after_commit_test.rb

gem 'activerecord', '4.2.0'
# gem 'activerecord', '4.1.8'
# gem 'activerecord', '4.0.12'

require 'active_record'
require 'minitest/autorun'
require 'logger'

# Ensure backward compatibility with Minitest 4
Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'postgresql', database: 'ar_test_postgres')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.text :content
    t.string :author
    t.integer :total_lines
  end
end

class Post < ActiveRecord::Base
  after_commit :calculate_total_lines, if: -> (post) { post.previous_changes.include?(:content) }

  def calculate_total_lines
    update! total_lines: content.split("\n").length
  end
end

class BugTest < Minitest::Test
  def test_without_transaction
    puts "ActiveRecord #{ActiveRecord.version}"
    post = Post.create! content: "Lets discuss Rails 5.\n", author: 'Prathamesh'

    assert_equal 1, post.total_lines
  end

  def test_within_transaction
    puts "ActiveRecord #{ActiveRecord.version}"
    Post.transaction do
      post = Post.create! content: "Lets discuss Ruby 2.2 today.\n", author: 'Prathamesh'

      assert_equal 1, post.total_lines
    end
  end
end

# ActiveRecord 4.0.12
#   1) Failure:
# BugTest#test_within_transaction [after_commit_test.rb:45]:
# Expected: 1
#   Actual: nil

# 2 runs, 2 assertions, 1 failures, 0 errors, 0 skips

# ActiveRecord 4.1.8
#   1) Failure:
# BugTest#test_within_transaction [after_commit_test.rb:45]:
# Expected: 1
#   Actual: nil

# 2 runs, 2 assertions, 1 failures, 0 errors, 0 skips

# Finished in 0.026370s, 75.8438 runs/s, 75.8438 assertions/s.

# ActiveRecord 4.2.0
#   1) Failure:
# BugTest#test_within_transaction [after_commit_test.rb:45]:
# Expected: 1
#   Actual: nil

# 2 runs, 2 assertions, 1 failures, 0 errors, 0 skips

# ActiveRecord 5.0.0.alpha
#   1) Failure:
# BugTest#test_within_transaction [after_commit_test.rb:48]:
# Expected: 1
#   Actual: nil

# 2 runs, 2 assertions, 1 failures, 0 errors, 0 skips