division.rb

class Division < ActiveRecord::Base
  has_many :agencies, :dependent => :destroy
  belongs_to :country
  
  validates_presence_of :name, :country
  validates_uniqueness_of :name, :case_sensitive => false
end

division_factory.rb

Factory.define :division do |f|  
  f.name Faker::Name.name

  f.association :country, :factory => :country
end

division_test.rb

require 'test_helper'

class DivisionTest < ActiveSupport::TestCase
  subject { Factory(:division) }
  
  should_validate_uniqueness_of(:name, :case_sensitive => false)
  should_have_many(:agencies)
  should_belong_to(:country)
end

gistfile4.txt

mickael@mickael-laptop:~/projects/pabd$ rake test:units
(in /home/mickael/projects/pabd)
/usr/bin/ruby1.8 -I"lib:test" "/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake/rake_test_loader.rb" "test/unit/user_test.rb" "test/unit/country_test.rb" "test/unit/delivery_test.rb" "test/unit/function_test.rb" "test/unit/service_test.rb" "test/unit/assignment_test.rb" "test/unit/division_test.rb" "test/unit/stage_test.rb" "test/unit/helpers/divisions_helper_test.rb" "test/unit/helpers/countries_helper_test.rb" "test/unit/helpers/users_helper_test.rb" "test/unit/helpers/home_helper_test.rb" "test/unit/helpers/user_sessions_helper_test.rb" "test/unit/helpers/admin/stages_helper_test.rb" "test/unit/helpers/admin/account_helper_test.rb" "test/unit/helpers/admin/subcontract_types_helper_test.rb" "test/unit/helpers/admin/services_helper_test.rb" "test/unit/helpers/admin/admin_helper_test.rb" "test/unit/helpers/admin/skills_helper_test.rb" "test/unit/helpers/admin/functions_helper_test.rb" "test/unit/helpers/admin/accounts_helper_test.rb" "test/unit/helpers/admin/administration_helper_test.rb" "test/unit/helpers/admin/deliveries_helper_test.rb" "test/unit/helpers/admin/assignments_helper_test.rb" "test/unit/helpers/admin/account_types_helper_test.rb" "test/unit/helpers/admin/agencies_helper_test.rb" "test/unit/subcontract_type_test.rb" "test/unit/account_type_test.rb" "test/unit/account_test.rb" "test/unit/skill_test.rb" "test/unit/agency_test.rb" 
Loaded suite /var/lib/gems/1.8/gems/rake-0.8.7/lib/rake/rake_test_loader
Started
...................................
Finished in 1.863244 seconds.

35 tests, 35 assertions, 0 failures, 0 errors

should_validate_uniqueness_of :name, :case_sensitive => false

Thank's that's solve my issue.