diff --git a/examples/rendering/sector_layout.dart b/examples/rendering/sector_layout.dart
index ac3fc4699e..a6fc547357 100644
--- a/examples/rendering/sector_layout.dart
+++ b/examples/rendering/sector_layout.dart
@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:async';
 import 'package:flutter/rendering.dart';
 import 'lib/sector_layout.dart';
 
diff --git a/examples/stocks/lib/main.dart b/examples/stocks/lib/main.dart
index 314a3b57a5..61e7d5d4d9 100644
--- a/examples/stocks/lib/main.dart
+++ b/examples/stocks/lib/main.dart
@@ -11,6 +11,7 @@ import 'dart:ui' as ui;
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/painting.dart';
+import 'package:flutter/rendering.dart';
 
 import 'stock_data.dart';
 
diff --git a/examples/stocks/lib/stock_home.dart b/examples/stocks/lib/stock_home.dart
index 0d18aec008..33d9cdd5de 100644
--- a/examples/stocks/lib/stock_home.dart
+++ b/examples/stocks/lib/stock_home.dart
@@ -112,7 +112,7 @@ class StockHomeState extends State<StockHome> {
         ),
         new DrawerItem(
           icon: 'device/dvr',
-          onPressed: () { debugDumpApp(); },
+          onPressed: () { debugDumpApp(); debugDumpRenderTree(); },
           child: new Text('Dump App to Console')
         ),
         new DrawerDivider(),
diff --git a/packages/flutter/lib/src/gestures/arena.dart b/packages/flutter/lib/src/gestures/arena.dart
index 17e70da4ec..184a314ac2 100644
--- a/packages/flutter/lib/src/gestures/arena.dart
+++ b/packages/flutter/lib/src/gestures/arena.dart
@@ -45,6 +45,8 @@ class GestureArenaEntry {
 class _GestureArenaState {
   final List<GestureArenaMember> members = new List<GestureArenaMember>();
   bool isOpen = true;
+  bool isHeld = false;
+  bool hasPendingSweep = false;
 
   void add(GestureArenaMember member) {
     assert(isOpen);
@@ -72,6 +74,46 @@ class GestureArena {
     _tryToResolveArena(key, state);
   }
 
+  /// Force resolution on this arena, giving the win to the first member
+  void sweep(Object key) {
+    _GestureArenaState state = _arenas[key];
+    if (state == null)
+      return;  // This arena either never existed or has been resolved.
+    assert(!state.isOpen);
+    if (state.isHeld) {
+      state.hasPendingSweep = true;
+      return;  // This arena is being held for a long-lived member
+    }
+    _arenas.remove(key);
+    if (!state.members.isEmpty) {
+      // First member wins
+      state.members.first.acceptGesture(key);
+      // Give all the other members the bad news
+      for (int i = 1; i < state.members.length; i++)
+        state.members[i].rejectGesture(key);
+    }
+  }
+
+  /// Prevent the arena from being swept
+  void hold(Object key) {
+    _GestureArenaState state = _arenas[key];
+    if (state == null)
+      return;  // This arena either never existed or has been resolved.
+    state.isHeld = true;
+  }
+
+  /// Release a hold, allowing the arena to be swept
+  /// If a sweep was attempted on a held arena, the sweep will be done
+  /// on release
+  void release(Object key) {
+    _GestureArenaState state = _arenas[key];
+    if (state == null)
+      return;  // This arena either never existed or has been resolved.
+    state.isHeld = false;
+    if (state.hasPendingSweep)
+      sweep(key);
+  }
+
   void _tryToResolveArena(Object key, _GestureArenaState state) {
     assert(_arenas[key] == state);
     assert(!state.isOpen);
diff --git a/packages/flutter/lib/src/material/scrollbar_painter.dart b/packages/flutter/lib/src/material/scrollbar_painter.dart
index 16b2175553..cd839f43f0 100644
--- a/packages/flutter/lib/src/material/scrollbar_painter.dart
+++ b/packages/flutter/lib/src/material/scrollbar_painter.dart
@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'dart:async';
-import 'dart:ui' as ui;
 
 import 'package:flutter/animation.dart';
 import 'package:flutter/rendering.dart';
diff --git a/packages/flutter/lib/src/painting/text_style.dart b/packages/flutter/lib/src/painting/text_style.dart
index 9ca3de29a9..cf241df700 100644
--- a/packages/flutter/lib/src/painting/text_style.dart
+++ b/packages/flutter/lib/src/painting/text_style.dart
@@ -252,25 +252,131 @@ class TextStyle {
     List<String> result = <String>[];
     if (color != null)
       result.add('${prefix}color: $color');
-    // TODO(hansmuller): escape the fontFamily string.
     if (fontFamily != null)
-      result.add('${prefix}fontFamily: "$fontFamily"');
+      result.add('${prefix}family: "$fontFamily"');
     if (fontSize != null)
-      result.add('${prefix}fontSize: $fontSize');
-    if (fontWeight != null)
-      result.add('${prefix}fontWeight: $fontWeight');
-    if (fontStyle != null)
-      result.add('${prefix}fontStyle: $fontStyle');
-    if (textAlign != null)
-      result.add('${prefix}textAlign: $textAlign');
-    if (textBaseline != null)
-      result.add('${prefix}textBaseline: $textBaseline');
-    if (decoration != null)
-      result.add('${prefix}decoration: $decoration');
-    if (decorationColor != null)
-      result.add('${prefix}decorationColor: $decorationColor');
-    if (decorationStyle != null)
-      result.add('${prefix}decorationStyle: $decorationStyle');
+      result.add('${prefix}size: $fontSize');
+    if (fontWeight != null) {
+      switch (fontWeight) {
+        case FontWeight.w100:
+          result.add('${prefix}weight: 100');
+          break;
+        case FontWeight.w200:
+          result.add('${prefix}weight: 200');
+          break;
+        case FontWeight.w300:
+          result.add('${prefix}weight: 300');
+          break;
+        case FontWeight.w400:
+          result.add('${prefix}weight: 400');
+          break;
+        case FontWeight.w500:
+          result.add('${prefix}weight: 500');
+          break;
+        case FontWeight.w600:
+          result.add('${prefix}weight: 600');
+          break;
+        case FontWeight.w700:
+          result.add('${prefix}weight: 700');
+          break;
+        case FontWeight.w800:
+          result.add('${prefix}weight: 800');
+          break;
+        case FontWeight.w900:
+          result.add('${prefix}weight: 900');
+          break;
+      }
+    }
+    if (fontStyle != null) {
+      switch (fontStyle) {
+        case FontStyle.normal:
+          result.add('${prefix}style: normal');
+          break;
+        case FontStyle.italic:
+          result.add('${prefix}style: italic');
+          break;
+      }
+    }
+    if (textAlign != null) {
+      switch (textAlign) {
+        case TextAlign.left:
+          result.add('${prefix}align: left');
+          break;
+        case TextAlign.right:
+          result.add('${prefix}align: right');
+          break;
+        case TextAlign.center:
+          result.add('${prefix}align: center');
+          break;
+      }
+    }
+    if (textBaseline != null) {
+      switch (textBaseline) {
+        case TextBaseline.alphabetic:
+          result.add('${prefix}baseline: alphabetic');
+          break;
+        case TextBaseline.ideographic:
+          result.add('${prefix}baseline: ideographic');
+          break;
+      }
+    }
+    if (decoration != null || decorationColor != null || decorationStyle != null) {
+      String decorationDescription = '${prefix}decoration: ';
+      bool haveDecorationDescription = false;
+      if (decorationStyle != null) {
+        switch (decorationStyle) {
+          case TextDecorationStyle.solid:
+            decorationDescription += 'solid';
+            break;
+          case TextDecorationStyle.double:
+            decorationDescription += 'double';
+            break;
+          case TextDecorationStyle.dotted:
+            decorationDescription += 'dotted';
+            break;
+          case TextDecorationStyle.dashed:
+            decorationDescription += 'dashed';
+            break;
+          case TextDecorationStyle.wavy:
+            decorationDescription += 'wavy';
+            break;
+        }
+        haveDecorationDescription = true;
+      }
+      if (decorationColor != null) {
+        if (haveDecorationDescription)
+          decorationDescription += ' ';
+        decorationDescription += '$decorationColor';
+        haveDecorationDescription = true;
+      }
+      if (decoration != null) {
+        if (haveDecorationDescription)
+          decorationDescription += ' ';
+        bool multipleDecorations = false;
+        for (TextDecoration value in decoration) {
+          if (multipleDecorations)
+            decorationDescription += '+';
+          switch (value) {
+            case TextDecoration.none:
+              decorationDescription += 'none';
+              break;
+            case TextDecoration.underline:
+              decorationDescription += 'underline';
+              break;
+            case TextDecoration.overline:
+              decorationDescription += 'overline';
+              break;
+            case TextDecoration.lineThrough:
+              decorationDescription += 'line-through';
+              break;
+          }
+          multipleDecorations = true;
+        }
+        haveDecorationDescription = true;
+      }
+      assert(haveDecorationDescription);
+      result.add(decorationDescription);
+    }
     if (result.isEmpty)
       return '$prefix<no style specified>';
     return result.join('\n');
diff --git a/packages/flutter/lib/src/rendering/binding.dart b/packages/flutter/lib/src/rendering/binding.dart
index 3484b40469..e501ff39fa 100644
--- a/packages/flutter/lib/src/rendering/binding.dart
+++ b/packages/flutter/lib/src/rendering/binding.dart
@@ -244,6 +244,8 @@ class FlutterBinding extends HitTestTarget {
       pointerRouter.route(event);
       if (event.type == 'pointerdown')
         GestureArena.instance.close(event.pointer);
+      else if (event.type == 'pointerup')
+        GestureArena.instance.sweep(event.pointer);
     }
   }
 }
diff --git a/packages/flutter/lib/src/rendering/object.dart b/packages/flutter/lib/src/rendering/object.dart
index 606d4fb988..be74fec813 100644
--- a/packages/flutter/lib/src/rendering/object.dart
+++ b/packages/flutter/lib/src/rendering/object.dart
@@ -1139,11 +1139,18 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
   /// Returns a description of the tree rooted at this node.
   /// If the prefix argument is provided, then every line in the output
   /// will be prefixed by that string.
-  String toStringDeep([String prefix = '']) {
+  String toStringDeep([String prefixLineOne = '', String prefixOtherLines = '']) {
     RenderObject debugPreviousActiveLayout = _debugActiveLayout;
     _debugActiveLayout = null;
-    prefix += '  ';
-    String result = '$this\n${debugDescribeSettings(prefix)}${debugDescribeChildren(prefix)}';
+    String result = '$prefixLineOne$this\n';
+    final String childrenDescription = debugDescribeChildren(prefixOtherLines);
+    final String settingsPrefix = childrenDescription != '' ? '$prefixOtherLines \u2502 ' : '$prefixOtherLines   ';
+    result += debugDescribeSettings(settingsPrefix);
+    if (childrenDescription != '')
+      result += '$prefixOtherLines \u2502\n';
+    else
+      result += '$prefixOtherLines\n';
+    result += childrenDescription;
     _debugActiveLayout = debugPreviousActiveLayout;
     return result;
   }
@@ -1198,7 +1205,7 @@ abstract class RenderObjectWithChildMixin<ChildType extends RenderObject> implem
   }
   String debugDescribeChildren(String prefix) {
     if (child != null)
-      return '${prefix}child: ${child.toStringDeep(prefix)}';
+      return '${child.toStringDeep("$prefix \u2514\u2500child: ", "$prefix  ")}';
     return '';
   }
 }
@@ -1442,13 +1449,19 @@ abstract class ContainerRenderObjectMixin<ChildType extends RenderObject, Parent
 
