class DynamicMenuLinkMock

class DynamicMenuLinkMock extends MenuLinkMock {
  
  /**
   * The current user.
   *
   * @var \Drupal\Core\Session\AccountInterface
   */
  protected $currentUser;
  
  /**
   * Sets the current user.
   *
   * Allows the menu link to return the right title and route.
   *
   * @param \Drupal\Core\Session\AccountInterface $current_user
   *   The current user.
   *
   * @return $this
   */
  public function setCurrentUser(AccountInterface $current_user) {
    $this->currentUser = $current_user;
    return $this;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getTitle() {
    if ($this->currentUser
      ->isAuthenticated()) {
      return 'Log out';
    }
    else {
      return 'Log in';
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function getRouteName() {
    if ($this->currentUser
      ->isAuthenticated()) {
      return 'user.logout';
    }
    else {
      return 'user.login';
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function getCacheContexts() {
    return [
      'user.roles:authenticated',
    ];
  }

}