translation missing: ja~ 系のエラー。日本語、英語どちらも対応させる。

    config.i18n.available_locales = %i[ja en]
    config.i18n.default_locale = :ja

 it 'is invalid without a title' do
     post = Post.new()
     post.valid?
     expect(post.errors.messages[:title]).to include('can`t be blank')
  end

 Failure/Error: expect(post.errors.messages[:title]).to 
include('Can not be blank')
expected #<ActiveModel::DeprecationHandlingMessageArray(["translation missing: ja.activerecord.errors.models.post.attributes.title.blank"])> to include "Can not be blank"

translation missing: 
ja.activerecord.errors.models.post.attributes.title.blank"

ja:
  activerecord:
    errors:
      models:
        post:
          attributes:
            title:
              blank: "タイトルが空白です"

pry(main)> I18n.t("activerecord.errors.models.post.attributes.title.blank")
=> "タイトルが空白です。"

 it 'is invalid without a title' do
     post = Post.new()
     post.valid?
     - expect(post.errors.messages[:title]).to include('can`t be blank')
     + expect(post.errors.messages[:title]).to include(I18n.t("activerecord.errors.models.post.attributes.title.blank"))

  end