   String debugDescribeChildren(String prefix) {
     String result = '';
-    int count = 1;
-    ChildType child = _firstChild;
-    while (child != null) {
-      result += '${prefix}child $count: ${child.toStringDeep(prefix)}';
-      count += 1;
-      final ParentDataType childParentData = child.parentData;
-      child = childParentData.nextSibling;
+    if (_firstChild != null) {
+      ChildType child = _firstChild;
+      int count = 1;
+      while (child != _lastChild) {
+        result += '${child.toStringDeep("$prefix \u251C\u2500child $count: ", "$prefix \u2502")}';
+        count += 1;
+        final ParentDataType childParentData = child.parentData;
+        child = childParentData.nextSibling;
+      }
+      if (child != null) {
+        assert(child == _lastChild);
+        result += '${child.toStringDeep("$prefix \u2514\u2500child $count: ", "$prefix  ")}';
+      }
     }
     return result;
   }
diff --git a/packages/flutter/lib/src/rendering/proxy_box.dart b/packages/flutter/lib/src/rendering/proxy_box.dart
index d68ec6c8a9..5dffe9a5cf 100644
--- a/packages/flutter/lib/src/rendering/proxy_box.dart
+++ b/packages/flutter/lib/src/rendering/proxy_box.dart
@@ -883,6 +883,7 @@ class FractionalOffset {
     value = 37 * value + y.hashCode;
     return value;
   }
+  String toString() => '$runtimeType($x, $y)';
 }
 
 /// Applies a transformation before painting its child
@@ -1016,7 +1017,7 @@ class RenderTransform extends RenderProxyBox {
   String debugDescribeSettings(String prefix) {
     List<String> result = _transform.toString().split('\n').map((String s) => '$prefix  $s\n').toList();
     result.removeLast();
-    return '${super.debugDescribeSettings(prefix)}${prefix}transform matrix:\n${result.join()}\n${prefix}origin: $origin\n';
+    return '${super.debugDescribeSettings(prefix)}${prefix}transform matrix:\n${result.join()}\n${prefix}origin: $origin\nalignment: $alignment\n';
   }
 }
 
diff --git a/packages/flutter/lib/src/widgets/binding.dart b/packages/flutter/lib/src/widgets/binding.dart
index c73678c52e..8ceeb73244 100644
--- a/packages/flutter/lib/src/widgets/binding.dart
+++ b/packages/flutter/lib/src/widgets/binding.dart
@@ -92,6 +92,9 @@ void runApp(Widget app) {
 void debugDumpApp() {
   assert(WidgetFlutterBinding.instance != null);
   assert(WidgetFlutterBinding.instance.renderViewElement != null);
+  String mode = 'RELEASE MODE';
+  assert(() { mode = 'CHECKED MODE'; return true; });
+  print('${WidgetFlutterBinding.instance.runtimeType} - $mode');
   WidgetFlutterBinding.instance.renderViewElement.toStringDeep().split('\n').forEach(print);
 }
 
diff --git a/packages/flutter/lib/src/widgets/framework.dart b/packages/flutter/lib/src/widgets/framework.dart
index 5ff36a3ab8..1cfd022b49 100644
--- a/packages/flutter/lib/src/widgets/framework.dart
+++ b/packages/flutter/lib/src/widgets/framework.dart
@@ -394,8 +394,11 @@ abstract class State<T extends StatefulComponent> {
 
   void debugFillDescription(List<String> description) {
     description.add('$hashCode');
-    if (_debugLifecycleState != _StateLifecycle.ready)
-      description.add('$_debugLifecycleState');
+    assert(() {
+      if (_debugLifecycleState != _StateLifecycle.ready)
+        description.add('$_debugLifecycleState');
+      return true;
+    });
     if (_config == null)
       description.add('no config');
     if (_element == null)
@@ -829,9 +832,7 @@ abstract class Element<T extends Widget> implements BuildContext {
   String toStringDeep([String prefixLineOne = '', String prefixOtherLines = '']) {
     String result = '$prefixLineOne$this\n';
     List<Element> children = <Element>[];
-    visitChildren((Element child) {
-      children.add(child);
-    });
+    visitChildren(children.add);
     if (children.length > 0) {
       Element last = children.removeLast();
       for (Element child in children)
diff --git a/packages/flutter_sprites/lib/src/physics_debug.dart b/packages/flutter_sprites/lib/src/physics_debug.dart
index cc3bc0c618..30f877c929 100644
--- a/packages/flutter_sprites/lib/src/physics_debug.dart
+++ b/packages/flutter_sprites/lib/src/physics_debug.dart
@@ -4,14 +4,22 @@ class _PhysicsDebugDraw extends box2d.DebugDraw {
   _PhysicsDebugDraw(
     box2d.ViewportTransform transform,
     this.physicsNode
-  ) : super(transform);
+  ) : super(transform) {
+    appendFlags(
+      box2d.DebugDraw.JOINT_BIT |
+      box2d.DebugDraw.CENTER_OF_MASS_BIT |
+      box2d.DebugDraw.WIREFRAME_DRAWING_BIT
+    );
+  }
 
   PhysicsNode physicsNode;
 
   PaintingCanvas canvas;
 
   void drawSegment(Vector2 p1, Vector2 p2, box2d.Color3i color) {
-    Paint paint = new Paint()..color = _toColor(color);
+    Paint paint = new Paint()
+      ..color = _toColor(color)
+      ..strokeWidth = 1.0;
     canvas.drawLine(_toPoint(p1), _toPoint(p2), paint);
   }
 
@@ -33,7 +41,6 @@ class _PhysicsDebugDraw extends box2d.DebugDraw {
   }
 
   void drawCircle(Vector2 center, num radius, box2d.Color3i color, [Vector2 axis]) {
-    print("drawCircle: $center");
     Paint paint = new Paint()
       ..color = _toColor(color)
       ..setStyle(ui.PaintingStyle.stroke)
diff --git a/packages/flutter_sprites/lib/src/sprite_box.dart b/packages/flutter_sprites/lib/src/sprite_box.dart
index f2bc2f4db5..356b48b1d9 100644
--- a/packages/flutter_sprites/lib/src/sprite_box.dart
+++ b/packages/flutter_sprites/lib/src/sprite_box.dart
@@ -32,8 +32,10 @@ class SpriteBox extends RenderBox {
     if (value == _rootNode) return;
 
     // Ensure that the root node has a size
-    assert(value.size.width > 0);
-    assert(value.size.height > 0);
+    assert(_transformMode == SpriteBoxTransformMode.nativePoints
+      || value.size.width > 0);
+    assert(_transformMode == SpriteBoxTransformMode.nativePoints
+      || value.size.height > 0);
 
     // Remove sprite box references
     if (_rootNode != null) _removeSpriteBoxReference(_rootNode);
@@ -101,11 +103,11 @@ class SpriteBox extends RenderBox {
     assert(rootNode != null);
     assert(rootNode._spriteBox == null);
 
-    // Setup root node
-    this.rootNode = rootNode;
-
     // Setup transform mode
     this.transformMode = mode;
+
+    // Setup root node
+    this.rootNode = rootNode;
   }
 
   void _removeSpriteBoxReference(Node node) {
@@ -310,6 +312,8 @@ class SpriteBox extends RenderBox {
         rootNode.size = new Size(systemWidth, systemHeight);
         break;
       case SpriteBoxTransformMode.nativePoints:
+        systemWidth = size.width;
+        systemHeight = size.height;
         break;
       default:
         assert(false);
diff --git a/packages/unit/test/engine/insert_before_test.dart b/packages/unit/test/engine/insert_before_test.dart
index 4af3b4bbb3..ffd94ef7c1 100644
--- a/packages/unit/test/engine/insert_before_test.dart
+++ b/packages/unit/test/engine/insert_before_test.dart
@@ -6,15 +6,15 @@ void main() {
   Document document = new Document();
 
   test("should throw with invalid arguments", () {
-    var parent = document.createElement("div");
-    var child = document.createElement("div");
+    Element parent = document.createElement("div");
+    Element child = document.createElement("div");
     parent.appendChild(child);
     // TODO(eseidel): This should throw!
     // expect(() {
     //   parent.insertBefore([parent]);
     // }, throws);
     expect(() {
-      child.insertBefore([parent]);
+      child.insertBefore(<Node>[parent]);
     }, throws);
   });
 
diff --git a/packages/unit/test/engine/replace_child_test.dart b/packages/unit/test/engine/replace_child_test.dart
index ba40e156e0..42dfce4718 100644
--- a/packages/unit/test/engine/replace_child_test.dart
+++ b/packages/unit/test/engine/replace_child_test.dart
@@ -5,36 +5,36 @@ import 'package:test/test.dart';
 import 'dom_utils.dart';
 
 void main() {
-  var document = new Document();
+  Document document = new Document();
 
   test("should replace elements", () {
-    var parent = document.createElement("div");
-    var oldChild = parent.appendChild(document.createElement("div"));
-    var newChild = document.createElement("div");
-    oldChild.replaceWith([newChild]);
+    Element parent = document.createElement("div");
+    Element oldChild = parent.appendChild(document.createElement("div"));
+    Element newChild = document.createElement("div");
+    oldChild.replaceWith(<Node>[newChild]);
     expect(oldChild.parentNode, isNull);
     expect(newChild.parentNode, equals(parent));
   });
 
