troubleshooting mongo mapper issue for someone

result.txt

$ ruby test_custom_data.rb 
Loaded suite test_custom_data
Started
.F..
Finished in 0.018501 seconds.

  1) Failure:
test_creating_a_thing_with_a_foo(MyTest) [test_custom_data.rb:58]:
<"--- !ruby/object:Foo \nfirst: 1st\nsecond: 2nd\n"> expected but was
<#<Foo:0x1023a5ce8 @first="1st", @second="2nd">>.

4 tests, 5 assertions, 1 failures, 0 errors

test_custom_data.rb

require 'rubygems'
require 'test/unit'
require 'mongo_mapper'
require 'yaml'

MongoMapper.database = 'test_custom_data'

class Foo
  attr_reader :first, :second
  
  def initialize first, second
    @first, @second = first, second
  end

  def self.to_mongo(value)
    return value if value.nil?
    if value
      # check if value is already yamlized and if so just return it
      if value =~ /^---/
        value
      else
        YAML.dump(value)
      end
    else
      nil
    end
  end

  def self.from_mongo(value)
    value ? YAML.load(value) : nil
  end

  # so foos know if they are equal
  def ==(other)
    other.is_a?(self.class) && first == other.first && second == other.second
  end
end

class Thing
  include MongoMapper::Document
  key :title, String
  key :name, Foo  
end

class MyTest < Test::Unit::TestCase
  def test_foo_is_serializable
    foo = Foo.new("1st", "2nd")
    assert_equal Foo.to_mongo(foo), YAML.dump(foo)
  end

  def test_foo_is_deserializable
    foo = Foo.new("1st", "2nd")
    as_yaml = YAML.dump(foo)
    assert_equal Foo.from_mongo(as_yaml), YAML.load(as_yaml)
  end
  
  def test_serialization
    foo = Foo.new('1st', '2nd')
    assert_equal(foo, Foo.from_mongo(Foo.to_mongo(foo)))
  end

  def test_creating_a_thing
    t = Time.now.to_s
    thing = Thing.find(Thing.create(:title => t).id)
    assert_equal thing.title, t
  end
  
  def test_creating_a_thing_with_a_foo
    foo = Foo.new("1st", "2nd")    
    t = Time.now.to_s
    thing = Thing.find(Thing.create(:title => t, :name => foo).id)
    assert_equal t, thing.title
    assert_equal foo, thing.name
  end
end