require 'abstract_unit' class ParamsWrapperForApiTest < ActionController::TestCase class UsersController < ActionController::API attr_accessor :last_parameters wrap_parameters :person, format: [:json] def test self.last_parameters = params.except(:controller, :action).to_unsafe_h head :ok end end class Person; end tests UsersController def test_specify_wrapper_name @request.env['CONTENT_TYPE'] = 'application/json' post :test, params: { 'username' => 'sikachu' } expected = { 'username' => 'sikachu', 'person' => { 'username' => 'sikachu' }} assert_equal expected, @controller.last_parameters end end