view core/tests/Drupal/Tests/BrowserTestBase.php @ 16:c2387f117808

Routine composer update

<?php

namespace Drupal\Tests;

use Behat\Mink\Driver\GoutteDriver;
use Behat\Mink\Element\Element;
use Behat\Mink\Mink;
use Behat\Mink\Selector\SelectorsHandler;
use Behat\Mink\Session;
use Drupal\Component\Render\FormattableMarkup;
use Drupal\Component\Serialization\Json;
use Drupal\Component\Utility\Html;
use Drupal\Component\Utility\UrlHelper;
use Drupal\Core\Database\Database;
use Drupal\Core\Session\AccountInterface;
use Drupal\Core\Session\AnonymousUserSession;
use Drupal\Core\Test\FunctionalTestSetupTrait;
use Drupal\Core\Test\TestSetupTrait;
use Drupal\Core\Url;
use Drupal\Core\Utility\Error;
use Drupal\FunctionalTests\AssertLegacyTrait;
use Drupal\Tests\block\Traits\BlockCreationTrait;
use Drupal\Tests\node\Traits\ContentTypeCreationTrait;
use Drupal\Tests\node\Traits\NodeCreationTrait;
use Drupal\Tests\user\Traits\UserCreationTrait;
use PHPUnit\Framework\TestCase;
use Psr\Http\Message\RequestInterface;
use Psr\Http\Message\ResponseInterface;
use Symfony\Component\CssSelector\CssSelectorConverter;

/**
 * Provides a test case for functional Drupal tests.
 *
 * Tests extending BrowserTestBase must exist in the
 * Drupal\Tests\yourmodule\Functional namespace and live in the
 * modules/yourmodule/tests/src/Functional directory.
 *
 * Tests extending this base class should only translate text when testing
 * translation functionality. For example, avoid wrapping test text with t()
 * or TranslatableMarkup().
 *
 * @ingroup testing
 */
abstract class BrowserTestBase extends TestCase {

  use FunctionalTestSetupTrait;
  use TestSetupTrait;
  use AssertHelperTrait;
  use BlockCreationTrait {
    placeBlock as drupalPlaceBlock;
  }
  use AssertLegacyTrait;
  use RandomGeneratorTrait;
  use SessionTestTrait;
  use NodeCreationTrait {
    getNodeByTitle as drupalGetNodeByTitle;
    createNode as drupalCreateNode;
  }
  use ContentTypeCreationTrait {
    createContentType as drupalCreateContentType;
  }
  use ConfigTestTrait;
  use TestRequirementsTrait;
  use UserCreationTrait {
    createRole as drupalCreateRole;
    createUser as drupalCreateUser;
  }
  use XdebugRequestTrait;
  use PhpunitCompatibilityTrait;

  /**
   * The database prefix of this test run.
   *
   * @var string
   */
  protected $databasePrefix;

  /**
   * Time limit in seconds for the test.
   *
   * @var int
   */
  protected $timeLimit = 500;

  /**
   * The translation file directory for the test environment.
   *
   * This is set in BrowserTestBase::prepareEnvironment().
   *
   * @var string
   */
  protected $translationFilesDirectory;

  /**
   * The config importer that can be used in a test.
   *
   * @var \Drupal\Core\Config\ConfigImporter
   */
  protected $configImporter;

  /**
   * Modules to enable.
   *
   * The test runner will merge the $modules lists from this class, the class
   * it extends, and so on up the class hierarchy. It is not necessary to
   * include modules in your list that a parent class has already declared.
   *
   * @var string[]
   *
   * @see \Drupal\Tests\BrowserTestBase::installDrupal()
   */
  protected static $modules = [];

  /**
   * The profile to install as a basis for testing.
   *
   * @var string
   */
  protected $profile = 'testing';

  /**
   * The current user logged in using the Mink controlled browser.
   *
   * @var \Drupal\user\UserInterface
   */
  protected $loggedInUser = FALSE;

  /**
   * An array of custom translations suitable for drupal_rewrite_settings().
   *
   * @var array
   */
  protected $customTranslations;

  /*
   * Mink class for the default driver to use.
   *
   * Shoud be a fully qualified class name that implements
   * Behat\Mink\Driver\DriverInterface.
   *
   * Value can be overridden using the environment variable MINK_DRIVER_CLASS.
   *
   * @var string.
   */
  protected $minkDefaultDriverClass = GoutteDriver::class;

  /*
   * Mink default driver params.
   *
   * If it's an array its contents are used as constructor params when default
   * Mink driver class is instantiated.
   *
   * Can be overridden using the environment variable MINK_DRIVER_ARGS. In this
   * case that variable should be a JSON array, for example:
   * '["firefox", null, "http://localhost:4444/wd/hub"]'.
   *
   *
   * @var array
   */
  protected $minkDefaultDriverArgs;

  /**
   * Mink session manager.
   *
   * This will not be initialized if there was an error during the test setup.
   *
   * @var \Behat\Mink\Mink|null
   */
  protected $mink;

  /**
   * {@inheritdoc}
   *
   * Browser tests are run in separate processes to prevent collisions between
   * code that may be loaded by tests.
   */
  protected $runTestInSeparateProcess = TRUE;

  /**
   * {@inheritdoc}
   */
  protected $preserveGlobalState = FALSE;

  /**
   * Class name for HTML output logging.
   *
   * @var string
   */
  protected $htmlOutputClassName;

  /**
   * Directory name for HTML output logging.
   *
   * @var string
   */
  protected $htmlOutputDirectory;

  /**
   * Counter storage for HTML output logging.
   *
   * @var string
   */
  protected $htmlOutputCounterStorage;

