diff --git a/core/tests/Drupal/KernelTests/KernelTestBase.php b/core/tests/Drupal/KernelTests/KernelTestBase.php
index a9999936a0..cb54372bd9 100644
--- a/core/tests/Drupal/KernelTests/KernelTestBase.php
+++ b/core/tests/Drupal/KernelTests/KernelTestBase.php
@@ -22,11 +22,13 @@
 use Drupal\Tests\PhpunitCompatibilityTrait;
 use Drupal\Tests\RandomGeneratorTrait;
 use Drupal\Tests\TestRequirementsTrait;
+use Drupal\Tests\TestVarDumper;
 use Drupal\TestTools\Comparator\MarkupInterfaceComparator;
 use PHPUnit\Framework\Exception;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\VarDumper\VarDumper;
 use org\bovigo\vfs\vfsStream;
 use org\bovigo\vfs\visitor\vfsStreamPrintVisitor;
 use Symfony\Cmf\Component\Routing\RouteObjectInterface;
@@ -228,6 +230,10 @@
   public static function setUpBeforeClass() {
     parent::setUpBeforeClass();
 
+    if (class_exists(VarDumper::class)) {
+      VarDumper::setHandler(TestVarDumper::class . '::varDumperHandler');
+    }
+
     // Change the current dir to DRUPAL_ROOT.
     chdir(static::getDrupalRoot());
   }
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index 4845bf86bd..394179c432 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -23,6 +23,7 @@
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
 use Symfony\Component\CssSelector\CssSelectorConverter;
+use Symfony\Component\VarDumper\VarDumper;
 
 /**
  * Provides a test case for functional Drupal tests.
@@ -220,6 +221,17 @@ public function __construct($name = NULL, array $data = [], $dataName = '') {
     $this->root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public static function setUpBeforeClass() {
+    parent::setUpBeforeClass();
+
+    if (class_exists(VarDumper::class)) {
+      VarDumper::setHandler(TestVarDumper::class . '::varDumperHandler');
+    }
+  }
+
   /**
    * Initializes Mink sessions.
    */
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php.orig b/core/tests/Drupal/Tests/BrowserTestBase.php.orig
new file mode 100644
index 0000000000..4845bf86bd
--- /dev/null
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php.orig
@@ -0,0 +1,758 @@
+<?php
+
+namespace Drupal\Tests;
+
+use Behat\Mink\Driver\GoutteDriver;
+use Behat\Mink\Element\Element;
+use Behat\Mink\Mink;
+use Behat\Mink\Selector\SelectorsHandler;
+use Behat\Mink\Session;
+use Drupal\Component\Serialization\Json;
+use Drupal\Core\Database\Database;
+use Drupal\Core\Test\FunctionalTestSetupTrait;
+use Drupal\Core\Test\TestSetupTrait;
+use Drupal\Core\Utility\Error;
+use Drupal\FunctionalTests\AssertLegacyTrait;
+use Drupal\Tests\block\Traits\BlockCreationTrait;
+use Drupal\Tests\node\Traits\ContentTypeCreationTrait;
+use Drupal\Tests\node\Traits\NodeCreationTrait;
+use Drupal\Tests\user\Traits\UserCreationTrait;
+use Drupal\TestTools\Comparator\MarkupInterfaceComparator;
+use GuzzleHttp\Cookie\CookieJar;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ResponseInterface;
+use Symfony\Component\CssSelector\CssSelectorConverter;
+
+/**
+ * Provides a test case for functional Drupal tests.
+ *
+ * Tests extending BrowserTestBase must exist in the
+ * Drupal\Tests\yourmodule\Functional namespace and live in the
+ * modules/yourmodule/tests/src/Functional directory.
+ *
+ * Tests extending this base class should only translate text when testing
+ * translation functionality. For example, avoid wrapping test text with t()
+ * or TranslatableMarkup().
