Handling specimen creation inconsistencies between AutoFixture and Moq

Question

I am using AutoMoqCustomization in my test conventions.

Consider the code below. Everything works great until I add a constructor to one of the concrete classes. W

Answer 1

As there's no extensibility point in Moq that enables AutoFixture to hook in and supply a value of ThingOne, there's not a whole lot you can do.

However, you can use the SetReturnsDefault<T> method of Moq. Modifying the above test would then be like this:

[Theory, BasicConventions]
public void WhyCannotInstantiateProxyOfClass(
    ThingOne one, ThingTwo two, IThingBuilders builder, SomeClass sut)
{
    Assert.IsAssignableFrom<IThings>(one);
    Assert.IsAssignableFrom<IThings>(two);
    Mock.Get(builder).SetReturnsDefault(one); // Add this to make the test pass

    var actual = sut.GetCommands(builder);

    Assert.Equal(1, actual.OfType<ThingOne>().Count());
    Assert.Equal(1, actual.OfType<ThingTwo>().Count());
}

This is a bit easier than having to write a specific Setup/Returns pair, but not much. You could move that code to an AutoFixture Customization, but again, since this is a generic method on a a Mock instance, you'll explicitly need to call this for e.g. ThingOne in order to set the default for that return type. Not particularly flexible.