  /**
   * Counter for HTML output logging.
   *
   * @var int
   */
  protected $htmlOutputCounter = 1;

  /**
   * HTML output output enabled.
   *
   * @var bool
   */
  protected $htmlOutputEnabled = FALSE;

  /**
   * The file name to write the list of URLs to.
   *
   * This file is read by the PHPUnit result printer.
   *
   * @var string
   *
   * @see \Drupal\Tests\Listeners\HtmlOutputPrinter
   */
  protected $htmlOutputFile;

  /**
   * HTML output test ID.
   *
   * @var int
   */
  protected $htmlOutputTestId;

  /**
   * The base URL.
   *
   * @var string
   */
  protected $baseUrl;

  /**
   * The original array of shutdown function callbacks.
   *
   * @var array
   */
  protected $originalShutdownCallbacks = [];

  /**
   * The number of meta refresh redirects to follow, or NULL if unlimited.
   *
   * @var null|int
   */
  protected $maximumMetaRefreshCount = NULL;

  /**
   * The number of meta refresh redirects followed during ::drupalGet().
   *
   * @var int
   */
  protected $metaRefreshCount = 0;

  /**
   * The app root.
   *
   * @var string
   */
  protected $root;

  /**
   * The original container.
   *
   * Move this to \Drupal\Core\Test\FunctionalTestSetupTrait once TestBase no
   * longer provides the same value.
   *
   * @var \Symfony\Component\DependencyInjection\ContainerInterface
   */
  protected $originalContainer;

  /**
   * {@inheritdoc}
   */
  public function __construct($name = NULL, array $data = [], $dataName = '') {
    parent::__construct($name, $data, $dataName);

    $this->root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
  }

  /**
   * Initializes Mink sessions.
   */
  protected function initMink() {
    $driver = $this->getDefaultDriverInstance();

    if ($driver instanceof GoutteDriver) {
      // Turn off curl timeout. Having a timeout is not a problem in a normal
      // test running, but it is a problem when debugging. Also, disable SSL
      // peer verification so that testing under HTTPS always works.
      /** @var \GuzzleHttp\Client $client */
      $client = $this->container->get('http_client_factory')->fromOptions([
        'timeout' => NULL,
        'verify' => FALSE,
      ]);

      // Inject a Guzzle middleware to generate debug output for every request
      // performed in the test.
      $handler_stack = $client->getConfig('handler');
      $handler_stack->push($this->getResponseLogHandler());

      $driver->getClient()->setClient($client);
    }

    $selectors_handler = new SelectorsHandler([
      'hidden_field_selector' => new HiddenFieldSelector()
    ]);
    $session = new Session($driver, $selectors_handler);
    $this->mink = new Mink();
    $this->mink->registerSession('default', $session);
    $this->mink->setDefaultSessionName('default');
    $this->registerSessions();

    $this->initFrontPage();

    return $session;
  }

  /**
   * Visits the front page when initializing Mink.
   *
   * According to the W3C WebDriver specification a cookie can only be set if
   * the cookie domain is equal to the domain of the active document. When the
   * browser starts up the active document is not our domain but 'about:blank'
   * or similar. To be able to set our User-Agent and Xdebug cookies at the
   * start of the test we now do a request to the front page so the active
   * document matches the domain.
   *
   * @see https://w3c.github.io/webdriver/webdriver-spec.html#add-cookie
   * @see https://www.w3.org/Bugs/Public/show_bug.cgi?id=20975
   */
  protected function initFrontPage() {
    $session = $this->getSession();
    $session->visit($this->baseUrl);
  }

  /**
   * Gets an instance of the default Mink driver.
   *
   * @return Behat\Mink\Driver\DriverInterface
   *   Instance of default Mink driver.
   *
   * @throws \InvalidArgumentException
   *   When provided default Mink driver class can't be instantiated.
   */
  protected function getDefaultDriverInstance() {
    // Get default driver params from environment if available.
    if ($arg_json = $this->getMinkDriverArgs()) {
      $this->minkDefaultDriverArgs = json_decode($arg_json, TRUE);
    }

    // Get and check default driver class from environment if available.
    if ($minkDriverClass = getenv('MINK_DRIVER_CLASS')) {
      if (class_exists($minkDriverClass)) {
        $this->minkDefaultDriverClass = $minkDriverClass;
      }
      else {
        throw new \InvalidArgumentException("Can't instantiate provided $minkDriverClass class by environment as default driver class.");
      }
    }

    if (is_array($this->minkDefaultDriverArgs)) {
      // Use ReflectionClass to instantiate class with received params.
      $reflector = new \ReflectionClass($this->minkDefaultDriverClass);
      $driver = $reflector->newInstanceArgs($this->minkDefaultDriverArgs);
    }
    else {
      $driver = new $this->minkDefaultDriverClass();
    }
    return $driver;
  }

  /**
   * Creates the directory to store browser output.
   *
   * Creates the directory to store browser output in if a file to write
   * URLs to has been created by \Drupal\Tests\Listeners\HtmlOutputPrinter.
   */
  protected function initBrowserOutputFile() {
    $browser_output_file = getenv('BROWSERTEST_OUTPUT_FILE');
    $this->htmlOutputEnabled = is_file($browser_output_file);
    if ($this->htmlOutputEnabled) {
      $this->htmlOutputFile = $browser_output_file;
      $this->htmlOutputClassName = str_replace("\\", "_", get_called_class());
      $this->htmlOutputDirectory = DRUPAL_ROOT . '/sites/simpletest/browser_output';
      if (file_prepare_directory($this->htmlOutputDirectory, FILE_CREATE_DIRECTORY) && !file_exists($this->htmlOutputDirectory . '/.htaccess')) {
        file_put_contents($this->htmlOutputDirectory . '/.htaccess', "<IfModule mod_expires.c>\nExpiresActive Off\n</IfModule>\n");
      }
      $this->htmlOutputCounterStorage = $this->htmlOutputDirectory . '/' . $this->htmlOutputClassName . '.counter';
      $this->htmlOutputTestId = str_replace('sites/simpletest/', '', $this->siteDirectory);
      if (is_file($this->htmlOutputCounterStorage)) {
        $this->htmlOutputCounter = max(1, (int) file_get_contents($this->htmlOutputCounterStorage)) + 1;
      }
    }
  }

