public async Task Test_Delete_Id_Action_OfType_TestModel()
        {
            var controller = new CommandController <int, TestModel>(mediator);

            var action_payload = new TestModel {
                Id = 1
            };
            var current_result = await controller.Delete(action_payload.Id);

            var result_as_noContentResult = ((NoContentResult)current_result);

            // testing action return type
            Assert.IsInstanceOfType(current_result, typeof(NoContentResult));
            // or simply
            Assert.IsTrue(current_result is IActionResult);
            // testing status code
            Assert.IsTrue(result_as_noContentResult.StatusCode == 204);
        }