<?php

declare(strict_types=1);

namespace Drupal\Tests\language\Functional;

use Drupal\Core\Cache\Cache;
use Drupal\Core\Url;
use Drupal\file\Entity\File;
use Drupal\language\Entity\ConfigurableLanguage;
use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationBrowser;
use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationSelected;
use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationSession;
use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUrl;
use Drupal\Tests\BrowserTestBase;
use Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUser;
use Drupal\user\Plugin\LanguageNegotiation\LanguageNegotiationUserAdmin;
use Drupal\Core\Language\Language;
use Drupal\Core\Language\LanguageInterface;
use Symfony\Component\HttpFoundation\Request;
use Drupal\language\LanguageNegotiatorInterface;
use Drupal\block\Entity\Block;
use Symfony\Component\HttpFoundation\Session\Session;
use Symfony\Component\HttpFoundation\Session\Storage\MockArraySessionStorage;

/**
 * Tests the language UI for language switching.
 *
 * The uses cases that get tested, are:
 * - URL (path) > default: Test that the URL prefix setting gets precedence over
 *   the default language. The browser language preference does not have any
 *   influence.
 * - URL (path) > browser > default: Test that the URL prefix setting gets
 *   precedence over the browser language preference, which in turn gets
 *   precedence over the default language.
 * - URL (domain) > default: Tests that the URL domain setting gets precedence
 *   over the default language.
 *
 * The paths that are used for each of these, are:
 * - admin/config: Tests the UI using the precedence rules.
 * - zh-hans/admin/config: Tests the UI in Chinese.
 * - blah-blah/admin/config: Tests the 404 page.
 *
 * @group language
 */
class LanguageUILanguageNegotiationTest extends BrowserTestBase {

  /**
   * {@inheritdoc}
   */
  protected static $configSchemaCheckerExclusions = [
    // Necessary to allow setting `selected_langcode` to NULL.
    // @see testUILanguageNegotiation()
    'language.negotiation',
  ];

  /**
   * The admin user for testing.
   *
   * @var \Drupal\user\Entity\User
   */
  protected $adminUser;

  /**
   * Modules to install.
   *
   * We marginally use interface translation functionality here, so need to use
   * the locale module instead of language only, but the 90% of the test is
   * about the negotiation process which is solely in language module.
   *
   * @var array
   */
  protected static $modules = [
    'locale',
    'language_test',
    'block',
    'user',
    'content_translation',
  ];

  /**
   * {@inheritdoc}
   */
  protected $defaultTheme = 'stark';

  /**
   * {@inheritdoc}
   */
  protected function setUp(): void {
    parent::setUp();

    $this->adminUser = $this->drupalCreateUser([
      'administer languages',
      'translate interface',
      'access administration pages',
      'administer blocks',
    ]);
    $this->drupalLogin($this->adminUser);
  }

  /**
   * Tests for language switching by URL path.
   */
  public function testUILanguageNegotiation(): void {
    // A few languages to switch to.
    // This one is unknown, should get the default lang version.
    $langcode_unknown = 'blah-blah';
    // For testing browser lang preference.
    $langcode_browser_fallback = 'vi';
    // For testing path prefix.
    $langcode = 'zh-hans';
    // For setting browser language preference to 'vi'.
    $http_header_browser_fallback = ["Accept-Language" => "$langcode_browser_fallback;q=1"];
    // For setting browser language preference to some unknown.
    $http_header_blah = ["Accept-Language" => "blah;q=1"];

    // Create a private file for testing accessible by the admin user.
    \Drupal::service('file_system')->mkdir($this->privateFilesDirectory . '/test');
    $filepath = 'private://test/private-file-test.txt';
    $contents = "file_put_contents() doesn't seem to appreciate empty strings so let's put in some data.";
    file_put_contents($filepath, $contents);
    $file = File::create([
      'uri' => $filepath,
      'uid' => $this->adminUser->id(),
    ]);
    $file->save();

    // Setup the site languages by installing two languages.
    // Set the default language in order for the translated string to be
    // registered into database when seen by t(). Without doing this, our target
    // string is for some reason not found when doing translate search. This
    // might be some bug.
    $default_language = \Drupal::languageManager()->getDefaultLanguage();
    ConfigurableLanguage::createFromLangcode($langcode_browser_fallback)->save();
    $this->config('system.site')->set('default_langcode', $langcode_browser_fallback)->save();
    ConfigurableLanguage::createFromLangcode($langcode)->save();

