class method self.load_schema_if_pending!

# File activerecord/lib/active_record/migration.rb, line 582
      def load_schema_if_pending!
        if Base.connection.migration_context.needs_migration? || !Base.connection.migration_context.any_migrations?
          # Roundtrip to Rake to allow plugins to hook into database initialization.
          root = defined?(ENGINE_ROOT) ? ENGINE_ROOT : Rails.root
          FileUtils.cd(root) do
            current_config = Base.connection_config
            Base.clear_all_connections!
            system("bin/rails db:test:prepare")
            # Establish a new connection, the old database may be gone (db:test:prepare uses purge)
            Base.establish_connection(current_config)
          end
          check_pending!
        end
      end