+ *
+ * @ingroup testing
+ */
+abstract class BrowserTestBase extends TestCase {
+
+  use FunctionalTestSetupTrait;
+  use UiHelperTrait {
+    FunctionalTestSetupTrait::refreshVariables insteadof UiHelperTrait;
+  }
+  use TestSetupTrait;
+  use BlockCreationTrait {
+    placeBlock as drupalPlaceBlock;
+  }
+  use AssertLegacyTrait;
+  use RandomGeneratorTrait;
+  use NodeCreationTrait {
+    getNodeByTitle as drupalGetNodeByTitle;
+    createNode as drupalCreateNode;
+  }
+  use ContentTypeCreationTrait {
+    createContentType as drupalCreateContentType;
+  }
+  use ConfigTestTrait;
+  use TestRequirementsTrait;
+  use UserCreationTrait {
+    createRole as drupalCreateRole;
+    createUser as drupalCreateUser;
+  }
+  use XdebugRequestTrait;
+  use PhpunitCompatibilityTrait;
+
+  /**
+   * The database prefix of this test run.
+   *
+   * @var string
+   */
+  protected $databasePrefix;
+
+  /**
+   * Time limit in seconds for the test.
+   *
+   * @var int
+   */
+  protected $timeLimit = 500;
+
+  /**
+   * The translation file directory for the test environment.
+   *
+   * This is set in BrowserTestBase::prepareEnvironment().
+   *
+   * @var string
+   */
+  protected $translationFilesDirectory;
+
+  /**
+   * The config importer that can be used in a test.
+   *
+   * @var \Drupal\Core\Config\ConfigImporter
+   */
+  protected $configImporter;
+
+  /**
+   * Modules to enable.
+   *
+   * The test runner will merge the $modules lists from this class, the class
+   * it extends, and so on up the class hierarchy. It is not necessary to
+   * include modules in your list that a parent class has already declared.
+   *
+   * @var string[]
+   *
+   * @see \Drupal\Tests\BrowserTestBase::installDrupal()
+   */
+  protected static $modules = [];
+
+  /**
+   * The profile to install as a basis for testing.
+   *
+   * @var string
+   */
+  protected $profile = 'testing';
+
+  /**
+   * The theme to install as the default for testing.
+   *
+   * Defaults to the install profile's default theme, if it specifies any.
+   *
+   * @var string
+   */
+  protected $defaultTheme;
+
+  /**
+   * An array of custom translations suitable for drupal_rewrite_settings().
+   *
+   * @var array
+   */
+  protected $customTranslations;
+
+  /*
+   * Mink class for the default driver to use.
+   *
+   * Should be a fully-qualified class name that implements
+   * Behat\Mink\Driver\DriverInterface.
+   *
+   * Value can be overridden using the environment variable MINK_DRIVER_CLASS.
+   *
+   * @var string
+   */
+  protected $minkDefaultDriverClass = GoutteDriver::class;
+
+  /*
+   * Mink default driver params.
+   *
+   * If it's an array its contents are used as constructor params when default
+   * Mink driver class is instantiated.
+   *
+   * Can be overridden using the environment variable MINK_DRIVER_ARGS. In this
+   * case that variable should be a JSON array, for example:
+   * '["firefox", null, "http://localhost:4444/wd/hub"]'.
+   *
+   *
+   * @var array
+   */
+  protected $minkDefaultDriverArgs;
+
+  /**
+   * Mink session manager.
+   *
+   * This will not be initialized if there was an error during the test setup.
+   *
+   * @var \Behat\Mink\Mink|null
+   */
+  protected $mink;
+
+  /**
+   * {@inheritdoc}
+   *
+   * Browser tests are run in separate processes to prevent collisions between
+   * code that may be loaded by tests.
+   */
+  protected $runTestInSeparateProcess = TRUE;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $preserveGlobalState = FALSE;
+
+  /**
+   * The base URL.
+   *
+   * @var string
+   */
+  protected $baseUrl;
+
+  /**
+   * The original array of shutdown function callbacks.
+   *
+   * @var array
+   */
+  protected $originalShutdownCallbacks = [];
+
+  /**
+   * The app root.
+   *
+   * @var string
+   */
+  protected $root;
+
+  /**
+   * The original container.
+   *
+   * Move this to \Drupal\Core\Test\FunctionalTestSetupTrait once TestBase no
+   * longer provides the same value.
