gem 'activerecord', '5.1.0.beta1'
#gem 'activerecord', '5.0.2'
require 'active_record'
require "minitest/autorun"
require 'minitest/pride'
require 'logger'

ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
  end
  create_table :comments, force: true do |t|
    t.integer :post_id
    t.string :text
  end
end

class Post < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

class SelectUnsavedBugTest < MiniTest::Test
  def setup
    @post = Post.create!
    @post.comments << Comment.create!(text: "First comment")
  end

  def test_association_stuff
    @post.comments.build text: "Second comment"
    assert_equal @post.comments.select{ |x| x.text == "Second comment" },
                 @post.comments.to_a.select{ |x| x.text == "Second comment" }
  end
end