  /**
   * Get the Mink driver args from an environment variable, if it is set. Can
   * be overridden in a derived class so it is possible to use a different
   * value for a subset of tests, e.g. the JavaScript tests.
   *
   *  @return string|false
   *   The JSON-encoded argument string. False if it is not set.
   */
  protected function getMinkDriverArgs() {
    return getenv('MINK_DRIVER_ARGS');
  }

  /**
   * Provides a Guzzle middleware handler to log every response received.
   *
   * @return callable
   *   The callable handler that will do the logging.
   */
  protected function getResponseLogHandler() {
    return function (callable $handler) {
      return function (RequestInterface $request, array $options) use ($handler) {
        return $handler($request, $options)
          ->then(function (ResponseInterface $response) use ($request) {
            if ($this->htmlOutputEnabled) {

              $caller = $this->getTestMethodCaller();
              $html_output = 'Called from ' . $caller['function'] . ' line ' . $caller['line'];
              $html_output .= '<hr />' . $request->getMethod() . ' request to: ' . $request->getUri();

              // On redirect responses (status code starting with '3') we need
              // to remove the meta tag that would do a browser refresh. We
              // don't want to redirect developers away when they look at the
              // debug output file in their browser.
              $body = $response->getBody();
              $status_code = (string) $response->getStatusCode();
              if ($status_code[0] === '3') {
                $body = preg_replace('#<meta http-equiv="refresh" content=.+/>#', '', $body, 1);
              }
              $html_output .= '<hr />' . $body;
              $html_output .= $this->formatHtmlOutputHeaders($response->getHeaders());

              $this->htmlOutput($html_output);
            }
            return $response;
          });
      };
    };
  }

  /**
   * Registers additional Mink sessions.
   *
   * Tests wishing to use a different driver or change the default driver should
   * override this method.
   *
   * @code
   *   // Register a new session that uses the MinkPonyDriver.
   *   $pony = new MinkPonyDriver();
   *   $session = new Session($pony);
   *   $this->mink->registerSession('pony', $session);
   * @endcode
   */
  protected function registerSessions() {}

  /**
   * {@inheritdoc}
   */
  protected function setUp() {
    // Installing Drupal creates 1000s of objects. Garbage collection of these
    // objects is expensive. This appears to be causing random segmentation
    // faults in PHP 5.x due to https://bugs.php.net/bug.php?id=72286. Once
    // Drupal is installed is rebuilt, garbage collection is re-enabled.
    $disable_gc = version_compare(PHP_VERSION, '7', '<') && gc_enabled();
    if ($disable_gc) {
      gc_collect_cycles();
      gc_disable();
    }
    parent::setUp();

    $this->setupBaseUrl();

    // Install Drupal test site.
    $this->prepareEnvironment();
    $this->installDrupal();

    // Setup Mink.
    $session = $this->initMink();

    $cookies = $this->extractCookiesFromRequest(\Drupal::request());
    foreach ($cookies as $cookie_name => $values) {
      foreach ($values as $value) {
        $session->setCookie($cookie_name, $value);
      }
    }

    // Set up the browser test output file.
    $this->initBrowserOutputFile();
    // If garbage collection was disabled prior to rebuilding container,
    // re-enable it.
    if ($disable_gc) {
      gc_enable();
    }

    // Ensure that the test is not marked as risky because of no assertions. In
    // PHPUnit 6 tests that only make assertions using $this->assertSession()
    // can be marked as risky.
    $this->addToAssertionCount(1);
  }

  /**
   * Ensures test files are deletable within file_unmanaged_delete_recursive().
   *
   * Some tests chmod generated files to be read only. During
   * BrowserTestBase::cleanupEnvironment() and other cleanup operations,
   * these files need to get deleted too.
   *
   * @param string $path
   *   The file path.
   */
  public static function filePreDeleteCallback($path) {
    // When the webserver runs with the same system user as phpunit, we can
    // make read-only files writable again. If not, chmod will fail while the
    // file deletion still works if file permissions have been configured
    // correctly. Thus, we ignore any problems while running chmod.
    @chmod($path, 0700);
  }

  /**
   * Clean up the Simpletest environment.
   */
  protected function cleanupEnvironment() {
    // Remove all prefixed tables.
    $original_connection_info = Database::getConnectionInfo('simpletest_original_default');
    $original_prefix = $original_connection_info['default']['prefix']['default'];
    $test_connection_info = Database::getConnectionInfo('default');
    $test_prefix = $test_connection_info['default']['prefix']['default'];
    if ($original_prefix != $test_prefix) {
      $tables = Database::getConnection()->schema()->findTables('%');
      foreach ($tables as $table) {
        if (Database::getConnection()->schema()->dropTable($table)) {
          unset($tables[$table]);
        }
      }
    }

    // Delete test site directory.
    file_unmanaged_delete_recursive($this->siteDirectory, [$this, 'filePreDeleteCallback']);
  }

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

    // Destroy the testing kernel.
    if (isset($this->kernel)) {
      $this->cleanupEnvironment();
      $this->kernel->shutdown();
    }

