.net 等待 Async Void 方法调用以进行单元测试

我有一个方法如下:

private async void DoStuff(long idToLookUp)
{
    IOrder order = await orderService.LookUpIdAsync(idToLookUp);   

    // Close the search
    IsSearchShowing = false;
}    

//Other stuff in case you want to see it
public DelegateCommand<long> DoLookupCommand{ get; set; }
ViewModel()
{
     DoLookupCommand= new DelegateCommand<long>(DoStuff);
}    

我try 这样进行单元测试:

[TestMethod]
public void TestDoStuff()
{
    //+ Arrange
    myViewModel.IsSearchShowing = true;

    // container is my Unity container and it setup in the init method.
    container.Resolve<IOrderService>().Returns(orderService);
    orderService = Substitute.For<IOrderService>();
    orderService.LookUpIdAsync(Arg.Any<long>())
                .Returns(new Task<IOrder>(() => null));

    //+ Act
    myViewModel.DoLookupCommand.Execute(0);

    //+ Assert
    myViewModel.IsSearchShowing.Should().BeFalse();
}

在我完成模拟的LookUpIdAsync之前，会调用我的断言.在我的普通代码中，这正是我想要的.但对于我的单元测试，我不想这样.

我正在从使用BackgroundWorker转换为Async/Await.对于后台工作人员，这项功能正常运行，因为我可以等待后台工作人员完成.

但似乎没有办法等待异步void方法...

How can I unit test this method?