class Group
  include Mongoid::Document
  embeds_many :users, cascade_callbacks: true
end

class User
  include Mongoid::Document
  field :email, type: String
  field :email_md5, type: String

  embedded_in :group

  before_save :calculate_md5

  def calculate_md5
    self.email_md5 = Digest::MD5.hexdigest(email)
  end
end

require 'rails_helper'

RSpec.describe Group, type: :model do
  before do
    @group= Group.new(users: [{ email: 'test' }])
    @group.save
  end

  it 'saves email_md5 on create' do
    email_md5 = @group.reload.users[0].email_md5
    expect(email_md5).to eq Digest::MD5.hexdigest('test')
  end

  describe 'on update' do
    before do
      @group.update(users: [{ email: 'test2' }])
    end

    it 'calculate email_md5' do
      email_md5 = @group.users[0].email_md5
      expect(email_md5).to eq Digest::MD5.hexdigest('test2')
    end

    it 'actually saves email' do
      email = @group.reload.users[0].email
      expect(email).to eq 'test2'
    end

    it 'actually saves email_md5' do
      email_md5 = @group.reload.users[0].email_md5
      expect(email_md5).not_to be_blank
    end
  end
end