   test("should replace text", () {
-    var parent = document.createElement("div");
-    var oldChild = parent.appendChild(document.createText(" it's a text "));
-    var newChild = document.createElement("div");
-    oldChild.replaceWith([newChild]);
+    Element parent = document.createElement("div");
+    Node oldChild = parent.appendChild(document.createText(" it's a text "));
+    Element newChild = document.createElement("div");
+    oldChild.replaceWith(<Node>[newChild]);
     expect(oldChild.parentNode, isNull);
     expect(newChild.parentNode, equals(parent));
   });
 
   test("should replace children with a fragment", () {
-    var fragment = document.createDocumentFragment();
-    var child1 = fragment.appendChild(document.createElement("div"));
-    var child2 = fragment.appendChild(document.createText(" text "));
-    var child3 = fragment.appendChild(document.createText(" "));
-    var child4 = fragment.appendChild(document.createElement("div"));
-    var parent = document.createElement("div");
-    var oldChild = parent.appendChild(document.createElement("div"));
-    var lastChild = parent.appendChild(document.createElement("div"));
-    oldChild.replaceWith([fragment]);
+    DocumentFragment fragment = document.createDocumentFragment();
+    Element child1 = fragment.appendChild(document.createElement("div"));
+    Node child2 = fragment.appendChild(document.createText(" text "));
+    Node child3 = fragment.appendChild(document.createText(" "));
+    Element child4 = fragment.appendChild(document.createElement("div"));
+    Element parent = document.createElement("div");
+    Element oldChild = parent.appendChild(document.createElement("div"));
+    Element lastChild = parent.appendChild(document.createElement("div"));
+    oldChild.replaceWith(<Node>[fragment]);
     expect(child1.parentNode, equals(parent));
     expect(child2.parentNode, equals(parent));
     expect(child3.parentNode, equals(parent));
diff --git a/packages/unit/test/gestures/arena_test.dart b/packages/unit/test/gestures/arena_test.dart
index ccc861b50a..4f0d062fd6 100644
--- a/packages/unit/test/gestures/arena_test.dart
+++ b/packages/unit/test/gestures/arena_test.dart
@@ -66,4 +66,176 @@ void main() {
     expect(secondAcceptRan, isFalse);
     expect(secondRejectRan, isTrue);
   });
+
+  test('Should win by sweep', () {
+    GestureArena arena = new GestureArena();
+
+    int primaryKey = 4;
+    bool firstAcceptRan = false;
+    bool firstRejectRan = false;
+    bool secondAcceptRan = false;
+    bool secondRejectRan = false;
+
+    TestGestureArenaMember first = new TestGestureArenaMember(
+      onAcceptGesture: (int key) {
+        expect(key, equals(primaryKey));
+        firstAcceptRan = true;
+      },
+      onRejectGesture: (int key) {
+        expect(key, equals(primaryKey));
+        firstRejectRan = true;
+      }
+    );
+
+    TestGestureArenaMember second = new TestGestureArenaMember(
+      onAcceptGesture: (int key) {
+        expect(key, equals(primaryKey));
+        secondAcceptRan = true;
+      },
+      onRejectGesture: (int key) {
+        expect(key, equals(primaryKey));
+        secondRejectRan = true;
+      }
+    );
+
+    arena.add(primaryKey, first);
+    arena.add(primaryKey, second);
+    arena.close(primaryKey);
+
+    expect(firstAcceptRan, isFalse);
+    expect(firstRejectRan, isFalse);
+    expect(secondAcceptRan, isFalse);
+    expect(secondRejectRan, isFalse);
+
+    arena.sweep(primaryKey);
+
+    expect(firstAcceptRan, isTrue);
+    expect(firstRejectRan, isFalse);
+    expect(secondAcceptRan, isFalse);
+    expect(secondRejectRan, isTrue);
+  });
+
+  test('Should win on release after hold sweep release', () {
+    GestureArena arena = new GestureArena();
+
+    int primaryKey = 4;
+    bool firstAcceptRan = false;
+    bool firstRejectRan = false;
+    bool secondAcceptRan = false;
+    bool secondRejectRan = false;
+
+    TestGestureArenaMember first = new TestGestureArenaMember(
+      onAcceptGesture: (int key) {
+        expect(key, equals(primaryKey));
+        firstAcceptRan = true;
+      },
+      onRejectGesture: (int key) {
+        expect(key, equals(primaryKey));
+        firstRejectRan = true;
+      }
+    );
+
+    TestGestureArenaMember second = new TestGestureArenaMember(
+      onAcceptGesture: (int key) {
+        expect(key, equals(primaryKey));
+        secondAcceptRan = true;
+      },
+      onRejectGesture: (int key) {
+        expect(key, equals(primaryKey));
+        secondRejectRan = true;
+      }
+    );
+
+    arena.add(primaryKey, first);
+    arena.add(primaryKey, second);
+    arena.close(primaryKey);
+
+    expect(firstAcceptRan, isFalse);
+    expect(firstRejectRan, isFalse);
+    expect(secondAcceptRan, isFalse);
+    expect(secondRejectRan, isFalse);
+
+    arena.hold(primaryKey);
+
+    expect(firstAcceptRan, isFalse);
+    expect(firstRejectRan, isFalse);
+    expect(secondAcceptRan, isFalse);
+    expect(secondRejectRan, isFalse);
+
+    arena.sweep(primaryKey);
+
+    expect(firstAcceptRan, isFalse);
+    expect(firstRejectRan, isFalse);
+    expect(secondAcceptRan, isFalse);
+    expect(secondRejectRan, isFalse);
+
+    arena.release(primaryKey);
+
+    expect(firstAcceptRan, isTrue);
+    expect(firstRejectRan, isFalse);
+    expect(secondAcceptRan, isFalse);
+    expect(secondRejectRan, isTrue);
+  });
+
+  test('Should win on sweep after hold release sweep', () {
+    GestureArena arena = new GestureArena();
+
+    int primaryKey = 4;
+    bool firstAcceptRan = false;
+    bool firstRejectRan = false;
+    bool secondAcceptRan = false;
+    bool secondRejectRan = false;
+
+    TestGestureArenaMember first = new TestGestureArenaMember(
+      onAcceptGesture: (int key) {
+        expect(key, equals(primaryKey));
+        firstAcceptRan = true;
+      },
+      onRejectGesture: (int key) {
+        expect(key, equals(primaryKey));
+        firstRejectRan = true;
+      }
+    );
+
+    TestGestureArenaMember second = new TestGestureArenaMember(
+      onAcceptGesture: (int key) {
+        expect(key, equals(primaryKey));
+        secondAcceptRan = true;
+      },
+      onRejectGesture: (int key) {
+        expect(key, equals(primaryKey));
+        secondRejectRan = true;
+      }
+    );
+
+    arena.add(primaryKey, first);
+    arena.add(primaryKey, second);
+    arena.close(primaryKey);
+
+    expect(firstAcceptRan, isFalse);
+    expect(firstRejectRan, isFalse);
+    expect(secondAcceptRan, isFalse);
+    expect(secondRejectRan, isFalse);
+
+    arena.hold(primaryKey);
+
+    expect(firstAcceptRan, isFalse);
+    expect(firstRejectRan, isFalse);
+    expect(secondAcceptRan, isFalse);
+    expect(secondRejectRan, isFalse);
+
+    arena.release(primaryKey);
+
+    expect(firstAcceptRan, isFalse);
+    expect(firstRejectRan, isFalse);
+    expect(secondAcceptRan, isFalse);
+    expect(secondRejectRan, isFalse);
+
+    arena.sweep(primaryKey);
+
+    expect(firstAcceptRan, isTrue);
+    expect(firstRejectRan, isFalse);
+    expect(secondAcceptRan, isFalse);
+    expect(secondRejectRan, isTrue);
+  });
 }
diff --git a/packages/unit/test/gestures/long_press_test.dart b/packages/unit/test/gestures/long_press_test.dart
index 133901f9fc..ce95e3ab27 100644
--- a/packages/unit/test/gestures/long_press_test.dart
+++ b/packages/unit/test/gestures/long_press_test.dart
@@ -26,7 +26,7 @@ void main() {
       longPressRecognized = true;
     };
 
-    new FakeAsync().run((async) {
+    new FakeAsync().run((FakeAsync async) {
       longPress.addPointer(down);
       GestureArena.instance.close(5);
       expect(longPressRecognized, isFalse);
@@ -50,7 +50,7 @@ void main() {
       longPressRecognized = true;
     };
 
-    new FakeAsync().run((async) {
+    new FakeAsync().run((FakeAsync async) {
       longPress.addPointer(down);
       GestureArena.instance.close(5);
       expect(longPressRecognized, isFalse);
@@ -82,7 +82,7 @@ void main() {
       longPressRecognized = true;
     };
 
-    new FakeAsync().run((async) {
+    new FakeAsync().run((FakeAsync async) {
       showPress.addPointer(down);
       longPress.addPointer(down);
       GestureArena.instance.close(5);
diff --git a/packages/unit/test/gestures/show_press_test.dart b/packages/unit/test/gestures/show_press_test.dart
index d5e5dd5e9f..1206fbf52f 100644
--- a/packages/unit/test/gestures/show_press_test.dart
+++ b/packages/unit/test/gestures/show_press_test.dart
@@ -26,7 +26,7 @@ void main() {
       showPressRecognized = true;
     };
 
-    new FakeAsync().run((async) {
+    new FakeAsync().run((FakeAsync async) {
       showPress.addPointer(down);
       GestureArena.instance.close(5);
       expect(showPressRecognized, isFalse);
@@ -48,7 +48,7 @@ void main() {
       showPressRecognized = true;
     };
 