    // Ensure that internal logged in variable is reset.
    $this->loggedInUser = FALSE;

    if ($this->mink) {
      $this->mink->stopSessions();
    }

    // Restore original shutdown callbacks.
    if (function_exists('drupal_register_shutdown_function')) {
      $callbacks = &drupal_register_shutdown_function();
      $callbacks = $this->originalShutdownCallbacks;
    }
  }

  /**
   * Returns Mink session.
   *
   * @param string $name
   *   (optional) Name of the session. Defaults to the active session.
   *
   * @return \Behat\Mink\Session
   *   The active Mink session object.
   */
  public function getSession($name = NULL) {
    return $this->mink->getSession($name);
  }

  /**
   * Obtain the HTTP client for the system under test.
   *
   * Use this method for arbitrary HTTP requests to the site under test. For
   * most tests, you should not get the HTTP client and instead use navigation
   * methods such as drupalGet() and clickLink() in order to benefit from
   * assertions.
   *
   * Subclasses which substitute a different Mink driver should override this
   * method and provide a Guzzle client if the Mink driver provides one.
   *
   * @return \GuzzleHttp\ClientInterface
   *   The client with BrowserTestBase configuration.
   *
   * @throws \RuntimeException
   *   If the Mink driver does not support a Guzzle HTTP client, throw an
   *   exception.
   */
  protected function getHttpClient() {
    /* @var $mink_driver \Behat\Mink\Driver\DriverInterface */
    $mink_driver = $this->getSession()->getDriver();
    if ($mink_driver instanceof GoutteDriver) {
      return $mink_driver->getClient()->getClient();
    }
    throw new \RuntimeException('The Mink client type ' . get_class($mink_driver) . ' does not support getHttpClient().');
  }

  /**
   * Returns WebAssert object.
   *
   * @param string $name
   *   (optional) Name of the session. Defaults to the active session.
   *
   * @return \Drupal\Tests\WebAssert
   *   A new web-assert option for asserting the presence of elements with.
   */
  public function assertSession($name = NULL) {
    $this->addToAssertionCount(1);
    return new WebAssert($this->getSession($name), $this->baseUrl);
  }

  /**
   * Prepare for a request to testing site.
   *
   * The testing site is protected via a SIMPLETEST_USER_AGENT cookie that is
   * checked by drupal_valid_test_ua().
   *
   * @see drupal_valid_test_ua()
   */
  protected function prepareRequest() {
    $session = $this->getSession();
    $session->setCookie('SIMPLETEST_USER_AGENT', drupal_generate_test_ua($this->databasePrefix));
  }

  /**
   * Builds an a absolute URL from a system path or a URL object.
   *
   * @param string|\Drupal\Core\Url $path
   *   A system path or a URL.
   * @param array $options
   *   Options to be passed to Url::fromUri().
   *
   * @return string
   *   An absolute URL stsring.
   */
  protected function buildUrl($path, array $options = []) {
    if ($path instanceof Url) {
      $url_options = $path->getOptions();
      $options = $url_options + $options;
      $path->setOptions($options);
      return $path->setAbsolute()->toString();
    }
    // The URL generator service is not necessarily available yet; e.g., in
    // interactive installer tests.
    elseif ($this->container->has('url_generator')) {
      $force_internal = isset($options['external']) && $options['external'] == FALSE;
      if (!$force_internal && UrlHelper::isExternal($path)) {
        return Url::fromUri($path, $options)->toString();
      }
      else {
        $uri = $path === '<front>' ? 'base:/' : 'base:/' . $path;
        // Path processing is needed for language prefixing.  Skip it when a
        // path that may look like an external URL is being used as internal.
        $options['path_processing'] = !$force_internal;
        return Url::fromUri($uri, $options)
          ->setAbsolute()
          ->toString();
      }
    }
    else {
      return $this->getAbsoluteUrl($path);
    }
  }

  /**
   * Retrieves a Drupal path or an absolute path.
   *
   * @param string|\Drupal\Core\Url $path
   *   Drupal path or URL to load into Mink controlled browser.
   * @param array $options
   *   (optional) Options to be forwarded to the url generator.
   * @param string[] $headers
   *   An array containing additional HTTP request headers, the array keys are
   *   the header names and the array values the header values. This is useful
   *   to set for example the "Accept-Language" header for requesting the page
   *   in a different language. Note that not all headers are supported, for
   *   example the "Accept" header is always overridden by the browser. For
   *   testing REST APIs it is recommended to obtain a separate HTTP client
   *   using getHttpClient() and performing requests that way.
   *
   * @return string
   *   The retrieved HTML string, also available as $this->getRawContent()
   *
   * @see \Drupal\Tests\BrowserTestBase::getHttpClient()
   */
  protected function drupalGet($path, array $options = [], array $headers = []) {
    $options['absolute'] = TRUE;
    $url = $this->buildUrl($path, $options);

    $session = $this->getSession();

    $this->prepareRequest();
    foreach ($headers as $header_name => $header_value) {
      $session->setRequestHeader($header_name, $header_value);
    }

    $session->visit($url);
    $out = $session->getPage()->getContent();

    // Ensure that any changes to variables in the other thread are picked up.
    $this->refreshVariables();

    // Replace original page output with new output from redirected page(s).
    if ($new = $this->checkForMetaRefresh()) {
      $out = $new;
      // We are finished with all meta refresh redirects, so reset the counter.
      $this->metaRefreshCount = 0;
    }