+   *
+   * @var \Symfony\Component\DependencyInjection\ContainerInterface
+   */
+  protected $originalContainer;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __construct($name = NULL, array $data = [], $dataName = '') {
+    parent::__construct($name, $data, $dataName);
+
+    $this->root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
+  }
+
+  /**
+   * Initializes Mink sessions.
+   */
+  protected function initMink() {
+    $driver = $this->getDefaultDriverInstance();
+
+    if ($driver instanceof GoutteDriver) {
+      // Turn off curl timeout. Having a timeout is not a problem in a normal
+      // test running, but it is a problem when debugging. Also, disable SSL
+      // peer verification so that testing under HTTPS always works.
+      /** @var \GuzzleHttp\Client $client */
+      $client = $this->container->get('http_client_factory')->fromOptions([
+        'timeout' => NULL,
+        'verify' => FALSE,
+      ]);
+
+      // Inject a Guzzle middleware to generate debug output for every request
+      // performed in the test.
+      $handler_stack = $client->getConfig('handler');
+      $handler_stack->push($this->getResponseLogHandler());
+
+      $driver->getClient()->setClient($client);
+    }
+
+    $selectors_handler = new SelectorsHandler([
+      'hidden_field_selector' => new HiddenFieldSelector(),
+    ]);
+    $session = new Session($driver, $selectors_handler);
+    $this->mink = new Mink();
+    $this->mink->registerSession('default', $session);
+    $this->mink->setDefaultSessionName('default');
+    $this->registerSessions();
+
+    $this->initFrontPage();
+
+    // Copies cookies from the current environment, for example, XDEBUG_SESSION
+    // in order to support Xdebug.
+    // @see BrowserTestBase::initFrontPage()
+    $cookies = $this->extractCookiesFromRequest(\Drupal::request());
+    foreach ($cookies as $cookie_name => $values) {
+      foreach ($values as $value) {
+        $session->setCookie($cookie_name, $value);
+      }
+    }
+
+    return $session;
+  }
+
+  /**
+   * Visits the front page when initializing Mink.
+   *
+   * According to the W3C WebDriver specification a cookie can only be set if
+   * the cookie domain is equal to the domain of the active document. When the
+   * browser starts up the active document is not our domain but 'about:blank'
+   * or similar. To be able to set our User-Agent and Xdebug cookies at the
+   * start of the test we now do a request to the front page so the active
+   * document matches the domain.
+   *
+   * @see https://w3c.github.io/webdriver/webdriver-spec.html#add-cookie
+   * @see https://www.w3.org/Bugs/Public/show_bug.cgi?id=20975
+   */
+  protected function initFrontPage() {
+    $session = $this->getSession();
+    $session->visit($this->baseUrl);
+  }
+
+  /**
+   * Gets an instance of the default Mink driver.
+   *
+   * @return Behat\Mink\Driver\DriverInterface
+   *   Instance of default Mink driver.
+   *
+   * @throws \InvalidArgumentException
+   *   When provided default Mink driver class can't be instantiated.
+   */
+  protected function getDefaultDriverInstance() {
+    // Get default driver params from environment if available.
+    if ($arg_json = $this->getMinkDriverArgs()) {
+      $this->minkDefaultDriverArgs = json_decode($arg_json, TRUE);
+    }
+
+    // Get and check default driver class from environment if available.
+    if ($minkDriverClass = getenv('MINK_DRIVER_CLASS')) {
+      if (class_exists($minkDriverClass)) {
+        $this->minkDefaultDriverClass = $minkDriverClass;
+      }
+      else {
+        throw new \InvalidArgumentException("Can't instantiate provided $minkDriverClass class by environment as default driver class.");
+      }
+    }
+
+    if (is_array($this->minkDefaultDriverArgs)) {
+      // Use ReflectionClass to instantiate class with received params.
+      $reflector = new \ReflectionClass($this->minkDefaultDriverClass);
+      $driver = $reflector->newInstanceArgs($this->minkDefaultDriverArgs);
+    }
+    else {
+      $driver = new $this->minkDefaultDriverClass();
+    }
+    return $driver;
+  }
+
+  /**
+   * Get the Mink driver args from an environment variable, if it is set. Can
+   * be overridden in a derived class so it is possible to use a different
+   * value for a subset of tests, e.g. the JavaScript tests.
