AutoMockFunction.cs

using System;
using Autofac.Extras.Moq;
using Moq;
using NUnit.Framework;

namespace Sandbox
{
    public class AutoMockFunctionTests
    {
        [Test]
        public void FooTest()
        {
            using (var autoMock = AutoMock.GetLoose())
            {
                var foo = Mock.Of<IFoo>(f => f.DoFoo() == "fooResult");
                Func<string, IFoo> fooFactory = x => foo;

                autoMock.Provide(fooFactory);

                var sut = autoMock.Create<ClassUnderTest>();
                var result = sut.Do("factoryParam");

                Assert.That(result, Is.EqualTo("fooResult"));
            }
        }
    }

    public class ClassUnderTest
    {
        private readonly Func<string, IFoo> _fooFactory;

        public ClassUnderTest(Func<string, IFoo> fooFactory)
        {
            _fooFactory = fooFactory;
        }

        public string Do(string value)
        {
            var foo = _fooFactory(value);
            return foo.DoFoo();
        }
    }

    public interface IFoo
    {
        string DoFoo();
    }
}