tripal/tests/DatabaseSeeders/UsersTableSeeder.php

<?php

namespace Tests\DatabaseSeeders;

use StatonLab\TripalTestSuite\Database\Seeder;

class UsersTableSeeder extends Seeder {

  /**
   * Seeds the database with users.
   */
  public function up() {
    $new_user = [
      'name' => 'test user',
      'pass' => 'secret',
      'mail' => 'test@example.com',
      'status' => 1,
      'init' => 'Email',
      'roles' => [
        DRUPAL_AUTHENTICATED_RID => 'authenticated user',
      ],
    ];

    // The first parameter is sent blank so a new user is created.
    user_save(new \stdClass(), $new_user);
  }
}