+   *
+   *  @return string|false
+   *   The JSON-encoded argument string. False if it is not set.
+   */
+  protected function getMinkDriverArgs() {
+    return getenv('MINK_DRIVER_ARGS');
+  }
+
+  /**
+   * Provides a Guzzle middleware handler to log every response received.
+   *
+   * @return callable
+   *   The callable handler that will do the logging.
+   */
+  protected function getResponseLogHandler() {
+    return function (callable $handler) {
+      return function (RequestInterface $request, array $options) use ($handler) {
+        return $handler($request, $options)
+          ->then(function (ResponseInterface $response) use ($request) {
+            if ($this->htmlOutputEnabled) {
+
+              $caller = $this->getTestMethodCaller();
+              $html_output = 'Called from ' . $caller['function'] . ' line ' . $caller['line'];
+              $html_output .= '<hr />' . $request->getMethod() . ' request to: ' . $request->getUri();
+
+              // On redirect responses (status code starting with '3') we need
+              // to remove the meta tag that would do a browser refresh. We
+              // don't want to redirect developers away when they look at the
+              // debug output file in their browser.
+              $body = $response->getBody();
+              $status_code = (string) $response->getStatusCode();
+              if ($status_code[0] === '3') {
+                $body = preg_replace('#<meta http-equiv="refresh" content=.+/>#', '', $body, 1);
+              }
+              $html_output .= '<hr />' . $body;
+              $html_output .= $this->formatHtmlOutputHeaders($response->getHeaders());
+
+              $this->htmlOutput($html_output);
+            }
+            return $response;
+          });
+      };
+    };
+  }
+
+  /**
+   * Registers additional Mink sessions.
+   *
+   * Tests wishing to use a different driver or change the default driver should
+   * override this method.
+   *
+   * @code
+   *   // Register a new session that uses the MinkPonyDriver.
+   *   $pony = new MinkPonyDriver();
+   *   $session = new Session($pony);
+   *   $this->mink->registerSession('pony', $session);
+   * @endcode
+   */
+  protected function registerSessions() {}
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    // Allow tests to compare MarkupInterface objects via assertEquals().
+    $this->registerComparator(new MarkupInterfaceComparator());
+
+    $this->setupBaseUrl();
+
+    // Install Drupal test site.
+    $this->prepareEnvironment();
+    $this->installDrupal();
+
+    // Setup Mink.
+    $this->initMink();
+
+    // Set up the browser test output file.
+    $this->initBrowserOutputFile();
+
+    // Ensure that the test is not marked as risky because of no assertions. In
+    // PHPUnit 6 tests that only make assertions using $this->assertSession()
+    // can be marked as risky.
+    $this->addToAssertionCount(1);
+  }
+
+  /**
+   * Ensures test files are deletable.
+   *
+   * Some tests chmod generated files to be read only. During
+   * BrowserTestBase::cleanupEnvironment() and other cleanup operations,
+   * these files need to get deleted too.
+   *
+   * @param string $path
+   *   The file path.
+   *
+   * @see \Drupal\Core\File\FileSystemInterface::deleteRecursive()
+   */
+  public static function filePreDeleteCallback($path) {
+    // When the webserver runs with the same system user as phpunit, we can
+    // make read-only files writable again. If not, chmod will fail while the
+    // file deletion still works if file permissions have been configured
+    // correctly. Thus, we ignore any problems while running chmod.
+    @chmod($path, 0700);
+  }
+
+  /**
+   * Clean up the Simpletest environment.
+   */
+  protected function cleanupEnvironment() {
+    // Remove all prefixed tables.
