Railsでlib以下に作った自作クラスを呼び出す

config/environment.rbに自作クラスをrequire

---

lib/
　├ assets/
　├ tasks/
　└ test.rb <-追加

test.rb

class Test
    def aa
        puts "aa"
    end
end

config/environment.rbを編集

environment.rb

# Load the Rails application.
require_relative 'application'
require 'test' #これを追記

# Initialize the Rails application.
Rails.application.initialize!

使えるかテスト

 % rails c
Running via Spring preloader in process 62643
Loading development environment (Rails 6.0.3.2)
[1] pry(main)> Test
=> Test

以上