    // Log only for JavascriptTestBase tests because for Goutte we log with
    // ::getResponseLogHandler.
    if ($this->htmlOutputEnabled && !($this->getSession()->getDriver() instanceof GoutteDriver)) {
      $html_output = 'GET request to: ' . $url .
        '<hr />Ending URL: ' . $this->getSession()->getCurrentUrl();
      $html_output .= '<hr />' . $out;
      $html_output .= $this->getHtmlOutputHeaders();
      $this->htmlOutput($html_output);
    }

    return $out;
  }

  /**
   * Takes a path and returns an absolute path.
   *
   * @param string $path
   *   A path from the Mink controlled browser content.
   *
   * @return string
   *   The $path with $base_url prepended, if necessary.
   */
  protected function getAbsoluteUrl($path) {
    global $base_url, $base_path;

    $parts = parse_url($path);
    if (empty($parts['host'])) {
      // Ensure that we have a string (and no xpath object).
      $path = (string) $path;
      // Strip $base_path, if existent.
      $length = strlen($base_path);
      if (substr($path, 0, $length) === $base_path) {
        $path = substr($path, $length);
      }
      // Ensure that we have an absolute path.
      if (empty($path) || $path[0] !== '/') {
        $path = '/' . $path;
      }
      // Finally, prepend the $base_url.
      $path = $base_url . $path;
    }
    return $path;
  }

  /**
   * Logs in a user using the Mink controlled browser.
   *
   * If a user is already logged in, then the current user is logged out before
   * logging in the specified user.
   *
   * Please note that neither the current user nor the passed-in user object is
   * populated with data of the logged in user. If you need full access to the
   * user object after logging in, it must be updated manually. If you also need
   * access to the plain-text password of the user (set by drupalCreateUser()),
   * e.g. to log in the same user again, then it must be re-assigned manually.
   * For example:
   * @code
   *   // Create a user.
   *   $account = $this->drupalCreateUser(array());
   *   $this->drupalLogin($account);
   *   // Load real user object.
   *   $pass_raw = $account->passRaw;
   *   $account = User::load($account->id());
   *   $account->passRaw = $pass_raw;
   * @endcode
   *
   * @param \Drupal\Core\Session\AccountInterface $account
   *   User object representing the user to log in.
   *
   * @see drupalCreateUser()
   */
  protected function drupalLogin(AccountInterface $account) {
    if ($this->loggedInUser) {
      $this->drupalLogout();
    }

    $this->drupalGet('user/login');
    $this->submitForm([
      'name' => $account->getUsername(),
      'pass' => $account->passRaw,
    ], t('Log in'));

    // @see BrowserTestBase::drupalUserIsLoggedIn()
    $account->sessionId = $this->getSession()->getCookie($this->getSessionName());
    $this->assertTrue($this->drupalUserIsLoggedIn($account), new FormattableMarkup('User %name successfully logged in.', ['%name' => $account->getAccountName()]));

    $this->loggedInUser = $account;
    $this->container->get('current_user')->setAccount($account);
  }

  /**
   * Logs a user out of the Mink controlled browser and confirms.
   *
   * Confirms logout by checking the login page.
   */
  protected function drupalLogout() {
    // Make a request to the logout page, and redirect to the user page, the
    // idea being if you were properly logged out you should be seeing a login
    // screen.
    $assert_session = $this->assertSession();
    $this->drupalGet('user/logout', ['query' => ['destination' => 'user']]);
    $assert_session->fieldExists('name');
    $assert_session->fieldExists('pass');

    // @see BrowserTestBase::drupalUserIsLoggedIn()
    unset($this->loggedInUser->sessionId);
    $this->loggedInUser = FALSE;
    $this->container->get('current_user')->setAccount(new AnonymousUserSession());
  }

  /**
   * Fills and submits a form.
   *
   * @param array $edit
   *   Field data in an associative array. Changes the current input fields
   *   (where possible) to the values indicated.
   *
   *   A checkbox can be set to TRUE to be checked and should be set to FALSE to
   *   be unchecked.
   * @param string $submit
   *   Value of the submit button whose click is to be emulated. For example,
   *   'Save'. The processing of the request depends on this value. For example,
   *   a form may have one button with the value 'Save' and another button with
   *   the value 'Delete', and execute different code depending on which one is
   *   clicked.
   * @param string $form_html_id
   *   (optional) HTML ID of the form to be submitted. On some pages
   *   there are many identical forms, so just using the value of the submit
   *   button is not enough. For example: 'trigger-node-presave-assign-form'.
   *   Note that this is not the Drupal $form_id, but rather the HTML ID of the
   *   form, which is typically the same thing but with hyphens replacing the
   *   underscores.
   */
  protected function submitForm(array $edit, $submit, $form_html_id = NULL) {
    $assert_session = $this->assertSession();

    // Get the form.
    if (isset($form_html_id)) {
      $form = $assert_session->elementExists('xpath', "//form[@id='$form_html_id']");
      $submit_button = $assert_session->buttonExists($submit, $form);
      $action = $form->getAttribute('action');
    }
    else {
      $submit_button = $assert_session->buttonExists($submit);
      $form = $assert_session->elementExists('xpath', './ancestor::form', $submit_button);
      $action = $form->getAttribute('action');
    }

    // Edit the form values.
    foreach ($edit as $name => $value) {
      $field = $assert_session->fieldExists($name, $form);

      // Provide support for the values '1' and '0' for checkboxes instead of
      // TRUE and FALSE.
      // @todo Get rid of supporting 1/0 by converting all tests cases using
      // this to boolean values.
      $field_type = $field->getAttribute('type');
      if ($field_type === 'checkbox') {
        $value = (bool) $value;
      }

      $field->setValue($value);
    }

    // Submit form.
    $this->prepareRequest();
    $submit_button->press();