-    new FakeAsync().run((async) {
+    new FakeAsync().run((FakeAsync async) {
       showPress.addPointer(down);
       GestureArena.instance.close(5);
       expect(showPressRecognized, isFalse);
diff --git a/packages/unit/test/rendering/box_test.dart b/packages/unit/test/rendering/box_test.dart
index 878237fbb1..680ede0236 100644
--- a/packages/unit/test/rendering/box_test.dart
+++ b/packages/unit/test/rendering/box_test.dart
@@ -11,7 +11,7 @@ void main() {
         backgroundColor: const Color(0xFF00FF00),
         gradient: new RadialGradient(
           center: Point.origin, radius: 500.0,
-          colors: [Colors.yellow[500], Colors.blue[500]]),
+          colors: <Color>[Colors.yellow[500], Colors.blue[500]]),
         boxShadow: shadows[3])
     );
     layout(root);
@@ -34,7 +34,7 @@ void main() {
       child: inner
     );
     RenderBox flex = new RenderFlex(
-      children: [padding],
+      children: <RenderBox>[padding],
       direction: FlexDirection.vertical,
       alignItems: FlexAlignItems.stretch
     );
diff --git a/packages/unit/test/rendering/flex_test.dart b/packages/unit/test/rendering/flex_test.dart
index 4ce08a1233..0d223c9aac 100644
--- a/packages/unit/test/rendering/flex_test.dart
+++ b/packages/unit/test/rendering/flex_test.dart
@@ -6,7 +6,7 @@ import 'rendering_tester.dart';
 void main() {
   test('Overconstrained flex', () {
     RenderDecoratedBox box = new RenderDecoratedBox(decoration: new BoxDecoration());
-    RenderFlex flex = new RenderFlex(children: [ box ]);
+    RenderFlex flex = new RenderFlex(children: <RenderBox>[box]);
     layout(flex, constraints: const BoxConstraints(
       minWidth: 200.0, maxWidth: 100.0, minHeight: 200.0, maxHeight: 100.0)
     );
@@ -24,7 +24,7 @@ void main() {
   test('Parent data', () {
     RenderDecoratedBox box1 = new RenderDecoratedBox(decoration: new BoxDecoration());
     RenderDecoratedBox box2 = new RenderDecoratedBox(decoration: new BoxDecoration());
-    RenderFlex flex = new RenderFlex(children: [ box1, box2 ]);
+    RenderFlex flex = new RenderFlex(children: <RenderBox>[box1, box2]);
     layout(flex, constraints: const BoxConstraints(
       minWidth: 0.0, maxWidth: 100.0, minHeight: 0.0, maxHeight: 100.0)
     );
@@ -33,7 +33,8 @@ void main() {
     expect(box2.size.width, equals(0.0));
     expect(box2.size.height, equals(0.0));
 
-    box2.parentData.flex = 1;
+    final FlexParentData box2ParentData = box2.parentData;
+    box2ParentData.flex = 1;
     flex.markNeedsLayout();
     pumpFrame();
     expect(box1.size.width, equals(0.0));
@@ -47,8 +48,9 @@ void main() {
     RenderDecoratedBox box2 = new RenderDecoratedBox(decoration: new BoxDecoration());
     RenderFlex flex = new RenderFlex();
     flex.setupParentData(box2);
-    box2.parentData.flex = 2;
-    flex.addAll([box1, box2]);
+    final FlexParentData box2ParentData = box2.parentData;
+    box2ParentData.flex = 2;
+    flex.addAll(<RenderBox>[box1, box2]);
     layout(flex, constraints: const BoxConstraints(
       minWidth: 0.0, maxWidth: 100.0, minHeight: 0.0, maxHeight: 100.0)
     );
diff --git a/packages/unit/test/rendering/grid_test.dart b/packages/unit/test/rendering/grid_test.dart
index 60852a2e8a..8646ba3068 100644
--- a/packages/unit/test/rendering/grid_test.dart
+++ b/packages/unit/test/rendering/grid_test.dart
@@ -5,7 +5,7 @@ import 'rendering_tester.dart';
 
 void main() {
   test('Basic grid layout test', () {
-    List<RenderBox> children = [
+    List<RenderBox> children = <RenderBox>[
       new RenderDecoratedBox(decoration: new BoxDecoration()),
       new RenderDecoratedBox(decoration: new BoxDecoration()),
       new RenderDecoratedBox(decoration: new BoxDecoration()),
@@ -15,7 +15,7 @@ void main() {
     RenderGrid grid = new RenderGrid(children: children, maxChildExtent: 100.0);
     layout(grid, constraints: const BoxConstraints(maxWidth: 200.0));
 
-    children.forEach((child) {
+    children.forEach((RenderBox child) {
       expect(child.size.width, equals(100.0), reason: "child width");
       expect(child.size.height, equals(100.0), reason: "child height");
     });
@@ -29,7 +29,7 @@ void main() {
 
     pumpFrame();
 
-    children.forEach((child) {
+    children.forEach((RenderBox child) {
       expect(child.size.width, equals(50.0), reason: "child width");
       expect(child.size.height, equals(50.0), reason: "child height");
     });
diff --git a/packages/unit/test/rendering/stack_test.dart b/packages/unit/test/rendering/stack_test.dart
index 8a2fb726d6..8fc40a5611 100644
--- a/packages/unit/test/rendering/stack_test.dart
+++ b/packages/unit/test/rendering/stack_test.dart
@@ -19,7 +19,7 @@ void main() {
         backgroundColor: const Color(0xFFFF0000)
       ));
 
-    RenderBox stack = new RenderStack(children: [red, green]);
+    RenderBox stack = new RenderStack(children: <RenderBox>[red, green]);
     (green.parentData as StackParentData)
       ..top = 0.0
       ..right = 0.0
diff --git a/packages/unit/test/widget/block_test.dart b/packages/unit/test/widget/block_test.dart
index 141313ea2b..b0722d9c83 100644
--- a/packages/unit/test/widget/block_test.dart
+++ b/packages/unit/test/widget/block_test.dart
@@ -10,7 +10,7 @@ void main() {
   test('Cannot scroll a non-overflowing block', () {
     testWidgets((WidgetTester tester) {
       tester.pumpWidget(
-        new Block([
+        new Block(<Widget>[
           new Container(
             height: 200.0, // less than 600, the height of the test area
             child: new Text('Hello')
@@ -37,7 +37,7 @@ void main() {
   test('Can scroll an overflowing block', () {
     testWidgets((WidgetTester tester) {
       tester.pumpWidget(
-        new Block([
+        new Block(<Widget>[
           new Container(
             height: 2000.0, // more than 600, the height of the test area
             child: new Text('Hello')
diff --git a/packages/unit/test/widget/center_test.dart b/packages/unit/test/widget/center_test.dart
index 340e08de9f..ee21e6b499 100644
--- a/packages/unit/test/widget/center_test.dart
+++ b/packages/unit/test/widget/center_test.dart
@@ -6,7 +6,7 @@ import 'widget_tester.dart';
 void main() {
   test('Can be placed in an infinte box', () {
     testWidgets((WidgetTester tester) {
-      tester.pumpWidget(new Block([new Center()]));
+      tester.pumpWidget(new Block(<Widget>[new Center()]));
     });
   });
 }
diff --git a/packages/unit/test/widget/coordinates_test.dart b/packages/unit/test/widget/coordinates_test.dart
index e6ee66bb9f..3bd3808555 100644
--- a/packages/unit/test/widget/coordinates_test.dart
+++ b/packages/unit/test/widget/coordinates_test.dart
@@ -11,7 +11,7 @@ void main() {
       Key keyB = new GlobalKey();
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             top: 100.0,
             left: 100.0,
diff --git a/packages/unit/test/widget/date_picker_test.dart b/packages/unit/test/widget/date_picker_test.dart
index d0c00eee67..0fdbdc49bb 100644
--- a/packages/unit/test/widget/date_picker_test.dart
+++ b/packages/unit/test/widget/date_picker_test.dart
@@ -8,7 +8,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       DateTime currentValue;
 
-      Widget widget = new Block([
+      Widget widget = new Block(<Widget>[
         new DatePicker(
           selectedDate: new DateTime.utc(2015, 6, 9, 7, 12),
           firstDate: new DateTime.utc(2013),
diff --git a/packages/unit/test/widget/dismissable_test.dart b/packages/unit/test/widget/dismissable_test.dart
index b9a7b5f3cc..3c717f225b 100644
--- a/packages/unit/test/widget/dismissable_test.dart
+++ b/packages/unit/test/widget/dismissable_test.dart
@@ -8,7 +8,7 @@ import 'widget_tester.dart';
 const double itemExtent = 100.0;
 ScrollDirection scrollDirection = ScrollDirection.vertical;
 DismissDirection dismissDirection = DismissDirection.horizontal;
-List<int> dismissedItems = [];
+List<int> dismissedItems = <int>[];
 
 void handleOnResized(item) {
   expect(dismissedItems.contains(item), isFalse);
@@ -117,7 +117,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       scrollDirection = ScrollDirection.vertical;
       dismissDirection = DismissDirection.horizontal;
-      dismissedItems = [];
+      dismissedItems = <int>[];
 
       tester.pumpWidget(widgetBuilder());
       expect(dismissedItems, isEmpty);
@@ -136,7 +136,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       scrollDirection = ScrollDirection.horizontal;
       dismissDirection = DismissDirection.vertical;
-      dismissedItems = [];
+      dismissedItems = <int>[];
 
       tester.pumpWidget(widgetBuilder());
       expect(dismissedItems, isEmpty);
@@ -155,7 +155,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       scrollDirection = ScrollDirection.vertical;
       dismissDirection = DismissDirection.left;
-      dismissedItems = [];
+      dismissedItems = <int>[];
 
       tester.pumpWidget(widgetBuilder());
       expect(dismissedItems, isEmpty);
@@ -174,7 +174,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       scrollDirection = ScrollDirection.vertical;
       dismissDirection = DismissDirection.right;
-      dismissedItems = [];
+      dismissedItems = <int>[];
 
       tester.pumpWidget(widgetBuilder());
       expect(dismissedItems, isEmpty);
@@ -193,7 +193,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       scrollDirection = ScrollDirection.horizontal;
       dismissDirection = DismissDirection.up;
-      dismissedItems = [];
+      dismissedItems = <int>[];
 
       tester.pumpWidget(widgetBuilder());
       expect(dismissedItems, isEmpty);
@@ -212,7 +212,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       scrollDirection = ScrollDirection.horizontal;
       dismissDirection = DismissDirection.down;
-      dismissedItems = [];
+      dismissedItems = <int>[];
 
       tester.pumpWidget(widgetBuilder());
       expect(dismissedItems, isEmpty);
@@ -233,7 +233,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       scrollDirection = ScrollDirection.horizontal;
       dismissDirection = DismissDirection.down;
-      dismissedItems = [];
+      dismissedItems = <int>[];
 
