将模拟的依赖项注入到ViewModel中，而单元测试的行为不符合预期

Question

I'm trying to do unit testing in view model by using Moq and dependency injection

Basically, I have model: Class PersonModel containing properties FirstName , LastName , Input , Output - no logic or any methods in here.

In my ViewModel , I have:

public class ViewModel
{
    private IGetService getService;
    private Personmodel personModel;
    private string result;

    public ViewModel(IGetService getService)
    {
        personModel= new Personmodel ();
        this.getService = getService;
    }

    public string FullName
    {
        get { return personModel.FirstName + " " + personModel.LastName; }
    }
    public string Result
    {
        get { return result; }
        set { result = value; }
    }

    public string FirstName
    {
        get { return personModel.FirstName; }
        set { personModel.FirstName = value; }
    }

    public string LastName
    {
        get { return personModel.LastName; }
        set { personModel.LastName = value; }
    }

    public string Input
    {
        get { return personModel.Input; }
        set { personModel.Input= value; }
    }

    public string Output
    {
        get { return personModel.Output; }
        set { personModel.Output= value; }
    }

    public string Result
    {
        get { return result; }
        set { result = value; }
    }        
    public void ResultFromModelToView()
    {
        getService.GetOutput(personModel);
        Result = string.Join(",", FullName,personModel.Output);            
    }
}

For IGetService ,

public interface IGetService
{
    void GetOutput(PersonModel personModel);
}   

The implementation of GetService is pretty much getting personModel.Outout value depending on business logic

Here is my ViewModelTests

public class ViewModelTests
{

    private Mock<IGetService> GetServiceMock{ get; set; }
    private ViewModel ViewModel { get; set; }

    [TestInitialize()]
    public void Initialize()
    {
        GetServiceMock= new Mock<IGetService>();
        ViewModel = new ViewModel (GetServiceMock.Object);
    }

    [TestMethod()]
    public void GetResultTests()
    {
        // Arrange
        GetServiceMock.Setup(x =>  x.GetOutput(It.Is<PersonModel>(
            p=> p.FirstName == "FirstName" &&
                    p.LastName == "LastName" &&
                    p.Input == "Input"
            )));

        // Act
        ViewModel.ResultFromModelToView();

        // Assert
        Assert.AreEqual(ViewModel.Result, "FirstName,LastName,Output");

    }
}

When I run the test I'm getting

Assert failed, with expected result of ",,"

What have I missed?

Answer 1

Given the design of the view model, you were not assigning values to the model that would allow the test to be exercised to completion based on how the mock was set up. You would also need to have the mock mimic the expected behavior of setting the output on the model when GetOutput was invoked.

The expectation in the assertion is also wrong because ViewModel.FullName is defined as

public string FullName {
    get { return personModel.FirstName + " " + personModel.LastName; }
}

Note the space between the names and not the comma of the expected result "FirstName,LastName,Output" . Which would cause the test to fail even if you provided the necessary values to the view model.

Review the following changes made to the test based on the original example provided

[TestClass]
public class ViewModelTests {

    private Mock<IGetService> GetServiceMock{ get; set; }
    private ViewModel ViewModel { get; set; }

    [TestInitialize()]
    public void Initialize()
    {
        GetServiceMock= new Mock<IGetService>();
        ViewModel = new ViewModel (GetServiceMock.Object);
    }

    [TestMethod()]
    public void GetResultTests() {
        // Arrange
        var expectedFirstName = "FirstName";
        var expectedLastName = "LastName";
        var expectedInput = "Input";
        var expectedOutput = "Output";
        var expectedResult = "FirstName LastName,Output";

        //set properties on view model
        ViewModel.FirstName = expectedFirstName;
        ViewModel.LastName = expectedLastName;
        ViewModel.Input = expectedInput;

        //Arrange mock to expect specific model
        GetServiceMock
            .Setup(_ => _.GetOutput(It.Is<PersonModel>(p=> 
                p.FirstName == expectedFirstName &&
                p.LastName == expectedLastName &&
                p.Input == expectedInput
            )))
            .Callback((PersonModel p) => { // <-- use callback to set Output on model
                p.Output = expectedOutput;
            });

        // Act
        ViewModel.ResultFromModelToView();
        actualResult = ViewModel.Result;

        // Assert
        Assert.AreEqual(expectedResult, actualResult);
    }
}