Rails issue #18695

test.rb

# Activate the gem you are reporting the issue against.
unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
source 'https://rubygems.org'
gem 'activerecord', '4.2.0'
gem 'pg', '0.18'
gem 'pry-byebug'
  GEMFILE
 
  system 'bundle'
end
 
require 'bundler'
Bundler.setup(:default)
require 'active_record'
require 'minitest/autorun'
require 'logger'
require 'pry-byebug'

ISSUE = 18695

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

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

ActiveRecord::Schema.define do
  enable_extension "uuid-ossp"

  create_table "#{ISSUE}_settings", id: false do |t|
    t.uuid :user_id
  end
 
  execute "ALTER TABLE \"#{ISSUE}_settings\" ADD PRIMARY KEY (user_id);"
end

class BugTest < Minitest::Test
  def teardown
    ActiveRecord::Base.connection.execute("drop table \"#{ISSUE}_settings\"")
  end

  def test_schema_dumper
    dumper = ActiveRecord::SchemaDumper.send(:new, ActiveRecord::Base.connection)
    strio = StringIO.new    
    dumper.send(:table, "#{ISSUE}_settings", strio)
    assert_match /\bid:\s*:uuid\b/, strio.string
  end
end