class Account
  include Mongoid::Document

  field :period_started_at, type: Time

  has_many :consumption_periods, dependent: :destroy, validate: false

  def current_consumption
    consumption_periods.find_or_create_by(started_at: period_started_at)
  end
end

class ConsumptionPeriod
  include Mongoid::Document

  belongs_to :account

  field :started_at, type: Time
end

Account.destroy_all

100.times do |i|
  print "."

  account = Account.create!(period_started_at: Time.now.utc)
  created_consumption = account.current_consumption

  account.reload # changes the value of period_started_at, sometimes causing the consumption reference to break

  unless created_consumption == account.current_consumption
    puts "Error: expected #{created_consumption} but was #{account.current_consumption}"
  end
end