UserEditedOwnAccountTest.php

<?php

namespace Drupal\Tests\user\Functional;

use Drupal\Tests\BrowserTestBase;
use Drupal\user\UserInterface;

/**
 * Tests user edited own account can still log in.
 *
 * @group user
 */
class UserEditedOwnAccountTest extends BrowserTestBase {
    
    /**
     * {@inheritdoc}
     */
    protected $defaultTheme = 'stark';
    public function testUserEditedOwnAccount() {
        // Change account setting 'Who can register accounts?' to Administrators
        // only.
        $this->config('user.settings')
            ->set('register', UserInterface::REGISTER_ADMINISTRATORS_ONLY)
            ->save();
        // Create a new user account and log in.
        $account = $this->drupalCreateUser([
            'change own username',
        ]);
        $this->drupalLogin($account);
        // Change own username.
        $edit = [];
        $edit['name'] = $this->randomMachineName();
        $this->drupalPostForm('user/' . $account->id() . '/edit', $edit, t('Save'));
        // Log out.
        $this->drupalLogout();
        // Set the new name on the user account and attempt to log back in.
        $account->name = $edit['name'];
        $this->drupalLogin($account);
    }

}