public async Task ActDefer_success()
{
var map = new MapItem <TestItem, int>("Id", x => x.ItemId)
{
ActDefer = async(cache, x, y) => await Task.Run(() => x.ItemId = y).ConfigureAwait(false)
};
var item = new TestItem();
await map.Defer(null, item, 3).ConfigureAwait(false);
Assert.That(item.ItemId, Is.EqualTo(3));
}