test script for rails/rails#10865

bug_10865.rb

#!/usr/bin/env ruby
unless File.exists?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', github: 'rails/rails', branch: 'master'
    gem 'sqlite3'
  GEMFILE

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

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

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts do |t|
    t.integer :comments_count
  end
  create_table :comments do |t|
    t.references :post
  end
end

class Post < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post, counter_cache: true
end

class BugTest < MiniTest::Unit::TestCase

  # this test case
  #   - passes with master, 4.0.0
  #   - fails with 3.2.13
  def test_belongs_to_counter_with_append

    post = Post.create!
    comment = Comment.create!

    post.comments << comment
    post.reload

    assert_equal 1, post.comments.count
    assert_equal 1, post.comments_count

  end
  
  # this test case passes with master, 4.0.0
  def test_belongs_to_counter_with_assignment

    post = Post.create!
    comment = Comment.new

    comment.post = post
    comment.save
    post.reload

    assert_equal 1, post.comments_count
    assert_equal 1, post.comments.count

  end


  # this test case
  #   - fails with master, 4.0.0
  #   - passes with 3.2.13
  def test_belongs_to_counter_with_assignment

    post = Post.create!
    comment = Comment.create!

    comment.post = post
    post.reload

    # changes to comment has not been saved yet, but counter cache has been
    # updated
    assert_equal 0, post.comments.count
    assert_equal 1, post.comments_count

    comment.save
    post.reload

    # changes to comment has been saved, and counter cache is updated again
    assert_equal 1, post.comments.count
    assert_equal 1, post.comments_count # fail

  end

end