class Article
  include Mongoid::Document
  embeds_many :comments
  field :title, localize: true
end

class Comment
  include Mongoid::Document
  embedded_in :article
  field :title, localize: true
end

@article= Article.new
@a= @article.comments.build(title: "A")
@c= @article.comments.build(title: "C")
@b= @article.comments.build(title: "B")
@article.save!
assert_equal @article.comments.asc(:title).to_a,  [@a, @b, @c] #fails
assert_equal @article.comments.desc(:title).to_a, [@c, @b, @a]