WebTestBase.php

<?php

/**
 * @file
 * Definition of Drupal\simpletest\WebTestBase.
 */
namespace Drupal\simpletest;

use Drupal\Core\DrupalKernel;
use Drupal\Core\Database\Database;
use Drupal\Core\Database\ConnectionNotDefinedException;
use PDO;
use stdClass;
use DOMDocument;
use DOMXPath;
use SimpleXMLElement;

/**
 * Test case for typical Drupal tests.
 */
abstract class WebTestBase extends TestBase {

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

  /**
   * The URL currently loaded in the internal browser.
   *
   * @var string
   */
  protected $url;

  /**
   * The handle of the current cURL connection.
   *
   * @var resource
   */
  protected $curlHandle;

  /**
   * The headers of the page currently loaded in the internal browser.
   *
   * @var Array
   */
  protected $headers;

  /**
   * The content of the page currently loaded in the internal browser.
   *
   * @var string
   */
  protected $content;

  /**
   * The content of the page currently loaded in the internal browser (plain text version).
   *
   * @var string
   */
  protected $plainTextContent;

  /**
   * The value of the Drupal.settings JavaScript variable for the page currently loaded in the internal browser.
   *
   * @var Array
   */
  protected $drupalSettings;

  /**
   * The parsed version of the page.
   *
   * @var SimpleXMLElement
   */
  protected $elements = NULL;

  /**
   * The current user logged in using the internal browser.
   *
   * @var bool
   */
  protected $loggedInUser = FALSE;

  /**
   * The current cookie file used by cURL.
   *
   * We do not reuse the cookies in further runs, so we do not need a file
   * but we still need cookie handling, so we set the jar to NULL.
   */
  protected $cookieFile = NULL;

  /**
   * Additional cURL options.
   *
   * Drupal\simpletest\WebTestBase itself never sets this but always obeys what is
   * set.
   */
  protected $additionalCurlOptions = array();

  /**
   * The original user, before it was changed to a clean uid = 1 for testing purposes.
   *
   * @var object
   */
  protected $originalUser = NULL;

  /**
   * The original shutdown handlers array, before it was cleaned for testing purposes.
   *
   * @var array
   */
  protected $originalShutdownCallbacks = array();

  /**
   * HTTP authentication method
   */
  protected $httpauth_method = CURLAUTH_BASIC;

  /**
   * HTTP authentication credentials (<username>:<password>).
   */
  protected $httpauth_credentials = NULL;

  /**
   * The current session name, if available.
   */
  protected $session_name = NULL;

  /**
   * The current session ID, if available.
   */
  protected $session_id = NULL;

  /**
   * Whether the files were copied to the test files directory.
   */
  protected $generatedTestFiles = FALSE;

  /**
   * The maximum number of redirects to follow when handling responses.
   */
  protected $maximumRedirects = 5;

  /**
   * The number of redirects followed during the handling of a request.
   */
  protected $redirect_count;

  /**
   * The kernel used in this test.
   */
  protected $kernel;

  /**
   * Constructor for Drupal\simpletest\WebTestBase.
   */
  function __construct($test_id = NULL) {
    parent::__construct($test_id);
    $this->skipClasses[__CLASS__] = TRUE;
  }

  /**
   * Get a node from the database based on its title.
   *
   * @param $title
   *   A node title, usually generated by $this->randomName().
   * @param $reset
   *   (optional) Whether to reset the entity cache.
   *
   * @return
   *   A node entity matching $title.
   */
  function drupalGetNodeByTitle($title, $reset = FALSE) {
    if ($reset) {
      entity_get_controller('node')
        ->resetCache();
    }
    $nodes = entity_load_multiple_by_properties('node', array(
      'title' => $title,
    ));

    // Load the first node returned from the database.
    $returned_node = reset($nodes);
    return $returned_node;
  }

  /**
   * Creates a node based on default settings.
   *
   * @param array $settings
   *   (optional) An associative array of settings for the node, as used in
   *   entity_create(). Override the defaults by specifying the key and value
   *   in the array, for example:
   *   @code
   *     $this->drupalCreateNode(array(
   *       'title' => t('Hello, world!'),
   *       'type' => 'article',
   *     ));
   *   @endcode
   *   The following defaults are provided:
   *   - body: Random string using the default filter format:
   *     @code
   *       $settings['body'][LANGUAGE_NOT_SPECIFIED][0] = array(
   *         'value' => $this->randomName(32),
   *         'format' => filter_default_format(),
   *       );
   *     @endcode
   *   - title: Random string.
   *   - comment: COMMENT_NODE_OPEN.
   *   - changed: REQUEST_TIME.
   *   - promote: NODE_NOT_PROMOTED.
   *   - log: Empty string.
   *   - status: NODE_PUBLISHED.
   *   - sticky: NODE_NOT_STICKY.
   *   - type: 'page'.
   *   - langcode: LANGUAGE_NOT_SPECIFIED. (If a 'langcode' key is provided in
   *     the array, this language code will also be used for a randomly
   *     generated body field for that language, and the body for
   *     LANGUAGE_NOT_SPECIFIED will remain empty.)
   *   - uid: The currently logged in user, or the user running test.
   *   - revision: 1. (Backwards-compatible binary flag indicating whether a
   *     new revision should be created; use 1 to specify a new revision.)
   *
   * @return Drupal\node\Node
   *   The created node entity.
   */
  protected function drupalCreateNode(array $settings = array()) {

    // Populate defaults array.
    $settings += array(
      'body' => array(
        LANGUAGE_NOT_SPECIFIED => array(
          array(),
        ),
      ),
      'title' => $this
        ->randomName(8),
      'changed' => REQUEST_TIME,
      'promote' => NODE_NOT_PROMOTED,
      'revision' => 1,
      'log' => '',
      'status' => NODE_PUBLISHED,
      'sticky' => NODE_NOT_STICKY,
      'type' => 'page',
      'langcode' => LANGUAGE_NOT_SPECIFIED,
    );

    // Add in comment settings for nodes.
    if (module_exists('comment')) {
      $settings += array(
        'comment' => COMMENT_NODE_OPEN,
      );
    }

    // Use the original node's created time for existing nodes.
    if (isset($settings['created']) && !isset($settings['date'])) {
      $settings['date'] = format_date($settings['created'], 'custom', 'Y-m-d H:i:s O');
    }

    // If the node's user uid is not specified manually, use the currently
    // logged in user if available, or else the user running the test.
    if (!isset($settings['uid'])) {
      if ($this->loggedInUser) {
        $settings['uid'] = $this->loggedInUser->uid;
      }
      else {
        global $user;
        $settings['uid'] = $user->uid;
      }
    }

    // Merge body field value and format separately.
    $body = array(
      'value' => $this
        ->randomName(32),
      'format' => filter_default_format(),
    );
    if (empty($settings['body'][$settings['langcode']])) {
      $settings['body'][$settings['langcode']][0] = array();
    }
    $settings['body'][$settings['langcode']][0] += $body;
    $node = entity_create('node', $settings);
    if (!empty($settings['revision'])) {
      $node
        ->setNewRevision();
    }
    $node
      ->save();

    // Small hack to link revisions to our test user.
    db_update('node_revision')
      ->fields(array(
      'uid' => $node->uid,
    ))
      ->condition('vid', $node->vid)
      ->execute();
    return $node;
  }

  /**
   * Creates a custom content type based on default settings.
   *
   * @param $settings
   *   An array of settings to change from the defaults.
   *   Example: 'type' => 'foo'.
   * @return
   *   Created content type.
   */
  protected function drupalCreateContentType($settings = array()) {

    // Find a non-existent random type name.
    do {
      $name = strtolower($this
        ->randomName(8));
    } while (node_type_load($name));

    // Populate defaults array.
    $defaults = array(
      'type' => $name,
      'name' => $name,
      'base' => 'node_content',
      'description' => '',
      'help' => '',
      'title_label' => 'Title',
      'body_label' => 'Body',
      'has_title' => 1,
      'has_body' => 1,
    );

    // Imposed values for a custom type.
    $forced = array(
      'orig_type' => '',
      'old_type' => '',
      'module' => 'node',
      'custom' => 1,
      'modified' => 1,
      'locked' => 0,
    );
    $type = $forced + $settings + $defaults;
    $type = (object) $type;
    $saved_type = node_type_save($type);
    node_types_rebuild();
    menu_router_rebuild();
    node_add_body_field($type);
    $this
      ->assertEqual($saved_type, SAVED_NEW, t('Created content type %type.', array(
      '%type' => $type->type,
    )));

    // Reset permissions so that permissions for this content type are available.
    $this
      ->checkPermissions(array(), TRUE);
    return $type;
  }

  /**
   * Get a list files that can be used in tests.
   *
   * @param $type
   *   File type, possible values: 'binary', 'html', 'image', 'javascript', 'php', 'sql', 'text'.
   * @param $size
   *   File size in bytes to match. Please check the tests/files folder.
   * @return
   *   List of files that match filter.
   */
  protected function drupalGetTestFiles($type, $size = NULL) {
    if (empty($this->generatedTestFiles)) {

      // Generate binary test files.
      $lines = array(
        64,
        1024,
      );
      $count = 0;
      foreach ($lines as $line) {
        simpletest_generate_file('binary-' . $count++, 64, $line, 'binary');
      }

      // Generate text test files.
      $lines = array(
        16,
        256,
        1024,
        2048,
        20480,
      );
      $count = 0;
      foreach ($lines as $line) {
        simpletest_generate_file('text-' . $count++, 64, $line);
      }

      // Copy other test files from simpletest.
      $original = drupal_get_path('module', 'simpletest') . '/files';
      $files = file_scan_directory($original, '/(html|image|javascript|php|sql)-.*/');
      foreach ($files as $file) {
        file_unmanaged_copy($file->uri, variable_get('file_public_path', conf_path() . '/files'));
      }
      $this->generatedTestFiles = TRUE;
    }
    $files = array();

    // Make sure type is valid.
    if (in_array($type, array(
      'binary',
      'html',
      'image',
      'javascript',
      'php',
      'sql',
      'text',
    ))) {
      $files = file_scan_directory('public://', '/' . $type . '\\-.*/');

      // If size is set then remove any files that are not of that size.
      if ($size !== NULL) {
        foreach ($files as $file) {
          $stats = stat($file->uri);
          if ($stats['size'] != $size) {
            unset($files[$file->uri]);
          }
        }
      }
    }
    usort($files, array(
      $this,
      'drupalCompareFiles',
    ));
    return $files;
  }

  /**
   * Compare two files based on size and file name.
   */
  protected function drupalCompareFiles($file1, $file2) {
    $compare_size = filesize($file1->uri) - filesize($file2->uri);
    if ($compare_size) {

      // Sort by file size.
      return $compare_size;
    }
    else {

      // The files were the same size, so sort alphabetically.
      return strnatcmp($file1->name, $file2->name);
    }
  }

