MOQ单元测试-返回类型

Question

I am very new to MOQ and have an issue I cannot solve. I have the following code I am testing (I am testing first one - ValidateInputBankFile ):

    #region Constructor

    private readonly IErrorRepository _errorRepository;
    private readonly IFileSystem _fileSystem;
    public IP_BankInfoDeserializer(IErrorRepository errorRepository, IFileSystem fileSystem)
    {
        _errorRepository = errorRepository;
        _fileSystem = fileSystem;
    }
    #endregion

    public IP_BankInfo ValidateInputBankFile(string sPath, App.BankType bankType)
    {
        if (!_fileSystem.FileExists((sPath)))
            return null;

        //first retrieve representative bank info
        var tmpInfo = DeserializeBankInfo(bankType);

        if (tmpInfo == null)
            return null;//Does not exist

        return tmpInfo;
    }

    public IP_BankInfo DeserializeBankInfo(App.BankType bankType)
    {
        if (!IsFileCorrect(bankType))
            return null;

        IP_BankInfo info = new IP_BankInfo();

        using (var stream = new StreamReader(Directory.GetCurrentDirectory() + Path.DirectorySeparatorChar + sFolder + Path.DirectorySeparatorChar +
                                              bankType.ToString() + ".xml"))
        {
            XmlSerializer serializer = new XmlSerializer(typeof(IP_BankInfo));
            try
            {
                info = serializer.Deserialize(stream) as IP_BankInfo;
            }
            catch (Exception ex)
            {
                info = null;
            }
        }

        return info;
    }

This is my test method:

    [TestMethod]
    public void ValidateInputBank_ExistingPath_ExistingBank()
    {
        Mock<IFileSystem> fileSystem = new Mock<IFileSystem>();
        fileSystem.Setup(n => n.FileExists(null)).Returns(true);

        Mock<IP_BankInfoDeserializer> mocSerializer = new Mock<IP_BankInfoDeserializer>();
        mocSerializer.Setup(n => n.DeserializeBankInfo(App.BankType.UniCredit)).Returns(new Models.IP_BankInfo());

        var result = mocSerializer.Object.ValidateInputBankFile(null, App.BankType.UniCredit);

        //Assert.AreEqual(serializer.Object.ValidateInputBankFile(null, App.BankType.UniCredit), new Models.IP_BankInfo());
    }

What I am trying to do, is to avoid call to DeserializeBankInfo , return new IP_BankInfo and so that I can check it under my final assert stage.

The problem is that my var result always returns null. I don't understand what am I doing wrong?

Also it fails on the following code mocSerializer.Setup(n => n.DeserializeBankInfo(App.BankType.UniCredit)).Returns(()=>null); , yet I am passing correct parameters.

Answer 1

To answer your question

The problem is that my var result always returns null. I don't understand what am I doing wrong?

ValidateInputBankFile is never setup and you use loose mocks, therefore it will return null.

Use Strict mocks by passing MockBehavior.Strict in the constructor of your mock and you will have an exception telling you that your method was not setup.

Apply a Setup to return an appropriate value on that mock for the ValidateInputBankFile method and it will behave correctly.

A word of advice

You are calling methods on a mocked object from within your test :

var result = mocSerializer.Object.ValidateInputBankFile(null, App.BankType.UniCredit);

As a rule of thumb, you should never call method on a xxx.Object.MyMethod()

the reason why you should not do that is because you're basically just calling your "arrange" part of the test.

I feel like I need to ask you what you are trying to achieve by doing so, because you're basically just testing your test .

Answer 2

Personally to me it looks like you are attempting to test your class but as the same time mock it so that not all of the class runs. I see this as incorrect, effectively how do you know that the deserialisation code is working correctly?

If your answer is another test where you mock other functionality in your class I would reply saying that you need to abstract out the deserialisation functionality of the BankInfo into another interface/class that you can mock and inject this into your IBankInfoValidator .

This means that you are splitting out your validation from the deserialisation of the object, this will help both in testing and maintainability/extensibility in the future if your use case changes.

Personally I'd scrap your tests just now, start looking to abstract out the deserialisation of your object and then think about testing it as separate classes.