+    $original_connection_info = Database::getConnectionInfo('simpletest_original_default');
+    $original_prefix = $original_connection_info['default']['prefix']['default'];
+    $test_connection_info = Database::getConnectionInfo('default');
+    $test_prefix = $test_connection_info['default']['prefix']['default'];
+    if ($original_prefix != $test_prefix) {
+      $tables = Database::getConnection()->schema()->findTables('%');
+      foreach ($tables as $table) {
+        if (Database::getConnection()->schema()->dropTable($table)) {
+          unset($tables[$table]);
+        }
+      }
+    }
+
+    // Delete test site directory.
+    \Drupal::service('file_system')->deleteRecursive($this->siteDirectory, [$this, 'filePreDeleteCallback']);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function tearDown() {
+    parent::tearDown();
+
+    // Destroy the testing kernel.
+    if (isset($this->kernel)) {
+      $this->cleanupEnvironment();
+      $this->kernel->shutdown();
+    }
+
+    // Ensure that internal logged in variable is reset.
+    $this->loggedInUser = FALSE;
+
+    if ($this->mink) {
+      $this->mink->stopSessions();
+    }
+
+    // Restore original shutdown callbacks.
+    if (function_exists('drupal_register_shutdown_function')) {
+      $callbacks = &drupal_register_shutdown_function();
+      $callbacks = $this->originalShutdownCallbacks;
+    }
+  }
+
+  /**
+   * Returns Mink session.
+   *
+   * @param string $name
+   *   (optional) Name of the session. Defaults to the active session.
+   *
+   * @return \Behat\Mink\Session
+   *   The active Mink session object.
+   */
+  public function getSession($name = NULL) {
+    return $this->mink->getSession($name);
+  }
+
+  /**
+   * Get session cookies from current session.
+   *
+   * @return \GuzzleHttp\Cookie\CookieJar
+   *   A cookie jar with the current session.
+   */
+  protected function getSessionCookies() {
+    $domain = parse_url($this->getUrl(), PHP_URL_HOST);
+    $session_id = $this->getSession()->getCookie($this->getSessionName());
+    $cookies = CookieJar::fromArray([$this->getSessionName() => $session_id], $domain);
+
+    return $cookies;
+  }
+
+  /**
+   * Obtain the HTTP client for the system under test.
+   *
+   * Use this method for arbitrary HTTP requests to the site under test. For
+   * most tests, you should not get the HTTP client and instead use navigation
+   * methods such as drupalGet() and clickLink() in order to benefit from
+   * assertions.
+   *
+   * Subclasses which substitute a different Mink driver should override this
+   * method and provide a Guzzle client if the Mink driver provides one.
+   *
+   * @return \GuzzleHttp\ClientInterface
+   *   The client with BrowserTestBase configuration.
+   *
+   * @throws \RuntimeException
+   *   If the Mink driver does not support a Guzzle HTTP client, throw an
+   *   exception.
+   */
+  protected function getHttpClient() {
+    /* @var $mink_driver \Behat\Mink\Driver\DriverInterface */
+    $mink_driver = $this->getSession()->getDriver();
+    if ($mink_driver instanceof GoutteDriver) {
+      return $mink_driver->getClient()->getClient();
+    }
+    throw new \RuntimeException('The Mink client type ' . get_class($mink_driver) . ' does not support getHttpClient().');
+  }
+
+  /**
+   * Helper function to get the options of select field.
+   *
+   * @param \Behat\Mink\Element\NodeElement|string $select
+   *   Name, ID, or Label of select field to assert.
+   * @param \Behat\Mink\Element\Element $container
+   *   (optional) Container element to check against. Defaults to current page.
+   *
+   * @return array
+   *   Associative array of option keys and values.
+   */
+  protected function getOptions($select, Element $container = NULL) {
+    if (is_string($select)) {
+      $select = $this->assertSession()->selectExists($select, $container);
+    }
+    $options = [];
+    /* @var \Behat\Mink\Element\NodeElement $option */
+    foreach ($select->findAll('xpath', '//option') as $option) {
+      $label = $option->getText();
+      $value = $option->getAttribute('value') ?: $label;
+      $options[$value] = $label;
+    }
+    return $options;
+  }
+
+  /**
+   * Installs Drupal into the Simpletest site.