       tester.pumpWidget(widgetBuilder());
       Element itemElement = tester.findText('0');
@@ -261,7 +261,7 @@ void main() {
         child: new Container(
           width: 100.0,
           height: 1000.0,
-          child: new Column([
+          child: new Column(<Widget>[
             new Test1215DismissableComponent('1'),
             new Test1215DismissableComponent('2')
           ])
diff --git a/packages/unit/test/widget/draggable_test.dart b/packages/unit/test/widget/draggable_test.dart
index fc7ad01093..9b30893052 100644
--- a/packages/unit/test/widget/draggable_test.dart
+++ b/packages/unit/test/widget/draggable_test.dart
@@ -12,8 +12,8 @@ void main() {
       List accepted = [];
 
       tester.pumpWidget(new Navigator(
-        routes: {
-          '/': (RouteArguments args) { return new Column([
+        routes: <String, RouteBuilder>{
+          '/': (RouteArguments args) { return new Column(<Widget>[
               new Draggable(
                 navigator: args.navigator,
                 data: 1,
diff --git a/packages/unit/test/widget/drawer_test.dart b/packages/unit/test/widget/drawer_test.dart
index 9cbea0686e..631ae43ef9 100644
--- a/packages/unit/test/widget/drawer_test.dart
+++ b/packages/unit/test/widget/drawer_test.dart
@@ -11,7 +11,7 @@ void main() {
       NavigatorState navigator;
       tester.pumpWidget(
         new MaterialApp(
-          routes: {
+          routes: <String, RouteBuilder>{
             '/': (RouteArguments args) {
               navigator = args.navigator;
               new Container();
@@ -40,7 +40,7 @@ void main() {
       tester.pumpWidget(new Container()); // throw away the old App and its Navigator
       tester.pumpWidget(
         new MaterialApp(
-          routes: {
+          routes: <String, RouteBuilder>{
             '/': (RouteArguments args) {
               navigator = args.navigator;
               new Container();
diff --git a/packages/unit/test/widget/duplicate_key_test.dart b/packages/unit/test/widget/duplicate_key_test.dart
index ff9f59d167..9040b6aee7 100644
--- a/packages/unit/test/widget/duplicate_key_test.dart
+++ b/packages/unit/test/widget/duplicate_key_test.dart
@@ -8,7 +8,7 @@ class Item {
   GlobalKey key2 = new GlobalKey();
   String toString() => "Item($key1, $key2)";
 }
-List<Item> items = [new Item(), new Item()];
+List<Item> items = <Item>[new Item(), new Item()];
 
 class StatefulLeaf extends StatefulComponent {
   StatefulLeaf({ GlobalKey key }) : super(key: key);
@@ -34,7 +34,7 @@ class KeyedWrapper extends StatelessComponent {
 }
 
 Widget builder() {
-  return new Column([
+  return new Column(<Widget>[
     new KeyedWrapper(items[1].key1, items[1].key2),
     new KeyedWrapper(items[0].key1, items[0].key2)
   ]);
diff --git a/packages/unit/test/widget/flex_test.dart b/packages/unit/test/widget/flex_test.dart
index a1e58afcc4..87d354834e 100644
--- a/packages/unit/test/widget/flex_test.dart
+++ b/packages/unit/test/widget/flex_test.dart
@@ -12,11 +12,11 @@ void main() {
           decoration: const BoxDecoration(
             backgroundColor: const Color(0xFF00FF00)
           ),
-          child: new Stack([
+          child: new Stack(<Widget>[
             new Positioned(
               top: 10.0,
               left: 10.0,
-              child: new Column([
+              child: new Column(<Widget>[
                 new GestureDetector(
                   onTap: () {
                     didReceiveTap = true;
diff --git a/packages/unit/test/widget/focus_test.dart b/packages/unit/test/widget/focus_test.dart
index b4c0427732..d270564a1f 100644
--- a/packages/unit/test/widget/focus_test.dart
+++ b/packages/unit/test/widget/focus_test.dart
@@ -23,7 +23,7 @@ void main() {
       GlobalKey keyB = new GlobalKey();
       tester.pumpWidget(
         new Focus(
-          child: new Column([
+          child: new Column(<Widget>[
             // reverse these when you fix https://github.com/flutter/engine/issues/1495
             new TestFocusable('b', 'B FOCUSED', keyB),
             new TestFocusable('a', 'A FOCUSED', keyA),
diff --git a/packages/unit/test/widget/homogeneous_viewport_test.dart b/packages/unit/test/widget/homogeneous_viewport_test.dart
index 87131c23ac..3f96271e90 100644
--- a/packages/unit/test/widget/homogeneous_viewport_test.dart
+++ b/packages/unit/test/widget/homogeneous_viewport_test.dart
@@ -36,7 +36,7 @@ void main() {
 
       tester.pumpWidget(builder());
 
-      StatefulComponentElement element = tester.findElement((element) => element.widget is FlipComponent);
+      StatefulComponentElement element = tester.findElement((Element element) => element.widget is FlipComponent);
       FlipComponentState testComponent = element.state;
 
       expect(callbackTracker, equals([0, 1, 2, 3, 4, 5]));
diff --git a/packages/unit/test/widget/input_test.dart b/packages/unit/test/widget/input_test.dart
index 3aedb0f36d..ec3d58db7c 100644
--- a/packages/unit/test/widget/input_test.dart
+++ b/packages/unit/test/widget/input_test.dart
@@ -37,7 +37,7 @@ void main() {
           child: new Input(
             key: inputKey,
             placeholder: 'Placeholder',
-            onChanged: (value) { inputValue = value; }
+            onChanged: (String value) { inputValue = value; }
           )
         );
       }
diff --git a/packages/unit/test/widget/mixed_viewport_test.dart b/packages/unit/test/widget/mixed_viewport_test.dart
index 59037ef753..f5532a8528 100644
--- a/packages/unit/test/widget/mixed_viewport_test.dart
+++ b/packages/unit/test/widget/mixed_viewport_test.dart
@@ -31,7 +31,7 @@ void main() {
 
       tester.pumpWidget(builder());
 
-      StatefulComponentElement element = tester.findElement((element) => element.widget is FlipComponent);
+      StatefulComponentElement element = tester.findElement((Element element) => element.widget is FlipComponent);
       FlipComponentState testComponent = element.state;
 
       expect(callbackTracker, equals([0, 1, 2, 3, 4, 5]));
diff --git a/packages/unit/test/widget/multichild_test.dart b/packages/unit/test/widget/multichild_test.dart
index 6db41dc6b3..e2f7b3428d 100644
--- a/packages/unit/test/widget/multichild_test.dart
+++ b/packages/unit/test/widget/multichild_test.dart
@@ -7,7 +7,7 @@ import 'widget_tester.dart';
 
 void checkTree(WidgetTester tester, List<BoxDecoration> expectedDecorations) {
   MultiChildRenderObjectElement element =
-      tester.findElement((element) => element is MultiChildRenderObjectElement);
+      tester.findElement((Element element) => element is MultiChildRenderObjectElement);
   expect(element, isNotNull);
   expect(element.renderObject is RenderStack, isTrue);
   RenderStack renderObject = element.renderObject;
@@ -17,7 +17,8 @@ void checkTree(WidgetTester tester, List<BoxDecoration> expectedDecorations) {
       expect(child is RenderDecoratedBox, isTrue);
       RenderDecoratedBox decoratedBox = child;
       expect(decoratedBox.decoration, equals(decoration));
-      child = decoratedBox.parentData.nextSibling;
+      final StackParentData decoratedBoxParentData = decoratedBox.parentData;
+      child = decoratedBoxParentData.nextSibling;
     }
     expect(child, isNull);
   } catch (e) {
@@ -31,67 +32,67 @@ void main() {
     testWidgets((WidgetTester tester) {
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(decoration: kBoxDecorationA),
           new DecoratedBox(decoration: kBoxDecorationB),
           new DecoratedBox(decoration: kBoxDecorationC),
         ])
       );
 
-      checkTree(tester, [kBoxDecorationA, kBoxDecorationB, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA, kBoxDecorationB, kBoxDecorationC]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(decoration: kBoxDecorationA),
           new DecoratedBox(decoration: kBoxDecorationC),
         ])
       );
 
-      checkTree(tester, [kBoxDecorationA, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA, kBoxDecorationC]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(decoration: kBoxDecorationA),
           new DecoratedBox(key: new Key('b'), decoration: kBoxDecorationB),
           new DecoratedBox(decoration: kBoxDecorationC),
         ])
       );
 
-      checkTree(tester, [kBoxDecorationA, kBoxDecorationB, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA, kBoxDecorationB, kBoxDecorationC]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(key: new Key('b'), decoration: kBoxDecorationB),
           new DecoratedBox(decoration: kBoxDecorationC),
           new DecoratedBox(key: new Key('a'), decoration: kBoxDecorationA),
         ])
       );
 
-      checkTree(tester, [kBoxDecorationB, kBoxDecorationC, kBoxDecorationA]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationB, kBoxDecorationC, kBoxDecorationA]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(key: new Key('a'), decoration: kBoxDecorationA),
           new DecoratedBox(decoration: kBoxDecorationC),
           new DecoratedBox(key: new Key('b'), decoration: kBoxDecorationB),
         ])
       );
 
-      checkTree(tester, [kBoxDecorationA, kBoxDecorationC, kBoxDecorationB]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA, kBoxDecorationC, kBoxDecorationB]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(decoration: kBoxDecorationC),
         ])
       );
 
-      checkTree(tester, [kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationC]);
 
       tester.pumpWidget(
-        new Stack([])
+        new Stack(<Widget>[])
       );
 
-      checkTree(tester, []);
+      checkTree(tester, <BoxDecoration>[]);
 
     });
   });
@@ -100,17 +101,17 @@ void main() {
     testWidgets((WidgetTester tester) {
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(decoration: kBoxDecorationA),
           new DecoratedBox(decoration: kBoxDecorationB),
           new DecoratedBox(decoration: kBoxDecorationC),
         ])
       );
 
-      checkTree(tester, [kBoxDecorationA, kBoxDecorationB, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA, kBoxDecorationB, kBoxDecorationC]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(decoration: kBoxDecorationA),
           new Container(
             child: new DecoratedBox(decoration: kBoxDecorationB)
@@ -119,10 +120,10 @@ void main() {
         ])
       );
 
