection = _kEmptyConfig.textDirection;
 
@@ -556,7 +606,9 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
       _markDirty();
 
     _label = config.label;
+    _decreasedValue = config.decreasedValue;
     _value = config.value;
+    _increasedValue = config.increasedValue;
     _hint = config.hint;
     _flags = config._flags;
     _textDirection = config.textDirection;
@@ -564,6 +616,15 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
     _actionsAsBits = config._actionsAsBits;
     _mergeAllDescendantsIntoThisNode = config.isMergingSemanticsOfDescendants;
     _replaceChildren(childrenInInversePaintOrder ?? const <SemanticsNode>[]);
+
+    assert(
+      !_canPerformAction(SemanticsAction.increase) || (_value == '') == (_increasedValue == ''),
+      'A SemanticsNode with action "increase" needs to be annotated with either both "value" and "increasedValue" or neither',
+    );
+    assert(
+      !_canPerformAction(SemanticsAction.decrease) || (_value == '') == (_decreasedValue == ''),
+      'A SemanticsNode with action "increase" needs to be annotated with either both "value" and "decreasedValue" or neither',
+    );
   }
 
 
@@ -578,6 +639,8 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
     String label = _label;
     String hint = _hint;
     String value = _value;
+    String increasedValue = _increasedValue;
+    String decreasedValue = _decreasedValue;
     TextDirection textDirection = _textDirection;
     Set<SemanticsTag> mergedTags = tags == null ? null : new Set<SemanticsTag>.from(tags);
 
@@ -589,6 +652,10 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
         textDirection ??= node._textDirection;
         if (value == '' || value == null)
           value = node._value;
+        if (increasedValue == '' || increasedValue == null)
+          increasedValue = node._increasedValue;
+        if (decreasedValue == '' || decreasedValue == null)
+          decreasedValue = node._decreasedValue;
         if (node.tags != null) {
           mergedTags ??= new Set<SemanticsTag>();
           mergedTags.addAll(node.tags);
@@ -614,6 +681,8 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
       actions: actions,
       label: label,
       value: value,
+      increasedValue: increasedValue,
+      decreasedValue: decreasedValue,
       hint: hint,
       textDirection: textDirection,
       rect: rect,
@@ -648,6 +717,8 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
       rect: data.rect,
       label: data.label,
       value: data.value,
+      decreasedValue: data.decreasedValue,
+      increasedValue: data.increasedValue,
       hint: data.hint,
       textDirection: data.textDirection,
       transform: data.transform?.storage ?? _kIdentityTransform,
@@ -707,6 +778,8 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
     properties.add(new FlagProperty('isButton', value: _hasFlag(SemanticsFlags.isButton), ifTrue: 'button'));
     properties.add(new StringProperty('label', _label, defaultValue: ''));
     properties.add(new StringProperty('value', _value, defaultValue: ''));
+    properties.add(new StringProperty('increasedValue', _increasedValue, defaultValue: ''));
+    properties.add(new StringProperty('decreasedValue', _decreasedValue, defaultValue: ''));
     properties.add(new StringProperty('hint', _hint, defaultValue: ''));
     properties.add(new EnumProperty<TextDirection>('textDirection', _textDirection, defaultValue: null));
   }
@@ -1018,6 +1091,7 @@ class SemanticsConfiguration {
   ///
   /// Whenever the user performs `action` the provided `handler` is called.
   void addAction(SemanticsAction action, VoidCallback handler) {
+    assert(handler != null);
     _actions[action] = handler;
     _actionsAsBits |= action.index;
     _hasBeenAnnotated = true;
@@ -1050,10 +1124,11 @@ class SemanticsConfiguration {
   /// [value] and [hint] in the following order: [value], [label], [hint].
   /// The concatenated value is then used as the `Text` description.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   String get label => _label;
   String _label = '';
   set label(String label) {
+    assert(label != null);
     _label = label;
     _hasBeenAnnotated = true;
   }
@@ -1065,14 +1140,51 @@ class SemanticsConfiguration {
   /// [label] and [hint] in the following order: [value], [label], [hint].
   /// The concatenated value is then used as the `Text` description.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
+  ///
+  /// See also:
+  ///  * [decreasedValue], describes what [value] will be after performing
+  ///    [SemanticsAction.decrease]
+  ///  * [increasedValue], describes what [value] will be after performing
+  ///    [SemanticsAction.increase]
   String get value => _value;
   String _value = '';
   set value(String value) {
+    assert(value != null);
     _value = value;
     _hasBeenAnnotated = true;
   }
 