+   */
+  public function installDrupal() {
+    $this->initUserSession();
+    $this->prepareSettings();
+    $this->doInstall();
+    $this->initSettings();
+    $container = $this->initKernel(\Drupal::request());
+    $this->initConfig($container);
+    $this->installDefaultThemeFromClassProperty($container);
+    $this->installModulesFromClassProperty($container);
+    $this->rebuildAll();
+  }
+
+  /**
+   * Prevents serializing any properties.
+   *
+   * Browser tests are run in a separate process. To do this PHPUnit creates a
+   * script to run the test. If it fails, the test result object will contain a
+   * stack trace which includes the test object. It will attempt to serialize
+   * it. Returning an empty array prevents it from serializing anything it
+   * should not.
+   *
+   * @return array
+   *   An empty array.
+   *
+   * @see vendor/phpunit/phpunit/src/Util/PHP/Template/TestCaseMethod.tpl.dist
+   */
+  public function __sleep() {
+    return [];
+  }
+
+  /**
+   * Translates a CSS expression to its XPath equivalent.
+   *
+   * The search is relative to the root element (HTML tag normally) of the page.
+   *
+   * @param string $selector
+   *   CSS selector to use in the search.
+   * @param bool $html
+   *   (optional) Enables HTML support. Disable it for XML documents.
+   * @param string $prefix
+   *   (optional) The prefix for the XPath expression.
+   *
+   * @return string
+   *   The equivalent XPath of a CSS expression.
+   */
+  protected function cssSelectToXpath($selector, $html = TRUE, $prefix = 'descendant-or-self::') {
+    return (new CssSelectorConverter($html))->toXPath($selector, $prefix);
+  }
+
+  /**
+   * Performs an xpath search on the contents of the internal browser.
+   *
+   * The search is relative to the root element (HTML tag normally) of the page.
+   *
+   * @param string $xpath
+   *   The xpath string to use in the search.
+   * @param array $arguments
+   *   An array of arguments with keys in the form ':name' matching the
+   *   placeholders in the query. The values may be either strings or numeric
+   *   values.
+   *
+   * @return \Behat\Mink\Element\NodeElement[]
+   *   The list of elements matching the xpath expression.
+   */
+  protected function xpath($xpath, array $arguments = []) {
+    $xpath = $this->assertSession()->buildXPathQuery($xpath, $arguments);
+    return $this->getSession()->getPage()->findAll('xpath', $xpath);
+  }
+
+  /**
+   * Configuration accessor for tests. Returns non-overridden configuration.
+   *
+   * @param string $name
+   *   Configuration name.
+   *
+   * @return \Drupal\Core\Config\Config
+   *   The configuration object with original configuration data.
+   */
+  protected function config($name) {
+    return $this->container->get('config.factory')->getEditable($name);
+  }
+
+  /**
+   * Returns all response headers.
+   *
+   * @return array
+   *   The HTTP headers values.
+   *
+   * @deprecated in drupal:8.8.0 and is removed from drupal:9.0.0.
+   *   Use $this->getSession()->getResponseHeaders() instead.
+   *
+   * @see https://www.drupal.org/node/3067207
+   */
+  protected function drupalGetHeaders() {
+    @trigger_error('Drupal\Tests\BrowserTestBase::drupalGetHeaders() is deprecated in drupal:8.8.0 and is removed from drupal:9.0.0. Use $this->getSession()->getResponseHeaders() instead. See https://www.drupal.org/node/3067207', E_USER_DEPRECATED);
+    return $this->getSession()->getResponseHeaders();
+  }
+
+  /**
+   * Gets the value of an HTTP response header.
+   *
+   * If multiple requests were required to retrieve the page, only the headers
+   * from the last request will be checked by default.
+   *
+   * @param string $name
+   *   The name of the header to retrieve. Names are case-insensitive (see RFC
+   *   2616 section 4.2).
+   *
+   * @return string|null
+   *   The HTTP header value or NULL if not found.
+   */
+  protected function drupalGetHeader($name) {
+    return $this->getSession()->getResponseHeader($name);
+  }
+
+  /**
+   * Gets the JavaScript drupalSettings variable for the currently-loaded page.
