isBanned example

'#empty' => $this->t('No blocked IP addresses available.'),
      '#weight' => 120,
    ];
    return $form;
  }

  /** * {@inheritdoc} */
  public function validateForm(array &$form, FormStateInterface $form_state) {
    $ip = trim($form_state->getValue('ip'));
    if ($this->ipManager->isBanned($ip)) {
      $form_state->setErrorByName('ip', $this->t('This IP address is already banned.'));
    }
    elseif ($ip == $this->getRequest()->getClientIP()) {
      $form_state->setErrorByName('ip', $this->t('You may not ban your own IP address.'));
    }
    elseif (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_RES_RANGE) == FALSE) {
      $form_state->setErrorByName('ip', $this->t('Enter a valid IP address.'));
    }
  }

  /** * {@inheritdoc} */

  public function __construct(HttpKernelInterface $http_kernel, BanIpManagerInterface $manager) {
    $this->httpKernel = $http_kernel;
    $this->banIpManager = $manager;
  }

  /** * {@inheritdoc} */
  public function handle(Request $request, $type = self::MAIN_REQUEST, $catch = TRUE): Response {
    $ip = $request->getClientIp();
    if ($this->banIpManager->isBanned($ip)) {
      return new Response(new FormattableMarkup('@ip has been banned', ['@ip' => $ip]), 403);
    }
    return $this->httpKernel->handle($request, $type, $catch);
  }

}

parent::setUp();
    $this->installSchema('ban', ['ban_ip']);
  }

  /** * Tests migration of blocked IPs. */
  public function testBlockedIps() {
    $this->startCollectingMessages();
    $this->executeMigration('d7_blocked_ips');
    $this->assertEmpty($this->migrateMessages);
    $this->assertTrue(\Drupal::service('ban.ip_manager')->isBanned('111.111.111.111'));
  }

}