Rails - Oct 2009 - Rails /w Ruby 1.9.1p243 - Unit Test assert_equal question

Hi everyone

I am new to Rails. My platform is Ubuntu 9.04 with Ruby 1.9.1p243 and
Rails 2.3.4. I am reading SitePoint''s Simply Rails 2 book. On page
240, the author shows how to test the associations between Story and
Vote model.

The code is below

app/models/story.rb:
----------------------------
class Story < ActiveRecord::Base
  validates_presence_of :name, :link
  has_many :votes
end

app/models/vote.rb:
-----------------------------
class Vote < ActiveRecord::Base
  belongs_to :story
end



test/fixtures/stories.yml:
------------------------------------

one:
  name: My Shiny Weblog
  link: http://www.google.com/

two:
  name: Another stupid site
  link: http://www.apple.com/


test/fixtures/votes.yml:
----------------------------------

one:
  story: one

two:
  story: one



test/unit/story_test.rb:
--------------------------------

def test_should_have_a_votes_association
  assert_equal [ votes(:one), votes(:two) ], stories(:one).votes
end



$ rake test:units

The output of assert return failure. So I do trial-and-error fix and
manage to fix it by swap the position of votes(:one) and votes(:two)
order so the test method become:
  assert_equal [ votes(:two), votes(:one) ], stories(:one).votes
Can some Rails experts explain to me why the order of vote inside the
array could affect the assert_equal measure?
Thank you so much

On Oct 16, 1:31 am, mojo
<jonesle...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> def test_should_have_a_votes_association
>   assert_equal [ votes(:one), votes(:two) ], stories(:one).votes
> end
>
> $ rake test:units
>
> The output of assert return failure. So I do trial-and-error fix and
> manage to fix it by swap the position of votes(:one) and votes(:two)
> order so the test method become:
>   assert_equal [ votes(:two), votes(:one) ], stories(:one).votes
> Can some Rails experts explain to me why the order of vote inside the
> array could affect the assert_equal measure?
> Thank you so much
because arrays are fundamentally ordered collections so for an array
== means same elements and in the same order. Whenever you get
something out of the database and there is no order clause (eg if you
do Vote.all, or the association you have here) the database is free to
return stuff in any order it wants to. Quite often it will be mostly
the same order each time but you shouldn''t rely on that (more often
than not it will something to do with the order things are stored in
on disk.

Fred