RoR rspec with field auto increment

Question

Rails 6
Database PostgresSQL

File migration:

class CreateCategoriesCodeSequence < ActiveRecord::Migration[6.1]
  def up
    execute <<-SQL
      CREATE SEQUENCE categories_code_seq;
    SQL
  end

  def down
    execute <<-SQL
      DROP SEQUENCE categories_code_seq CASCADE;
    SQL
  end
end

class AssignSequenceToTableCategories < ActiveRecord::Migration[6.1]
  def up
    execute <<-SQL
      ALERT SEQUENCE categories_code_seq OWNED by categories.code;
      ALERT TABLE categories ALTER COLUMN code SET DEFAULT nextval('categories_code_seq');
    SQL
  end

  def down
    execute <<-SQL
      ALERT SEQUENCE categories_code_seq OWNED by NONE;
    SQL
  end
end

File FactoryBot:

FactoryBot.define do
  factory :category do
    sequence(:code) { |number| number }
    name { SecureRandom.hex(3) }
  end
end

File rspec:

...
let_it_be(:category) { FactoryBot.create(:category) }
let_it_be(:category_1) { FactoryBot.create(:category) }

describe 'POST #create' do
  subject do
   post_api '/api/v1/categories', params
   response
  end

  let(:params) do
    {
      name: 'cate_1'
    }
  end

  context 'Test create' do
    it {
      expect(subject).to have_http_status(:ok)
    }
  end
end

Controller categories call this function to create new record

  def create!(form)
    ActiveRecord::Base.transaction do
      Category.create!(from)
    end
  end

This is result

When I add rescue in function create!, I see error duplicate code field.

Field code is unique

FactoryBot sequence not map with nextval('categories_code_seq').
When I add a test post create new category, I get respond error 500. Because code is duplicate. Maybe nextval('categories_code_seq') don't increase follow FactoryBot sequence.

How can create case test with postgresql sequence field?