code: function(n, desc){
          this.obj.should.have.property('length');
          var len = this.obj.length;
          this.assert(
              n == len
              , function(){ return 'expected ' + this.inspect + ' to have a length of ' + n + ' but got ' + len + (desc ? " | " + desc : "") }
              , function(){ return 'expected ' + this.inspect + ' to not have a length of ' + len + (desc ? " | " + desc : "") });
          return this;
      }
docs: Assert property "length" exists and has value of _n_.
  
  @param {Number} n
  @param {String} description
  @api public