    // We will look for this string in the admin/config screen to see if the
    // corresponding translated string is shown.
    $default_string = 'Hide descriptions';

    // First visit this page to make sure our target string is searchable.
    $this->drupalGet('admin/config');

    // Now the t()'ed string is in db so switch the language back to default.
    // This will rebuild the container so we need to rebuild the container in
    // the test environment.
    $this->config('system.site')->set('default_langcode', $default_language->getId())->save();
    $this->config('language.negotiation')->set('url.prefixes.en', '')->save();
    $this->rebuildContainer();

    // Translate the string.
    $language_browser_fallback_string = "In $langcode_browser_fallback In $langcode_browser_fallback In $langcode_browser_fallback";
    $language_string = "In $langcode In $langcode In $langcode";
    // Do a translate search of our target string.
    $search = [
      'string' => $default_string,
      'langcode' => $langcode_browser_fallback,
    ];
    $this->drupalGet('admin/config/regional/translate');
    $this->submitForm($search, 'Filter');
    $textarea = $this->assertSession()->elementExists('xpath', '//textarea');
    $lid = $textarea->getAttribute('name');
    $edit = [
      $lid => $language_browser_fallback_string,
    ];
    $this->drupalGet('admin/config/regional/translate');
    $this->submitForm($edit, 'Save translations');

    $search = [
      'string' => $default_string,
      'langcode' => $langcode,
    ];
    $this->drupalGet('admin/config/regional/translate');
    $this->submitForm($search, 'Filter');
    $textarea = $this->assertSession()->elementExists('xpath', '//textarea');
    $lid = $textarea->getAttribute('name');
    $edit = [
      $lid => $language_string,
    ];
    $this->drupalGet('admin/config/regional/translate');
    $this->submitForm($edit, 'Save translations');

    // Configure selected language negotiation to use zh-hans.
    $edit = ['selected_langcode' => $langcode];
    $this->drupalGet('admin/config/regional/language/detection/selected');
    $this->submitForm($edit, 'Save configuration');
    $test = [
      'language_negotiation' => [LanguageNegotiationSelected::METHOD_ID],
      'path' => 'admin/config',
      'expect' => $language_string,
      'expected_method_id' => LanguageNegotiationSelected::METHOD_ID,
      'http_header' => $http_header_browser_fallback,
      'message' => 'SELECTED: UI language is switched based on selected language.',
    ];
    $this->doRunTest($test);

    // An invalid language is selected.
    $this->config('language.negotiation')->set('selected_langcode', NULL)->save();
    $test = [
      'language_negotiation' => [LanguageNegotiationSelected::METHOD_ID],
      'path' => 'admin/config',
      'expect' => $default_string,
      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
      'http_header' => $http_header_browser_fallback,
      'message' => 'SELECTED > DEFAULT: UI language is switched based on selected language.',
    ];
    $this->doRunTest($test);

    // No selected language is available.
    $this->config('language.negotiation')->set('selected_langcode', $langcode_unknown)->save();
    $test = [
      'language_negotiation' => [LanguageNegotiationSelected::METHOD_ID],
      'path' => 'admin/config',
      'expect' => $default_string,
      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
      'http_header' => $http_header_browser_fallback,
      'message' => 'SELECTED > DEFAULT: UI language is switched based on selected language.',
    ];
    $this->doRunTest($test);

