Attempts a drag gesture consisting of a pointer down, a move by the given offset, and a pointer up.
Source
Future<Null> scrollAt(Point startLocation, Offset offset, { int pointer: 1 }) {
return TestAsyncUtils.guard(() async {
TestGesture gesture = await startGesture(startLocation, pointer: pointer);
await gesture.moveBy(offset);
await gesture.up();
return null;
});
}