使用 Moq 对服务进行单元测试时返回数据 null

Question

I am having a problem when using the Moq for unit testing the a function which accepts number of parameters. I did the bellow steps to moq the service.

1. Created a mock object to interface. the relevant method in the interface contains four arguments namely int type, a collection and a object. so i initailized the variable needed for those first,

2. Then setup the mock object to return aa predefined type of object.

3. After that the relevant method in the service class is called with the required arguments the method does not return the object that it is supposed to return (moq object) but it rather returns a null object.

Am I missing anything in the code bellow?

 Collection<MyDocumentSample spec = new Collection<MyDocumentSample()
 { 
  new MyIdSample() { SampleID = 1234 } };
  int index = 0;
  int maxNoOfRows = 2;
  MyDocumentListSortFields sortFeild = new
  MyDocumentListSortFields() 
  { 
       Descending = false, 
       SortField = MyDocumentListSortFields.SortFields.Date 
  };


var bundleOfObjects = new bundleOfObjects { Entry = new List<bundleOfObjects.EntryComponent() };

MySampleDocument resource_1 = new MySampleDocument();
resource_1.Id = "1005823";
resource_1.Description = "Test 1";
resource_1.Created = "11/20/2017 12:59:47 PM";


bundleOfObjects.AddTobundleOfObjects(resource_1, null);
var m_documentWrapperHelperMock = new Mock<IDocumentSampleHelper();
var m_configMock = new Mock<IConfiguration();

m_documentWrapperHelperMock.Setup(x => x.GetSampleDocumentsWithOffSets(spec, index, maxNoOfRows, sortFeild)).Returns(bundleOfObjects);


var service = new MySampleDocumentService(m_configMock.Object, m_documentWrapperHelperMock.Object);

Answer 1

After that the relevant method in the service class is called with the required arguments the method does not return the object that it is supposed to return (moq object) but it rather returns a null object.

In its default mode Moq will return null when a mock is not invoked like how it was setup, including parameters. Verify that you invoke the mocked member the same way it was setup to be invoked.

It is most likely that the mocking framework is unable to validate equality of the hard-coded values used to setup the mocked method.

To make mocks more flexible with regards to arguments you can use It.IsAny<T>() to let the mock know to accept any instance passed to it.

m_documentWrapperHelperMock
    .Setup(_ => _.GetSampleDocumentsWithOffSets(
                     It.IsAny<Collection<MyDocumentSample>>(), 
                     It.IsAny<int>(), 
                     It.IsAny<int>(), 
                     It.IsAny<MyDocumentListSortFields>()
                 )
    ).Returns(bundleOfObjects);

Reference Moq Quickstart