How to inherit one mock from another?-CodePudding

Say i have this example code:

interface IBase {
    int BaseProperty { get; }
}
interface IDerived : IBase {
    int DerivedProperty { get; }
}

and i like to write mocks for both interfaces.

Base mock is easy:

class BaseMock : Mock<IBase> {
    public int BaseProperty { get; set; } = 42;
    public BaseMock() {
        SetupGet(o => o.BaseProperty).Returns(BaseProperty);
    }
}

but im not sure how to correctly write derived mock:

class DerivedMock : Mock<IDerived> {
    public int BaseProperty { get; set; } = 42;
    public int DerivedProperty { get; set; } = 73;
    public DerivedMock() {
        // setups related to IBase
        SetupGet(o => o.BaseProperty).Returns(BaseProperty);

        // setups related to IDerived
        SetupGet(o => o.DerivedProperty).Returns(DerivedProperty);
    }
}

this implementation will work as expected, but im forced to copy bassically whole content of BaseMock class here and that is not DRY ...

ideally i would like to inherit DerivedMock from BaseMock, but then setups related to IDerived would not compile (o is IBase and i it to be IDerived)...

I appreciate any kick in the right direction :)

CodePudding user response：

Rafał Rutkowski kicked me to right direction and i ended up with this code for anyone else interested:

interface IBase {
    int BaseProperty { get; }
}
interface IDerived : IBase {
    int DerivedProperty { get; }
}

class BaseMock : Mock<IBase>, IBase {
    public int BaseProperty { get; set; } = 42;

    public BaseMock() {
        SetupAll(this, this);
    }

    public static void SetupAll<TBase>([NotNull] Mock<TBase> mock, [NotNull] TBase instance)
        where TBase : class, IBase {
        mock.SetupGet(o => o.BaseProperty).Returns(instance.BaseProperty);
    }
}


class DerivedMock : Mock<IDerived>, IDerived {
    public int BaseProperty { get; set; } = 42;
    public int DerivedProperty { get; set; } = 73;

    public DerivedMock() {
        SetupAll(this, this);
    }

    public static void SetupAll<TDerived>([NotNull] Mock<TDerived> mock, [NotNull] TDerived instance) 
        where TDerived : class, IDerived {
        BaseMock.SetupAll(mock, instance);
        mock.SetupGet(o => o.DerivedProperty).Returns(instance.DerivedProperty);
    }
}

public class UnitTest1
{
    public void Test() {
        BaseMock baseMock = new BaseMock();
        IBase baseObject = baseMock.Object;

        baseMock.BaseProperty = 37;
        Assert.AreEqual(37, baseObject.BaseProperty);
        baseMock.VerifyGet(o => o.BaseProperty, Times.Never);
        
        // ----------------

        DerivedMock derivedMock = new DerivedMock();
        IDerived derivedObject = derivedMock.Object;

        derivedMock.BaseProperty = 42;
        derivedMock.DerivedProperty = 73;
        Assert.AreEqual(42, derivedObject.BaseProperty);
        Assert.AreEqual(73, derivedObject.DerivedProperty);
    }
}

reason why i wrote it this way is that i can dynamicall change property value AND verify that it was readed / written.

CodePudding user response：

You don't inherit from the Mock class. Instead you use Mock's Object property to get the mocked object. To reuse setting up IBase mock, you can do something like this:

    private static void SetupBase<T>(Mock<T> mock)
        where T : class, IBase
    {
        // setup base methods and properties
        mock.SetupGet(x => x.BaseProperty).Returns(1);
    }

    private static void SetupDerived(Mock<IDerived> mock)
    {
        SetupBase(mock);

        // setup derived methods and properties
    }

    [Test]
    public void Test()
    {
        var derivedMock = new Mock<IDerived>();
        SetupDerived(derivedMock);
        var derived = derivedMock.Object;

        Assert.AreEqual(1, derived.BaseProperty);

        derivedMock.SetupGet(x => x.BaseProperty).Returns(2);
        Assert.AreEqual(2, derived.BaseProperty);
    }