-      checkTree(tester, [kBoxDecorationA, kBoxDecorationB, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA, kBoxDecorationB, kBoxDecorationC]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(decoration: kBoxDecorationA),
           new Container(
             child: new Container(
@@ -133,10 +134,10 @@ void main() {
         ])
       );
 
-      checkTree(tester, [kBoxDecorationA, kBoxDecorationB, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA, kBoxDecorationB, kBoxDecorationC]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Container(
             child: new Container(
               child: new DecoratedBox(decoration: kBoxDecorationB)
@@ -149,10 +150,10 @@ void main() {
         ])
       );
 
-      checkTree(tester, [kBoxDecorationB, kBoxDecorationA, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationB, kBoxDecorationA, kBoxDecorationC]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Container(
             child: new DecoratedBox(decoration: kBoxDecorationB)
           ),
@@ -163,10 +164,10 @@ void main() {
         ])
       );
 
-      checkTree(tester, [kBoxDecorationB, kBoxDecorationA, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationB, kBoxDecorationA, kBoxDecorationC]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Container(
             key: new Key('b'),
             child: new DecoratedBox(decoration: kBoxDecorationB)
@@ -178,10 +179,10 @@ void main() {
         ])
       );
 
-      checkTree(tester, [kBoxDecorationB, kBoxDecorationA]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationB, kBoxDecorationA]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Container(
             key: new Key('a'),
             child: new DecoratedBox(decoration: kBoxDecorationA)
@@ -193,29 +194,29 @@ void main() {
         ])
       );
 
-      checkTree(tester, [kBoxDecorationA, kBoxDecorationB]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA, kBoxDecorationB]);
 
       tester.pumpWidget(
-        new Stack([ ])
+        new Stack(<Widget>[])
       );
 
-      checkTree(tester, []);
+      checkTree(tester, <BoxDecoration>[]);
     });
   });
 
   test('MultiChildRenderObjectElement with stateful components', () {
     testWidgets((WidgetTester tester) {
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(decoration: kBoxDecorationA),
           new DecoratedBox(decoration: kBoxDecorationB),
         ])
       );
 
-      checkTree(tester, [kBoxDecorationA, kBoxDecorationB]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA, kBoxDecorationB]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new FlipComponent(
             left: new DecoratedBox(decoration: kBoxDecorationA),
             right: new DecoratedBox(decoration: kBoxDecorationB)
@@ -224,15 +225,15 @@ void main() {
         ])
       );
 
-      checkTree(tester, [kBoxDecorationA, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA, kBoxDecorationC]);
 
       flipStatefulComponent(tester);
       tester.pump();
 
-      checkTree(tester, [kBoxDecorationB, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationB, kBoxDecorationC]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new FlipComponent(
             left: new DecoratedBox(decoration: kBoxDecorationA),
             right: new DecoratedBox(decoration: kBoxDecorationB)
@@ -240,15 +241,15 @@ void main() {
         ])
       );
 
-      checkTree(tester, [kBoxDecorationB]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationB]);
 
       flipStatefulComponent(tester);
       tester.pump();
 
-      checkTree(tester, [kBoxDecorationA]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationA]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new FlipComponent(
             key: new Key('flip'),
             left: new DecoratedBox(decoration: kBoxDecorationA),
@@ -258,7 +259,7 @@ void main() {
       );
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(key: new Key('c'), decoration: kBoxDecorationC),
           new FlipComponent(
             key: new Key('flip'),
@@ -268,15 +269,15 @@ void main() {
         ])
       );
 
-      checkTree(tester, [kBoxDecorationC, kBoxDecorationA]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationC, kBoxDecorationA]);
 
       flipStatefulComponent(tester);
       tester.pump();
 
-      checkTree(tester, [kBoxDecorationC, kBoxDecorationB]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationC, kBoxDecorationB]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new FlipComponent(
             key: new Key('flip'),
             left: new DecoratedBox(decoration: kBoxDecorationA),
@@ -286,7 +287,7 @@ void main() {
         ])
       );
 
-      checkTree(tester, [kBoxDecorationB, kBoxDecorationC]);
+      checkTree(tester, <BoxDecoration>[kBoxDecorationB, kBoxDecorationC]);
     });
   });
 }
diff --git a/packages/unit/test/widget/parent_data_test.dart b/packages/unit/test/widget/parent_data_test.dart
index 2d692d0956..bc5eb2e922 100644
--- a/packages/unit/test/widget/parent_data_test.dart
+++ b/packages/unit/test/widget/parent_data_test.dart
@@ -16,7 +16,7 @@ class TestParentData {
 
 void checkTree(WidgetTester tester, List<TestParentData> expectedParentData) {
   MultiChildRenderObjectElement element =
-      tester.findElement((element) => element is MultiChildRenderObjectElement);
+      tester.findElement((Element element) => element is MultiChildRenderObjectElement);
   expect(element, isNotNull);
   expect(element.renderObject is RenderStack, isTrue);
   RenderStack renderObject = element.renderObject;
@@ -31,7 +31,7 @@ void checkTree(WidgetTester tester, List<TestParentData> expectedParentData) {
       expect(parentData.right, equals(expected.right));
       expect(parentData.bottom, equals(expected.bottom));
       expect(parentData.left, equals(expected.left));
-      child = decoratedBox.parentData.nextSibling;
+      child = (decoratedBox.parentData as StackParentData).nextSibling;
     }
     expect(child, isNull);
   } catch (e) {
@@ -61,7 +61,7 @@ void main() {
     testWidgets((WidgetTester tester) {
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new DecoratedBox(decoration: kBoxDecorationA),
           new Positioned(
             top: 10.0,
@@ -72,14 +72,14 @@ void main() {
         ])
       );
 
-      checkTree(tester, [
+      checkTree(tester, <TestParentData>[
         kNonPositioned,
         new TestParentData(top: 10.0, left: 10.0),
         kNonPositioned,
       ]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             bottom: 5.0,
             right: 7.0,
@@ -94,7 +94,7 @@ void main() {
         ])
       );
 
-      checkTree(tester, [
+      checkTree(tester, <TestParentData>[
         new TestParentData(bottom: 5.0, right: 7.0),
         new TestParentData(top: 10.0, left: 10.0),
         kNonPositioned,
@@ -105,7 +105,7 @@ void main() {
       DecoratedBox kDecoratedBoxC = new DecoratedBox(decoration: kBoxDecorationC);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             bottom: 5.0,
             right: 7.0,
@@ -120,14 +120,14 @@ void main() {
         ])
       );
 
-      checkTree(tester, [
+      checkTree(tester, <TestParentData>[
         new TestParentData(bottom: 5.0, right: 7.0),
         new TestParentData(top: 10.0, left: 10.0),
         kNonPositioned,
       ]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             bottom: 6.0,
             right: 8.0,
@@ -142,14 +142,14 @@ void main() {
         ])
       );
 
-      checkTree(tester, [
+      checkTree(tester, <TestParentData>[
         new TestParentData(bottom: 6.0, right: 8.0),
         new TestParentData(left: 10.0, right: 10.0),
         kNonPositioned,
       ]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           kDecoratedBoxA,
           new Positioned(
             left: 11.0,
@@ -160,14 +160,14 @@ void main() {
         ])
       );
 
-      checkTree(tester, [
+      checkTree(tester, <TestParentData>[
         kNonPositioned,
         new TestParentData(left: 11.0, right: 12.0),
         kNonPositioned,
       ]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           kDecoratedBoxA,
           new Positioned(
             right: 10.0,
@@ -182,14 +182,14 @@ void main() {
         ])
       );
 
-      checkTree(tester, [
+      checkTree(tester, <TestParentData>[
         kNonPositioned,
         new TestParentData(right: 10.0),
         new TestParentData(top: 8.0),
       ]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             right: 10.0,
             child: new FlipComponent(left: kDecoratedBoxA, right: kDecoratedBoxB)
@@ -197,19 +197,19 @@ void main() {
         ])
       );
 
-      checkTree(tester, [
+      checkTree(tester, <TestParentData>[
         new TestParentData(right: 10.0),
       ]);
 
       flipStatefulComponent(tester);
       tester.pump();
 
-      checkTree(tester, [
+      checkTree(tester, <TestParentData>[
         new TestParentData(right: 10.0),
       ]);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             top: 7.0,
             child: new FlipComponent(left: kDecoratedBoxA, right: kDecoratedBoxB)
@@ -217,22 +217,22 @@ void main() {
         ])
       );
 
-      checkTree(tester, [
+      checkTree(tester, <TestParentData>[
         new TestParentData(top: 7.0),
       ]);
 
       flipStatefulComponent(tester);
       tester.pump();
 
-      checkTree(tester, [
+      checkTree(tester, <TestParentData>[
         new TestParentData(top: 7.0),
       ]);
 
       tester.pumpWidget(
-        new Stack([])
+        new Stack(<Widget>[])
       );
 
-      checkTree(tester, []);
+      checkTree(tester, <TestParentData>[]);
     });
   });
 
@@ -241,7 +241,7 @@ void main() {
       expect(cachedException, isNull);
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             top: 5.0,
             bottom: 8.0,
@@ -257,14 +257,14 @@ void main() {
       expect(cachedException, isNotNull);
       cachedException = null;
 
-      tester.pumpWidget(new Stack([]));
+      tester.pumpWidget(new Stack(<Widget>[]));
 
-      checkTree(tester, []);
+      checkTree(tester, <TestParentData>[]);
       expect(cachedException, isNull);
 
       tester.pumpWidget(
         new Container(
-          child: new Flex([
+          child: new Flex(<Widget>[
             new Positioned(
               top: 6.0,
               left: 7.0,
@@ -278,10 +278,10 @@ void main() {
       cachedException = null;
 
       tester.pumpWidget(
-        new Stack([])
+        new Stack(<Widget>[])
       );
 
-      checkTree(tester, []);
+      checkTree(tester, <TestParentData>[]);
     });
   });
 }
diff --git a/packages/unit/test/widget/progress_indicator_test.dart b/packages/unit/test/widget/progress_indicator_test.dart
index de3541b24d..9a5c971f8f 100644
--- a/packages/unit/test/widget/progress_indicator_test.dart
+++ b/packages/unit/test/widget/progress_indicator_test.dart
@@ -8,11 +8,11 @@ import 'widget_tester.dart';
 void main() {
   test('LinearProgressIndicator changes when its value changes', () {
     testWidgets((WidgetTester tester) {
-      tester.pumpWidget(new Block([new LinearProgressIndicator(value: 0.0)]));
+      tester.pumpWidget(new Block(<Widget>[new LinearProgressIndicator(value: 0.0)]));
 
