return unmanagedInstance(modelReference, Factories.constant(instance), Actions.doNothing());
    }

    public static <T> Builder unmanagedInstance(ModelReference<T> modelReference, final Factory<? extends T> factory) {
        return unmanagedInstance(modelReference, factory, Actions.doNothing());
    }

        def barList = []
        def factory = Mock(org.gradle.internal.Factory) {
            create() >> barList
        }
        def barRegistration = ModelRegistrations.unmanagedInstance(barReference, factory).descriptor(descriptor).build()
        registry.register(barRegistration)
        def foo = registry.atStateOrLater(fooReference.path, ModelNode.State.Discovered)

        then: