Gemfile

source 'https://rubygems.org'

gem 'activerecord'
gem 'blamer'
gem 'pg'
gem 'pry'
gem 'parallel'

test.rb

require 'bundler'
Bundler.require

class Foo < ActiveRecord::Base
  establish_connection adapter: 'postgresql', database: 'test_blamer'
  connection.create_table table_name, force: true do |t|
    t.string :name
    t.userstamps
  end
end

class Foo < ActiveRecord::Base
end

class User
  cattr_accessor :current_user
  attr_accessor :id

  def initialize kwargs
    @id = kwargs.fetch(:id)
  end

  def id
    @id
  end
end

puts 'testing single threaded'
Parallel.each((0..100), in_threads: 1) do |i|
  expected_id = rand(0..1)
  User.current_user = User.new id: expected_id
  foo = Foo.create!
  foo.reload
  fail "#{i} -> expected #{foo.created_by} to equal #{expected_id}" unless foo.created_by == expected_id
end

puts 'testing 2-threaded'
Parallel.each((0..100), in_threads: 2) do |i|
  expected_id = rand(0..1)
  User.current_user = User.new id: expected_id
  foo = Foo.create!
  foo.reload
  fail "#{i} -> expected #{foo.created_by} to equal #{expected_id}" unless foo.created_by == expected_id
end