Shoulda requires a database record

I fell into a trap today when creating some tests using Shoulda.

I had a user model and for that a test. In the user model I had this validation:

validates_uniqueness_of :email

and in the test this:

should_validate_uniqueness_of :email

But weird enough I got this failure:

1) Failure:
test: User should require case sensitive unique value for email. (UserTest)
[/usr/lib/ruby/gems/1.8/gems/thoughtbot-shoulda-2.10.1/lib/shoulda/assertions.rb:50:in `assert_accepts'
/usr/lib/ruby/gems/1.8/gems/thoughtbot-shoulda-2.10.1/lib/shoulda/active_record/macros.rb:88:in `__bind_1243608769_500830'
/usr/lib/ruby/gems/1.8/gems/thoughtbot-shoulda-2.10.1/lib/shoulda/context.rb:253:in `call'
/usr/lib/ruby/gems/1.8/gems/thoughtbot-shoulda-2.10.1/lib/shoulda/context.rb:253:in `test: User should require case sensitive unique value for email. ']:
Can't find first User

I even got it when I changed the :case_sensitive option.

Turns out that Shoulda requires there to be a record in the database. So by just creating a record I got rid of the failures:

Factory(:user)

Update

In recent versions of Shoulda this is solved by defining a subject block:

class UserTest < ActiveSupport::TestCase
  subject { Factory(:user) }

  should_validate_uniqueness_of :email
end