Testing validations with I18n and validators_on

question_test.rb

require 'test_helper'

class QuestionTest < ActiveSupport::TestCase
  include ActionView::Helpers::TranslationHelper
  
  test "title is required" do
    question = Question.new.tap(&:valid?)
    assert_includes question.errors[:title],
      t('errors.messages.blank')
  end
  
  test "title is required" do
    validators = Question.validators_on(:title)
    klass = ActiveRecord::Validations::PresenceValidator
    refute_empty validators.grep(klass)
  end
  
  delegate :validators_on, to: Question
  
  test "title is required" do
    refute_empty validators_on(:title).grep PresenceValidator
  end
  
private
  
  def self.const_missing(const)
    return unless const =~ /Validator\z/
    ActiveRecord::Validations.const_get(const)
  end
end