    // Ensure that any changes to variables in the other thread are picked up.
    $this->refreshVariables();

    // Check if there are any meta refresh redirects (like Batch API pages).
    if ($this->checkForMetaRefresh()) {
      // We are finished with all meta refresh redirects, so reset the counter.
      $this->metaRefreshCount = 0;
    }

    // Log only for JavascriptTestBase tests because for Goutte we log with
    // ::getResponseLogHandler.
    if ($this->htmlOutputEnabled && !($this->getSession()->getDriver() instanceof GoutteDriver)) {
      $out = $this->getSession()->getPage()->getContent();
      $html_output = 'POST request to: ' . $action .
        '<hr />Ending URL: ' . $this->getSession()->getCurrentUrl();
      $html_output .= '<hr />' . $out;
      $html_output .= $this->getHtmlOutputHeaders();
      $this->htmlOutput($html_output);
    }

  }

  /**
   * Executes a form submission.
   *
   * It will be done as usual POST request with Mink.
   *
   * @param \Drupal\Core\Url|string $path
   *   Location of the post form. Either a Drupal path or an absolute path or
   *   NULL to post to the current page. For multi-stage forms you can set the
   *   path to NULL and have it post to the last received page. Example:
   *
   *   @code
   *   // First step in form.
   *   $edit = array(...);
   *   $this->drupalPostForm('some_url', $edit, 'Save');
   *
   *   // Second step in form.
   *   $edit = array(...);
   *   $this->drupalPostForm(NULL, $edit, 'Save');
   *   @endcode
   * @param array $edit
   *   Field data in an associative array. Changes the current input fields
   *   (where possible) to the values indicated.
   *
   *   When working with form tests, the keys for an $edit element should match
   *   the 'name' parameter of the HTML of the form. For example, the 'body'
   *   field for a node has the following HTML:
   *   @code
   *   <textarea id="edit-body-und-0-value" class="text-full form-textarea
   *    resize-vertical" placeholder="" cols="60" rows="9"
   *    name="body[0][value]"></textarea>
   *   @endcode
   *   When testing this field using an $edit parameter, the code becomes:
   *   @code
   *   $edit["body[0][value]"] = 'My test value';
   *   @endcode
   *
   *   A checkbox can be set to TRUE to be checked and should be set to FALSE to
   *   be unchecked. Multiple select fields can be tested using 'name[]' and
   *   setting each of the desired values in an array:
   *   @code
   *   $edit = array();
   *   $edit['name[]'] = array('value1', 'value2');
   *   @endcode
   *   @todo change $edit to disallow NULL as a value for Drupal 9.
   *     https://www.drupal.org/node/2802401
   * @param string $submit
   *   Value of the submit button whose click is to be emulated. For example,
   *   'Save'. The processing of the request depends on this value. For example,
   *   a form may have one button with the value 'Save' and another button with
   *   the value 'Delete', and execute different code depending on which one is
   *   clicked.
   *
   *   This function can also be called to emulate an Ajax submission. In this
   *   case, this value needs to be an array with the following keys:
   *   - path: A path to submit the form values to for Ajax-specific processing.
   *   - triggering_element: If the value for the 'path' key is a generic Ajax
   *     processing path, this needs to be set to the name of the element. If
   *     the name doesn't identify the element uniquely, then this should
   *     instead be an array with a single key/value pair, corresponding to the
   *     element name and value. The \Drupal\Core\Form\FormAjaxResponseBuilder
   *     uses this to find the #ajax information for the element, including
   *     which specific callback to use for processing the request.
   *
   *   This can also be set to NULL in order to emulate an Internet Explorer
   *   submission of a form with a single text field, and pressing ENTER in that
   *   textfield: under these conditions, no button information is added to the
   *   POST data.
   * @param array $options
   *   Options to be forwarded to the url generator.
   *
   * @return string
   *   (deprecated) The response content after submit form. It is necessary for
   *   backwards compatibility and will be removed before Drupal 9.0. You should
   *   just use the webAssert object for your assertions.
   */
  protected function drupalPostForm($path, $edit, $submit, array $options = []) {
    if (is_object($submit)) {
      // Cast MarkupInterface objects to string.
      $submit = (string) $submit;
    }
    if ($edit === NULL) {
      $edit = [];
    }
    if (is_array($edit)) {
      $edit = $this->castSafeStrings($edit);
    }

    if (isset($path)) {
      $this->drupalGet($path, $options);
    }

    $this->submitForm($edit, $submit);

    return $this->getSession()->getPage()->getContent();
  }

  /**
   * Helper function to get the options of select field.
   *
   * @param \Behat\Mink\Element\NodeElement|string $select
   *   Name, ID, or Label of select field to assert.
   * @param \Behat\Mink\Element\Element $container
   *   (optional) Container element to check against. Defaults to current page.
   *
   * @return array
   *   Associative array of option keys and values.
   */
  protected function getOptions($select, Element $container = NULL) {
    if (is_string($select)) {
      $select = $this->assertSession()->selectExists($select, $container);
    }
    $options = [];
    /* @var \Behat\Mink\Element\NodeElement $option */
    foreach ($select->findAll('xpath', '//option') as $option) {
      $label = $option->getText();
      $value = $option->getAttribute('value') ?: $label;
      $options[$value] = $label;
    }
    return $options;
  }

  /**
   * Installs Drupal into the Simpletest site.
   */
  public function installDrupal() {
    $this->initUserSession();
    $this->prepareSettings();
    $this->doInstall();
    $this->initSettings();
    $container = $this->initKernel(\Drupal::request());
    $this->initConfig($container);
    $this->installModulesFromClassProperty($container);
    $this->rebuildAll();
  }