  /**
   * Create a user with a given set of permissions.
   *
   * @param array $permissions
   *   Array of permission names to assign to user. Note that the user always
   *   has the default permissions derived from the "authenticated users" role.
   *
   * @return object|false
   *   A fully loaded user object with pass_raw property, or FALSE if account
   *   creation fails.
   */
  protected function drupalCreateUser(array $permissions = array()) {

    // Create a role with the given permission set, if any.
    $rid = FALSE;
    if ($permissions) {
      $rid = $this
        ->drupalCreateRole($permissions);
      if (!$rid) {
        return FALSE;
      }
    }

    // Create a user assigned to that role.
    $edit = array();
    $edit['name'] = $this
      ->randomName();
    $edit['mail'] = $edit['name'] . '@example.com';
    $edit['pass'] = user_password();
    $edit['status'] = 1;
    if ($rid) {
      $edit['roles'] = array(
        $rid => $rid,
      );
    }
    $account = entity_create('user', $edit);
    $account
      ->save();
    $this
      ->assertTrue(!empty($account->uid), t('User created with name %name and pass %pass', array(
      '%name' => $edit['name'],
      '%pass' => $edit['pass'],
    )), t('User login'));
    if (empty($account->uid)) {
      return FALSE;
    }

    // Add the raw password so that we can log in as this user.
    $account->pass_raw = $edit['pass'];
    return $account;
  }

  /**
   * Internal helper function; Create a role with specified permissions.
   *
   * @param array $permissions
   *   Array of permission names to assign to role.
   * @param string $rid
   *   (optional) The role ID (machine name). Defaults to a random name.
   * @param string $name
   *   (optional) The label for the role. Defaults to a random string.
   *
   * @return string
   *   Role ID of newly created role, or FALSE if role creation failed.
   */
  protected function drupalCreateRole(array $permissions, $rid = NULL, $name = NULL) {

    // Generate a random, lowercase machine name if none was passed.
    if (!isset($rid)) {
      $rid = strtolower($this
        ->randomName(8));
    }

    // Generate a random label.
    if (!isset($name)) {
      $name = $this
        ->randomString(8);
    }

    // Check the all the permissions strings are valid.
    if (!$this
      ->checkPermissions($permissions)) {
      return FALSE;
    }

    // Create new role.
    $role = new stdClass();
    $role->rid = $rid;
    $role->name = $name;
    $result = user_role_save($role);
    $this
      ->assertIdentical($result, SAVED_NEW, t('Created role ID @rid with name @name.', array(
      '@name' => var_export($role->name, TRUE),
      '@rid' => var_export($role->rid, TRUE),
    )), t('Role'));
    if ($result === SAVED_NEW) {

      // Grant the specified permissions to the role, if any.
      if (!empty($permissions)) {
        user_role_grant_permissions($role->rid, $permissions);
        $assigned_permissions = db_query('SELECT permission FROM {role_permission} WHERE rid = :rid', array(
          ':rid' => $role->rid,
        ))
          ->fetchCol();
        $missing_permissions = array_diff($permissions, $assigned_permissions);
        if (!$missing_permissions) {
          $this
            ->pass(t('Created permissions: @perms', array(
            '@perms' => implode(', ', $permissions),
          )), t('Role'));
        }
        else {
          $this
            ->fail(t('Failed to create permissions: @perms', array(
            '@perms' => implode(', ', $missing_permissions),
          )), t('Role'));
        }
      }
      return $role->rid;
    }
    else {
      return FALSE;
    }
  }

  /**
   * Check to make sure that the array of permissions are valid.
   *
   * @param $permissions
   *   Permissions to check.
   * @param $reset
   *   Reset cached available permissions.
   * @return
   *   TRUE or FALSE depending on whether the permissions are valid.
   */
  protected function checkPermissions(array $permissions, $reset = FALSE) {
    $available =& drupal_static(__FUNCTION__);
    if (!isset($available) || $reset) {
      $available = array_keys(module_invoke_all('permission'));
    }
    $valid = TRUE;
    foreach ($permissions as $permission) {
      if (!in_array($permission, $available)) {
        $this
          ->fail(t('Invalid permission %permission.', array(
          '%permission' => $permission,
        )), t('Role'));
        $valid = FALSE;
      }
    }
    return $valid;
  }

  /**
   * Log in a user with the internal 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 global $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->pass_raw;
   *   $account = user_load($account->uid);
   *   $account->pass_raw = $pass_raw;
   * @endcode
   *
   * @param $user
   *   User object representing the user to log in.
   *
   * @see drupalCreateUser()
   */
  protected function drupalLogin($user) {
    if ($this->loggedInUser) {
      $this
        ->drupalLogout();
    }
    $edit = array(
      'name' => $user->name,
      'pass' => $user->pass_raw,
    );
    $this
      ->drupalPost('user', $edit, t('Log in'));

    // If a "log out" link appears on the page, it is almost certainly because
    // the login was successful.
    $pass = $this
      ->assertLink(t('Log out'), 0, t('User %name successfully logged in.', array(
      '%name' => $user->name,
    )), t('User login'));
    if ($pass) {
      $this->loggedInUser = $user;
    }
  }

  /**
   * Generate a token for the currently logged in user.
   */
  protected function drupalGetToken($value = '') {
    $private_key = drupal_get_private_key();
    return drupal_hmac_base64($value, $this->session_id . $private_key);
  }

  /*
   * Logs a user out of the internal browser, then check the login page to confirm logout.
   */
  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.
    $this
      ->drupalGet('user/logout', array(
      'query' => array(
        'destination' => 'user',
      ),
    ));
    $this
      ->assertResponse(200, t('User was logged out.'));
    $pass = $this
      ->assertField('name', t('Username field found.'), t('Logout'));
    $pass = $pass && $this
      ->assertField('pass', t('Password field found.'), t('Logout'));
    if ($pass) {
      $this->loggedInUser = FALSE;
    }
  }

  /**
   * Sets up a Drupal site for running functional and integration tests.
   *
   * Generates a random database prefix and installs Drupal with the specified
   * installation profile in Drupal\simpletest\WebTestBase::$profile into the
   * prefixed database. Afterwards, installs any additional modules specified by
   * the test.
   *
   * After installation all caches are flushed and several configuration values
   * are reset to the values of the parent site executing the test, since the
   * default values may be incompatible with the environment in which tests are
   * being executed.
   *
   * @param ...
   *   List of modules to enable for the duration of the test. This can be
   *   either a single array or a variable number of string arguments.
   *
   * @see Drupal\simpletest\WebTestBase::prepareDatabasePrefix()
   * @see Drupal\simpletest\WebTestBase::changeDatabasePrefix()
   * @see Drupal\simpletest\WebTestBase::prepareEnvironment()
   */
  protected function setUp() {
    global $user, $conf;

    // When running tests through the Simpletest UI (vs. on the command line),
    // Simpletest's batch conflicts with the installer's batch. Batch API does
    // not support the concept of nested batches (in which the nested is not
    // progressive), so we need to temporarily pretend there was no batch.
    // Backup the currently running Simpletest batch.
    $this->originalBatch = batch_get();

    // Create the database prefix for this test.
    $this
      ->prepareDatabasePrefix();

    // Prepare the environment for running tests.
    $this
      ->prepareEnvironment();
    if (!$this->setupEnvironment) {
      return FALSE;
    }

    // Reset all statics and variables to perform tests in a clean environment.
    $conf = array();
    drupal_static_reset();

    // Change the database prefix.
    // All static variables need to be reset before the database prefix is
    // changed, since Drupal\Core\Utility\CacheArray implementations attempt to
    // write back to persistent caches when they are destructed.
    $this
      ->changeDatabasePrefix();
    if (!$this->setupDatabasePrefix) {
      return FALSE;
    }

    // Set the 'simpletest_parent_profile' variable to add the parent profile's
    // search path to the child site's search paths.
    // @see drupal_system_listing()
    $conf['simpletest_parent_profile'] = $this->originalProfile;

    // Set installer parameters.
    // @see install.php, install.core.inc
    $connection_info = Database::getConnectionInfo();
    $this->root_user = (object) array(
      'name' => 'admin',
      'mail' => 'admin@example.com',
      'pass_raw' => $this
        ->randomName(),
    );
    $settings = array(
      'interactive' => FALSE,
      'parameters' => array(
        'profile' => $this->profile,
        'langcode' => 'en',
      ),
      'forms' => array(
        'install_settings_form' => $connection_info['default'],
        'install_configure_form' => array(
          'site_name' => 'Drupal',
          'site_mail' => 'simpletest@example.com',
          'account' => array(
            'name' => $this->root_user->name,
            'mail' => $this->root_user->mail,
            'pass' => array(
              'pass1' => $this->root_user->pass_raw,
              'pass2' => $this->root_user->pass_raw,
            ),
          ),
          // form_type_checkboxes_value() requires NULL instead of FALSE values
          // for programmatic form submissions to disable a checkbox.
          'update_status_module' => array(
            1 => NULL,
            2 => NULL,
          ),
        ),
      ),
    );

    // Replace the global $user session with an anonymous user to resemble a
    // regular installation.
    $user = drupal_anonymous_user();

    // Reset the static batch to remove Simpletest's batch operations.
    $batch =& batch_get();
    $batch = array();
    $variables = array(
      'file_public_path' => $this->public_files_directory,
      'file_private_path' => $this->private_files_directory,
      'file_temporary_path' => $this->temp_files_directory,
      'locale_translate_file_directory' => $this->translation_files_directory,
    );
    foreach ($variables as $name => $value) {
      $GLOBALS['conf'][$name] = $value;
    }

    // Execute the non-interactive installer.
    require_once DRUPAL_ROOT . '/core/includes/install.core.inc';
    install_drupal($settings);
    $this
      ->rebuildContainer();
    foreach ($variables as $name => $value) {
      variable_set($name, $value);
    }

    // Restore the original Simpletest batch.
    $batch =& batch_get();
    $batch = $this->originalBatch;

    // Revert install_begin_request() cache and lock service overrides.
    unset($conf['cache_classes']);
    unset($conf['lock_backend']);

    // Set path variables.
    // Set 'parent_profile' of simpletest to add the parent profile's
    // search path to the child site's search paths.
    // @see drupal_system_listing()
    config('simpletest.settings')
      ->set('parent_profile', $this->originalProfile)
      ->save();

    // Collect modules to install.
    $class = get_class($this);
    $modules = array();
    while ($class) {
      if (property_exists($class, 'modules')) {
        $modules = array_merge($modules, $class::$modules);
      }
      $class = get_parent_class($class);
    }
    if ($modules) {
      $success = module_enable($modules, TRUE);
      $this
        ->assertTrue($success, t('Enabled modules: %modules', array(
        '%modules' => implode(', ', $modules),
      )));
      $this
        ->rebuildContainer();
    }

    // Reset/rebuild all data structures after enabling the modules.
    $this
      ->resetAll();

