setup_fixtures

# File activerecord/lib/active_record/fixtures.rb, line 932
    def setup_fixtures(config = ActiveRecord::Base)
      if pre_loaded_fixtures && !use_transactional_fixtures
        raise RuntimeError, 'pre_loaded_fixtures requires use_transactional_fixtures'
      end

      @fixture_cache = {}
      @fixture_connections = []
      @@already_loaded_fixtures ||= {}

      # Load fixtures once and begin transaction.
      if run_in_transaction?
        if @@already_loaded_fixtures[self.class]
          @loaded_fixtures = @@already_loaded_fixtures[self.class]
        else
          @loaded_fixtures = load_fixtures(config)
          @@already_loaded_fixtures[self.class] = @loaded_fixtures
        end
        @fixture_connections = enlist_fixture_connections
        @fixture_connections.each do |connection|
          connection.begin_transaction joinable: false
        end
      # Load fixtures for every test.
      else
        ActiveRecord::FixtureSet.reset_cache
        @@already_loaded_fixtures[self.class] = nil
        @loaded_fixtures = load_fixtures(config)
      end

      # Instantiate fixtures for every test if requested.
      instantiate_fixtures(config) if use_instantiated_fixtures
    end