+   *
+   * @return array
+   *   The JSON decoded drupalSettings value from the current page.
+   */
+  protected function getDrupalSettings() {
+    $html = $this->getSession()->getPage()->getContent();
+    if (preg_match('@<script type="application/json" data-drupal-selector="drupal-settings-json">([^<]*)</script>@', $html, $matches)) {
+      return Json::decode($matches[1]);
+    }
+    return [];
+  }
+
+  /**
+   * Retrieves the current calling line in the class under test.
+   *
+   * @return array
+   *   An associative array with keys 'file', 'line' and 'function'.
+   */
+  protected function getTestMethodCaller() {
+    $backtrace = debug_backtrace();
+    // Find the test class that has the test method.
+    while ($caller = Error::getLastCaller($backtrace)) {
+      // If we match PHPUnit's TestCase::runTest, then the previously processed
+      // caller entry is where our test method sits.
+      if (isset($last_caller) && isset($caller['function']) && $caller['function'] === 'PHPUnit\Framework\TestCase->runTest()') {
+        // Return the last caller since that has to be the test class.
+        $caller = $last_caller;
+        break;
+      }
+
+      // If the test method is implemented by a test class's parent then the
+      // class name of $this will not be part of the backtrace.
+      // In that case we process the backtrace until the caller is not a
+      // subclass of $this and return the previous caller.
+      if (isset($last_caller) && (!isset($caller['class']) || !is_subclass_of($this, $caller['class']))) {
+        // Return the last caller since that has to be the test class.
+        $caller = $last_caller;
+        break;
+      }
+
+      if (isset($caller['class']) && $caller['class'] === get_class($this)) {
+        break;
+      }
+
+      // Otherwise we have not reached our test class yet: save the last caller
+      // and remove an element from to backtrace to process the next call.
+      $last_caller = $caller;
+      array_shift($backtrace);
+    }
+
+    return $caller;
+  }
+
+  /**
+   * Transforms a nested array into a flat array suitable for drupalPostForm().
+   *
+   * @param array $values
+   *   A multi-dimensional form values array to convert.
+   *
+   * @return array
+   *   The flattened $edit array suitable for BrowserTestBase::drupalPostForm().
+   */
+  protected function translatePostValues(array $values) {
+    $edit = [];
+    // The easiest and most straightforward way to translate values suitable for
+    // BrowserTestBase::drupalPostForm() is to actually build the POST data
+    // string and convert the resulting key/value pairs back into a flat array.
+    $query = http_build_query($values);
+    foreach (explode('&', $query) as $item) {
+      list($key, $value) = explode('=', $item);
+      $edit[urldecode($key)] = urldecode($value);
+    }
+    return $edit;
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/TestVarDumper.php b/core/tests/Drupal/Tests/TestVarDumper.php
new file mode 100644
index 0000000000..46a45f331f
--- /dev/null
+++ b/core/tests/Drupal/Tests/TestVarDumper.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace Drupal\Tests;
+
+use Symfony\Component\VarDumper\Cloner\VarCloner;
+use Symfony\Component\VarDumper\Dumper\CliDumper;
+
+/**
+ * Provides handlers for the Symfony VarDumper to work within tests.
+ *
+ * This allows the dump() function to produce output on the terminal without
+ * causing PHPUnit to complain.
+ */
+class TestVarDumper {
+
+  /**
+   * Handler for \Symfony\Component\VarDumper\VarDumper.
+   */
+  public static function varDumperHandler($var) {
+    $cloner = new VarCloner();
+
+    // Need to write a newline before any output.
+    fwrite(STDOUT, "\n");
+
+    $dumper = new CliDumper(self::class . '::cliDumperCallback');
+
+    $dumper->setColors(TRUE);
+    $dumper->dump($cloner->cloneVar($var));
+  }
+
+  /**
+   * Callback for \Symfony\Component\VarDumper\Dumper\CliDumper.
+   */
+  public static function cliDumperCallback($line, $depth, $indent_pad) {
+    if ($depth != -1) {
+      fwrite(STDOUT, str_repeat($indent_pad, $depth) . $line . "\n");
+    }
+  }
+
+}