Example of how to use AutoFixture with NSubstitute

I use NSubstitute a lot. And I love it.

I am just looking into AutoFixture. It seems great!

I have seen AutoFixture for NSubstitute and seen a few examples in Moq on how to use this feature.

But I can't seem to translate it into NSubstitute.

I tried this:

var fixture = new Fixture().Customize(new AutoNSubstituteCustomization());  
var addDest = Substitute.For<IPerson>();

Using:

public interface IPersonEntity
{    
   int ID { get; set; }
   string FirstName { get; set;}
   string LastName { get; set;}
   DateTime DateOfBirth { get; set; }
   char Gender { get; set; }    
}

And I get an object, but none of the properties are populated (kind of the point of AutoFixture).

I also tried:

var fixture = new Fixture().Customize(new AutoNSubstituteCustomization());
var result = fixture.Create<IPersonEntity>();

That also gave me an object with no populated properties. (Note if I do the above with a PersonEntity class, then the properties are all populated.)

I am sure that there is a way to make this work, but I can't seem to find it.

So, given my IPersonEntity interface above, does anyone know how to use AutoFixture and NSubstitute to give me a populated IPersonEntity object?

Solution

Instead of customizing the Fixture instance with the AutoNSubstituteCustomization you may use the customization below:

var fixture = new Fixture().Customize(
    new AutoPopulatedNSubstitutePropertiesCustomization());

var result = fixture.Create<IPersonEntity>();
// -> All properties should be populated now.

The AutoPopulatedNSubstitutePropertiesCustomization is defined as:

internal class AutoPopulatedNSubstitutePropertiesCustomization
    : ICustomization
{
    public void Customize(IFixture fixture)
    {
        fixture.ResidueCollectors.Add(
            new Postprocessor(
                new NSubstituteBuilder(
                    new MethodInvoker(
                        new NSubstituteMethodQuery())),
                new AutoPropertiesCommand(
                    new PropertiesOnlySpecification())));
    }

    private class PropertiesOnlySpecification : IRequestSpecification
    {
        public bool IsSatisfiedBy(object request)
        {
            return request is PropertyInfo;
        }
    }
}

The difference with the AutoNSubstituteCustomization is that the above customization is also decorated with a Postprocessor instance to automatically set values for all the public properties of the requested type.

References:

The above solution is inspired by the following blog articles by Mark Seemann: