测试在seeds.rb文件中编写的方法

Question

我在seeds.rb文件中写了一些带有一些方法的ruby类 负责在数据库中的不同表中上传内容 现在我已经为该类中的方法编写了一些测试.. 但在运行我的测试后，我得到的错误就像是 ------------------- -------------------错误
 未捕获的异常：未初始化的常量“ModelName”

---------------test file -----------------

    require_relative "../../db/seeds"
    require "minitest_helper"
    it "should  create a object" do
        object = class_name.new('file_name.csv')
        object1 = object.find_and_create_object('Region', :name => 'region_name')
        object1.id.wont_be_nil
    end
--------------------seeds.rb file ---------------
  module Gen
    def find_or_create_object(model_name, attributes)
     target_model = model_name.classify.constantize
     target_model.where(attributes).first_or_create
    end
  end
  class class_name
    include Gen 
    def create_object
         find_or_create_object('modelname',{value_hash})
    end
  end
but if i am running db:seed then everything is working ...(no error) ---