🐛 AutoNSubstitute does not use ForPartsOf for abstract classes

[rcdailey]

I want to express my SUT as a parameter to my NUnit test case via AutoData. My SUT is an abstract class with virtual methods. The resulting proxy was created via Substitute.For<T>(), which means that methods I invoke on it do not actually call the real code in that abstract class. The solution to this for abstract classes to use Substitute.ForPartsOf<T>() instead.

Example:

public abstract class BaseCommand
{
    public virtual void DoThing()
    {
        // Do meaningful things
    }
}

In my test:

[TestFixture]
public class BaseCommandTest
{
    [Test, AutoMockData]
    public async Task All_directories_are_created(BaseCommand sut)
    {
        sut.DoThing(); // This does NOT execute code in `BaseCommand.DoThing()`!
    }
}

For completeness, my AutoMockData class is as follows:

public sealed class AutoMockDataAttribute : AutoDataAttribute
{
    public AutoMockDataAttribute()
        : base(NSubstituteFixture.Create)
    {
    }
}

public static class NSubstituteFixture
{
    public static Fixture Create()
    {
        var fixture = new Fixture
        {
            OmitAutoProperties = true
        };

        fixture.Customize(new AutoNSubstituteCustomization
        {
            ConfigureMembers = true
        });

        return fixture;
    }
}

[rcdailey]

Rather than doing this automatically for abstract classes, which likely would be disruptive and break existing tests, perhaps it would be better to introduce a new PartialAttribute or something that can be used like this:

[Partial] BaseCommand sut

This would ultimately result in Substitute.ForPartsOf<T>().