Structuremap registration via IContainer vs ObjectFactory

StructuremapTests.cs

using Machine.Specifications;
using NUnit.Framework;
using StructureMap;

namespace StructuremapTests
{
    // structuremap version 3.1.6.186, Machine Specification 0.9.3, Machine.Specifications.Should 0.8.0
    class Program
    {
        [Test]
        public void get_the_default_instance()
        {
            var container = new Container(x => { x.For<ITest>().Use<Test>(); });

            container.GetInstance<ITest>()
                .ShouldBeOfExactType<Test>();
            
            container.GetInstance<ITest>()
                .ShouldBeOfExactType<Test>();
        }

        [Test]
        public void should_throw_on_get_instance_from_ObjectFactory()
        {
            var container = new Container(x => { x.For<ITest>().Use<Test>(); });
            
            Assert.Throws<StructureMapConfigurationException>(() => ObjectFactory.GetInstance<ITest>());
        }

        [Test]
        public void get_instance_when_registered_via_ObjectFactory()
        {
            ObjectFactory.Initialize((x) =>
            {
                x.For<ITest>().Use<Test>();
            });

            var instance = ObjectFactory.GetInstance<ITest>();
            instance.ShouldBeOfExactType<Test>();
        }

        public interface ITest
        {
            int Id { get; set; }
        }
       
        public class Test : ITest
        {
            public int Id { get; set; }
            public string Name { get; set; }
        }
    }
}