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: dynamic_form_test.rb
    path of file: ./repos/expertiza/vendor/plugins/dynamic_form/test
    
    the code of the file until where you have to start completion: require 'test_helper'
require 'action_
    
  def setup_post
    @post = Post.new
    def @post.errors
      #noinspection RubyDefParenthesesInspection
      Class.new {
        def [](field)
          case field.to_s
          when "author_name"
            ["can't be empty"]
          when "body"
            ['foo']
          else
            []
          end
        end
        def empty?
          false
        end
        def count
          1
        end
        def full_messages
          [ "Author name can't be empty" ]
        end
      }.new
    end