How to use the clay.set_primary_storage function in clay

'it is possible to set the default storage mechanism': function(){
        function FakeMechanismTwo (){models.storage.Mechanism.call(this)};
        util.inherits(FakeMechanismTwo, models.storage.Mechanism);

        var fake2 = new FakeMechanismTwo();

        models.set_primary_storage(fake2)

        var Build = models.declare('Build', function (it, kind){
            it.has.field("name", kind.string);
        });

        assert.deepEqual(fake2, Build._meta.storage);
    },
    'it defaults to the redis storage mechanism': function(){

OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE. */

var vows = require('vows')
, should = require('should')
, crypto = require('crypto')
, _ = require('underscore')._;

var models = require('clay');
var mock = new models.storage.Mechanism();

models.set_primary_storage(mock);

vows.describe('A Model').addBatch({
    'after declared': {
        topic: function () {
            return models.declare("Person", function(it, kind){
                it.has.field("username", kind.alphanumeric);
                it.has.field("email_address", kind.email);
                it.has.field("birthdate", kind.datetime);
                it.has.field("created_at", kind.auto);
                it.has.field("zipcode", kind.numeric);
                it.has.field("password", kind.string);

                it.validates.uniquenessOf("username");

                it.validates.presenceOf("username");
                it.validates.presenceOf("email_address");

OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE. */

var vows = require('vows')
, should = require('should')
, crypto = require('crypto')
, _ = require('underscore')._;

var models = require('clay');
var mock = new models.storage.Mechanism();

models.set_primary_storage(mock);

var Foo = models.declare("Foo", function(it, kind){
    it.has.method('work', function(msg){
        return "foooooooooooooooooo"
    });
});

var Bar = models.declare("Bar", function(it, kind){
    it.has.method('work', function(msg){
        return "baaaaarrrrrrrrrrrrr"
    });
});

vows.describe('Model issues').addBatch({
    'can be declared sequentially': {
        topic: {