为什么这些 NSubstitute 参数匹配器不匹配？

Question

我自己编写了一个非常基本的 MediatR 实现；了解它解决的问题。 （我冒昧地稍微改变了命名，因为 MediatR 并没有真正实现原始的 GoF Mediator 模式。请不要介意。） 我已经实现了 IServiceCollection 的扩展方法，该方法可以扫描程序集广告调用

IServiceCollection.AddTransient(IRequestHandler<SomeRequestType>, SomeRequestTypeHandler);

以获取所有

IRequestHandler<TRequest>

实现。

手动测试时，它就像一个魅力。但是，当添加以下自动化测试来断言为

AddTransient()

和

IRequestHandler<VoidDispatcherRequest>

调用

VoidDispatcherRequestHandler

时，测试将不会通过。 这是为什么？

    [Fact]
    public void When__Given__Then()
    {
        // Arrange
        var serviceCollection = Substitute.For<IServiceCollection>();

        // Act
        RequestDispatcherRegistrar.AddRequestDispatcher(serviceCollection);

        // Assert
        serviceCollection.Received()
            .AddTransient(Arg.Is<Type>(t => t == typeof(IRequestHandler<VoidDispatcherRequest>)),
                Arg.Is<Type>(t => t == typeof(VoidDispatcherRequestHandler)));
    }

产生以下错误：

System.ArgumentNullException: Value cannot be null. (Parameter 'serviceType')

System.ArgumentNullException
Value cannot be null. (Parameter 'serviceType')
   at System.ThrowHelper.Throw(String paramName)
   at Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions.AddTransient(IServiceCollection services, Type serviceType, Type implementationType)
   at Presentation.Functional.UnitTest1.When__Given__Then() in [...]
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr).

以下是接口及其实现：

public interface IRequest : IBaseRequest { }

public interface IBaseRequest { }

public class VoidDispatcherRequest : IRequest { }

public interface IRequestHandler<in TRequest>
    where TRequest : IRequest
{
    Task HandleAsync(TRequest request, CancellationToken cancellationToken);
}

public class VoidDispatcherRequestHandler : IRequestHandler<VoidDispatcherRequest>
{
    public Task HandleAsync(VoidDispatcherRequest request, CancellationToken cancellationToken)
    {
        throw new NotImplementedException();
    }
}

实际上，我更喜欢这样编写测试：

    [Fact]
    public void When__Given__Then()
    {
        // Arrange
        var serviceCollection = Substitute.For<IServiceCollection>();

        // Act
        RequestDispatcherRegistrar.AddRequestDispatcher(serviceCollection);

        // Assert
        serviceCollection.Received()
            .AddTransient(typeof(IRequestHandler<VoidDispatcherRequest>), typeof(VoidDispatcherRequestHandler));
    }

但这会产生以下错误：

NSubstitute.Exceptions.ReceivedCallsException: Expected to receive a call matching:

NSubstitute.Exceptions.ReceivedCallsException
Expected to receive a call matching:
    Add(ServiceType: Application.IRequestHandler`1[Presentation.Functional.VoidDispatcherRequest] Lifetime: Transient ImplementationType: Presentation.Functional.VoidDispatcherRequestHandler)
Actually received no matching calls.
Received 5 non-matching calls (non-matching arguments indicated with '*' characters):
    Add(*ServiceType: Application.IRequestHandler`2[Presentation.Functional.DispatcherRequest,Presentation.Functional.DispatcherResponse] Lifetime: Transient ImplementationType: Presentation.Functional.DispatcherRequestHandler*)
    [...]
    **Add(*ServiceType: Application.IRequestHandler`1[Presentation.Functional.VoidDispatcherRequest] Lifetime: Transient ImplementationType: Presentation.Functional.VoidDispatcherRequestHandler*)**
    [...]
    Add(*ServiceType: Application.IRequestDispatcher Lifetime: Transient ImplementationFactory: Application.IRequestDispatcher <AddRequestDispatcher>b__0_0(System.IServiceProvider)*)

   at NSubstitute.Core.ReceivedCallsExceptionThrower.Throw(ICallSpecification callSpecification, IEnumerable`1 matchingCalls, IEnumerable`1 nonMatchingCalls, Quantity requiredQuantity)
   at NSubstitute.Routing.Handlers.CheckReceivedCallsHandler.Handle(ICall call)
   at NSubstitute.Routing.Route.Handle(ICall call)
   at NSubstitute.Core.CallRouter.Route(ICall call)
   at NSubstitute.Proxies.CastleDynamicProxy.CastleForwardingInterceptor.Intercept(IInvocation invocation)
   at Castle.DynamicProxy.AbstractInvocation.Proceed()
   at NSubstitute.Proxies.CastleDynamicProxy.ProxyIdInterceptor.Intercept(IInvocation invocation)
   at Castle.DynamicProxy.AbstractInvocation.Proceed()
   at Castle.Proxies.ObjectProxy.Add(ServiceDescriptor item)
   at Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions.AddTransient(IServiceCollection services, Type serviceType, Type implementationType)
   at Presentation.Functional.UnitTest1.When__Given__Then() in [...]
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)

注意正确的调用实际上是如何列在所做的调用中的。

我知道项目名称目前不是最佳的。请不要介意。

Answer 1

您似乎正在尝试测试 IServiceCollection.AddTransient 是否在 RequestDispatcherRegistrar.AddRequestDispatcher 方法中正确调用。但是，在尝试验证这些调用时，您遇到了 NSubstitute 问题。让我们分解一下问题和潜在的解决方案。

NSubstitute 和 AddTransient 的问题 NSubstitute 对 IServiceCollection 的行为：

NSubstitute 的 IServiceCollection 模拟本身并不支持验证 AddTransient 调用的细节，尤其是当方法签名涉及类型参数时。

AddTransient 方法签名：

AddTransient 方法是 IServiceCollection 上的扩展方法，它在内部使用 ServiceDescriptor 调用 Add。当使用 NSubstitute 验证对 AddTransient 的调用时，确保验证中使用准确的方法签名和参数至关重要。

验证 AddTransient 调用的解决方案

1. 使用带有自定义验证的 IServiceCollection 模拟 您需要验证是否使用正确的参数调用了 AddTransient。但是，由于 IServiceCollection 是一个具有扩展方法的接口，因此您可能必须验证正在添加的底层 ServiceDescriptor：

   [事实] 公共无效当__Given__Then() { // 安排 var serviceCollection = Substitute.For(); var serviceDescriptors = new List();

    // Use a callback to capture the ServiceDescriptors being added
    serviceCollection
        .When(x => x.Add(Arg.Any<ServiceDescriptor>()))
        .Do(x => serviceDescriptors.Add(x.Arg<ServiceDescriptor>()));
   
    // Act
    RequestDispatcherRegistrar.AddRequestDispatcher(serviceCollection);
   
    // Assert
    Assert.Contains(serviceDescriptors, sd =>
        sd.ServiceType == typeof(IRequestHandler<VoidDispatcherRequest>) &&
        sd.ImplementationType == typeof(VoidDispatcherRequestHandler) &&
        sd.Lifetime == ServiceLifetime.Transient);
   

   }

了解更多