    // Use the test mail class instead of the default mail handler class.
    variable_set('mail_system', array(
      'default-system' => 'Drupal\\Core\\Mail\\VariableLog',
    ));
    drupal_set_time_limit($this->timeLimit);

    // Temporary fix so that when running from run-tests.sh we don't get an
    // empty current path which would indicate we're on the home page.
    $path = current_path();
    if (empty($path)) {
      _current_path('run-tests');
    }
    $this->setup = TRUE;
  }

  /**
   * Reset all data structures after having enabled new modules.
   *
   * This method is called by Drupal\simpletest\WebTestBase::setUp() after enabling
   * the requested modules. It must be called again when additional modules
   * are enabled later.
   */
  protected function resetAll() {

    // Clear all database and static caches and rebuild data structures.
    drupal_flush_all_caches();

    // Reload global $conf array and permissions.
    $this
      ->refreshVariables();
    $this
      ->checkPermissions(array(), TRUE);
  }

  /**
   * Refresh the in-memory set of variables. Useful after a page request is made
   * that changes a variable in a different thread.
   *
   * In other words calling a settings page with $this->drupalPost() with a changed
   * value would update a variable to reflect that change, but in the thread that
   * made the call (thread running the test) the changed variable would not be
   * picked up.
   *
   * This method clears the variables cache and loads a fresh copy from the database
   * to ensure that the most up-to-date set of variables is loaded.
   */
  protected function refreshVariables() {
    global $conf;
    cache('bootstrap')
      ->delete('variables');
    $conf = variable_initialize();
  }

  /**
   * Delete created files and temporary files directory, delete the tables created by setUp(),
   * and reset the database prefix.
   */
  protected function tearDown() {

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

    // Ensure that internal logged in variable and cURL options are reset.
    $this->loggedInUser = FALSE;
    $this->additionalCurlOptions = array();

    // Reload module list and implementations to ensure that test module hooks
    // aren't called after tests.
    system_list_reset();
    module_list_reset();
    module_implements_reset();

    // Reset the Field API.
    field_cache_clear();

    // Rebuild caches.
    $this
      ->refreshVariables();

    // Close the CURL handler.
    $this
      ->curlClose();
  }

  /**
   * Initializes the cURL connection.
   *
   * If the simpletest_httpauth_credentials variable is set, this function will
   * add HTTP authentication headers. This is necessary for testing sites that
   * are protected by login credentials from public access.
   * See the description of $curl_options for other options.
   */
  protected function curlInitialize() {
    global $base_url;
    if (!isset($this->curlHandle)) {
      $this->curlHandle = curl_init();

      // Some versions/configurations of cURL break on a NULL cookie jar, so
      // supply a real file.
      if (empty($this->cookieFile)) {
        $this->cookieFile = $this->public_files_directory . '/cookie.jar';
      }
      $curl_options = array(
        CURLOPT_COOKIEJAR => $this->cookieFile,
        CURLOPT_URL => $base_url,
        CURLOPT_FOLLOWLOCATION => FALSE,
        CURLOPT_RETURNTRANSFER => TRUE,
        CURLOPT_SSL_VERIFYPEER => FALSE,
        // Required to make the tests run on HTTPS.
        CURLOPT_SSL_VERIFYHOST => FALSE,
        // Required to make the tests run on HTTPS.
        CURLOPT_HEADERFUNCTION => array(
          &$this,
          'curlHeaderCallback',
        ),
        CURLOPT_USERAGENT => $this->databasePrefix,
      );
      if (isset($this->httpauth_credentials)) {
        $curl_options[CURLOPT_HTTPAUTH] = $this->httpauth_method;
        $curl_options[CURLOPT_USERPWD] = $this->httpauth_credentials;
      }

      // curl_setopt_array() returns FALSE if any of the specified options
      // cannot be set, and stops processing any further options.
      $result = curl_setopt_array($this->curlHandle, $this->additionalCurlOptions + $curl_options);
      if (!$result) {
        throw new \UnexpectedValueException('One or more cURL options could not be set.');
      }

      // By default, the child session name should be the same as the parent.
      $this->session_name = session_name();
    }

    // We set the user agent header on each request so as to use the current
    // time and a new uniqid.
    if (preg_match('/simpletest\\d+/', $this->databasePrefix, $matches)) {
      curl_setopt($this->curlHandle, CURLOPT_USERAGENT, drupal_generate_test_ua($matches[0]));
    }
  }

  /**
   * Initializes and executes a cURL request.
   *
   * @param $curl_options
   *   An associative array of cURL options to set, where the keys are constants
   *   defined by the cURL library. For a list of valid options, see
   *   http://www.php.net/manual/function.curl-setopt.php
   * @param $redirect
   *   FALSE if this is an initial request, TRUE if this request is the result
   *   of a redirect.
   *
   * @return
   *   The content returned from the call to curl_exec().
   *
   * @see curlInitialize()
   */
  protected function curlExec($curl_options, $redirect = FALSE) {
    $this
      ->curlInitialize();

    // cURL incorrectly handles URLs with a fragment by including the
    // fragment in the request to the server, causing some web servers
    // to reject the request citing "400 - Bad Request". To prevent
    // this, we strip the fragment from the request.
    // TODO: Remove this for Drupal 8, since fixed in curl 7.20.0.
    if (!empty($curl_options[CURLOPT_URL]) && strpos($curl_options[CURLOPT_URL], '#')) {
      $original_url = $curl_options[CURLOPT_URL];
      $curl_options[CURLOPT_URL] = strtok($curl_options[CURLOPT_URL], '#');
    }
    $url = empty($curl_options[CURLOPT_URL]) ? curl_getinfo($this->curlHandle, CURLINFO_EFFECTIVE_URL) : $curl_options[CURLOPT_URL];
    if (!empty($curl_options[CURLOPT_POST])) {

      // This is a fix for the Curl library to prevent Expect: 100-continue
      // headers in POST requests, that may cause unexpected HTTP response
      // codes from some webservers (like lighttpd that returns a 417 error
      // code). It is done by setting an empty "Expect" header field that is
      // not overwritten by Curl.
      $curl_options[CURLOPT_HTTPHEADER][] = 'Expect:';
    }
    curl_setopt_array($this->curlHandle, $this->additionalCurlOptions + $curl_options);
    if (!$redirect) {

      // Reset headers, the session ID and the redirect counter.
      $this->session_id = NULL;
      $this->headers = array();
      $this->redirect_count = 0;
    }
    $content = curl_exec($this->curlHandle);
    $status = curl_getinfo($this->curlHandle, CURLINFO_HTTP_CODE);

    // cURL incorrectly handles URLs with fragments, so instead of
    // letting cURL handle redirects we take of them ourselves to
    // to prevent fragments being sent to the web server as part
    // of the request.
    // TODO: Remove this for Drupal 8, since fixed in curl 7.20.0.
    if (in_array($status, array(
      300,
      301,
      302,
      303,
      305,
      307,
    )) && $this->redirect_count < $this->maximumRedirects) {
      if ($this
        ->drupalGetHeader('location')) {
        $this->redirect_count++;
        $curl_options = array();
        $curl_options[CURLOPT_URL] = $this
          ->drupalGetHeader('location');
        $curl_options[CURLOPT_HTTPGET] = TRUE;
        return $this
          ->curlExec($curl_options, TRUE);
      }
    }
    $this
      ->drupalSetContent($content, isset($original_url) ? $original_url : curl_getinfo($this->curlHandle, CURLINFO_EFFECTIVE_URL));
    $message_vars = array(
      '!method' => !empty($curl_options[CURLOPT_NOBODY]) ? 'HEAD' : (empty($curl_options[CURLOPT_POSTFIELDS]) ? 'GET' : 'POST'),
      '@url' => isset($original_url) ? $original_url : $url,
      '@status' => $status,
      '!length' => format_size(strlen($this
        ->drupalGetContent())),
    );
    $message = t('!method @url returned @status (!length).', $message_vars);
    $this
      ->assertTrue($this
      ->drupalGetContent() !== FALSE, $message, t('Browser'));
    return $this
      ->drupalGetContent();
  }

  /**
   * Reads headers and registers errors received from the tested site.
   *
   * @see _drupal_log_error().
   *
   * @param $curlHandler
   *   The cURL handler.
   * @param $header
   *   An header.
   */
  protected function curlHeaderCallback($curlHandler, $header) {

    // Header fields can be extended over multiple lines by preceding each
    // extra line with at least one SP or HT. They should be joined on receive.
    // Details are in RFC2616 section 4.
    if ($header[0] == ' ' || $header[0] == "\t") {

      // Normalize whitespace between chucks.
      $this->headers[] = array_pop($this->headers) . ' ' . trim($header);
    }
    else {
      $this->headers[] = $header;
    }

    // Errors are being sent via X-Drupal-Assertion-* headers,
    // generated by _drupal_log_error() in the exact form required
    // by Drupal\simpletest\WebTestBase::error().
    if (preg_match('/^X-Drupal-Assertion-[0-9]+: (.*)$/', $header, $matches)) {

      // Call Drupal\simpletest\WebTestBase::error() with the parameters from the header.
      call_user_func_array(array(
        &$this,
        'error',
      ), unserialize(urldecode($matches[1])));
    }

    // Save cookies.
    if (preg_match('/^Set-Cookie: ([^=]+)=(.+)/', $header, $matches)) {
      $name = $matches[1];
      $parts = array_map('trim', explode(';', $matches[2]));
      $value = array_shift($parts);
      $this->cookies[$name] = array(
        'value' => $value,
        'secure' => in_array('secure', $parts),
      );
      if ($name == $this->session_name) {
        if ($value != 'deleted') {
          $this->session_id = $value;
        }
        else {
          $this->session_id = NULL;
        }
      }
    }

    // This is required by cURL.
    return strlen($header);
  }

  /**
   * Close the cURL handler and unset the handler.
   */
  protected function curlClose() {
    if (isset($this->curlHandle)) {
      curl_close($this->curlHandle);
      unset($this->curlHandle);
    }
  }

  /**
   * Parse content returned from curlExec using DOM and SimpleXML.
   *
   * @return
   *   A SimpleXMLElement or FALSE on failure.
   */
  protected function parse() {
    if (!$this->elements) {

      // DOM can load HTML soup. But, HTML soup can throw warnings, suppress
      // them.
      $htmlDom = new DOMDocument();
      @$htmlDom
        ->loadHTML('<?xml encoding="UTF-8">' . $this
        ->drupalGetContent());
      if ($htmlDom) {
        $this
          ->pass(t('Valid HTML found on "@path"', array(
          '@path' => $this
            ->getUrl(),
        )), t('Browser'));

        // It's much easier to work with simplexml than DOM, luckily enough
        // we can just simply import our DOM tree.
        $this->elements = simplexml_import_dom($htmlDom);
      }
    }
    if (!$this->elements) {
      $this
        ->fail(t('Parsed page successfully.'), t('Browser'));
    }
    return $this->elements;
  }

