How do I test extension method of Nhibernate which

Question

I have a class like below where using Fluent Nhibernate I am getting data from database

public class MyActualClass
{
    public MyActualClass(ISessionFactory sessionFactory)
    {
        this.sessionFactory = sessionFactory;
    }

    public List<AnnualInformation> GetData()
    {
        using (session = sessionFactory.OpenSession())  
        {  
            var result = session.QueryOver<AnnualInformation>() 
                         .SelectList(list => list  
                                     .Select(x => x.Id)  
                                     .Select(x => x.CreationDate)  
                                     .Select(x => x.AnnualAmount)  
                                     .Select(x => x.AnnualCurrency)  
                                     .Select(() => monthlyAlias.MonthlyAmount)  
                                     .Select(() => monthlyAlias.MonthlyCurrency)  
                                     .Select(() => shareAlias.CurrentSharevalue)  
                                     .Select(() => miscAlias.MarketValueAmount)  
                                     ).Where(a => a.Id == 123456).List<AnnualInformation>();  
        }
    }
} 

I Have written unit test case for above method like below

public class MyTestClass
{
    private static ISessionFactory sessionFactory;
    private static ISession session;

    public MyTestClass()
    {
        sessionFactory = A.Fake<ISessionFactory>();
        session = A.Fake<ISession>();

        A.CallTo(() => sessionFactory.OpenSession()).Returns(session);
    }

    [Fact]
    public void MyTest()
    {
        var annualDetails = 
                new AnnualInformation
                {
                    Id= 1,
                    AnnualCurrency= "string",
                    AnnualAmount= "Example"
                }
         var listOfAnnualInformation=
            new List<AnnualInformation>
            {
                annualDetails 
            };  

        A.CallTo(session.QueryOver<AnnualInformation>()).WithReturnType<IList<AnnualInformation>>().Returns(listOfAnnualInformation);
        var myInstance = new MyActualClass(sessionFactory);
        myInstance.GetData();
    }
}  

Actually if you see below code

session.QueryOver() .SelectList(...

will return "result" in method GetData(). After that I am manipulating "result" datastructure to get Id, CreationDate, AnnualAmount, AnnualCurrency
Therefore it is very important that some value is returned from "result". My problem is the count of resulty is always 0.

I want the below line of code

A.CallTo(session.QueryOver()).WithReturnType>().Returns(listOfAnnualInformation);

to return a list with atleast one element. Now i believe i clarified my requirements

Please suggest what should be done here ?

Answer 1

Based on the new code (which still doesn't quite compile - missing ;, result isn't returned from GetData, and if it were, the return type of GetData should be IList<AnnualInformation>, but with those changes I was able to get a test to run) I can offer some commentary:

A.CallTo(session.QueryOver<AnnualInformation>()).WithReturnType<IList<AnnualInformation>>()
    .Returns(listOfAnnualInformation);

Configures the object that comes back from calling session.QueryOver<AnnualInformation>(). (Note there's no lambda here, so this line actually calls QueryOver.)
session is a Fake, and so when you call QueryOver<AnnualInformation>() on this line, it will return a new Fake IQueryOver. The "WithReturnType…Returns…" configures the new Fake IQueryOver to return listOfAnnualInformation when any method that returns a IList<AnnualInformation> is called.

However, when Fakes' methods are called, unless they've been configured to do something different, they return a new object. So inside GetData when you call QueryOver, you get a different fake IQueryOver, which has not been configured at all. That's one problem.

Second problem: the call to SelectList will return yet another faked IQueryOver.

We can work around all these things:

var aFakeQueryOver = A.Fake<IQueryOver<AnnualInformation, AnnualInformation>>();
A.CallTo(aFakeQueryOver).WithReturnType<IQueryOver<AnnualInformation, AnnualInformation>>()
    .Returns(aFakeQueryOver);
A.CallTo(aFakeQueryOver).WithReturnType<IList<AnnualInformation>>()
    .Returns(listOfAnnualInformation);

A.CallTo((() => session.QueryOver<AnnualInformation>())).Returns(aFakeQueryOver);

And now the faking behaves as we want. However, all we've done is short-circuit all the logic in GetData, except to see that it uses the sessionFactory to open a session, and then QueryOver on that session. SelectList and Where and List have all been bypassed.

My usual advice in this situation is to make your data access layer as thin as possible and to integration test it. Alternatively, I've seen people suggest having NHibernate use an in-memory MySql database. Still an integration test of sorts, but at least it's more isolated.