       List<Layer> layers1 = tester.layers;
 
-      tester.pumpWidget(new Block([new LinearProgressIndicator(value: 0.5)]));
+      tester.pumpWidget(new Block(<Widget>[new LinearProgressIndicator(value: 0.5)]));
 
       List<Layer> layers2 = tester.layers;
       expect(layers1, isNot(equals(layers2)));
diff --git a/packages/unit/test/widget/render_object_widget_test.dart b/packages/unit/test/widget/render_object_widget_test.dart
index 76088a6998..61e8944952 100644
--- a/packages/unit/test/widget/render_object_widget_test.dart
+++ b/packages/unit/test/widget/render_object_widget_test.dart
@@ -19,7 +19,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       tester.pumpWidget(new DecoratedBox(decoration: kBoxDecorationA));
       OneChildRenderObjectElement element =
-          tester.findElement((element) => element is OneChildRenderObjectElement);
+          tester.findElement((Element element) => element is OneChildRenderObjectElement);
       expect(element, isNotNull);
       expect(element.renderObject is RenderDecoratedBox, isTrue);
       RenderDecoratedBox renderObject = element.renderObject;
@@ -27,7 +27,7 @@ void main() {
       expect(renderObject.position, equals(BoxDecorationPosition.background));
 
       tester.pumpWidget(new DecoratedBox(decoration: kBoxDecorationB));
-      element = tester.findElement((element) => element is OneChildRenderObjectElement);
+      element = tester.findElement((Element element) => element is OneChildRenderObjectElement);
       expect(element, isNotNull);
       expect(element.renderObject is RenderDecoratedBox, isTrue);
       renderObject = element.renderObject;
@@ -41,7 +41,7 @@ void main() {
 
       void checkFullTree() {
         OneChildRenderObjectElement element =
-            tester.findElement((element) => element is OneChildRenderObjectElement);
+            tester.findElement((Element element) => element is OneChildRenderObjectElement);
         expect(element, isNotNull);
         expect(element.renderObject is RenderDecoratedBox, isTrue);
         RenderDecoratedBox renderObject = element.renderObject;
@@ -57,7 +57,7 @@ void main() {
 
       void childBareTree() {
         OneChildRenderObjectElement element =
-            tester.findElement((element) => element is OneChildRenderObjectElement);
+            tester.findElement((Element element) => element is OneChildRenderObjectElement);
         expect(element, isNotNull);
         expect(element.renderObject is RenderDecoratedBox, isTrue);
         RenderDecoratedBox renderObject = element.renderObject;
@@ -136,7 +136,7 @@ void main() {
       ));
 
       OneChildRenderObjectElement element =
-          tester.findElement((element) => element is OneChildRenderObjectElement);
+          tester.findElement((Element element) => element is OneChildRenderObjectElement);
       expect(element.renderObject is RenderDecoratedBox, isTrue);
       RenderDecoratedBox parent = element.renderObject;
       expect(parent.child is RenderDecoratedBox, isTrue);
@@ -152,7 +152,7 @@ void main() {
       ));
 
       element =
-          tester.findElement((element) => element is OneChildRenderObjectElement);
+          tester.findElement((Element element) => element is OneChildRenderObjectElement);
       expect(element.renderObject is RenderDecoratedBox, isTrue);
       expect(element.renderObject, equals(parent));
       expect(parent.child, isNull);
diff --git a/packages/unit/test/widget/reparent_state_test.dart b/packages/unit/test/widget/reparent_state_test.dart
index 804837f8f8..cf3cbc17e8 100644
--- a/packages/unit/test/widget/reparent_state_test.dart
+++ b/packages/unit/test/widget/reparent_state_test.dart
@@ -33,7 +33,7 @@ void main() {
 
       StateMarker grandchild = new StateMarker();
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Container(
             child: new StateMarker(key: left)
           ),
@@ -55,7 +55,7 @@ void main() {
 
       StateMarker newGrandchild = new StateMarker();
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Container(
             child: new StateMarker(
               key: right,
@@ -101,7 +101,7 @@ void main() {
       (key.currentState as StateMarkerState).marker = "marked";
 
       tester.pumpWidget(new ScrollableList<int>(
-        items: [0],
+        items: <int>[0],
         itemExtent: 100.0,
         itemBuilder: (BuildContext context, int item) {
           return new Container(
diff --git a/packages/unit/test/widget/set_state_3_test.dart b/packages/unit/test/widget/set_state_3_test.dart
index cfc2e3fc93..fcf2372fdf 100644
--- a/packages/unit/test/widget/set_state_3_test.dart
+++ b/packages/unit/test/widget/set_state_3_test.dart
@@ -27,7 +27,7 @@ class ChangerState extends State<Changer> {
 
   void test() { setState(() { _state = true; }); }
 
-  Widget build(BuildContext) => _state ? new Wrapper(config.child) : config.child;
+  Widget build(BuildContext context) => _state ? new Wrapper(config.child) : config.child;
 }
 
 class Wrapper extends StatelessComponent {
diff --git a/packages/unit/test/widget/shader_mask_test.dart b/packages/unit/test/widget/shader_mask_test.dart
index aa465abaa5..22c0360c71 100644
--- a/packages/unit/test/widget/shader_mask_test.dart
+++ b/packages/unit/test/widget/shader_mask_test.dart
@@ -10,8 +10,8 @@ ui.Shader createShader(Rect bounds) {
   return new LinearGradient(
       begin: Point.origin,
       end: new Point(0.0, bounds.height),
-      colors: [const Color(0x00FFFFFF), const Color(0xFFFFFFFF)],
-      stops: [0.1, 0.35]
+      colors: <Color>[const Color(0x00FFFFFF), const Color(0xFFFFFFFF)],
+      stops: <double>[0.1, 0.35]
   )
   .createShader();
 }
diff --git a/packages/unit/test/widget/size_observer_test.dart b/packages/unit/test/widget/size_observer_test.dart
index 95f9e44eeb..1eae694bdf 100644
--- a/packages/unit/test/widget/size_observer_test.dart
+++ b/packages/unit/test/widget/size_observer_test.dart
@@ -8,10 +8,10 @@ import 'widget_tester.dart';
 void main() {
   test('SizeObserver notices zero size', () {
     testWidgets((WidgetTester tester) {
-      List results = [];
+      List<Size> results = <Size>[];
       tester.pumpWidget(new Center(
         child: new SizeObserver(
-          callback: (size) { results.add(size); },
+          callback: (Size size) { results.add(size); },
           child: new Container(width:0.0, height:0.0)
         )
       ));
@@ -20,7 +20,7 @@ void main() {
       expect(results, equals([Size.zero]));
       tester.pumpWidget(new Center(
         child: new SizeObserver(
-          callback: (size) { results.add(size); },
+          callback: (Size size) { results.add(size); },
           child: new Container(width:100.0, height:0.0)
         )
       ));
@@ -29,7 +29,7 @@ void main() {
       expect(results, equals([Size.zero, const Size(100.0, 0.0)]));
       tester.pumpWidget(new Center(
         child: new SizeObserver(
-          callback: (size) { results.add(size); },
+          callback: (Size size) { results.add(size); },
           child: new Container(width:0.0, height:0.0)
         )
       ));
@@ -38,7 +38,7 @@ void main() {
       expect(results, equals([Size.zero, const Size(100.0, 0.0), Size.zero]));
       tester.pumpWidget(new Center(
         child: new SizeObserver(
-          callback: (size) { results.add(size); },
+          callback: (Size size) { results.add(size); },
           child: new Container(width:0.0, height:0.0)
         )
       ));
diff --git a/packages/unit/test/widget/snack_bar_test.dart b/packages/unit/test/widget/snack_bar_test.dart
index 1c3fb697fe..606a5b1628 100644
--- a/packages/unit/test/widget/snack_bar_test.dart
+++ b/packages/unit/test/widget/snack_bar_test.dart
@@ -11,7 +11,7 @@ void main() {
       Key tapTarget = new Key('tap-target');
 
       tester.pumpWidget(new MaterialApp(
-        routes: {
+        routes: <String, RouteBuilder>{
           '/': (RouteArguments args) {
             return new GestureDetector(
               onTap: () {
diff --git a/packages/unit/test/widget/snap_scrolling_test.dart b/packages/unit/test/widget/snap_scrolling_test.dart
index 9a193b4259..b55bfe4da1 100644
--- a/packages/unit/test/widget/snap_scrolling_test.dart
+++ b/packages/unit/test/widget/snap_scrolling_test.dart
@@ -35,7 +35,7 @@ Widget buildFrame() {
         key: scrollableListKey,
         snapOffsetCallback: snapOffsetCallback,
         scrollDirection: scrollDirection,
-        items: [0, 1, 2, 3, 4, 5, 7, 8, 9],
+        items: <int>[0, 1, 2, 3, 4, 5, 7, 8, 9],
         itemBuilder: buildItem,
         itemExtent: itemExtent
       )
diff --git a/packages/unit/test/widget/stack_test.dart b/packages/unit/test/widget/stack_test.dart
index 6bf00668b1..9d64024334 100644
--- a/packages/unit/test/widget/stack_test.dart
+++ b/packages/unit/test/widget/stack_test.dart
@@ -1,3 +1,4 @@
+import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:test/test.dart';
 
@@ -6,13 +7,13 @@ import 'widget_tester.dart';
 void main() {
   test('Can construct an empty Stack', () {
     testWidgets((WidgetTester tester) {
-      tester.pumpWidget(new Stack([]));
+      tester.pumpWidget(new Stack(<Widget>[]));
     });
   });
 
   test('Can construct an empty Centered Stack', () {
     testWidgets((WidgetTester tester) {
-      tester.pumpWidget(new Center(child: new Stack([])));
+      tester.pumpWidget(new Center(child: new Stack(<Widget>[])));
     });
   });
 
@@ -21,7 +22,7 @@ void main() {
       Key key = new Key('container');
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             left: 10.0,
             child: new Container(
@@ -33,14 +34,18 @@ void main() {
         ])
       );
 
-      Element container = tester.findElementByKey(key);
-      expect(container.renderObject.parentData.top, isNull);
-      expect(container.renderObject.parentData.right, isNull);
-      expect(container.renderObject.parentData.bottom, isNull);
-      expect(container.renderObject.parentData.left, equals(10.0));
+      Element container;
+      StackParentData parentData;
+
+      container = tester.findElementByKey(key);
+      parentData = container.renderObject.parentData;
+      expect(parentData.top, isNull);
+      expect(parentData.right, isNull);
+      expect(parentData.bottom, isNull);
+      expect(parentData.left, equals(10.0));
 
