'should not delete system.indexes collection': function(test) {
   var db = this.connection.db;
   databaseCleaner.clean(db, function () {
     db.collection('system.indexes', function (skip, collection) {
       collection.count({}, function (err, count) {
         test.ok(count > 0);
         test.done();
       });
     });
   });
 }
 'should delete all collections items': function(test) {
   var db = this.connection.db;
   databaseCleaner.clean(db, function () {
     db.collections( function (skip, collections) {
       var total_collections = collections.length;
       collections.forEach(function (collection) {
         if (collection.collectionName != 'system.indexes') {
           collection.count({}, function (err, count) {
             test.equal(count, 0);
             total_collections--;
             if (total_collections <= 0) {
               test.done();
             }
           });
         } else { 
           total_collections--; 
         }
       });
     });
   });
 },