Test MixedViewport

add/remove/add smoketest
basic vertical behaviour
basic horizontal behaviour

packages/unit/test/widget/mixed_viewport_test.dart

+import 'package:sky/widgets.dart';
+import 'package:test/test.dart';
+import 'package:quiver/testing/async.dart';
+
+import 'widget_tester.dart';
+
+class TestComponent extends StatefulComponent {
+  TestComponent(this.viewport);
+  MixedViewport viewport;
+  void syncConstructorArguments(TestComponent source) {
+    viewport = source.viewport;
+  }
+  bool _flag = true;
+  void go(bool flag) {
+    setState(() {
+      _flag = flag;
+    });
+  }
+  Widget build() {
+    return _flag ? viewport : new Text('Not Today');
+  }
+}
+
+void main() {
+  test('MixedViewport mount/dismount smoke test', () {
+    WidgetTester tester = new WidgetTester();
+
+    MixedViewportLayoutState layoutState = new MixedViewportLayoutState();
+
+    List<int> callbackTracker = <int>[];
+
+    // the root view is 800x600 in the test environment
+    // so if our widget is 100 pixels tall, it should fit exactly 6 times.
+
+    TestComponent testComponent;
+    Widget builder() {
+      testComponent = new TestComponent(new MixedViewport(
+        builder: (int i) {
+          callbackTracker.add(i);
+          return new Container(
+            key: new ValueKey<int>(i),
+            height: 100.0,
+            child: new Text("$i")
+          );
+        },
+        startOffset: 0.0,
+        layoutState: layoutState
+      ));
+      return testComponent;
+    }
+
+    tester.pumpFrame(builder);
+
+    expect(callbackTracker, equals([0, 1, 2, 3, 4, 5]));
+
+    callbackTracker.clear();
+    testComponent.go(false);
+    tester.pumpFrameWithoutChange();
+
+    expect(callbackTracker, equals([]));
+
+    callbackTracker.clear();
+    testComponent.go(true);
+    tester.pumpFrameWithoutChange();
+
+    expect(callbackTracker, equals([0, 1, 2, 3, 4, 5]));
+
+  });
+
+  test('MixedViewport vertical', () {
+    WidgetTester tester = new WidgetTester();
+
+    MixedViewportLayoutState layoutState = new MixedViewportLayoutState();
+
+    List<int> callbackTracker = <int>[];
+
+    // the root view is 800x600 in the test environment
+    // so if our widget is 200 pixels tall, it should fit exactly 3 times.
+    // but if we are offset by 300 pixels, there will be 4, numbered 1-4.
+
+    double offset = 300.0;
+
+    IndexedBuilder itemBuilder = (int i) {
+      callbackTracker.add(i);
+      return new Container(
+        key: new ValueKey<int>(i),
+        width: 500.0, // this should be ignored
+        height: 200.0,
+        child: new Text("$i")
+      );
+    };
+
+    TestComponent testComponent;
+    Widget builder() {
+      testComponent = new TestComponent(new MixedViewport(
+        builder: itemBuilder,
+        startOffset: offset,
+        layoutState: layoutState
+      ));
+      return testComponent;
+    }
+
+    tester.pumpFrame(builder);
+
+    // 0 is built to find its width
+    expect(callbackTracker, equals([0, 1, 2, 3, 4]));
+
+    callbackTracker.clear();
+
+    offset = 400.0; // now only 3 should fit, numbered 2-4.
+
+    tester.pumpFrame(builder);
+
+    // 0 and 1 aren't built, we know their size and nothing else changed
+    expect(callbackTracker, equals([2, 3, 4]));
+
+    callbackTracker.clear();
+
+  });
+
+  test('MixedViewport horizontal', () {
+    WidgetTester tester = new WidgetTester();
+
+    MixedViewportLayoutState layoutState = new MixedViewportLayoutState();
+
+    List<int> callbackTracker = <int>[];
+
+    // the root view is 800x600 in the test environment
+    // so if our widget is 200 pixels wide, it should fit exactly 4 times.
+    // but if we are offset by 300 pixels, there will be 5, numbered 1-5.
+
+    double offset = 300.0;
+
+    IndexedBuilder itemBuilder = (int i) {
+      callbackTracker.add(i);
+      return new Container(
+        key: new ValueKey<int>(i),
+        height: 500.0, // this should be ignored
+        width: 200.0,
+        child: new Text("$i")
+      );
+    };
+
+    TestComponent testComponent;
+    Widget builder() {
+      testComponent = new TestComponent(new MixedViewport(
+        builder: itemBuilder,
+        startOffset: offset,
+        layoutState: layoutState,
+        direction: ScrollDirection.horizontal
+      ));
+      return testComponent;
+    }
+
+    tester.pumpFrame(builder);
+
+    // 0 is built to find its width
+    expect(callbackTracker, equals([0, 1, 2, 3, 4, 5]));
+
+    callbackTracker.clear();
+
+    offset = 400.0; // now only 4 should fit, numbered 2-5.
+
+    tester.pumpFrame(builder);
+
+    // 0 and 1 aren't built, we know their size and nothing else changed
+    expect(callbackTracker, equals([2, 3, 4, 5]));
+
+    callbackTracker.clear();
+
+  });
+}

packages/unit/test/widget/widget_tester.dart

@@ -123,4 +123,8 @@ class WidgetTester {
     scheduler.beginFrame(frameTimeMs);
   }
 
+  void pumpFrameWithoutChange([double frameTimeMs = 0.0]) {
+    scheduler.beginFrame(frameTimeMs);
+  }
+
 }