+  /// The value that [value] will have after performing a
+  /// [SemanticsAction.decrease] action.
+  ///
+  /// This must be set if a handler for [SemanticsAction.decrease] is provided
+  /// and [value] is set.
+  ///
+  /// The reading direction is given by [textDirection].
+  String get decreasedValue => _decreasedValue;
+  String _decreasedValue = '';
+  set decreasedValue(String decreasedValue) {
+    assert(decreasedValue != null);
+    _decreasedValue = decreasedValue;
+    _hasBeenAnnotated = true;
+  }
+
+  /// The value that [value] will have after performing a
+  /// [SemanticsAction.increase] action.
+  ///
+  /// This must be set if a handler for [SemanticsAction.increase] is provided
+  /// and [value] is set.
+  ///
+  /// The reading direction is given by [textDirection].
+  String get increasedValue => _increasedValue;
+  String _increasedValue = '';
+  set increasedValue(String increasedValue) {
+    assert(increasedValue != null);
+    _increasedValue = increasedValue;
+    _hasBeenAnnotated = true;
+  }
+
   /// A brief description of the result of performing an action on this node.
   ///
   /// On iOS this is used for the `accessibilityHint` property defined in the
@@ -1080,15 +1192,17 @@ class SemanticsConfiguration {
   /// [label] and [value] in the following order: [value], [label], [hint].
   /// The concatenated value is then used as the `Text` description.
   ///
-  /// The text's reading direction is given by [textDirection].
+  /// The reading direction is given by [textDirection].
   String get hint => _hint;
   String _hint = '';
   set hint(String hint) {
+    assert(hint != null);
     _hint = hint;
     _hasBeenAnnotated = true;
   }
 
-  /// The reading direction for the text in [label], [value], and [hint].
+  /// The reading direction for the text in [label], [value], [hint],
+  /// [increasedValue], and [decreasedValue].
   TextDirection get textDirection => _textDirection;
   TextDirection _textDirection;
   set textDirection(TextDirection textDirection) {
@@ -1182,8 +1296,12 @@ class SemanticsConfiguration {
       otherString: other._label,
       otherTextDirection: other.textDirection,
     );
+    if (_decreasedValue == '' || _decreasedValue == null)
+      _decreasedValue = other._decreasedValue;
     if (_value == '' || _value == null)
       _value = other._value;
+    if (_increasedValue == '' || _increasedValue == null)
+      _increasedValue = other._increasedValue;
     _hint = _concatStrings(
       thisString: _hint,
       thisTextDirection: textDirection,
@@ -1202,7 +1320,9 @@ class SemanticsConfiguration {
       .._hasBeenAnnotated = _hasBeenAnnotated
       .._textDirection = _textDirection
       .._label = _label
+      .._increasedValue = _increasedValue
       .._value = _value
+      .._decreasedValue = _decreasedValue
       .._hint = _hint
       .._flags = _flags
       .._actionsAsBits = _actionsAsBits
diff --git a/packages/flutter/lib/src/widgets/basic.dart b/packages/flutter/lib/src/widgets/basic.dart
index 9126c972f5..a000c6a39b 100644
--- a/packages/flutter/lib/src/widgets/basic.dart
+++ b/packages/flutter/lib/src/widgets/basic.dart
@@ -4454,6 +4454,8 @@ class Semantics extends SingleChildRenderObjectWidget {
     this.button,
     this.label,
     this.value,
+    this.increasedValue,
+    this.decreasedValue,
     this.hint,
     this.textDirection,
     this.onTap,
@@ -4528,6 +4530,30 @@ class Semantics extends SingleChildRenderObjectWidget {
   ///    in TalkBack and VoiceOver.
   final String value;
 
+  /// The value that [value] will become after a [SemanticsAction.increase]
+  /// action has been performed on this widget.
+  ///
+  /// If a value is provided, [onIncrease] must also be set and there must
+  /// either be an ambient [Directionality] or an explicit [textDirection]
+  /// must be provided.
+  ///
+  /// See also:
+  ///  * [SemanticsConfiguration.increasedValue] for a description of how this
+  ///    is exposed in TalkBack and VoiceOver.
+  final String increasedValue;
+
+  /// The value that [value] will become after a [SemanticsAction.decrease]
+  /// action has been performed on this widget.
+  ///
+  /// If a value is provided, [onDecrease] must also be set and there must
+  /// either be an ambient [Directionality] or an explicit [textDirection]
+  /// must be provided.
+  ///
+  /// See also:
+  ///  * [SemanticsConfiguration.decreasedValue] for a description of how this
+  ///    is exposed in TalkBack and VoiceOver.
+  final String decreasedValue;
+
   /// Provides a brief textual description of the result of an action performed
   /// on the widget.
   ///
@@ -4539,7 +4565,8 @@ class Semantics extends SingleChildRenderObjectWidget {
   ///    in TalkBack and VoiceOver.
   final String hint;
 
