sky/unit/test/widget/positioned_test.dart

import 'package:flutter/animation.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/widgets.dart';
import 'package:test/test.dart';

import 'widget_tester.dart';

void main() {

  test('Can animate position data', () {
    testWidgets((WidgetTester tester) {

      final AnimatedRelativeRectValue rect = new AnimatedRelativeRectValue(
        new RelativeRect.fromRect(
          new Rect.fromLTRB(10.0, 20.0, 20.0, 30.0),
          new Rect.fromLTRB(0.0, 10.0, 100.0, 110.0)
        ),
        end: new RelativeRect.fromRect(
          new Rect.fromLTRB(80.0, 90.0, 90.0, 100.0),
          new Rect.fromLTRB(0.0, 10.0, 100.0, 110.0)
        ),
        curve: Curves.linear
      );
      final Performance performance = new Performance(
        duration: const Duration(seconds: 10)
      );
      final List<Size> sizes = <Size>[];
      final List<Point> positions = <Point>[];
      final GlobalKey key = new GlobalKey();

      void recordMetrics() {
        RenderBox box = key.currentContext.findRenderObject();
        BoxParentData boxParentData = box.parentData;
        sizes.add(box.size);
        positions.add(boxParentData.position);
      }

      tester.pumpWidget(
        new Center(
          child: new Container(
            height: 100.0,
            width: 100.0,
            child: new Stack(<Widget>[
              new PositionedTransition(
                rect: rect,
                performance: performance,
                child: new Container(
                  key: key
                )
              )
            ])
          )
        )
      ); // t=0
      recordMetrics();
      performance.play();
      tester.pump(); // t=0 again
      recordMetrics();
      tester.pump(const Duration(seconds: 1)); // t=1
      recordMetrics();
      tester.pump(const Duration(seconds: 1)); // t=2
      recordMetrics();
      tester.pump(const Duration(seconds: 3)); // t=5
      recordMetrics();
      tester.pump(const Duration(seconds: 5)); // t=10
      recordMetrics();

      expect(sizes, equals([const Size(10.0, 10.0), const Size(10.0, 10.0), const Size(10.0, 10.0), const Size(10.0, 10.0), const Size(10.0, 10.0), const Size(10.0, 10.0)]));
      expect(positions, equals([const Point(10.0, 10.0), const Point(10.0, 10.0), const Point(17.0, 17.0), const Point(24.0, 24.0), const Point(45.0, 45.0), const Point(80.0, 80.0)]));

    });
  });

}