  /**
   * Retrieves a Drupal path or an absolute path.
   *
   * @param $path
   *   Drupal path or URL to load into internal browser
   * @param $options
   *   Options to be forwarded to url().
   * @param $headers
   *   An array containing additional HTTP request headers, each formatted as
   *   "name: value".
   * @return
   *   The retrieved HTML string, also available as $this->drupalGetContent()
   */
  protected function drupalGet($path, array $options = array(), array $headers = array()) {
    $options['absolute'] = TRUE;

    // We re-using a CURL connection here. If that connection still has certain
    // options set, it might change the GET into a POST. Make sure we clear out
    // previous options.
    $out = $this
      ->curlExec(array(
      CURLOPT_HTTPGET => TRUE,
      CURLOPT_URL => url($path, $options),
      CURLOPT_NOBODY => FALSE,
      CURLOPT_HTTPHEADER => $headers,
    ));
    $this
      ->refreshVariables();

    // Ensure that any changes to variables in the other thread are picked up.
    // Replace original page output with new output from redirected page(s).
    if ($new = $this
      ->checkForMetaRefresh()) {
      $out = $new;
    }
    $this
      ->verbose('GET request to: ' . $path . '<hr />Ending URL: ' . $this
      ->getUrl() . '<hr />' . $out);
    return $out;
  }

  /**
   * Retrieve a Drupal path or an absolute path and JSON decode the result.
   */
  protected function drupalGetAJAX($path, array $options = array(), array $headers = array()) {
    $headers[] = 'X-Requested-With: XMLHttpRequest';
    return drupal_json_decode($this
      ->drupalGet($path, $options, $headers));
  }

  /**
   * Execute a POST request on a Drupal page.
   * It will be done as usual POST request with SimpleBrowser.
   *
   * @param $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->drupalPost('some_url', $edit, t('Save'));
   *
   *   // Second step in form.
   *   $edit = array(...);
   *   $this->drupalPost(NULL, $edit, t('Save'));
   *   @endcode
   * @param  $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. Note that
   *   when a form contains file upload fields, other fields cannot start with
   *   the '@' character.
   *
   *   Multiple select fields can be set using name[] and setting each of the
   *   possible values. Example:
   *   @code
   *   $edit = array();
   *   $edit['name[]'] = array('value1', 'value2');
   *   @endcode
   * @param $submit
   *   Value of the submit button whose click is to be emulated. For example,
   *   t('Save'). The processing of the request depends on this value. For
   *   example, a form may have one button with the value t('Save') and another
   *   button with the value t('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,
   *     which is likely different than the $path parameter used for retrieving
   *     the initial form. Defaults to 'system/ajax'.
   *   - triggering_element: If the value for the 'path' key is 'system/ajax' or
   *     another 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 callback for the
   *     generic Ajax processing path 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 $options
   *   Options to be forwarded to url().
   * @param $headers
   *   An array containing additional HTTP request headers, each formatted as
   *   "name: value".
   * @param $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.
   * @param $extra_post
   *   (optional) A string of additional data to append to the POST submission.
   *   This can be used to add POST data for which there are no HTML fields, as
   *   is done by drupalPostAJAX(). This string is literally appended to the
   *   POST data, so it must already be urlencoded and contain a leading "&"
   *   (e.g., "&extra_var1=hello+world&extra_var2=you%26me").
   */
  protected function drupalPost($path, $edit, $submit, array $options = array(), array $headers = array(), $form_html_id = NULL, $extra_post = NULL) {
    $submit_matches = FALSE;
    $ajax = is_array($submit);
    if (isset($path)) {
      $this
        ->drupalGet($path, $options);
    }
    if ($this
      ->parse()) {
      $edit_save = $edit;

      // Let's iterate over all the forms.
      $xpath = "//form";
      if (!empty($form_html_id)) {
        $xpath .= "[@id='" . $form_html_id . "']";
      }
      $forms = $this
        ->xpath($xpath);
      foreach ($forms as $form) {

        // We try to set the fields of this form as specified in $edit.
        $edit = $edit_save;
        $post = array();
        $upload = array();
        $submit_matches = $this
          ->handleForm($post, $edit, $upload, $ajax ? NULL : $submit, $form);
        $action = isset($form['action']) ? $this
          ->getAbsoluteUrl((string) $form['action']) : $this
          ->getUrl();
        if ($ajax) {
          $action = $this
            ->getAbsoluteUrl(!empty($submit['path']) ? $submit['path'] : 'system/ajax');

          // Ajax callbacks verify the triggering element if necessary, so while
          // we may eventually want extra code that verifies it in the
          // handleForm() function, it's not currently a requirement.
          $submit_matches = TRUE;
        }

        // We post only if we managed to handle every field in edit and the
        // submit button matches.
        if (!$edit && ($submit_matches || !isset($submit))) {
          $post_array = $post;
          if ($upload) {

            // TODO: cURL handles file uploads for us, but the implementation
            // is broken. This is a less than elegant workaround. Alternatives
            // are being explored at #253506.
            foreach ($upload as $key => $file) {
              $file = drupal_realpath($file);
              if ($file && is_file($file)) {
                $post[$key] = '@' . $file;
              }
            }
          }
          else {
            foreach ($post as $key => $value) {

              // Encode according to application/x-www-form-urlencoded
              // Both names and values needs to be urlencoded, according to
              // http://www.w3.org/TR/html4/interact/forms.html#h-17.13.4.1
              $post[$key] = urlencode($key) . '=' . urlencode($value);
            }
            $post = implode('&', $post) . $extra_post;
          }
          $out = $this
            ->curlExec(array(
            CURLOPT_URL => $action,
            CURLOPT_POST => TRUE,
            CURLOPT_POSTFIELDS => $post,
            CURLOPT_HTTPHEADER => $headers,
          ));

          // 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;
          }
          $this
            ->verbose('POST request to: ' . $path . '<hr />Ending URL: ' . $this
            ->getUrl() . '<hr />Fields: ' . highlight_string('<?php ' . var_export($post_array, TRUE), TRUE) . '<hr />' . $out);
          return $out;
        }
      }

      // We have not found a form which contained all fields of $edit.
      foreach ($edit as $name => $value) {
        $this
          ->fail(t('Failed to set field @name to @value', array(
          '@name' => $name,
          '@value' => $value,
        )));
      }
      if (!$ajax && isset($submit)) {
        $this
          ->assertTrue($submit_matches, t('Found the @submit button', array(
          '@submit' => $submit,
        )));
      }
      $this
        ->fail(t('Found the requested form fields at @path', array(
        '@path' => $path,
      )));
    }
  }

  /**
   * Execute an Ajax submission.
   *
   * This executes a POST as ajax.js does. It uses the returned JSON data, an
   * array of commands, to update $this->content using equivalent DOM
   * manipulation as is used by ajax.js. It also returns the array of commands.
   *
   * @param $path
   *   Location of the form containing the Ajax enabled element to test. Can be
   *   either a Drupal path or an absolute path or NULL to use the current page.
   * @param $edit
   *   Field data in an associative array. Changes the current input fields
   *   (where possible) to the values indicated.
   * @param $triggering_element
   *   The name of the form element that is responsible for triggering the Ajax
   *   functionality to test. May be a string or, if the triggering element is
   *   a button, an associative array where the key is the name of the button
   *   and the value is the button label. i.e.) array('op' => t('Refresh')).
   * @param $ajax_path
   *   (optional) Override the path set by the Ajax settings of the triggering
   *   element. In the absence of both the triggering element's Ajax path and
   *   $ajax_path 'system/ajax' will be used.
   * @param $options
   *   (optional) Options to be forwarded to url().
   * @param $headers
   *   (optional) An array containing additional HTTP request headers, each
   *   formatted as "name: value". Forwarded to drupalPost().
   * @param $form_html_id
   *   (optional) HTML ID of the form to be submitted, use when there is more
   *   than one identical form on the same page and the value of the triggering
   *   element is not enough to identify the form. Note this is not the Drupal
   *   ID of the form but rather the HTML ID of the form.
   * @param $ajax_settings
   *   (optional) An array of Ajax settings which if specified will be used in
   *   place of the Ajax settings of the triggering element.
   *
   * @return
   *   An array of Ajax commands.
   *
   * @see drupalPost()
   * @see ajax.js
   */
  protected function drupalPostAJAX($path, $edit, $triggering_element, $ajax_path = NULL, array $options = array(), array $headers = array(), $form_html_id = NULL, $ajax_settings = NULL) {

    // Get the content of the initial page prior to calling drupalPost(), since
    // drupalPost() replaces $this->content.
    if (isset($path)) {
      $this
        ->drupalGet($path, $options);
    }
    $content = $this->content;
    $drupal_settings = $this->drupalSettings;
    $headers[] = 'X-Requested-With: XMLHttpRequest';

    // Get the Ajax settings bound to the triggering element.
    if (!isset($ajax_settings)) {
      if (is_array($triggering_element)) {
        $xpath = '//*[@name="' . key($triggering_element) . '" and @value="' . current($triggering_element) . '"]';
      }
      else {
        $xpath = '//*[@name="' . $triggering_element . '"]';
      }
      if (isset($form_html_id)) {
        $xpath = '//form[@id="' . $form_html_id . '"]' . $xpath;
      }
      $element = $this
        ->xpath($xpath);
      $element_id = (string) $element[0]['id'];
      $ajax_settings = $drupal_settings['ajax'][$element_id];
    }

    // Add extra information to the POST data as ajax.js does.
    $extra_post = '';
    if (isset($ajax_settings['submit'])) {
      foreach ($ajax_settings['submit'] as $key => $value) {
        $extra_post .= '&' . urlencode($key) . '=' . urlencode($value);
      }
    }
    $ajax_html_ids = array();
    foreach ($this
      ->xpath('//*[@id]') as $element) {
      $ajax_html_ids[] = (string) $element['id'];
    }
    if (!empty($ajax_html_ids)) {
      $extra_post .= '&' . urlencode('ajax_html_ids') . '=' . urlencode(implode(' ', $ajax_html_ids));
    }
    if (isset($drupal_settings['ajaxPageState'])) {
      $extra_post .= '&' . urlencode('ajax_page_state[theme]') . '=' . urlencode($drupal_settings['ajaxPageState']['theme']);
      $extra_post .= '&' . urlencode('ajax_page_state[theme_token]') . '=' . urlencode($drupal_settings['ajaxPageState']['theme_token']);
      foreach ($drupal_settings['ajaxPageState']['css'] as $key => $value) {
        $extra_post .= '&' . urlencode("ajax_page_state[css][{$key}]") . '=1';
      }
      foreach ($drupal_settings['ajaxPageState']['js'] as $key => $value) {
        $extra_post .= '&' . urlencode("ajax_page_state[js][{$key}]") . '=1';
      }
    }

    // Unless a particular path is specified, use the one specified by the
    // Ajax settings, or else 'system/ajax'.
    if (!isset($ajax_path)) {
      $ajax_path = isset($ajax_settings['url']) ? $ajax_settings['url'] : 'system/ajax';
    }

