slightly revised test using master

issue_27348_master.rb

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', github: 'rails/rails'
    gem 'arel', github: 'rails/arel'
    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.string :title
  end
end

class Post < ActiveRecord::Base
  def title
    @title.present? ? @title : 'Default Title'
  end
end

class BugTest < Minitest::Test
  def  test_attribute_definition
    Post.create!
    Post.reset_column_information

    post = Post.last

    assert_equal 'Default Title', post.title
    assert post.class.instance_variable_get(:@attribute_methods_generated)
  end

  def test_attribute_definition_with_marshal
    dump = Marshal.dump(Post.create!)
    Post.reset_column_information

    post = Marshal.load(dump)

    assert_equal 'Default Title', post.title
  end

  def test_attribute_definition_bool_with_marshal
    dump = Marshal.dump(Post.create!)
    Post.reset_column_information

    post = Marshal.load(dump)

    assert post.class.method_defined?(:title)
  end
end