title: DatabaseCleaner don't reset autoincrement index in rails test unit
body: <p>test/test_helper.rb :</p>
  
  <pre><code>ENV["RAILS_ENV"] ||= "test"
  require File.expand_path('../../config/environment', __FILE__)
  require 'rails/test_help'
  require 'database_cleaner'
  
  DatabaseCleaner.strategy = :transaction
  DatabaseCleaner.clean_with(:truncation, pre_count: true, reset_ids: true)
  
  class ActiveSupport::TestCase
    ActiveRecord::Migration.check_pending!
  
  
    def setup
      DatabaseCleaner.start
    end
  
  
    def teardown
      DatabaseCleaner.clean
      p '-------- DB Cleaned ---------'
    end
  
  end
  </code></pre>
  
  <p>My test unit file : (test1 and 2 are a duplicate)</p>
  
  <pre><code>require 'test_helper'
  
  class ItemTest &lt; ActiveSupport::TestCase
  
    test "test1" do
      i = Item.create!
  
      p ActiveRecord::Base.connection.execute("SELECT auto_increment FROM information_schema.tables WHERE table_schema = 'tmi_game_test' AND table_name = 'items';").first
  
      assert_equal 1, Item.count
      assert_equal 1, i.id
    end
  
    test "test2" do
      i = Item.create!
  
      p ActiveRecord::Base.connection.execute("SELECT auto_increment FROM information_schema.tables WHERE table_schema = 'tmi_game_test' AND table_name = 'items';").first
  
      assert_equal 1, Item.count
      assert_equal 1, i.id
    end
  
  end
  </code></pre>
  
  <p>result :</p>
  
  <pre><code># Running:
  
  [2]
  "-------- DB Cleaned ---------"
  .[3]
  "-------- DB Cleaned ---------"
  F
  
  Finished in 0.142886s, 13.9972 runs/s, 27.9944 assertions/s.
  
    1) Failure:
  ItemTest#test_test2 [test/models/item_test.rb:45]:
  Expected: 1
    Actual: 2
  
  2 runs, 4 assertions, 1 failures, 0 errors, 0 skips
  </code></pre>
  
  <p>Why dosn't works? where is my mistake?</p>