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             right: 10.0,
             child: new Container(
@@ -53,10 +58,11 @@ void main() {
       );
 
       container = tester.findElementByKey(key);
-      expect(container.renderObject.parentData.top, isNull);
-      expect(container.renderObject.parentData.right, equals(10.0));
-      expect(container.renderObject.parentData.bottom, isNull);
-      expect(container.renderObject.parentData.left, isNull);
+      parentData = container.renderObject.parentData;
+      expect(parentData.top, isNull);
+      expect(parentData.right, equals(10.0));
+      expect(parentData.bottom, isNull);
+      expect(parentData.left, isNull);
     });
   });
 
@@ -65,21 +71,24 @@ void main() {
       Key key = new Key('container');
       Container container = new Container(key: key, width: 10.0, height: 10.0);
 
-      tester.pumpWidget(new Stack([ new Positioned(left: 10.0, child: container) ]));
+      tester.pumpWidget(new Stack(<Widget>[ new Positioned(left: 10.0, child: container) ]));
       Element containerElement = tester.findElementByKey(key);
 
-      expect(containerElement.renderObject.parentData.top, isNull);
-      expect(containerElement.renderObject.parentData.right, isNull);
-      expect(containerElement.renderObject.parentData.bottom, isNull);
-      expect(containerElement.renderObject.parentData.left, equals(10.0));
+      StackParentData parentData;
+      parentData = containerElement.renderObject.parentData;
+      expect(parentData.top, isNull);
+      expect(parentData.right, isNull);
+      expect(parentData.bottom, isNull);
+      expect(parentData.left, equals(10.0));
 
-      tester.pumpWidget(new Stack([ container ]));
+      tester.pumpWidget(new Stack(<Widget>[ container ]));
       containerElement = tester.findElementByKey(key);
 
-      expect(containerElement.renderObject.parentData.top, isNull);
-      expect(containerElement.renderObject.parentData.right, isNull);
-      expect(containerElement.renderObject.parentData.bottom, isNull);
-      expect(containerElement.renderObject.parentData.left, isNull);
+      parentData = containerElement.renderObject.parentData;
+      expect(parentData.top, isNull);
+      expect(parentData.right, isNull);
+      expect(parentData.bottom, isNull);
+      expect(parentData.left, isNull);
     });
   });
 
@@ -90,7 +99,7 @@ void main() {
 
       tester.pumpWidget(
         new Center(
-          child: new Stack([
+          child: new Stack(<Widget>[
               new Container(key: child0Key, width: 20.0, height: 20.0),
               new Container(key: child1Key, width: 10.0, height: 10.0)
             ],
@@ -101,22 +110,24 @@ void main() {
       );
 
       Element child0 = tester.findElementByKey(child0Key);
-      expect(child0.renderObject.parentData.position, equals(const Point(0.0, 0.0)));
+      final StackParentData child0RenderObjectParentData = child0.renderObject.parentData;
+      expect(child0RenderObjectParentData.position, equals(const Point(0.0, 0.0)));
 
       Element child1 = tester.findElementByKey(child1Key);
-      expect(child1.renderObject.parentData.position, equals(const Point(5.0, 5.0)));
+      final StackParentData child1RenderObjectParentData = child1.renderObject.parentData;
+      expect(child1RenderObjectParentData.position, equals(const Point(5.0, 5.0)));
     });
   });
 
   test('Can construct an empty IndexedStack', () {
     testWidgets((WidgetTester tester) {
-      tester.pumpWidget(new IndexedStack([]));
+      tester.pumpWidget(new IndexedStack(<Widget>[]));
     });
   });
 
   test('Can construct an empty Centered IndexedStack', () {
     testWidgets((WidgetTester tester) {
-      tester.pumpWidget(new Center(child: new IndexedStack([])));
+      tester.pumpWidget(new Center(child: new IndexedStack(<Widget>[])));
     });
   });
 
@@ -126,9 +137,9 @@ void main() {
       List<int> itemsPainted;
 
       Widget buildFrame(int index) {
-        itemsPainted = [];
-        List<Widget> items = new List.generate(itemCount, (i) {
-          return new CustomPaint(child: new Text('$i'), callback: (_0, _1) { itemsPainted.add(i); });
+        itemsPainted = <int>[];
+        List<Widget> items = new List<Widget>.generate(itemCount, (i) {
+          return new CustomPaint(child: new Text('$i'), callback: (_, __) { itemsPainted.add(i); });
         });
         return new Center(child: new IndexedStack(items, index: index));
       }
@@ -154,8 +165,8 @@ void main() {
       List<int> itemsTapped;
 
       Widget buildFrame(int index) {
-        itemsTapped = [];
-        List<Widget> items = new List.generate(itemCount, (i) {
+        itemsTapped = <int>[];
+        List<Widget> items = new List<Widget>.generate(itemCount, (i) {
           return new GestureDetector(child: new Text('$i'), onTap: () { itemsTapped.add(i); });
         });
         return new Center(child: new IndexedStack(items, key: key, index: index));
diff --git a/packages/unit/test/widget/stateful_component_test.dart b/packages/unit/test/widget/stateful_component_test.dart
index 7e7f620a90..c545744d64 100644
--- a/packages/unit/test/widget/stateful_component_test.dart
+++ b/packages/unit/test/widget/stateful_component_test.dart
@@ -11,7 +11,7 @@ void main() {
 
       void checkTree(BoxDecoration expectedDecoration) {
         OneChildRenderObjectElement element =
-            tester.findElement((element) => element is OneChildRenderObjectElement);
+            tester.findElement((Element element) => element is OneChildRenderObjectElement);
         expect(element, isNotNull);
         expect(element.renderObject is RenderDecoratedBox, isTrue);
         RenderDecoratedBox renderObject = element.renderObject;
diff --git a/packages/unit/test/widget/syncing_test.dart b/packages/unit/test/widget/syncing_test.dart
index bf6bf8ecb9..77afd31e4a 100644
--- a/packages/unit/test/widget/syncing_test.dart
+++ b/packages/unit/test/widget/syncing_test.dart
@@ -112,13 +112,13 @@ void main() {
     testWidgets((WidgetTester tester) {
       Widget a = new TestWidget(persistentState: 0x61, syncedState: 0x41, child: new Text('apple'));
       Widget b = new TestWidget(persistentState: 0x62, syncedState: 0x42, child: new Text('banana'));
-      tester.pumpWidget(new Column([]));
+      tester.pumpWidget(new Column(<Widget>[]));
 
       GlobalKey keyA = new GlobalKey();
       GlobalKey keyB = new GlobalKey();
 
       tester.pumpWidget(
-        new Column([
+        new Column(<Widget>[
           new Container(
             key: keyA,
             child: a
@@ -143,7 +143,7 @@ void main() {
       expect(second.syncedState, equals(0x42));
 
       tester.pumpWidget(
-        new Column([
+        new Column(<Widget>[
           new Container(
             key: keyA,
             child: a
@@ -170,7 +170,7 @@ void main() {
       // since they are both "old" nodes, they shouldn't sync with each other even though they look alike
 
       tester.pumpWidget(
-        new Column([
+        new Column(<Widget>[
           new Container(
             key: keyA,
             child: b
diff --git a/packages/unit/test/widget/test_widgets.dart b/packages/unit/test/widget/test_widgets.dart
index f132925cac..2dff9da0b9 100644
--- a/packages/unit/test/widget/test_widgets.dart
+++ b/packages/unit/test/widget/test_widgets.dart
@@ -49,7 +49,7 @@ class TestBuildCounter extends StatelessComponent {
 
 void flipStatefulComponent(WidgetTester tester) {
   StatefulComponentElement stateElement =
-      tester.findElement((element) => element is StatefulComponentElement);
+      tester.findElement((Element element) => element is StatefulComponentElement);
   expect(stateElement, isNotNull);
   expect(stateElement.state is FlipComponentState, isTrue);
   FlipComponentState state = stateElement.state;
diff --git a/packages/unit/test/widget/transform_test.dart b/packages/unit/test/widget/transform_test.dart
index efa44cdf45..03c0eef907 100644
--- a/packages/unit/test/widget/transform_test.dart
+++ b/packages/unit/test/widget/transform_test.dart
@@ -8,7 +8,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       bool didReceiveTap = false;
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             top: 100.0,
             left: 100.0,
@@ -53,7 +53,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       bool didReceiveTap = false;
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             top: 100.0,
             left: 100.0,
@@ -98,7 +98,7 @@ void main() {
     testWidgets((WidgetTester tester) {
       bool didReceiveTap = false;
       tester.pumpWidget(
-        new Stack([
+        new Stack(<Widget>[
           new Positioned(
             top: 100.0,
             left: 100.0,
diff --git a/packages/unit/test/widget/widget_tester.dart b/packages/unit/test/widget/widget_tester.dart
index dbc599a5e8..e215572f17 100644
--- a/packages/unit/test/widget/widget_tester.dart
+++ b/packages/unit/test/widget/widget_tester.dart
@@ -24,11 +24,12 @@ class RootComponentState extends State<RootComponent> {
   Widget build(BuildContext context) => child;
 }
 
+typedef Point SizeToPointFunction(Size size);
+
 class WidgetTester {
   WidgetTester._(FakeAsync async)
     : async = async,
-      clock = async.getClock(new DateTime.utc(2015, 1, 1)) {
-  }
+      clock = async.getClock(new DateTime.utc(2015, 1, 1));
 
   final FakeAsync async;
   final Clock clock;
@@ -46,7 +47,7 @@ class WidgetTester {
   }
 
   List<Layer> _layers(Layer layer) {
-    List<Layer> result = [layer];
+    List<Layer> result = <Layer>[layer];
     if (layer is ContainerLayer) {
       ContainerLayer root = layer;
       Layer child = root.firstChild;
@@ -124,7 +125,7 @@ class WidgetTester {
     return _getElementPoint(element, (Size size) => size.bottomRight(Point.origin));
   }
 
-  Point _getElementPoint(Element element, Function sizeToPoint) {
+  Point _getElementPoint(Element element, SizeToPointFunction sizeToPoint) {
     assert(element != null);
     RenderBox box = element.renderObject as RenderBox;
     assert(box != null);