    // Submit the POST request.
    $return = drupal_json_decode($this
      ->drupalPost(NULL, $edit, array(
      'path' => $ajax_path,
      'triggering_element' => $triggering_element,
    ), $options, $headers, $form_html_id, $extra_post));

    // Change the page content by applying the returned commands.
    if (!empty($ajax_settings) && !empty($return)) {

      // ajax.js applies some defaults to the settings object, so do the same
      // for what's used by this function.
      $ajax_settings += array(
        'method' => 'replaceWith',
      );

      // DOM can load HTML soup. But, HTML soup can throw warnings, suppress
      // them.
      $dom = new DOMDocument();
      @$dom
        ->loadHTML($content);

      // XPath allows for finding wrapper nodes better than DOM does.
      $xpath = new DOMXPath($dom);
      foreach ($return as $command) {
        switch ($command['command']) {
          case 'settings':
            $drupal_settings = drupal_array_merge_deep($drupal_settings, $command['settings']);
            break;
          case 'insert':
            $wrapperNode = NULL;

            // When a command doesn't specify a selector, use the
            // #ajax['wrapper'] which is always an HTML ID.
            if (!isset($command['selector'])) {
              $wrapperNode = $xpath
                ->query('//*[@id="' . $ajax_settings['wrapper'] . '"]')
                ->item(0);
            }
            elseif (in_array($command['selector'], array(
              'head',
              'body',
            ))) {
              $wrapperNode = $xpath
                ->query('//' . $command['selector'])
                ->item(0);
            }
            if ($wrapperNode) {

              // ajax.js adds an enclosing DIV to work around a Safari bug.
              $newDom = new DOMDocument();
              @$newDom
                ->loadHTML('<div>' . $command['data'] . '</div>');
              $newNode = $dom
                ->importNode($newDom->documentElement->firstChild->firstChild, TRUE);
              $method = isset($command['method']) ? $command['method'] : $ajax_settings['method'];

              // The "method" is a jQuery DOM manipulation function. Emulate
              // each one using PHP's DOMNode API.
              switch ($method) {
                case 'replaceWith':
                  $wrapperNode->parentNode
                    ->replaceChild($newNode, $wrapperNode);
                  break;
                case 'append':
                  $wrapperNode
                    ->appendChild($newNode);
                  break;
                case 'prepend':

                  // If no firstChild, insertBefore() falls back to
                  // appendChild().
                  $wrapperNode
                    ->insertBefore($newNode, $wrapperNode->firstChild);
                  break;
                case 'before':
                  $wrapperNode->parentNode
                    ->insertBefore($newNode, $wrapperNode);
                  break;
                case 'after':

                  // If no nextSibling, insertBefore() falls back to
                  // appendChild().
                  $wrapperNode->parentNode
                    ->insertBefore($newNode, $wrapperNode->nextSibling);
                  break;
                case 'html':
                  foreach ($wrapperNode->childNodes as $childNode) {
                    $wrapperNode
                      ->removeChild($childNode);
                  }
                  $wrapperNode
                    ->appendChild($newNode);
                  break;
              }
            }
            break;

          // @todo Add suitable implementations for these commands in order to
          //   have full test coverage of what ajax.js can do.
          case 'remove':
            break;
          case 'changed':
            break;
          case 'css':
            break;
          case 'data':
            break;
          case 'restripe':
            break;
          case 'add_css':
            break;
        }
      }
      $content = $dom
        ->saveHTML();
    }
    $this
      ->drupalSetContent($content);
    $this
      ->drupalSetSettings($drupal_settings);
    return $return;
  }

  /**
   * Runs cron in the Drupal installed by Simpletest.
   */
  protected function cronRun() {
    $this
      ->drupalGet('cron/' . state()
      ->get('system.cron_key'));
  }

  /**
   * Check 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-sensitive.
   *
   * @return
   *   Either the new page content or FALSE.
   */
  protected function checkForMetaRefresh() {
    if (strpos($this
      ->drupalGetContent(), '<meta ') && $this
      ->parse()) {
      $refresh = $this
        ->xpath('//meta[@http-equiv="Refresh"]');
      if (!empty($refresh)) {

        // Parse the content attribute of the meta tag for the format:
        // "[delay]: URL=[page_to_redirect_to]".
        if (preg_match('/\\d+;\\s*URL=(?P<url>.*)/i', $refresh[0]['content'], $match)) {
          return $this
            ->drupalGet($this
            ->getAbsoluteUrl(decode_entities($match['url'])));
        }
      }
    }
    return FALSE;
  }

  /**
   * Retrieves only the headers for a Drupal path or an absolute path.
   *
   * @param $path
   *   Drupal path or URL to load into internal browser
   * @param $options
   *   Options to be forwarded to url().
   * @param $headers
   *   An array containing additional HTTP request headers, each formatted as
   *   "name: value".
   * @return
   *   The retrieved headers, also available as $this->drupalGetContent()
   */
  protected function drupalHead($path, array $options = array(), array $headers = array()) {
    $options['absolute'] = TRUE;
    $out = $this
      ->curlExec(array(
      CURLOPT_NOBODY => TRUE,
      CURLOPT_URL => url($path, $options),
      CURLOPT_HTTPHEADER => $headers,
    ));
    $this
      ->refreshVariables();

    // Ensure that any changes to variables in the other thread are picked up.
    return $out;
  }

  /**
   * Handle form input related to drupalPost(). Ensure that the specified fields
   * exist and attempt to create POST data in the correct manner for the particular
   * field type.
   *
   * @param $post
   *   Reference to array of post values.
   * @param $edit
   *   Reference to array of edit values to be checked against the form.
   * @param $submit
   *   Form submit button value.
   * @param $form
   *   Array of form elements.
   * @return
   *   Submit value matches a valid submit input in the form.
   */
  protected function handleForm(&$post, &$edit, &$upload, $submit, $form) {

    // Retrieve the form elements.
    $elements = $form
      ->xpath('.//input[not(@disabled)]|.//textarea[not(@disabled)]|.//select[not(@disabled)]');
    $submit_matches = FALSE;
    foreach ($elements as $element) {

      // SimpleXML objects need string casting all the time.
      $name = (string) $element['name'];

      // This can either be the type of <input> or the name of the tag itself
      // for <select> or <textarea>.
      $type = isset($element['type']) ? (string) $element['type'] : $element
        ->getName();
      $value = isset($element['value']) ? (string) $element['value'] : '';
      $done = FALSE;
      if (isset($edit[$name])) {
        switch ($type) {
          case 'text':
          case 'tel':
          case 'textarea':
          case 'url':
          case 'number':
          case 'range':
          case 'color':
          case 'hidden':
          case 'password':
          case 'email':
          case 'search':
            $post[$name] = $edit[$name];
            unset($edit[$name]);
            break;
          case 'radio':
            if ($edit[$name] == $value) {
              $post[$name] = $edit[$name];
              unset($edit[$name]);
            }
            break;
          case 'checkbox':

            // To prevent checkbox from being checked.pass in a FALSE,
            // otherwise the checkbox will be set to its value regardless
            // of $edit.
            if ($edit[$name] === FALSE) {
              unset($edit[$name]);
              continue 2;
            }
            else {
              unset($edit[$name]);
              $post[$name] = $value;
            }
            break;
          case 'select':
            $new_value = $edit[$name];
            $options = $this
              ->getAllOptions($element);
            if (is_array($new_value)) {

              // Multiple select box.
              if (!empty($new_value)) {
                $index = 0;
                $key = preg_replace('/\\[\\]$/', '', $name);
                foreach ($options as $option) {
                  $option_value = (string) $option['value'];
                  if (in_array($option_value, $new_value)) {
                    $post[$key . '[' . $index++ . ']'] = $option_value;
                    $done = TRUE;
                    unset($edit[$name]);
                  }
                }
              }
              else {

                // No options selected: do not include any POST data for the
                // element.
                $done = TRUE;
                unset($edit[$name]);
              }
            }
            else {

              // Single select box.
              foreach ($options as $option) {
                if ($new_value == $option['value']) {
                  $post[$name] = $new_value;
                  unset($edit[$name]);
                  $done = TRUE;
                  break;
                }
              }
            }
            break;
          case 'file':
            $upload[$name] = $edit[$name];
            unset($edit[$name]);
            break;
        }
      }
      if (!isset($post[$name]) && !$done) {
        switch ($type) {
          case 'textarea':
            $post[$name] = (string) $element;
            break;
          case 'select':
            $single = empty($element['multiple']);
            $first = TRUE;
            $index = 0;
            $key = preg_replace('/\\[\\]$/', '', $name);
            $options = $this
              ->getAllOptions($element);
            foreach ($options as $option) {

              // For single select, we load the first option, if there is a
              // selected option that will overwrite it later.
              if ($option['selected'] || $first && $single) {
                $first = FALSE;
                if ($single) {
                  $post[$name] = (string) $option['value'];
                }
                else {
                  $post[$key . '[' . $index++ . ']'] = (string) $option['value'];
                }
              }
            }
            break;
          case 'file':
            break;
          case 'submit':
          case 'image':
            if (isset($submit) && $submit == $value) {
              $post[$name] = $value;
              $submit_matches = TRUE;
            }
            break;
          case 'radio':
          case 'checkbox':
            if (!isset($element['checked'])) {
              break;
            }

          // Deliberate no break.
          default:
            $post[$name] = $value;
        }
      }
    }
    return $submit_matches;
  }

  /**
   * Builds an XPath query.
   *
   * Builds an XPath query by replacing placeholders in the query by the value
   * of the arguments.
   *
   * XPath 1.0 (the version supported by libxml2, the underlying XML library
   * used by PHP) doesn't support any form of quotation. This function
   * simplifies the building of XPath expression.
   *
   * @param $xpath
   *   An XPath query, possibly with placeholders in the form ':name'.
   * @param $args
   *   An array of arguments with keys in the form ':name' matching the
   *   placeholders in the query. The values may be either strings or numeric
   *   values.
   * @return
   *   An XPath query with arguments replaced.
   */
  protected function buildXPathQuery($xpath, array $args = array()) {

    // Replace placeholders.
    foreach ($args as $placeholder => $value) {

      // XPath 1.0 doesn't support a way to escape single or double quotes in a
      // string literal. We split double quotes out of the string, and encode
      // them separately.
      if (is_string($value)) {

        // Explode the text at the quote characters.
        $parts = explode('"', $value);

        // Quote the parts.
        foreach ($parts as &$part) {
          $part = '"' . $part . '"';
        }

        // Return the string.
        $value = count($parts) > 1 ? 'concat(' . implode(', \'"\', ', $parts) . ')' : $parts[0];
      }
      $xpath = preg_replace('/' . preg_quote($placeholder) . '\\b/', $value, $xpath);
    }
    return $xpath;
  }

