Adding user/member to the Group programmatically

AFAIK, there is a addMember method in group.php.

 public function addMember(UserInterface $account, $values = []) {
    if (!$this->getMember($account)) {
      $this->addContent($account, 'group_membership', $values);
    }
  }

You can load a group and then call addMember function on it.

I am loading the group and then calling addMember function on it, something like this:

$roles = array('test_role');
$values = ['group_roles' => $roles, 'gid' => 1];
$account = $this->createUser();
$group = \Drupal\group\Entity\Group::load(1);
$group->addMember($account, $values);

This is not adding the member to the group. Are $values and $account parameters correct here? Or is something else wrong?