  /**
   * Returns whether a given user account is logged in.
   *
   * @param \Drupal\Core\Session\AccountInterface $account
   *   The user account object to check.
   *
   * @return bool
   *   Return TRUE if the user is logged in, FALSE otherwise.
   */
  protected function drupalUserIsLoggedIn(AccountInterface $account) {
    $logged_in = FALSE;

    if (isset($account->sessionId)) {
      $session_handler = $this->container->get('session_handler.storage');
      $logged_in = (bool) $session_handler->read($account->sessionId);
    }

    return $logged_in;
  }

  /**
   * Clicks the element with the given CSS selector.
   *
   * @param string $css_selector
   *   The CSS selector identifying the element to click.
   */
  protected function click($css_selector) {
    $this->getSession()->getDriver()->click($this->cssSelectToXpath($css_selector));
  }

  /**
   * Prevents serializing any properties.
   *
   * Browser tests are run in a separate process. To do this PHPUnit creates a
   * script to run the test. If it fails, the test result object will contain a
   * stack trace which includes the test object. It will attempt to serialize
   * it. Returning an empty array prevents it from serializing anything it
   * should not.
   *
   * @return array
   *   An empty array.
   *
   * @see vendor/phpunit/phpunit/src/Util/PHP/Template/TestCaseMethod.tpl.dist
   */
  public function __sleep() {
    return [];
  }

  /**
   * Logs a HTML output message in a text file.
   *
   * The link to the HTML output message will be printed by the results printer.
   *
   * @param string $message
   *   The HTML output message to be stored.
   *
   * @see \Drupal\Tests\Listeners\VerbosePrinter::printResult()
   */
  protected function htmlOutput($message) {
    if (!$this->htmlOutputEnabled) {
      return;
    }
    $message = '<hr />ID #' . $this->htmlOutputCounter . ' (<a href="' . $this->htmlOutputClassName . '-' . ($this->htmlOutputCounter - 1) . '-' . $this->htmlOutputTestId . '.html">Previous</a> | <a href="' . $this->htmlOutputClassName . '-' . ($this->htmlOutputCounter + 1) . '-' . $this->htmlOutputTestId . '.html">Next</a>)<hr />' . $message;
    $html_output_filename = $this->htmlOutputClassName . '-' . $this->htmlOutputCounter . '-' . $this->htmlOutputTestId . '.html';
    file_put_contents($this->htmlOutputDirectory . '/' . $html_output_filename, $message);
    file_put_contents($this->htmlOutputCounterStorage, $this->htmlOutputCounter++);
    file_put_contents($this->htmlOutputFile, file_create_url('sites/simpletest/browser_output/' . $html_output_filename) . "\n", FILE_APPEND);
  }

  /**
   * Returns headers in HTML output format.
   *
   * @return string
   *   HTML output headers.
   */
  protected function getHtmlOutputHeaders() {
    return $this->formatHtmlOutputHeaders($this->getSession()->getResponseHeaders());
  }

  /**
   * Formats HTTP headers as string for HTML output logging.
   *
   * @param array[] $headers
   *   Headers that should be formatted.
   *
   * @return string
   *   The formatted HTML string.
   */
  protected function formatHtmlOutputHeaders(array $headers) {
    $flattened_headers = array_map(function ($header) {
      if (is_array($header)) {
        return implode(';', array_map('trim', $header));
      }
      else {
        return $header;
      }
    }, $headers);
    return '<hr />Headers: <pre>' . Html::escape(var_export($flattened_headers, TRUE)) . '</pre>';
  }

  /**
   * Translates a CSS expression to its XPath equivalent.
   *
   * The search is relative to the root element (HTML tag normally) of the page.
   *
   * @param string $selector
   *   CSS selector to use in the search.
   * @param bool $html
   *   (optional) Enables HTML support. Disable it for XML documents.
   * @param string $prefix
   *   (optional) The prefix for the XPath expression.
   *
   * @return string
   *   The equivalent XPath of a CSS expression.
   */
  protected function cssSelectToXpath($selector, $html = TRUE, $prefix = 'descendant-or-self::') {
    return (new CssSelectorConverter($html))->toXPath($selector, $prefix);
  }

  /**
   * Searches elements using a CSS selector in the raw content.
   *
   * The search is relative to the root element (HTML tag normally) of the page.
   *
   * @param string $selector
   *   CSS selector to use in the search.
   *
   * @return \Behat\Mink\Element\NodeElement[]
   *   The list of elements on the page that match the selector.
   */
  protected function cssSelect($selector) {
    return $this->getSession()->getPage()->findAll('css', $selector);
  }

  /**
   * Follows a link by complete name.
   *
   * Will click the first link found with this link text.
   *
   * If the link is discovered and clicked, the test passes. Fail otherwise.
   *
   * @param string|\Drupal\Component\Render\MarkupInterface $label
   *   Text between the anchor tags.
   * @param int $index
   *   (optional) The index number for cases where multiple links have the same
   *   text. Defaults to 0.
   */
  protected function clickLink($label, $index = 0) {
    $label = (string) $label;
    $links = $this->getSession()->getPage()->findAll('named', ['link', $label]);
    $this->assertArrayHasKey($index, $links, 'The link ' . $label . ' was not found on the page.');
    $links[$index]->click();
  }

  /**
   * Retrieves the plain-text content from the current page.
   */
  protected function getTextContent() {
    return $this->getSession()->getPage()->getText();
  }