-  /// The reading direction of the [label], [value], and [hint].
+  /// The reading direction of the [label], [value], [hint], [increasedValue],
+  /// and [decreasedValue].
   ///
   /// Defaults to the ambient [Directionality].
   final TextDirection textDirection;
@@ -4625,6 +4652,9 @@ class Semantics extends SingleChildRenderObjectWidget {
   /// This is a request to increase the value represented by the widget. For
   /// example, this action might be recognized by a slider control.
   ///
+  /// If a [value] is set, [increasedValue] must also be provided and
+  /// [onIncrease] must ensure that [value] will be set to [increasedValue].
+  ///
   /// VoiceOver users on iOS can trigger this action by swiping up with one
   /// finger. TalkBack users on Android can trigger this action by pressing the
   /// volume up button.
@@ -4635,6 +4665,9 @@ class Semantics extends SingleChildRenderObjectWidget {
   /// This is a request to decrease the value represented by the widget. For
   /// example, this action might be recognized by a slider control.
   ///
+  /// If a [value] is set, [decreasedValue] must also be provided and
+  /// [onDecrease] must ensure that [value] will be set to [decreasedValue].
+  ///
   /// VoiceOver users on iOS can trigger this action by swiping down with one
   /// finger. TalkBack users on Android can trigger this action by pressing the
   /// volume down button.
@@ -4650,6 +4683,8 @@ class Semantics extends SingleChildRenderObjectWidget {
       button: button,
       label: label,
       value: value,
+      increasedValue: increasedValue,
+      decreasedValue: decreasedValue,
       hint: hint,
       textDirection: _getTextDirection(context),
       onTap: onTap,
@@ -4672,6 +4707,8 @@ class Semantics extends SingleChildRenderObjectWidget {
       ..selected = selected
       ..label = label
       ..value = value
+      ..increasedValue = increasedValue
+      ..decreasedValue = decreasedValue
       ..hint = hint
       ..textDirection = _getTextDirection(context)
       ..onTap = onTap
diff --git a/packages/flutter/test/rendering/semantics_test.dart b/packages/flutter/test/rendering/semantics_test.dart
index e06c6cc877..22373dff76 100644
--- a/packages/flutter/test/rendering/semantics_test.dart
+++ b/packages/flutter/test/rendering/semantics_test.dart
@@ -198,7 +198,7 @@ void main() {
 
     expect(
       minimalProperties.toStringDeep(minLevel: DiagnosticLevel.hidden),
-      'SemanticsNode#16(owner: null, isPartOfNodeMerging: false, Rect.fromLTRB(0.0, 0.0, 0.0, 0.0), actions: [], isSelected: false, isButton: false, label: "", value: "", hint: "", textDirection: null)\n',
+      'SemanticsNode#16(owner: null, isPartOfNodeMerging: false, Rect.fromLTRB(0.0, 0.0, 0.0, 0.0), actions: [], isSelected: false, isButton: false, label: "", value: "", increasedValue: "", decreasedValue: "", hint: "", textDirection: null)\n',
     );
 
     final SemanticsConfiguration config = new SemanticsConfiguration()
diff --git a/packages/flutter/test/widgets/semantics_test.dart b/packages/flutter/test/widgets/semantics_test.dart
index 120ef7093b..5e9c916f29 100644
--- a/packages/flutter/test/widgets/semantics_test.dart
+++ b/packages/flutter/test/widgets/semantics_test.dart
@@ -513,4 +513,36 @@ void main() {
 