    $tests = [
      // Default, browser preference should have no influence.
      [
        'language_negotiation' => [LanguageNegotiationUrl::METHOD_ID, LanguageNegotiationSelected::METHOD_ID],
        'path' => 'admin/config',
        'expect' => $default_string,
        'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
        'http_header' => $http_header_browser_fallback,
        'message' => 'URL (PATH) > DEFAULT: no language prefix, UI language is default and the browser language preference setting is not used.',
      ],
      // Language prefix.
      [
        'language_negotiation' => [LanguageNegotiationUrl::METHOD_ID, LanguageNegotiationSelected::METHOD_ID],
        'path' => "$langcode/admin/config",
        'expect' => $language_string,
        'expected_method_id' => LanguageNegotiationUrl::METHOD_ID,
        'http_header' => $http_header_browser_fallback,
        'message' => 'URL (PATH) > DEFAULT: with language prefix, UI language is switched based on path prefix',
      ],
      // Default, go by browser preference.
      [
        'language_negotiation' => [LanguageNegotiationUrl::METHOD_ID, LanguageNegotiationBrowser::METHOD_ID],
        'path' => 'admin/config',
        'expect' => $language_browser_fallback_string,
        'expected_method_id' => LanguageNegotiationBrowser::METHOD_ID,
        'http_header' => $http_header_browser_fallback,
        'message' => 'URL (PATH) > BROWSER: no language prefix, UI language is determined by browser language preference',
      ],
      // Prefix, switch to the language.
      [
        'language_negotiation' => [LanguageNegotiationUrl::METHOD_ID, LanguageNegotiationBrowser::METHOD_ID],
        'path' => "$langcode/admin/config",
        'expect' => $language_string,
        'expected_method_id' => LanguageNegotiationUrl::METHOD_ID,
        'http_header' => $http_header_browser_fallback,
        'message' => 'URL (PATH) > BROWSER: with language prefix, UI language is based on path prefix',
      ],
      // Default, browser language preference is not one of site's lang.
      [
        'language_negotiation' => [LanguageNegotiationUrl::METHOD_ID, LanguageNegotiationBrowser::METHOD_ID, LanguageNegotiationSelected::METHOD_ID],
        'path' => 'admin/config',
        'expect' => $default_string,
        'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
        'http_header' => $http_header_blah,
        'message' => 'URL (PATH) > BROWSER > DEFAULT: no language prefix and browser language preference set to unknown language should use default language',
      ],
    ];

    foreach ($tests as $test) {
      $this->doRunTest($test);
    }

    // Unknown language prefix should return 404.
    $definitions = \Drupal::languageManager()->getNegotiator()->getNegotiationMethods();
    // Enable only methods, which are either not limited to a specific language
    // type or are supporting the interface language type.
    $language_interface_method_definitions = array_filter($definitions, function ($method_definition) {
      return !isset($method_definition['types']) || (isset($method_definition['types']) && in_array(LanguageInterface::TYPE_INTERFACE, $method_definition['types']));
    });
    $this->config('language.types')
      ->set('negotiation.' . LanguageInterface::TYPE_INTERFACE . '.enabled', array_flip(array_keys($language_interface_method_definitions)))
      ->save();
    $this->drupalGet("$langcode_unknown/admin/config", [], $http_header_browser_fallback);
    $this->assertSession()->statusCodeEquals(404);

    // Set preferred langcode for user to NULL.
    $account = $this->loggedInUser;
    $account->preferred_langcode = NULL;
    $account->save();

    $test = [
      'language_negotiation' => [LanguageNegotiationUser::METHOD_ID, LanguageNegotiationSelected::METHOD_ID],
      'path' => 'admin/config',
      'expect' => $default_string,
      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
      'http_header' => [],
      'message' => 'USER > DEFAULT: no preferred user language setting, the UI language is default',
    ];
    $this->doRunTest($test);

    // Set preferred langcode for user to default langcode.
    $account = $this->loggedInUser;
    $account->preferred_langcode = $default_language->getId();
    $account->save();

    $test = [
      'language_negotiation' => [LanguageNegotiationUser::METHOD_ID, LanguageNegotiationUrl::METHOD_ID],
      'path' => "$langcode/admin/config",
      'expect' => $default_string,
      'expected_method_id' => LanguageNegotiationUser::METHOD_ID,
      'http_header' => [],
      'message' => 'USER > URL: User has default language as preferred user language setting, the UI language is default',
    ];
    $this->doRunTest($test);

    // Set preferred langcode for user to unknown language.
    $account = $this->loggedInUser;
    $account->preferred_langcode = $langcode_unknown;
    $account->save();

    $test = [
      'language_negotiation' => [LanguageNegotiationUser::METHOD_ID, LanguageNegotiationSelected::METHOD_ID],
      'path' => 'admin/config',
      'expect' => $default_string,
      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
      'http_header' => [],
      'message' => 'USER > DEFAULT: invalid preferred user language setting, the UI language is default',
    ];
    $this->doRunTest($test);

