You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: candidates_test.rb
    path of file: ./repos/friendly_id/test
    
    the code of the file until where you have to start completion: require "helper"

class CandidatesTest < TestCaseClass
  include Friendl
    
  def with_instances_of(klass = model_class, &block)
    transaction do
      city1 = klass.create! name: "New York", code: "JFK"
      city2 = klass.create! name: "New York", code: "EWR"
      yield city1, city2
    end
  end