If you need only use_transactional_fixtures option

only_ar_rspec-rails_import.rb

# Gemfile
gem 'rspec-rails', require: false

# spec_helper.rb

#
# IMPORT ONLY FIXTURE-RELATED CODE FROM rspec-rails
#

require 'rspec/rails/adapters'
require 'rspec/rails/fixture_support'

RSpec.configure do |config|
  # fixture support
  config.add_setting :use_transactional_fixtures
  config.add_setting :use_instantiated_fixtures
  config.add_setting :global_fixtures
  config.add_setting :fixture_path

  config.fixture_path               = "#{::Rails.root}/spec/fixtures"
  config.use_transactional_fixtures = true
  config.include RSpec::Rails::FixtureSupport
end

RSpec.configure do |config|
  config.backtrace_exclusion_patterns << /vendor\//
  config.backtrace_exclusion_patterns << %r{ lib/rspec/rails }
end