  /**
   * Performs an xpath search on the contents of the internal browser.
   *
   * The search is relative to the root element (HTML tag normally) of the page.
   *
   * @param string $xpath
   *   The xpath string to use in the search.
   * @param array $arguments
   *   An array of arguments with keys in the form ':name' matching the
   *   placeholders in the query. The values may be either strings or numeric
   *   values.
   *
   * @return \Behat\Mink\Element\NodeElement[]
   *   The list of elements matching the xpath expression.
   */
  protected function xpath($xpath, array $arguments = []) {
    $xpath = $this->assertSession()->buildXPathQuery($xpath, $arguments);
    return $this->getSession()->getPage()->findAll('xpath', $xpath);
  }

  /**
   * Configuration accessor for tests. Returns non-overridden configuration.
   *
   * @param string $name
   *   Configuration name.
   *
   * @return \Drupal\Core\Config\Config
   *   The configuration object with original configuration data.
   */
  protected function config($name) {
    return $this->container->get('config.factory')->getEditable($name);
  }

  /**
   * Returns all response headers.
   *
   * @return array
   *   The HTTP headers values.
   *
   * @deprecated Scheduled for removal in Drupal 9.0.0.
   *   Use $this->getSession()->getResponseHeaders() instead.
   */
  protected function drupalGetHeaders() {
    return $this->getSession()->getResponseHeaders();
  }

  /**
   * Gets the value of an HTTP response header.
   *
   * If multiple requests were required to retrieve the page, only the headers
   * from the last request will be checked by default.
   *
   * @param string $name
   *   The name of the header to retrieve. Names are case-insensitive (see RFC
   *   2616 section 4.2).
   *
   * @return string|null
   *   The HTTP header value or NULL if not found.
   */
  protected function drupalGetHeader($name) {
    return $this->getSession()->getResponseHeader($name);
  }

  /**
   * Get the current URL from the browser.
   *
   * @return string
   *   The current URL.
   */
  protected function getUrl() {
    return $this->getSession()->getCurrentUrl();
  }

  /**
   * Gets the JavaScript drupalSettings variable for the currently-loaded page.
   *
   * @return array
   *   The JSON decoded drupalSettings value from the current page.
   */
  protected function getDrupalSettings() {
    $html = $this->getSession()->getPage()->getHtml();
    if (preg_match('@<script type="application/json" data-drupal-selector="drupal-settings-json">([^<]*)</script>@', $html, $matches)) {
      return Json::decode($matches[1]);
    }
    return [];
  }

  /**
   * {@inheritdoc}
   */
  public static function assertEquals($expected, $actual, $message = '', $delta = 0.0, $maxDepth = 10, $canonicalize = FALSE, $ignoreCase = FALSE) {
    // Cast objects implementing MarkupInterface to string instead of
    // relying on PHP casting them to string depending on what they are being
    // comparing with.
    $expected = static::castSafeStrings($expected);
    $actual = static::castSafeStrings($actual);
    parent::assertEquals($expected, $actual, $message, $delta, $maxDepth, $canonicalize, $ignoreCase);
  }

  /**
   * Retrieves the current calling line in the class under test.
   *
   * @return array
   *   An associative array with keys 'file', 'line' and 'function'.
   */
  protected function getTestMethodCaller() {
    $backtrace = debug_backtrace();
    // Find the test class that has the test method.
    while ($caller = Error::getLastCaller($backtrace)) {
      if (isset($caller['class']) && $caller['class'] === get_class($this)) {
        break;
      }
      // If the test method is implemented by a test class's parent then the
      // class name of $this will not be part of the backtrace.
      // In that case we process the backtrace until the caller is not a
      // subclass of $this and return the previous caller.
      if (isset($last_caller) && (!isset($caller['class']) || !is_subclass_of($this, $caller['class']))) {
        // Return the last caller since that has to be the test class.
        $caller = $last_caller;
        break;
      }
      // Otherwise we have not reached our test class yet: save the last caller
      // and remove an element from to backtrace to process the next call.
      $last_caller = $caller;
      array_shift($backtrace);
    }

    return $caller;
  }

  /**
   * Transforms a nested array into a flat array suitable for drupalPostForm().
   *
   * @param array $values
   *   A multi-dimensional form values array to convert.
   *
   * @return array
   *   The flattened $edit array suitable for BrowserTestBase::drupalPostForm().
   */
  protected function translatePostValues(array $values) {
    $edit = [];
    // The easiest and most straightforward way to translate values suitable for
    // BrowserTestBase::drupalPostForm() is to actually build the POST data
    // string and convert the resulting key/value pairs back into a flat array.
    $query = http_build_query($values);
    foreach (explode('&', $query) as $item) {
      list($key, $value) = explode('=', $item);
      $edit[urldecode($key)] = urldecode($value);
    }
    return $edit;
  }

  /**
   * Checks for meta refresh tag and if found call drupalGet() recursively.
   *
   * This function looks for the http-equiv attribute to be set to "Refresh" and
   * is case-insensitive.
   *
   * @return string|false
   *   Either the new page content or FALSE.
   */
  protected function checkForMetaRefresh() {
    $refresh = $this->cssSelect('meta[http-equiv="Refresh"], meta[http-equiv="refresh"]');
    if (!empty($refresh) && (!isset($this->maximumMetaRefreshCount) || $this->metaRefreshCount < $this->maximumMetaRefreshCount)) {
      // Parse the content attribute of the meta tag for the format:
      // "[delay]: URL=[page_to_redirect_to]".
      if (preg_match('/\d+;\s*URL=(?<url>.*)/i', $refresh[0]->getAttribute('content'), $match)) {
        $this->metaRefreshCount++;
        return $this->drupalGet($this->getAbsoluteUrl(Html::decodeEntities($match['url'])));
      }
    }
    return FALSE;
  }

}