C# 模拟委托抛出转换类型异常

Question

我有一个委托，它指向没有参数的方法，它返回对象数据列表的列表。 我使用 nUnit、fixture 和 mock 进行测试。我已经创建了记录列表，我喜欢通过委托模拟我的静态方法，但我收到错误

 appTenantListHandlerMoq.Setup(_ => _).Returns(tenantsMoq);

MyClass

public class MyClass 
{
    public delegate Task<IEnumerable<AppTenant>> AppTenantListHandler();
    
    AppTenantListHandler appTenantListHandler;


    public MyClass ()
    {
        appTenantListHandler = new AppTenantListHandler(GetTenant);
    }

    public async Task Run(){
        var tenantList = await appTenantListHandler();
    }

    public static async Task<IEnumerable<AppTenant>> GetTenant()
    {
       List<AppTenant> dataList = new List<AppTenant>();
       
       return dataList;
        
    }
}

测试类

 [TestFixture]
public class MyClassTests
{
    private readonly MyClass sut;
    private Mock<MyClass> MyClassMoq;

    private readonly Mock<ILogger> loggerMoq;
    private readonly Mock<ITelemetryInitializer> telemetryInitializerMoq;
    
    


    public MyClassTests()
    {
        this.loggerMoq = new Mock<ILogger>();
        this.telemetryInitializerMoq = new Mock<ITelemetryInitializer>();
        this.MyClassMoq = new Mock<MyClass>();

        this.sut = new MyClass(loggerMoq.Object);
    }
    
    [SetUp]
    public void Setup()
    {
       
    }

    [Test]
    public void Test1()
    {
        //Arrange
        var fixture  = new Fixture();

        var tenantsMoq = fixture.CreateMany<AppTenant>(5);

        var appTenantListHandlerMoq = new Mock<MyClass.AppTenantListHandler>();

        appTenantListHandlerMoq.Setup(_ => _).Returns(tenantsMoq);


        //Act
        var actualResult = sut.RunAsync(this.telemetryInitializerMoq.Object);

        //Assert
        Assert.NotNull(actualResult);
    }
}

Error2 < /代码>

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Answer 1

要模拟委托，语法是：

appTenantListHandlerMoq.Setup(_ => _()).Returns(Task.FromResult(tenantsMoq));

但在您的情况下，这将引起注意，但实例 sut 不会调用模拟委托。您需要修改 MyClass 以注入模拟委托，如下所示：

public class MyClass 
{
    public delegate Task<IEnumerable<AppTenant>> AppTenantListHandler();
    
    AppTenantListHandler appTenantListHandler;


    public MyClass ()
        : this(new AppTenantListHandler(GetTenant))
    { }

    public MyClass (AppTenantListHandler appTenantListHandler )
    {
        this.appTenantListHandler = appTenantListHandler ;
    }
    ...
}

然后在测试中：

[Test]
public void Test1()
{
    //Arrange
    var fixture  = new Fixture();
    var tenantsMoq = fixture.CreateMany<AppTenant>(5);
    var appTenantListHandlerMoq = new Mock<MyClass.AppTenantListHandler>();
    appTenantListHandlerMoq.Setup(_ => _()).Returns(Task.FromResult(tenantsMoq));
    MyClass sut = new MyClass(appTenantListHandlerMoq);

    //Act
    var actualResult = sut.RunAsync(this.telemetryInitializerMoq.Object);

    //Assert
    Assert.NotNull(actualResult);
}