为什么添加构造函数会导致System.InvalidOperationException的MSpec测试失败？

Question

我有一个类的第一个版本

public class GenerateAuthorisationWorkflows : IGenerateAuthorisationWorkflows
{
    public IList<Guid> FromDtaObjects(IList<DtaObject> dtaObjects, Employee requestingEmployee)
    {
        foreach (var dtaObject in dtaObjects) { }
        return new List<Guid>();
    }

    public IList<Guid> FromDtaObjects()
    {
        return new List<Guid>();
    }
}

并对其进行MSpec测试

public abstract class specification_for_generate_workflows : Specification<GenerateAuthorisationWorkflows>
{
    protected static IWorkflowService workflowService;

    Establish context = () => { workflowService = DependencyOf<IWorkflowService>(); };
}

[Subject(typeof(GenerateAuthorisationWorkflows))]
public class when_generate_workflows_is_called_with_a_dta_object_list_and_an_employee : specification_for_generate_workflows
{
    static IList<Guid> result;
    static IList<DtaObject> dtaObjects;
    static Employee requestingEmployee;

    Establish context = () =>
    {
         var mocks = new MockRepository();
         var stubDtaObject1 = mocks.Stub<DtaObject>();
         var stubDtaObject2 = mocks.Stub<DtaObject>();
         var dtaObjectEnum = new List<DtaObject>{stubDtaObject1,stubDtaObject2}.GetEnumerator();
         dtaObjects = mocks.Stub<IList<DtaObject>>();
         dtaObjects.Stub(x => x.GetEnumerator()).Return(dtaObjectEnum).WhenCalled(x => x.ReturnValue = dtaObjectEnum);
         requestingEmployee = mocks.Stub<Employee>();
         mocks.ReplayAll();
    };

    Because of = () => result = subject.FromDtaObjects(dtaObjects, requestingEmployee);

    It should_enumerate_the_dta_objects = () => dtaObjects.received(x=> x.GetEnumerator());
    It should_call_workflow_host_helper = () => workflowService.AssertWasCalled(x => x.StartWorkflow());
}

使用这种配置，我的第一个测试通过了，而第二个测试失败了，正如预期的那样。我向类添加了一个构造函数来注入IWorkflowService。

public class GenerateAuthorisationWorkflows : IGenerateAuthorisationWorkflows
{
    IWorkflowService _workflowService;

    GenerateAuthorisationWorkflows(IWorkflowService workflowService)
    {
        _workflowService = workflowService;
    }

    public IList<Guid> FromDtaObjects(IList<DtaObject> dtaObjects, Employee requestingEmployee)
    {
        foreach (var dtaObject in dtaObjects)
        {
            Guid workflowKey = _workflowService.StartWorkflow();
        }

        return new List<Guid>();
    }

    public IList<Guid> FromDtaObjects()
    {
        return new List<Guid>();
    }
}

现在，当我运行测试时，它们在Because上失败了

System.InvalidOperationException: Sequence contains no elements
at System.Linq.Enumerable.First(IEnumerable`1 source)
at MSpecTests.EmployeeRequestSystem.Tasks.Workflows.when_generate_workflows_is_called_with_a_dta_object_list_and_an_employee.<.ctor>b__4() in GenerateAuthorisationWorkflowsSpecs.cs: line 76 

为了清楚起见，上面的第76行是：

Because of = () => result = subject.FromDtaObjects(dtaObjects, requestingEmployee);

我试着追踪这个问题，但一无所获。我曾尝试设置一个不带参数的构造函数，但它引发了相同的错误。我有类似的带有IoC依赖的类，使用MSpec/Rhino Mock可以很好地工作，我哪里错了？

Answer 1

Castle Windsor需要一个公共构造函数来实例化一个类。将public添加到构造函数可以实现正确的操作。

public class GenerateAuthorisationWorkflows : IGenerateAuthorisationWorkflows
{
    IWorkflowService _workflowService;

    public GenerateAuthorisationWorkflows(IWorkflowService workflowService)
    {
        _workflowService = workflowService;
    }

    public IList<Guid> FromDtaObjects(IList<DtaObject> dtaObjects, Employee requestingEmployee)
    {
        foreach (var dtaObject in dtaObjects)
        {
            Guid workflowKey = _workflowService.StartWorkflow();
        }

        return new List<Guid>();
    }

    public IList<Guid> FromDtaObjects()
    {
        return new List<Guid>();
    }
}

Answer 2

罗文看起来你回答了你自己的问题。显式声明访问修饰符！默认情况下，C#选择private。这些类型的错误很容易被忽略！

我还可以看到你的Establish代码块太复杂了。您测试的是实现细节，而不是行为。例如，您是

• 截断在工作流服务仅被调用一次的GetEnumerator loop.
• asserting内隐式进行的foreach调用
• 混合MSpec自动锁定和您自己的本地模拟

实际上，您并不是在测试是否为输入列表中的每个对象都获得了GUID。如果我是你，我会像这样测试行为...

public class GenerateAuthorisationWorkflows : IGenerateAuthorisationWorkflows
{
    private readonly IWorkflowService _service;

    public GenerateAuthorisationWorkflows(IWorkflowService service)
    {
        _service = service;
    }

    public List<Guid> FromDtaObjects(List<DtaObject> input, Employee requestor)
    {
        // I assume that the workflow service generates a new key
        // per input object. So, let's pretend the call looks like
        // this. Also using some LINQ to avoid the foreach or 
        // building up a local list.
        input.Select(x => _service.StartWorkflow(requestor, x)).ToList();
    }
}

[Subject(typeof(GenerateAuthorisationWorkflows))]
public class When_generating_authorisation_keys_for_this_input 
    : Specification<GenerateAuthorisationWorkflows>
{
    private static IWorkflowService _service;
    private static Employee _requestor = new Employee();
    private static List<DtaObject> _input = new List<DtaObject>() 
    {
        new DtaObject(),
        new DtaObject(),
    };
    private static List<Guid> _expected = new List<Guid>()
    {
        Guid.NewGuid(),
        Guid.NewGuid(),
    };

    private static List<Guid> _actual = new List<Guid>();

    Establish context = () =>
    {
        // LINQ that takes each item from each list in a pair. So
        // the service is stubbed to return a specific GUID per 
        // input DtaObject.
        _input.Zip(_expected, (input, output) => 
        {
            DependencyOf<IWorkflowService>().Stub(x => x.StartWorkflow(_requestor, input)).Return(output);
        });
    };

    Because of = () => _actual = Subject.FromDtaObjects(_input, _requestor);

    // This should be an MSpec collection assertion that 
    // ensures that the contents of the collections are
    // equivalent
    It should_get_a_unique_key_per_input = _actual.ShouldEqual(_expected);
}