  /**
   * Perform 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 $xpath
   *   The xpath string to use in the search.
   * @return
   *   The return value of the xpath search. For details on the xpath string
   *   format and return values see the SimpleXML documentation,
   *   http://php.net/manual/function.simplexml-element-xpath.php.
   */
  protected function xpath($xpath, array $arguments = array()) {
    if ($this
      ->parse()) {
      $xpath = $this
        ->buildXPathQuery($xpath, $arguments);
      $result = $this->elements
        ->xpath($xpath);

      // Some combinations of PHP / libxml versions return an empty array
      // instead of the documented FALSE. Forcefully convert any falsish values
      // to an empty array to allow foreach(...) constructions.
      return $result ? $result : array();
    }
    else {
      return FALSE;
    }
  }

  /**
   * Get all option elements, including nested options, in a select.
   *
   * @param $element
   *   The element for which to get the options.
   * @return
   *   Option elements in select.
   */
  protected function getAllOptions(SimpleXMLElement $element) {
    $options = array();

    // Add all options items.
    foreach ($element->option as $option) {
      $options[] = $option;
    }

    // Search option group children.
    if (isset($element->optgroup)) {
      foreach ($element->optgroup as $group) {
        $options = array_merge($options, $this
          ->getAllOptions($group));
      }
    }
    return $options;
  }

  /**
   * Pass if a link with the specified label is found, and optional with the
   * specified index.
   *
   * @param $label
   *   Text between the anchor tags.
   * @param $index
   *   Link position counting from zero.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The gorup this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE if the assertion succeeded, FALSE otherwise.
   */
  protected function assertLink($label, $index = 0, $message = '', $group = 'Other') {
    $links = $this
      ->xpath('//a[normalize-space(text())=:label]', array(
      ':label' => $label,
    ));
    $message = $message ? $message : t('Link with label %label found.', array(
      '%label' => $label,
    ));
    return $this
      ->assert(isset($links[$index]), $message, $group);
  }

  /**
   * Pass if a link with the specified label is not found.
   *
   * @param $label
   *   Text between the anchor tags.
   * @param $index
   *   Link position counting from zero.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE if the assertion succeeded, FALSE otherwise.
   */
  protected function assertNoLink($label, $message = '', $group = 'Other') {
    $links = $this
      ->xpath('//a[normalize-space(text())=:label]', array(
      ':label' => $label,
    ));
    $message = $message ? $message : t('Link with label %label not found.', array(
      '%label' => $label,
    ));
    return $this
      ->assert(empty($links), $message, $group);
  }

  /**
   * Pass if a link containing a given href (part) is found.
   *
   * @param $href
   *   The full or partial value of the 'href' attribute of the anchor tag.
   * @param $index
   *   Link position counting from zero.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE if the assertion succeeded, FALSE otherwise.
   */
  protected function assertLinkByHref($href, $index = 0, $message = '', $group = 'Other') {
    $links = $this
      ->xpath('//a[contains(@href, :href)]', array(
      ':href' => $href,
    ));
    $message = $message ? $message : t('Link containing href %href found.', array(
      '%href' => $href,
    ));
    return $this
      ->assert(isset($links[$index]), $message, $group);
  }

  /**
   * Pass if a link containing a given href (part) is not found.
   *
   * @param $href
   *   The full or partial value of the 'href' attribute of the anchor tag.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE if the assertion succeeded, FALSE otherwise.
   */
  protected function assertNoLinkByHref($href, $message = '', $group = 'Other') {
    $links = $this
      ->xpath('//a[contains(@href, :href)]', array(
      ':href' => $href,
    ));
    $message = $message ? $message : t('No link containing href %href found.', array(
      '%href' => $href,
    ));
    return $this
      ->assert(empty($links), $message, $group);
  }

  /**
   * Follows a link by name.
   *
   * Will click the first link found with this link text by default, or a
   * later one if an index is given. Match is case insensitive with
   * normalized space. The label is translated label. There is an assert
   * for successful click.
   *
   * @param $label
   *   Text between the anchor tags.
   * @param $index
   *   Link position counting from zero.
   * @return
   *   Page on success, or FALSE on failure.
   */
  protected function clickLink($label, $index = 0) {
    $url_before = $this
      ->getUrl();
    $urls = $this
      ->xpath('//a[normalize-space(text())=:label]', array(
      ':label' => $label,
    ));
    if (isset($urls[$index])) {
      $url_target = $this
        ->getAbsoluteUrl($urls[$index]['href']);
    }
    $this
      ->assertTrue(isset($urls[$index]), t('Clicked link %label (@url_target) from @url_before', array(
      '%label' => $label,
      '@url_target' => $url_target,
      '@url_before' => $url_before,
    )), t('Browser'));
    if (isset($url_target)) {
      return $this
        ->drupalGet($url_target);
    }
    return FALSE;
  }

  /**
   * Takes a path and returns an absolute path.
   *
   * @param $path
   *   A path from the internal browser content.
   * @return
   *   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 ($path[0] !== '/') {
        $path = '/' . $path;
      }

      // Finally, prepend the $base_url.
      $path = $base_url . $path;
    }
    return $path;
  }

  /**
   * Get the current URL from the cURL handler.
   *
   * @return
   *   The current URL.
   */
  protected function getUrl() {
    return $this->url;
  }

  /**
   * Gets the HTTP response headers of the requested page. Normally we are only
   * interested in the headers returned by the last request. However, if a page
   * is redirected or HTTP authentication is in use, multiple requests will be
   * required to retrieve the page. Headers from all requests may be requested
   * by passing TRUE to this function.
   *
   * @param $all_requests
   *   Boolean value specifying whether to return headers from all requests
   *   instead of just the last request. Defaults to FALSE.
   * @return
   *   A name/value array if headers from only the last request are requested.
   *   If headers from all requests are requested, an array of name/value
   *   arrays, one for each request.
   *
   *   The pseudonym ":status" is used for the HTTP status line.
   *
   *   Values for duplicate headers are stored as a single comma-separated list.
   */
  protected function drupalGetHeaders($all_requests = FALSE) {
    $request = 0;
    $headers = array(
      $request => array(),
    );
    foreach ($this->headers as $header) {
      $header = trim($header);
      if ($header === '') {
        $request++;
      }
      else {
        if (strpos($header, 'HTTP/') === 0) {
          $name = ':status';
          $value = $header;
        }
        else {
          list($name, $value) = explode(':', $header, 2);
          $name = strtolower($name);
        }
        if (isset($headers[$request][$name])) {
          $headers[$request][$name] .= ',' . trim($value);
        }
        else {
          $headers[$request][$name] = trim($value);
        }
      }
    }
    if (!$all_requests) {
      $headers = array_pop($headers);
    }
    return $headers;
  }

  /**
   * 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. However, if TRUE is passed as the second argument,
   * all requests will be processed from last to first until the header is
   * found.
   *
   * @param $name
   *   The name of the header to retrieve. Names are case-insensitive (see RFC
   *   2616 section 4.2).
   * @param $all_requests
   *   Boolean value specifying whether to check all requests if the header is
   *   not found in the last request. Defaults to FALSE.
   * @return
   *   The HTTP header value or FALSE if not found.
   */
  protected function drupalGetHeader($name, $all_requests = FALSE) {
    $name = strtolower($name);
    $header = FALSE;
    if ($all_requests) {
      foreach (array_reverse($this
        ->drupalGetHeaders(TRUE)) as $headers) {
        if (isset($headers[$name])) {
          $header = $headers[$name];
          break;
        }
      }
    }
    else {
      $headers = $this
        ->drupalGetHeaders();
      if (isset($headers[$name])) {
        $header = $headers[$name];
      }
    }
    return $header;
  }

  /**
   * Gets the current raw HTML of requested page.
   */
  protected function drupalGetContent() {
    return $this->content;
  }

  /**
   * Gets the value of the Drupal.settings JavaScript variable for the currently loaded page.
   */
  protected function drupalGetSettings() {
    return $this->drupalSettings;
  }

  /**
   * Gets an array containing all e-mails sent during this test case.
   *
   * @param $filter
   *   An array containing key/value pairs used to filter the e-mails that are returned.
   * @return
   *   An array containing e-mail messages captured during the current test.
   */
  protected function drupalGetMails($filter = array()) {
    $captured_emails = state()
      ->get('system.test_email_collector') ?: array();
    $filtered_emails = array();
    foreach ($captured_emails as $message) {
      foreach ($filter as $key => $value) {
        if (!isset($message[$key]) || $message[$key] != $value) {
          continue 2;
        }
      }
      $filtered_emails[] = $message;
    }
    return $filtered_emails;
  }

  /**
   * Sets the raw HTML content. This can be useful when a page has been fetched
   * outside of the internal browser and assertions need to be made on the
   * returned page.
   *
   * A good example would be when testing drupal_http_request(). After fetching
   * the page the content can be set and page elements can be checked to ensure
   * that the function worked properly.
   */
  protected function drupalSetContent($content, $url = 'internal:') {
    $this->content = $content;
    $this->url = $url;
    $this->plainTextContent = FALSE;
    $this->elements = FALSE;
    $this->drupalSettings = array();
    if (preg_match('/var drupalSettings = (.*?);/', $content, $matches)) {
      $this->drupalSettings = drupal_json_decode($matches[1]);
    }
  }

  /**
   * Sets the value of the Drupal.settings JavaScript variable for the currently loaded page.
   */
  protected function drupalSetSettings($settings) {
    $this->drupalSettings = $settings;
  }

  /**
   * Creates a typed data object and executes some basic assertions.
   *
   * @see Drupal\Core\TypedData\TypedDataManager::create().
   */
  protected function createTypedData($definition, $value = NULL, $context = array()) {

    // Save the type that was passed in so we can compare with it later.
    $type = $definition['type'];

    // Construct the object.
    $data = typed_data()
      ->create($definition, $value, $context);

    // Assert the definition of the wrapper.
    $this
      ->assertTrue($data instanceof \Drupal\Core\TypedData\TypedDataInterface, 'Typed data object is an instance of the typed data interface.');
    $definition = $data
      ->getDefinition();
    $this
      ->assertTrue(!empty($definition['label']), $definition['label'] . ' data definition was returned.');

    // Assert that the correct type was constructed.
    $this
      ->assertEqual($data
      ->getType(), $type, $definition['label'] . ' object returned type.');
    return $data;
  }

  /**
   * Pass if the internal browser's URL matches the given path.
   *
   * @param $path
   *   The expected system path.
   * @param $options
   *   (optional) Any additional options to pass for $path to url().
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertUrl($path, array $options = array(), $message = '', $group = 'Other') {
    if (!$message) {
      $message = t('Current URL is @url.', array(
        '@url' => var_export(url($path, $options), TRUE),
      ));
    }
    $options['absolute'] = TRUE;
    return $this
      ->assertEqual($this
      ->getUrl(), url($path, $options), $message, $group);
  }

