Rails - May 2010 - Rspec unit test fails sometimes (validation race condition)

I have code similar to this:

class Post
  has_many :comments
end

class Comment
  belongs_to :post
  validate :must_not_exceed_ten

  def must_not_exceed_ten
    errors.add_to_base(''Too many comments'') unless
post.comments.length
< 10
  end
end

and in the specs (Rspec + machinist):

post = Post.make
9.times { Comment.make(:post => post) }
comment = Comment.new(:post => post)
comment.save.should be_false

The weird thing about it is that it fails sometimes! Especially if I run
the whole test suite with rake command (the probability is higher). When
I check in the console post indeed has 11 comments. Can somebody give me
a reasonable explanation why this is happening? Is this some sort of a
race condition that I''m missing?
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In the specs it is actually 10.times instead of 9.

Milan Dobrota wrote:
> post = Post.make
> 9.times { Comment.make(:post => post) }
> comment = Comment.new(:post => post)
> comment.save.should be_false
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Milan Dobrota wrote:
> In the specs it is actually 10.times instead of 9.
> 
> Milan Dobrota wrote:
>> post = Post.make
>> 9.times { Comment.make(:post => post) }
>> comment = Comment.new(:post => post)
>> comment.save.should be_false
Well, there''s your problem, then -- you''ve already made your
10th
comment!

BTW, you should consider comments.count instead of .length -- let the DB 
do the counting.

Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
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No because validations happen before the object is saved. Validation 
will pass and the object will get saved properly. Well... sometimes. 
Sometimes not.

Marnen Laibow-Koser wrote:
> 
> Well, there''s your problem, then -- you''ve already made
your 10th
> comment!
> 
> BTW, you should consider comments.count instead of .length -- let the DB 
> do the counting.
> 
> Best,
> --
> Marnen Laibow-Koser
> http://www.marnen.org
> marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
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