I'm using AutoFixture with AutoMoqCustomization in my tests.

I have a service which is a dependency of the system under test:

ISomeService
{
    Task<IEnumerable<int>> Get();
}

I call it inside the system under test:

var collection = await _someService.Get(); // collection is empty

I don't care what's inside the collection, but I need the collection not to be empty. I do it this way:

_fixture.Freeze<Mock<ISomeService>>()
            .Setup(service => service.Get())
            .Returns(Task.FromResult(_fixture.CreateMany<int>()));

It looks like it should be done with a customization. I created and registered one:

public class TaskCollectionCustomization : ICustomization
{
    public void Customize(IFixture fixture)
    {
        fixture.Customizations.Add(
            new FilteringSpecimenBuilder(
                new TaskCollectionBuilder(),
                new GenericTypeSpecification(typeof(Task<>))));
    }

    private class TaskCollectionBuilder : ISpecimenBuilder
    {
        public object Create(object request, ISpecimenContext context)
        {
            // never enters here
        }
    }
}

The problem is it's Create method is never entered. Any ideas or ready-to-serve solutions?