class Test1
  include Mongoid::Document
  embeds_many :test2
end

class Test2
  include Mongoid::Document
  embedded_in :test1
  embeds_many :test3
end

class Test3
  include Mongoid::Document
  embedded_in :test2
end

# This all works fine
t = Test1.create
t.test2 << Test2.new
t.test2.first.test3.new
t.changed?
# => true
t.save

# This will now do nothing
t.test2.first.test3.new
t.changed?
# => false
t.test2.first.changed?
# => false
t.save
# returns true, yet it does nothing -- this is extremely dangerous/bad
t.test2.first.test3.last.persisted?
# => false