To test Laravel Backpack edit/update action we need to pass some extra parameters

LaravelBackpackObjectUpdateTest.php

<?php

namespace Tests\Feature;

use App\Models\Permission;
use App\Models\Role;
use Tests\TestCase;

/**
 * Class RoleTest
 * @package Tests\Feature
 * @group roles
 */
class RoleTest extends TestCase
{

    /**
     * @test
     */
    public function a_super_admin_can_update_role_permissions()
    {
        $this->superUserSignIn();

        /** @var Role $role */
        $role = factory(Role::class)->create();

        /** @var Permission $permission */
        $permission = factory(Permission::class)->create();

        $this->withSession(['_token' => 'FAKE_CSRF_TOKEN'])
            ->put( backpack_url('role') . '/' . $role->id, [
                'name' => $role->name,
                'permissions' => [$permission->id],
                'id' => $role->id,
            ])
            ->assertStatus(302)
        ;
        
        $role->refresh();
        $this->assertTrue($role->hasPermissionTo($permission));
    }
}