    // Set preferred langcode for user to non default.
    $account->preferred_langcode = $langcode;
    $account->save();

    $test = [
      'language_negotiation' => [LanguageNegotiationUser::METHOD_ID, LanguageNegotiationSelected::METHOD_ID],
      'path' => 'admin/config',
      'expect' => $language_string,
      'expected_method_id' => LanguageNegotiationUser::METHOD_ID,
      'http_header' => [],
      'message' => 'USER > DEFAULT: defined preferred user language setting, the UI language is based on user setting',
    ];
    $this->doRunTest($test);

    // Set preferred admin langcode for user to NULL.
    $account->preferred_admin_langcode = NULL;
    $account->save();

    $test = [
      'language_negotiation' => [LanguageNegotiationUserAdmin::METHOD_ID, LanguageNegotiationSelected::METHOD_ID],
      'path' => 'admin/config',
      'expect' => $default_string,
      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
      'http_header' => [],
      'message' => 'USER ADMIN > DEFAULT: no preferred user admin language setting, the UI language is default',
    ];
    $this->doRunTest($test);

    // Set preferred admin langcode for user to unknown language.
    $account->preferred_admin_langcode = $langcode_unknown;
    $account->save();

    $test = [
      'language_negotiation' => [LanguageNegotiationUserAdmin::METHOD_ID, LanguageNegotiationSelected::METHOD_ID],
      'path' => 'admin/config',
      'expect' => $default_string,
      'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
      'http_header' => [],
      'message' => 'USER ADMIN > DEFAULT: invalid preferred user admin language setting, the UI language is default',
    ];
    $this->doRunTest($test);

    // Set preferred admin langcode for user to non default.
    $account->preferred_admin_langcode = $langcode;
    $account->save();

    $test = [
      'language_negotiation' => [LanguageNegotiationUserAdmin::METHOD_ID, LanguageNegotiationSelected::METHOD_ID],
      'path' => 'admin/config',
      'expect' => $language_string,
      'expected_method_id' => LanguageNegotiationUserAdmin::METHOD_ID,
      'http_header' => [],
      'message' => 'USER ADMIN > DEFAULT: defined preferred user admin language setting, the UI language is based on user setting',
    ];
    $this->doRunTest($test);

    // Go by session preference.
    $language_negotiation_session_param = $this->randomMachineName();
    $edit = ['language_negotiation_session_param' => $language_negotiation_session_param];
    $this->drupalGet('admin/config/regional/language/detection/session');
    $this->submitForm($edit, 'Save configuration');
    $tests = [
      [
        'language_negotiation' => [LanguageNegotiationSession::METHOD_ID],
        'path' => "admin/config",
        'expect' => $default_string,
        'expected_method_id' => LanguageNegotiatorInterface::METHOD_ID,
        'http_header' => $http_header_browser_fallback,
        'message' => 'SESSION > DEFAULT: no language given, the UI language is default',
      ],
      [
        'language_negotiation' => [LanguageNegotiationSession::METHOD_ID],
        'path' => 'admin/config',
        'path_options' => ['query' => [$language_negotiation_session_param => $langcode]],
        'expect' => $language_string,
        'expected_method_id' => LanguageNegotiationSession::METHOD_ID,
        'http_header' => $http_header_browser_fallback,
        'message' => 'SESSION > DEFAULT: language given, UI language is determined by session language preference',
      ],
    ];
    foreach ($tests as $test) {
      $this->doRunTest($test);
    }
  }

  /**
   * Runs common tests for the language user interface.
   */
  protected function doRunTest($test): void {
    $test += ['path_options' => []];
    if (!empty($test['language_negotiation'])) {
      $method_weights = array_flip($test['language_negotiation']);
      $this->container->get('language_negotiator')->saveConfiguration(LanguageInterface::TYPE_INTERFACE, $method_weights);
    }
    if (!empty($test['language_negotiation_url_part'])) {
      $this->config('language.negotiation')
        ->set('url.source', $test['language_negotiation_url_part'])
        ->save();
    }
    if (!empty($test['language_test_domain'])) {
      \Drupal::state()->set('language_test.domain', $test['language_test_domain']);
    }
    $this->container->get('language_manager')->reset();
    $this->drupalGet($test['path'], $test['path_options'], $test['http_header']);
    $this->assertSession()->pageTextContains($test['expect']);
    $this->assertSession()->statusMessageContains('Language negotiation method: ' . $test['expected_method_id'], 'status');

