Moq.RaiseAsync触发事件时抛出NullReferenceException但Raise方法正常的问题求助

大家好，我最近在给一个.NET 8（.NET 9环境下也会出现同样问题）的项目写单元测试，用的是Moq 4.20.72版本，碰到了一个棘手的问题：

当我用同步方法mockCommunicator.Raise(e => e.VaccumPumpActivationEvent += null, 1, true);触发事件时，一切运行正常；但换成异步的await mockCommunicator.RaiseAsync(e => e.VaccumPumpActivationEvent += null, 1, true);就会直接抛出NullReferenceException。我翻了下Moq的源码，发现Mock.RaiseEventAsync内部会调用(Task)Mock.RaiseEvent(mock, expression, parts, arguments);，而RaiseEvent方法里有个分支可能会返回null，这会不会是问题根源？不过更大的概率应该是我用错了RaiseAsync的用法？

下面是我的最小复现代码：

应用项目核心代码 #

public class WorkingClass
{
    private readonly ICommunicator _Communicator;

    public WorkingClass(ICommunicator kommunikator)
    {
        this._Communicator = kommunikator;
        this._Communicator.VaccumPumpActivationEvent += this.Event_VaccumPumpActivation;
    }

    private void Event_VaccumPumpActivation(int nummer, bool istAktiviert)
    {
        Console.WriteLine($"EventFired with {nummer}, and {istAktiviert}");
    }
}

public delegate void VaccumPumpActivationDelegate(int nummer, bool istAktiviert);

public interface ICommunicator
{
    public event VaccumPumpActivationDelegate VaccumPumpActivationEvent;
}

测试项目依赖配置 #

<ItemGroup>
  <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
  <PackageReference Include="Microsoft.Testing.Extensions.CodeCoverage" Version="17.12.6" />
  <PackageReference Include="Microsoft.Testing.Extensions.TrxReport" Version="1.4.3" />
  <PackageReference Include="Moq" Version="4.20.72" />
  <PackageReference Include="MSTest" Version="3.6.4" />
</ItemGroup>

测试代码 #

using Moq;

namespace ConsoleAppBastelProjekt.UnitTests;

[TestClass]
public sealed class Test1
{
    [TestMethod]
    public async Task TestMethod1()
    {
        Mock<ICommunicator> mockCommunicator = new Mock<ICommunicator>();
        WorkingClass proband = new WorkingClass(mockCommunicator.Object);
        
        await mockCommunicator.RaiseAsync(e => e.VaccumPumpActivationEvent += null, 1, true);
    }
}

抛出的错误信息 #

System.NullReferenceException
HResult=0x80004003
Message = Object reference not set to an instance of an object.
Source = ConsoleAppBastelProjekt.UnitTests
Stacktrace: bei ConsoleAppBastelProjekt.UnitTests.Test1.d__0.MoveNext() in D:\Git\ForeignRepos\ConsoleAppBastelProjekt\ConsoleAppBastelProjekt.UnitTests\Test1.cs: Zeile16

有没有大佬能帮忙判断下这是Moq的bug，还是我使用RaiseAsync的姿势不对？麻烦指点一下，谢谢！

内容来源于stack exchange