It.Is reference types

[MarkDaviesEsendex]

Going to admit this straight away that I'm not sure if this is a bug or just a misuse of the framework but I shall outline what I'm seeing and maybe you can advice.

I have a that calls down to another class and I want to test that interaction, here is an example:

public class ClassToTest
{
    private readonly IDelegation _delegation;

    public ClassToTest(IDelegation delegation)
    {
        _delegation = delegation;
    }


    public void MethodToTest(MethodParameters parameters)
    {
        _delegation.DelegationMethod(parameters);

        parameters.InParameter = 10;
    }
}

public interface IDelegation
{
    void DelegationMethod(MethodParameters parameters);
}

public class MethodParameters
{
    public int InParameter { get; set; }
}

Simple enough test:

   public class UnitTest1
    {
    private readonly Mock<IDelegation> _delegationMock;
    private readonly ClassToTest _subjectUnderTest;

    public UnitTest1()
    {
        _delegationMock = new Mock<IDelegation>();
        _subjectUnderTest = new ClassToTest(_delegationMock.Object);
    }

    [Fact]
    public void ReferenceTesting()
    {
        _subjectUnderTest.MethodToTest(new MethodParameters {InParameter = 5});
        _delegationMock.Verify(delegation =>
            delegation.DelegationMethod(It.Is<MethodParameters>(parameters => parameters.InParameter == 5)));
    }
}  

The issue is, is that this test fails, looking into it (If I split the parameters.InParameter == 5 into a different method) it seems to think that the parameters.InParameter is 10.

I'm guessing when a method gets called it doesn't create a deep copy of the reference type being passed in and is instead capturing the reference, which obviously means that when I change the value in the MethodToTest method it is subsequently changing it in the _delegationMock class?

[stakx]

Yes, you're right. Moq doesn't create deep copies. (Why would it do that?) Your verification step only sees the final, changed state of the original object.

[MarkDaviesEsendex]

That's fair, just wanted some confirmation that I wasn't going crazy, I'll close this issue because I see why you wouldn't want to do something like this, thanks 👍