    // Get the private file and ensure it is a 200. It is important to
    // invalidate the router cache to ensure the routing system runs a full
    // match.
    Cache::invalidateTags(['route_match']);
    $this->drupalGet('system/files/test/private-file-test.txt');
    $this->assertSession()->statusCodeEquals(200);
  }

  /**
   * Tests URL language detection when the requested URL has no language.
   */
  public function testUrlLanguageFallback(): void {
    // Add the Italian language.
    $langcode_browser_fallback = 'it';
    ConfigurableLanguage::createFromLangcode($langcode_browser_fallback)->save();
    $languages = $this->container->get('language_manager')->getLanguages();

    // Enable the path prefix for the default language: this way any unprefixed
    // URL must have a valid fallback value.
    $edit = ['prefix[en]' => 'en'];
    $this->drupalGet('admin/config/regional/language/detection/url');
    $this->submitForm($edit, 'Save configuration');

    // Enable browser and URL language detection.
    $edit = [
      'language_interface[enabled][language-browser]' => TRUE,
      'language_interface[enabled][language-url]' => TRUE,
      'language_interface[weight][language-browser]' => -8,
      'language_interface[weight][language-url]' => -10,
    ];
    $this->drupalGet('admin/config/regional/language/detection');
    $this->submitForm($edit, 'Save settings');
    $this->drupalGet('admin/config/regional/language/detection');

    // Enable the language switcher block.
    $this->drupalPlaceBlock('language_block:' . LanguageInterface::TYPE_INTERFACE, ['id' => 'test_language_block']);

    // Log out, because for anonymous users, the "active" class is set by PHP
    // (which means we can easily test it here), whereas for authenticated users
    // it is set by JavaScript.
    $this->drupalLogout();

    // Place a site branding block in the header region.
    $this->drupalPlaceBlock('system_branding_block', [
      'region' => 'header',
      'id' => 'site_branding',
    ]);

    // Access the front page without specifying any valid URL language prefix
    // and having as browser language preference a non-default language.
    $http_header = ["Accept-Language" => "$langcode_browser_fallback;q=1"];
    $language = new Language(['id' => '']);
    $this->drupalGet('', ['language' => $language], $http_header);

    // Check that the language switcher active link matches the given browser
    // language.
    $href = Url::fromRoute('<front>')->toString() . $langcode_browser_fallback;
    $this->assertSession()->elementTextEquals('xpath', "//div[@id='block-test-language-block']//a[@class='language-link is-active' and starts-with(@href, '$href')]", $languages[$langcode_browser_fallback]->getName());

    // Check that URLs are rewritten using the given browser language.
    $this->assertSession()->elementTextEquals('xpath', "//div[@id='block-site-branding']/a[@rel='home' and @href='$href'][2]", 'Drupal');
  }

  /**
   * Tests URL handling when separate domains are used for multiple languages.
   */
  public function testLanguageDomain(): void {
    global $base_url;

    // Get the current host URI we're running on.
    $base_url_host = parse_url($base_url, PHP_URL_HOST);

    // Add the Italian language.
    ConfigurableLanguage::createFromLangcode('it')->save();

    $languages = $this->container->get('language_manager')->getLanguages();

    // Enable browser and URL language detection.
    $edit = [
      'language_interface[enabled][language-url]' => TRUE,
      'language_interface[weight][language-url]' => -10,
    ];
    $this->drupalGet('admin/config/regional/language/detection');
    $this->submitForm($edit, 'Save settings');

    // Do not allow blank domain.
    $edit = [
      'language_negotiation_url_part' => LanguageNegotiationUrl::CONFIG_DOMAIN,
      'domain[en]' => '',
    ];
    $this->drupalGet('admin/config/regional/language/detection/url');
    $this->submitForm($edit, 'Save configuration');
    $this->assertSession()->statusMessageContains('The domain may not be left blank for English', 'error');
    $this->rebuildContainer();

