Testing a PUT call with validation is failing

I am trying to add some validation to my controller but my tests are failing because the request is trying to treat the PUT call as if it was a string. My test looks like this:

PHP Code:

class UserRolesTest extends FeatureTestCase {

    /** @test */
    public function aUserCanAssignRolesToAnotherUser() {
        $this->createAuthenticatedUser(['user_admin']);
        $user = $this->createUser();

        $response = $this->put('/users/' . $user->id . '/roles', ['bin_approver']);

        $response->assertStatus(200);
        $response->assertJSONFragment(['bin_approver']);

        //asserting database has changed
    }
} 


My controller looks like this:

PHP Code:

<?php

namespace App\Controllers;


use CodeIgniter\API\ResponseTrait;
use App\Models\UserModel;

/**
 * Class Users
 * @package App\Controllers
 */
class Users extends BaseController {

    use ResponseTrait;

    /** @var UserModel */
    private $userModel;

    /**
     * Users constructor.
     */
    public function __construct() {
        $this->userModel = model(UserModel::class);
    }
    
    /**
     * The endpoint to update the roles for a user
     *
     * @param int $userId
     * @return \CodeIgniter\HTTP\Response|mixed
     */
    public function rolesUpdate($userId) {

        if (!$this->request->user->can('edit_users')) {
            return $this->failForbidden('User cannot edit users');
        }
        if ($this->request->user->id == $userId) {
            return $this->failForbidden('Users cannot edit their own roles');
        }

        if (!$this->validate([
            '*' => 'alpha_numeric_punct'
        ])) {
            $errors = $this->validator->getErrors();
            return $this->failValidationError($errors[0]);
        }

        //logic to get the user and save the roles

        return $this->response->setJSON($user->roles);
    }
} 


The error that I am getting is:

Code:

ErrorException : parse_str() expects parameter 1 to be string, array given
/var/www/html/vendor/codeigniter4/framework/system/HTTP/IncomingRequest.php:377
/var/www/html/vendor/codeigniter4/framework/system/Validation/Validation.php:339
/var/www/html/vendor/codeigniter4/framework/system/Controller.php:217
/var/www/html/app/Controllers/Users.php:82
/var/www/html/vendor/codeigniter4/framework/system/CodeIgniter.php:915
/var/www/html/vendor/codeigniter4/framework/system/CodeIgniter.php:401
/var/www/html/vendor/codeigniter4/framework/system/CodeIgniter.php:309
/var/www/html/vendor/codeigniter4/framework/system/Test/FeatureTestCase.php:182
/var/www/html/vendor/codeigniter4/framework/system/Test/FeatureTestCase.php:238
/var/www/html/tests/feature/UserRolesTest.php:16

This seems like a bug to me but I wanted to post here first to see if I am missing something. 

I also tried doing this with a POST call but that didn't work because when the validation library attaches the request, it tries to grab the data from the $_REQUEST super global and puts that into the request's data property but the request mock is never setting that super global.  I would rather use PUT anyway because it is the better action verb for my use case but that is another potential bug that I would like to be able to do at some point.

Any help you can give here would be much appreciated.