How to test #structuremap configuration using #mspec

FooContainer.cs

[Subject(typeof (CommonRegistry))]
    public class When_add_common_registry_to_a_container
    {
        Because of = () => ObjectFactory.Configure(x=>x.Scan(scanner=>
            {
                scanner.AssemblyContainingType<ISerializer>();
                scanner.LookForRegistries();
            }));

        It should_register_a_default_i_serializer = () => ObjectFactory.GetAllInstances<ISerializer>().Count.ShouldBeGreaterThan(0);

        It should_regisiter_serializer_as_singleton =
            () =>
            ObjectFactory.Model.PluginTypes.First(item => item.PluginType.UnderlyingSystemType == typeof (ISerializer))
                         .Lifecycle.ShouldEqual(StructureMapConstants.Singleton);
    }