Mocked interface doesn't mock-CodePudding

I met such a method in one project, and the similar and brief logic is shown as follows

public void BookAClass()
{
    _eventPublisher.Publish(new BookReadyEvent());
    //Using static class Reader to
    //read a configured Storage Place
    //to retrieve an ExamResultFile object
    var examResultFile = Reader.ReadFile("xxxx");
    var examResultLevel = _analyzer.AnalyseExameFile(examResultFile);

    if(examResultLevel == ExamResultEnum.Pass)
    {
        _eventPublisher.Publish(new BookCancelEvent());
    }
    else//examResultLevel == ExamResultEnum.Failed
    {
        _eventPublisher.Publish(new BookStartingEvent());
        //TODO
    }
}

And I tried to implement unit testing for two conditions: Pass and Failed. Regarding the Pass condition

[TestMethod()]
public void BookAClass_Pass_ExecuteAll()
{
    var analyzerService = new Mock<AnalyzerService>();
    analyzerService.Setup(analyzer =>
        analyzer.AnalyseExameFile(new ExamResultFile()))
        .Returns(ExamResultEnum.Pass);

    var student = new Student(analyzerService.Object);
    student.BookAClass();
}

Without a doubt, the unit testing failed, because AnalyseExameFile will accept an object from the response of Reader.ReadFile("xxxx"), rather than my fake data, which causes the examResultLevel to be null every time. As a result, the Pass condition will never be triggered.

I knew it would be better if consider the examResultFile as an input parameter, other than a returned object from the method invocated in the BookAClass. But the real scenario is much more complex, so I cannot refactor it now.

I wonder if there is any solution to implement unit testing for this condition?

CodePudding user response：

Yes, you can just tell Moq to ignore the argument you provided (and hence consider the setup to be fulfilled for all possible arguments).

In the simplest case, you could write:

analyzerService.Setup(analyzer =>
        analyzer.AnalyseExameFile(It.IsAny<ExamResultFile>()))
        .Returns(ExamResultEnum.Pass);

This declares that this setup shall be used for any invocations of AnalyseExameFile, regardless of the argument. In advanced scenarios, you can also do

analyzerService.Setup(analyzer =>
        analyzer.AnalyseExameFile(It.Is<ExamResultFile>(x => x.Name == "Hans")))
        .Returns(ExamResultEnum.Pass);

This uses the functor to define whether the arguments should match.

If you create your mock as var analyzerService = new Mock<AnalyzerService>(MockBehavior.Strict); You will be informed about a missing Setup for a call (one that silently returns null, as in your case).

CodePudding user response：

Instead of passing a new ExamResultFile instance you can use the It.IsAny function to ensure you are matching against any arguments you pass to AnalyseExameFile

analyzerService.Setup(analyzer =>
        analyzer.AnalyseExameFile(It.IsAny<ExamResultFile>()))
        .Returns(ExamResultEnum.Pass);