     semantics.dispose();
   });
+
+  testWidgets('Increased/decreased values are annotated', (WidgetTester tester) async {
+    final SemanticsTester semantics = new SemanticsTester(tester);
+
+    await tester.pumpWidget(
+      new Directionality(
+        textDirection: TextDirection.ltr,
+        child: new Semantics(
+          container: true,
+          value: '10s',
+          increasedValue: '11s',
+          decreasedValue: '9s',
+          onIncrease: () => () {},
+          onDecrease: () => () {},
+        ),
+      ),
+    );
+
+    expect(semantics, hasSemantics(new TestSemantics.root(
+      children: <TestSemantics>[
+        new TestSemantics.rootChild(
+          actions: SemanticsAction.increase.index | SemanticsAction.decrease.index,
+          textDirection: TextDirection.ltr,
+          value: '10s',
+          increasedValue: '11s',
+          decreasedValue: '9s',
+        ),
+      ],
+    ), ignoreTransform: true, ignoreRect: true, ignoreId: true));
+
+    semantics.dispose();
+  });
 }
diff --git a/packages/flutter/test/widgets/semantics_tester.dart b/packages/flutter/test/widgets/semantics_tester.dart
index 5656e5561c..0e2437dfac 100644
--- a/packages/flutter/test/widgets/semantics_tester.dart
+++ b/packages/flutter/test/widgets/semantics_tester.dart
@@ -36,6 +36,8 @@ class TestSemantics {
     this.actions: 0,
     this.label: '',
     this.value: '',
+    this.increasedValue: '',
+    this.decreasedValue: '',
     this.hint: '',
     this.textDirection,
     this.rect,
@@ -45,6 +47,8 @@ class TestSemantics {
   }) : assert(flags != null),
        assert(label != null),
        assert(value != null),
+       assert(increasedValue != null),
+       assert(decreasedValue != null),
        assert(hint != null),
        assert(children != null),
        tags = tags?.toSet() ?? new Set<SemanticsTag>();
@@ -56,6 +60,8 @@ class TestSemantics {
     this.actions: 0,
     this.label: '',
     this.value: '',
+    this.increasedValue: '',
+    this.decreasedValue: '',
     this.hint: '',
     this.textDirection,
     this.transform,
@@ -64,6 +70,8 @@ class TestSemantics {
   }) : id = 0,
        assert(flags != null),
        assert(label != null),
+       assert(increasedValue != null),
+       assert(decreasedValue != null),
        assert(value != null),
        assert(hint != null),
        rect = TestSemantics.rootRect,
@@ -86,6 +94,8 @@ class TestSemantics {
     this.label: '',
     this.hint: '',
     this.value: '',
+    this.increasedValue: '',
+    this.decreasedValue: '',
     this.textDirection,
     this.rect,
     Matrix4 transform,
@@ -94,6 +104,8 @@ class TestSemantics {
   }) : assert(flags != null),
        assert(label != null),
        assert(value != null),
+       assert(increasedValue != null),
+       assert(decreasedValue != null),
        assert(hint != null),
        transform = _applyRootChildScale(transform),
        assert(children != null),
@@ -117,6 +129,14 @@ class TestSemantics {
   /// A textual description for the value of this node.
   final String value;
 
+  /// What [value] will become after [SemanticsAction.increase] has been
+  /// performed.
+  final String increasedValue;
+
+  /// What [value] will become after [SemanticsAction.decrease] has been
+  /// performed.
+  final String decreasedValue;
+
   /// A brief textual description of the result of the action that can be
   /// performed on this node.
   final String hint;
@@ -190,11 +210,15 @@ class TestSemantics {
       return fail('expected node id $id to have label "$label" but found label "${nodeData.label}".');
     if (value != nodeData.value)
       return fail('expected node id $id to have value "$value" but found value "${nodeData.value}".');
+    if (increasedValue != nodeData.increasedValue)
+      return fail('expected node id $id to have increasedValue "$increasedValue" but found value "${nodeData.increasedValue}".');
+    if (decreasedValue != nodeData.decreasedValue)
+      return fail('expected node id $id to have decreasedValue "$decreasedValue" but found value "${nodeData.decreasedValue}".');
     if (hint != nodeData.hint)
       return fail('expected node id $id to have hint "$hint" but found hint "${nodeData.hint}".');
     if (textDirection != null && textDirection != nodeData.textDirection)
       return fail('expected node id $id to have textDirection "$textDirection" but found "${nodeData.textDirection}".');
-    if ((nodeData.label != '' || nodeData.value != '' || nodeData.hint != '') && nodeData.textDirection == null)
+    if ((nodeData.label != '' || nodeData.value != '' || nodeData.hint != '' || node.increasedValue != '' || node.decreasedValue != '') && nodeData.textDirection == null)
       return fail('expected node id $id, which has a label, value, or hint, to have a textDirection, but it did not.');
     if (!ignoreRect && rect != nodeData.rect)
       return fail('expected node id $id to have rect $rect but found rect ${nodeData.rect}.');