  /**
   * Pass if the raw text IS found on the loaded page, fail otherwise. Raw text
   * refers to the raw HTML that the page generated.
   *
   * @param $raw
   *   Raw (HTML) string to look for.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertRaw($raw, $message = '', $group = 'Other') {
    if (!$message) {
      $message = t('Raw "@raw" found', array(
        '@raw' => $raw,
      ));
    }
    return $this
      ->assert(strpos($this
      ->drupalGetContent(), $raw) !== FALSE, $message, $group);
  }

  /**
   * Pass if the raw text is NOT found on the loaded page, fail otherwise. Raw text
   * refers to the raw HTML that the page generated.
   *
   * @param $raw
   *   Raw (HTML) string to look for.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoRaw($raw, $message = '', $group = 'Other') {
    if (!$message) {
      $message = t('Raw "@raw" not found', array(
        '@raw' => $raw,
      ));
    }
    return $this
      ->assert(strpos($this
      ->drupalGetContent(), $raw) === FALSE, $message, $group);
  }

  /**
   * Pass if the text IS found on the text version of the page. The text version
   * is the equivalent of what a user would see when viewing through a web browser.
   * In other words the HTML has been filtered out of the contents.
   *
   * @param $text
   *   Plain text to look for.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertText($text, $message = '', $group = 'Other') {
    return $this
      ->assertTextHelper($text, $message, $group, FALSE);
  }

  /**
   * Pass if the text is NOT found on the text version of the page. The text version
   * is the equivalent of what a user would see when viewing through a web browser.
   * In other words the HTML has been filtered out of the contents.
   *
   * @param $text
   *   Plain text to look for.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoText($text, $message = '', $group = 'Other') {
    return $this
      ->assertTextHelper($text, $message, $group, TRUE);
  }

  /**
   * Helper for assertText and assertNoText.
   *
   * It is not recommended to call this function directly.
   *
   * @param $text
   *   Plain text to look for.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @param $not_exists
   *   TRUE if this text should not exist, FALSE if it should.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertTextHelper($text, $message = '', $group, $not_exists) {
    if ($this->plainTextContent === FALSE) {
      $this->plainTextContent = filter_xss($this
        ->drupalGetContent(), array());
    }
    if (!$message) {
      $message = !$not_exists ? t('"@text" found', array(
        '@text' => $text,
      )) : t('"@text" not found', array(
        '@text' => $text,
      ));
    }
    return $this
      ->assert($not_exists == (strpos($this->plainTextContent, $text) === FALSE), $message, $group);
  }

  /**
   * Pass if the text is found ONLY ONCE on the text version of the page.
   *
   * The text version is the equivalent of what a user would see when viewing
   * through a web browser. In other words the HTML has been filtered out of
   * the contents.
   *
   * @param $text
   *   Plain text to look for.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertUniqueText($text, $message = '', $group = 'Other') {
    return $this
      ->assertUniqueTextHelper($text, $message, $group, TRUE);
  }

  /**
   * Pass if the text is found MORE THAN ONCE on the text version of the page.
   *
   * The text version is the equivalent of what a user would see when viewing
   * through a web browser. In other words the HTML has been filtered out of
   * the contents.
   *
   * @param $text
   *   Plain text to look for.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoUniqueText($text, $message = '', $group = 'Other') {
    return $this
      ->assertUniqueTextHelper($text, $message, $group, FALSE);
  }

  /**
   * Helper for assertUniqueText and assertNoUniqueText.
   *
   * It is not recommended to call this function directly.
   *
   * @param $text
   *   Plain text to look for.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @param $be_unique
   *   TRUE if this text should be found only once, FALSE if it should be found more than once.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertUniqueTextHelper($text, $message = '', $group, $be_unique) {
    if ($this->plainTextContent === FALSE) {
      $this->plainTextContent = filter_xss($this
        ->drupalGetContent(), array());
    }
    if (!$message) {
      $message = '"' . $text . '"' . ($be_unique ? ' found only once' : ' found more than once');
    }
    $first_occurance = strpos($this->plainTextContent, $text);
    if ($first_occurance === FALSE) {
      return $this
        ->assert(FALSE, $message, $group);
    }
    $offset = $first_occurance + strlen($text);
    $second_occurance = strpos($this->plainTextContent, $text, $offset);
    return $this
      ->assert($be_unique == ($second_occurance === FALSE), $message, $group);
  }

  /**
   * Will trigger a pass if the Perl regex pattern is found in the raw content.
   *
   * @param $pattern
   *   Perl regex to look for including the regex delimiters.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertPattern($pattern, $message = '', $group = 'Other') {
    if (!$message) {
      $message = t('Pattern "@pattern" found', array(
        '@pattern' => $pattern,
      ));
    }
    return $this
      ->assert((bool) preg_match($pattern, $this
      ->drupalGetContent()), $message, $group);
  }

  /**
   * Will trigger a pass if the perl regex pattern is not present in raw content.
   *
   * @param $pattern
   *   Perl regex to look for including the regex delimiters.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoPattern($pattern, $message = '', $group = 'Other') {
    if (!$message) {
      $message = t('Pattern "@pattern" not found', array(
        '@pattern' => $pattern,
      ));
    }
    return $this
      ->assert(!preg_match($pattern, $this
      ->drupalGetContent()), $message, $group);
  }

  /**
   * Pass if the page title is the given string.
   *
   * @param $title
   *   The string the title should be.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertTitle($title, $message = '', $group = 'Other') {
    $actual = (string) current($this
      ->xpath('//title'));
    if (!$message) {
      $message = t('Page title @actual is equal to @expected.', array(
        '@actual' => var_export($actual, TRUE),
        '@expected' => var_export($title, TRUE),
      ));
    }
    return $this
      ->assertEqual($actual, $title, $message, $group);
  }

  /**
   * Pass if the page title is not the given string.
   *
   * @param $title
   *   The string the title should not be.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoTitle($title, $message = '', $group = 'Other') {
    $actual = (string) current($this
      ->xpath('//title'));
    if (!$message) {
      $message = t('Page title @actual is not equal to @unexpected.', array(
        '@actual' => var_export($actual, TRUE),
        '@unexpected' => var_export($title, TRUE),
      ));
    }
    return $this
      ->assertNotEqual($actual, $title, $message, $group);
  }

  /**
   * Asserts themed output.
   *
   * @param $callback
   *   The name of the theme function to invoke; e.g. 'links' for theme_links().
   * @param $variables
   *   An array of variables to pass to the theme function.
   * @param $expected
   *   The expected themed output string.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertThemeOutput($callback, array $variables = array(), $expected, $message = '', $group = 'Other') {
    $output = theme($callback, $variables);
    $this
      ->verbose('Variables:' . '<pre>' . check_plain(var_export($variables, TRUE)) . '</pre>' . '<hr />' . 'Result:' . '<pre>' . check_plain(var_export($output, TRUE)) . '</pre>' . '<hr />' . 'Expected:' . '<pre>' . check_plain(var_export($expected, TRUE)) . '</pre>' . '<hr />' . $output);
    if (!$message) {
      $message = '%callback rendered correctly.';
    }
    $message = format_string($message, array(
      '%callback' => 'theme_' . $callback . '()',
    ));
    return $this
      ->assertIdentical($output, $expected, $message, $group);
  }

  /**
   * Asserts that a field exists in the current page by the given XPath.
   *
   * @param $xpath
   *   XPath used to find the field.
   * @param $value
   *   (optional) Value of the field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertFieldByXPath($xpath, $value = NULL, $message = '', $group = 'Other') {
    $fields = $this
      ->xpath($xpath);

    // If value specified then check array for match.
    $found = TRUE;
    if (isset($value)) {
      $found = FALSE;
      if ($fields) {
        foreach ($fields as $field) {
          if (isset($field['value']) && $field['value'] == $value) {

            // Input element with correct value.
            $found = TRUE;
          }
          elseif (isset($field->option)) {

            // Select element found.
            if ($this
              ->getSelectedItem($field) == $value) {
              $found = TRUE;
            }
            else {

              // No item selected so use first item.
              $items = $this
                ->getAllOptions($field);
              if (!empty($items) && $items[0]['value'] == $value) {
                $found = TRUE;
              }
            }
          }
          elseif ((string) $field == $value) {

            // Text area with correct text.
            $found = TRUE;
          }
        }
      }
    }
    return $this
      ->assertTrue($fields && $found, $message, $group);
  }

  /**
   * Get the selected value from a select field.
   *
   * @param $element
   *   SimpleXMLElement select element.
   * @return
   *   The selected value or FALSE.
   */
  protected function getSelectedItem(SimpleXMLElement $element) {
    foreach ($element
      ->children() as $item) {
      if (isset($item['selected'])) {
        return $item['value'];
      }
      elseif ($item
        ->getName() == 'optgroup') {
        if ($value = $this
          ->getSelectedItem($item)) {
          return $value;
        }
      }
    }
    return FALSE;
  }

  /**
   * Asserts that a field does not exist in the current page by the given XPath.
   *
   * @param $xpath
   *   XPath used to find the field.
   * @param $value
   *   (optional) Value of the field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoFieldByXPath($xpath, $value = NULL, $message = '', $group = 'Other') {
    $fields = $this
      ->xpath($xpath);

    // If value specified then check array for match.
    $found = TRUE;
    if (isset($value)) {
      $found = FALSE;
      if ($fields) {
        foreach ($fields as $field) {
          if ($field['value'] == $value) {
            $found = TRUE;
          }
        }
      }
    }
    return $this
      ->assertFalse($fields && $found, $message, $group);
  }

  /**
   * Asserts that a field exists in the current page with the given name and value.
   *
   * @param $name
   *   Name of field to assert.
   * @param $value
   *   Value of the field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertFieldByName($name, $value = NULL, $message = NULL, $group = 'Browser') {
    if (!isset($message)) {
      if (!isset($value)) {
        $message = t('Found field with name @name', array(
          '@name' => var_export($name, TRUE),
        ));
      }
      else {
        $message = t('Found field with name @name and value @value', array(
          '@name' => var_export($name, TRUE),
          '@value' => var_export($value, TRUE),
        ));
      }
    }
    return $this
      ->assertFieldByXPath($this
      ->constructFieldXpath('name', $name), $value, $message, $group);
  }

  /**
   * Asserts that a field does not exist with the given name and value.
   *
   * @param $name
   *   Name of field to assert.
   * @param $value
   *   Value of the field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoFieldByName($name, $value = '', $message = '', $group = 'Browser') {
    return $this
      ->assertNoFieldByXPath($this
      ->constructFieldXpath('name', $name), $value, $message ? $message : t('Did not find field by name @name', array(
      '@name' => $name,
    )), $group);
  }

  /**
   * Asserts that a field exists in the current page with the given id and value.
   *
   * @param $id
   *   Id of field to assert.
   * @param $value
   *   Value of the field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertFieldById($id, $value = '', $message = '', $group = 'Browser') {
    return $this
      ->assertFieldByXPath($this
      ->constructFieldXpath('id', $id), $value, $message ? $message : t('Found field by id @id', array(
      '@id' => $id,
    )), $group);
  }

