unit-testing - Mocked 方法调用中的参数计数不匹配

Question

我有这个方法:

public void Valida(Validazione.IValidator<MyType> validator)
{
    // do something...
    Validazione.IMapper<MyType> mapper = new MyTypeMapper();
    ValidationResult result = validator.Validate(myTypeObj, mapper, new ValidationConfiguration());
    // ...continue doing something else
}

我想进行单元测试，所以我会模拟(使用 Moq 框架)validator 来控制 Validate 方法的结果，所以我写了这个单元测试:

[TestMethod]
public void Long_test_name_as_best_practice()
{
    // arrange
    MyAggregateRoot aggregateRoot = AggregateRoot.Stub();
    var mockedValidator = new Mock<Validazione.IValidator<MyType>>();

    mockedValidator.Setup(a => a.Validate(
        It.Is<MyType>(x => x.Id == Guid.Parse("3F2504E0-4F89-11D3-9A0C-0305E82C3301")),
        It.IsAny<Validazione.IMapper<MyType>>(), 
        It.IsAny<ValidationConfiguration>()
    )).Returns<Validazione.ValidationResult>(x => x = It.IsAny<Validazione.ValidationResult>());

    // act
    aggregateRoot.Valida(mockedValidator.Object);

    // Assert (now showed for readability sake)
}

它构建了，听起来我很正确，但最后我得到:

An exception of type 'System.Reflection.TargetParameterCountException' occurred in mscorlib.dll but was not handled in user code Additional information: Parameter count mismatch

我谷歌了一下，但我不明白原因。对我来说还可以。

评论后编辑

这是异常的堆栈跟踪:

   in System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   in System.Reflection.RuntimeMethodInfo.UnsafeInvoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   in System.Delegate.DynamicInvokeImpl(Object[] args)
   in System.Delegate.DynamicInvoke(Object[] args)
   in Moq.Extensions.InvokePreserveStack(Delegate del, Object[] args)
   in Moq.MethodCallReturn`2.Execute(ICallContext call)
   in Moq.ExecuteCall.HandleIntercept(ICallContext invocation, InterceptorContext ctx, CurrentInterceptContext localctx)
   in Moq.Interceptor.Intercept(ICallContext invocation)
   in Moq.Proxy.CastleProxyFactory.Interceptor.Intercept(IInvocation invocation)
   in Castle.DynamicProxy.AbstractInvocation.Proceed()
   in Castle.Proxies.IValidator`1Proxy.Validate(MyType myTypeObj, IMapper`1 mapper, ValidationConfiguration configuration)
   in MyNamespace.Valida(IValidator`1 validator) in c:\Sviluppo\ProjectName\Main\src\Project.MySubProject.Domain\filename.cs:riga 104
   in MyTestNamespace.Long_test_name_as_best_practice() in c:\Sviluppo\ProjectName\Main\src\Project.SubProject.Domain.Tests\Test_AggregateCommand.cs:riga 103

Answer 1

在Returns本条款Setup声明:

mockedValidator.Setup(a => a.Validate(
    It.Is<MyType>(x => x.Id == Guid.Parse("3F2504E0-4F89-11D3-9A0C-0305E82C3301")),
    It.IsAny<Validazione.IMapper<MyType>>(), 
    It.IsAny<ValidationConfiguration>()
)).Returns<Validazione.ValidationResult>(x => x = It.IsAny<Validazione.ValidationResult>());

看起来您并不关心此方法返回的内容。但是你给了 Returns声明一个Func<ValidationResult.ValidationResult> .这就是您的异常的来源。

此语法旨在允许您根据正在设置的方法的输入计算返回值(此处为 Validate )，因此您应该传入一个 Func 。使用与正在设置的方法相同的参数。由于您的方法有 3 个参数并且您给出 Returns取 1 的函数，存在参数不匹配。

如果你只想返回任何 ValidationResult ，改为这样做:

.Returns(It.IsAny<Validazione.ValidationResult>())

如果你真的想计算一个 ValidationResult基于 Validate 的参数，这样做:

.Returns<MyType, Validazione.IMapper<MyType>, ValidationConfiguration>
    ((m,t,c) => /* TODO: compute a ValidationResult */ )