    // Change the domain for the Italian language.
    $edit = [
      'language_negotiation_url_part' => LanguageNegotiationUrl::CONFIG_DOMAIN,
      'domain[en]' => $base_url_host,
      'domain[it]' => 'it.example.com',
    ];
    $this->drupalGet('admin/config/regional/language/detection/url');
    $this->submitForm($edit, 'Save configuration');
    $this->assertSession()->statusMessageContains('The configuration options have been saved', 'status');
    $this->rebuildContainer();

    // Try to use an invalid domain.
    $edit = [
      'language_negotiation_url_part' => LanguageNegotiationUrl::CONFIG_DOMAIN,
      'domain[en]' => $base_url_host,
      'domain[it]' => 'it.example.com/',
    ];
    $this->drupalGet('admin/config/regional/language/detection/url');
    $this->submitForm($edit, 'Save configuration');
    $this->assertSession()->statusMessageContains("The domain for Italian may only contain the domain name, not a trailing slash, protocol and/or port.", 'error');

    // Build the link we're going to test.
    $link = 'it.example.com' . rtrim(base_path(), '/') . '/admin';

    // Test URL in another language: http://it.example.com/admin.
    // Base path gives problems on the testbot, so $correct_link is hard-coded.
    // @see UrlAlterFunctionalTest::assertUrlOutboundAlter (path.test).
    $italian_url = Url::fromRoute('system.admin', [], ['language' => $languages['it']])->toString();
    $url_scheme = \Drupal::request()->isSecure() ? 'https://' : 'http://';
    $correct_link = $url_scheme . $link;
    $this->assertEquals($correct_link, $italian_url, "The right URL ($italian_url) in accordance with the chosen language");

    // Test HTTPS via options.
    $italian_url = Url::fromRoute('system.admin', [], ['https' => TRUE, 'language' => $languages['it']])->toString();
    $correct_link = 'https://' . $link;
    $this->assertSame($correct_link, $italian_url, "The right HTTPS URL (via options) ($italian_url) in accordance with the chosen language");

    // Test HTTPS via current URL scheme.
    $request = Request::create('', 'GET', [], [], [], ['HTTPS' => 'on']);
    $request->setSession(new Session(new MockArraySessionStorage()));
    $this->container->get('request_stack')->push($request);
    $italian_url = Url::fromRoute('system.admin', [], ['language' => $languages['it']])->toString();
    $correct_link = 'https://' . $link;
    $this->assertSame($correct_link, $italian_url, "The right URL (via current URL scheme) ($italian_url) in accordance with the chosen language");
  }

  /**
   * Tests persistence of negotiation settings for the content language type.
   */
  public function testContentCustomization(): void {
    // Customize content language settings from their defaults.
    $edit = [
      'language_content[configurable]' => TRUE,
      'language_content[enabled][language-url]' => FALSE,
      'language_content[enabled][language-session]' => TRUE,
    ];
    $this->drupalGet('admin/config/regional/language/detection');
    $this->submitForm($edit, 'Save settings');

    // Check if configurability persisted.
    $config = $this->config('language.types');
    $this->assertContains('language_interface', $config->get('configurable'), 'Interface language is configurable.');
    $this->assertContains('language_content', $config->get('configurable'), 'Content language is configurable.');

    // Ensure configuration was saved.
    $this->assertArrayNotHasKey('language-url', $config->get('negotiation.language_content.enabled'));
    $this->assertArrayHasKey('language-session', $config->get('negotiation.language_content.enabled'));
  }

  /**
   * Tests if the language switcher block gets deleted when a language type has been made not configurable.
   */
  public function testDisableLanguageSwitcher(): void {
    $block_id = 'test_language_block';

    // Enable the language switcher block.
    $this->drupalPlaceBlock('language_block:' . LanguageInterface::TYPE_CONTENT, ['id' => $block_id]);

    // Check if the language switcher block has been created.
    $block = Block::load($block_id);
    $this->assertNotEmpty($block, 'Language switcher block was created.');

    // Make sure language_content is not configurable.
    $edit = [
      'language_content[configurable]' => FALSE,
    ];
    $this->drupalGet('admin/config/regional/language/detection');
    $this->submitForm($edit, 'Save settings');
    $this->assertSession()->statusCodeEquals(200);

    // Check if the language switcher block has been removed.
    $block = Block::load($block_id);
    $this->assertNull($block, 'Language switcher block was removed.');
  }

}