  /**
   * Asserts that a field does not exist with the given id and value.
   *
   * @param $id
   *   Id of field to assert.
   * @param $value
   *   Value of the field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoFieldById($id, $value = '', $message = '', $group = 'Browser') {
    return $this
      ->assertNoFieldByXPath($this
      ->constructFieldXpath('id', $id), $value, $message ? $message : t('Did not find field by id @id', array(
      '@id' => $id,
    )), $group);
  }

  /**
   * Asserts that a checkbox field in the current page is checked.
   *
   * @param $id
   *   Id of field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertFieldChecked($id, $message = '', $group = 'Browser') {
    $elements = $this
      ->xpath('//input[@id=:id]', array(
      ':id' => $id,
    ));
    return $this
      ->assertTrue(isset($elements[0]) && !empty($elements[0]['checked']), $message ? $message : t('Checkbox field @id is checked.', array(
      '@id' => $id,
    )), $group);
  }

  /**
   * Asserts that a checkbox field in the current page is not checked.
   *
   * @param $id
   *   Id of field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoFieldChecked($id, $message = '', $group = 'Browser') {
    $elements = $this
      ->xpath('//input[@id=:id]', array(
      ':id' => $id,
    ));
    return $this
      ->assertTrue(isset($elements[0]) && empty($elements[0]['checked']), $message ? $message : t('Checkbox field @id is not checked.', array(
      '@id' => $id,
    )), $group);
  }

  /**
   * Asserts that a select option in the current page exists.
   *
   * @param $id
   *   Id of select field to assert.
   * @param $option
   *   Option to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertOption($id, $option, $message = '', $group = 'Browser') {
    $options = $this
      ->xpath('//select[@id=:id]/option[@value=:option]', array(
      ':id' => $id,
      ':option' => $option,
    ));
    return $this
      ->assertTrue(isset($options[0]), $message ? $message : t('Option @option for field @id exists.', array(
      '@option' => $option,
      '@id' => $id,
    )), $group);
  }

  /**
   * Asserts that a select option in the current page does not exist.
   *
   * @param $id
   *   Id of select field to assert.
   * @param $option
   *   Option to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoOption($id, $option, $message = '', $group = 'Browser') {
    $selects = $this
      ->xpath('//select[@id=:id]', array(
      ':id' => $id,
    ));
    $options = $this
      ->xpath('//select[@id=:id]/option[@value=:option]', array(
      ':id' => $id,
      ':option' => $option,
    ));
    return $this
      ->assertTrue(isset($selects[0]) && !isset($options[0]), $message ? $message : t('Option @option for field @id does not exist.', array(
      '@option' => $option,
      '@id' => $id,
    )), $group);
  }

  /**
   * Asserts that a select option in the current page is checked.
   *
   * @param $id
   *   Id of select field to assert.
   * @param $option
   *   Option to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   *
   * @todo $id is unusable. Replace with $name.
   */
  protected function assertOptionSelected($id, $option, $message = '', $group = 'Browser') {
    $elements = $this
      ->xpath('//select[@id=:id]//option[@value=:option]', array(
      ':id' => $id,
      ':option' => $option,
    ));
    return $this
      ->assertTrue(isset($elements[0]) && !empty($elements[0]['selected']), $message ? $message : t('Option @option for field @id is selected.', array(
      '@option' => $option,
      '@id' => $id,
    )), $group);
  }

  /**
   * Asserts that a select option in the current page is not checked.
   *
   * @param $id
   *   Id of select field to assert.
   * @param $option
   *   Option to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoOptionSelected($id, $option, $message = '', $group = 'Browser') {
    $elements = $this
      ->xpath('//select[@id=:id]//option[@value=:option]', array(
      ':id' => $id,
      ':option' => $option,
    ));
    return $this
      ->assertTrue(isset($elements[0]) && empty($elements[0]['selected']), $message ? $message : t('Option @option for field @id is not selected.', array(
      '@option' => $option,
      '@id' => $id,
    )), $group);
  }

  /**
   * Asserts that a field exists with the given name or id.
   *
   * @param $field
   *   Name or id of field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertField($field, $message = '', $group = 'Other') {
    return $this
      ->assertFieldByXPath($this
      ->constructFieldXpath('name', $field) . '|' . $this
      ->constructFieldXpath('id', $field), NULL, $message, $group);
  }

  /**
   * Asserts that a field does not exist with the given name or id.
   *
   * @param $field
   *   Name or id of field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoField($field, $message = '', $group = 'Other') {
    return $this
      ->assertNoFieldByXPath($this
      ->constructFieldXpath('name', $field) . '|' . $this
      ->constructFieldXpath('id', $field), NULL, $message, $group);
  }

  /**
   * Asserts that each HTML ID is used for just a single element.
   *
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   * @param $ids_to_skip
   *   An optional array of ids to skip when checking for duplicates. It is
   *   always a bug to have duplicate HTML IDs, so this parameter is to enable
   *   incremental fixing of core code. Whenever a test passes this parameter,
   *   it should add a "todo" comment above the call to this function explaining
   *   the legacy bug that the test wishes to ignore and including a link to an
   *   issue that is working to fix that legacy bug.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertNoDuplicateIds($message = '', $group = 'Other', $ids_to_skip = array()) {
    $status = TRUE;
    foreach ($this
      ->xpath('//*[@id]') as $element) {
      $id = (string) $element['id'];
      if (isset($seen_ids[$id]) && !in_array($id, $ids_to_skip)) {
        $this
          ->fail(t('The HTML ID %id is unique.', array(
          '%id' => $id,
        )), $group);
        $status = FALSE;
      }
      $seen_ids[$id] = TRUE;
    }
    return $this
      ->assert($status, $message, $group);
  }

  /**
   * Helper function: construct an XPath for the given set of attributes and value.
   *
   * @param $attribute
   *   Field attributes.
   * @param $value
   *   Value of field.
   *
   * @return
   *   XPath for specified values.
   */
  protected function constructFieldXpath($attribute, $value) {
    $xpath = '//textarea[@' . $attribute . '=:value]|//input[@' . $attribute . '=:value]|//select[@' . $attribute . '=:value]';
    return $this
      ->buildXPathQuery($xpath, array(
      ':value' => $value,
    ));
  }

  /**
   * Asserts the page responds with the specified response code.
   *
   * @param $code
   *   Response code. For example 200 is a successful page request. For a list
   *   of all codes see http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   Assertion result.
   */
  protected function assertResponse($code, $message = '', $group = 'Browser') {
    $curl_code = curl_getinfo($this->curlHandle, CURLINFO_HTTP_CODE);
    $match = is_array($code) ? in_array($curl_code, $code) : $curl_code == $code;
    return $this
      ->assertTrue($match, $message ? $message : t('HTTP response expected !code, actual !curl_code', array(
      '!code' => $code,
      '!curl_code' => $curl_code,
    )), $group);
  }

  /**
   * Asserts the page did not return the specified response code.
   *
   * @param $code
   *   Response code. For example 200 is a successful page request. For a list
   *   of all codes see http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Browser'; most tests do not override
   *   this default.
   *
   * @return
   *   Assertion result.
   */
  protected function assertNoResponse($code, $message = '', $group = 'Browser') {
    $curl_code = curl_getinfo($this->curlHandle, CURLINFO_HTTP_CODE);
    $match = is_array($code) ? in_array($curl_code, $code) : $curl_code == $code;
    return $this
      ->assertFalse($match, $message ? $message : t('HTTP response not expected !code, actual !curl_code', array(
      '!code' => $code,
      '!curl_code' => $curl_code,
    )), $group);
  }

  /**
   * Asserts that the most recently sent e-mail message has the given value.
   *
   * The field in $name must have the content described in $value.
   *
   * @param $name
   *   Name of field or message property to assert. Examples: subject, body, id, ...
   * @param $value
   *   Value of the field to assert.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'E-mail'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertMail($name, $value = '', $message = '', $group = 'E-mail') {
    $captured_emails = state()
      ->get('system.test_email_collector') ?: array();
    $email = end($captured_emails);
    return $this
      ->assertTrue($email && isset($email[$name]) && $email[$name] == $value, $message, $group);
  }

  /**
   * Asserts that the most recently sent e-mail message has the string in it.
   *
   * @param $field_name
   *   Name of field or message property to assert: subject, body, id, ...
   * @param $string
   *   String to search for.
   * @param $email_depth
   *   Number of emails to search for string, starting with most recent.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertMailString($field_name, $string, $email_depth, $message = '', $group = 'Other') {
    $mails = $this
      ->drupalGetMails();
    $string_found = FALSE;
    for ($i = count($mails) - 1; $i >= count($mails) - $email_depth && $i >= 0; $i--) {
      $mail = $mails[$i];

      // Normalize whitespace, as we don't know what the mail system might have
      // done. Any run of whitespace becomes a single space.
      $normalized_mail = preg_replace('/\\s+/', ' ', $mail[$field_name]);
      $normalized_string = preg_replace('/\\s+/', ' ', $string);
      $string_found = FALSE !== strpos($normalized_mail, $normalized_string);
      if ($string_found) {
        break;
      }
    }
    if (!$message) {
      $message = format_string('Expected text found in @field of email message: "@expected".', array(
        '@field' => $field_name,
        '@expected' => $string,
      ));
    }
    return $this
      ->assertTrue($string_found, $message, $group);
  }

  /**
   * Asserts that the most recently sent e-mail message has the pattern in it.
   *
   * @param $field_name
   *   Name of field or message property to assert: subject, body, id, ...
   * @param $regex
   *   Pattern to search for.
   * @param $message
   *   (optional) A message to display with the assertion. Do not translate
   *   messages: use format_string() to embed variables in the message text, not
   *   t(). If left blank, a default message will be displayed.
   * @param $group
   *   (optional) The group this message is in, which is displayed in a column
   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
   *   translate this string. Defaults to 'Other'; most tests do not override
   *   this default.
   *
   * @return
   *   TRUE on pass, FALSE on fail.
   */
  protected function assertMailPattern($field_name, $regex, $message = '', $group = 'Other') {
    $mails = $this
      ->drupalGetMails();
    $mail = end($mails);
    $regex_found = preg_match("/{$regex}/", $mail[$field_name]);
    if (!$message) {
      $message = format_string('Expected text found in @field of email message: "@expected".', array(
        '@field' => $field_name,
        '@expected' => $regex,
      ));
    }
    return $this
      ->assertTrue($regex_found, $message, $group);
  }

  /**
   * Outputs to verbose the most recent $count emails sent.
   *
   * @param $count
   *   Optional number of emails to output.
   */
  protected function verboseEmail($count = 1) {
    $mails = $this
      ->drupalGetMails();
    for ($i = count($mails) - 1; $i >= count($mails) - $count && $i >= 0; $i--) {
      $mail = $mails[$i];
      $this
        ->verbose(t('Email:') . '<pre>' . print_r($mail, TRUE) . '</pre>');
    }
  }

}