diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 9870754..92fed64 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -843,8 +843,10 @@ function drupal_valid_test_ua($new_prefix = NULL) {
   // a test environment.
   $test_prefix = FALSE;
 
-  // Perform a basic check on the User-Agent HTTP request header first. Any
-  // inbound request that uses the simpletest UA header needs to be validated.
+  // Perform a basic check on the Simpletest-user-agent cookie first. If it
+  // does not exists then perform a basic check on the User-Agent HTTP request
+  // header. Any inbound request that uses the simpletest UA header needs to be
+  // validated.
   $http_user_agent = isset($_SERVER['HTTP_USER_AGENT']) ? $_SERVER['HTTP_USER_AGENT'] : NULL;
   $user_agent = isset($_COOKIE['SIMPLETEST_USER_AGENT']) ? $_COOKIE['SIMPLETEST_USER_AGENT'] : $http_user_agent;
   if (isset($user_agent) && preg_match("/^(simpletest\d+);(.+);(.+);(.+)$/", $user_agent, $matches)) {
diff --git a/core/lib/Drupal/Core/Database/Database.php b/core/lib/Drupal/Core/Database/Database.php
index a1d9675..6a24a05 100644
--- a/core/lib/Drupal/Core/Database/Database.php
+++ b/core/lib/Drupal/Core/Database/Database.php
@@ -469,12 +469,20 @@ public static function convertDbUrlToConnectionInfo($url, $root) {
       'pass' => '',
       'fragment' => '',
     );
-    if ($info['path'][0] === '/') {
-      $info['path'] = substr($info['path'], 1);
+
+    // A SQLite database is special because it datebase connection is directly
+    // to the database file. The variable $info['path'] holds the location of
+    // the database file.
+    if ($info['scheme'] === 'sqlite') {
+      if ($info['path'][0] !== '/') {
+        $info['path'] = '/' . $info['path'];
+      }
+      $info['path'] = $root . $info['path'];
     }
-    if ($info['scheme'] === 'sqlite' && $info['path'][0] !== '/') {
-      $info['path'] = $root . '/' . $info['path'];
+    elseif ($info['path'][0] === '/') {
+      $info['path'] = substr($info['path'], 1);
     }
+
     $database = array(
       'driver' => $info['scheme'],
       'username' => $info['user'],
@@ -500,7 +508,7 @@ public static function convertDbUrlToConnectionInfo($url, $root) {
   public static function getConnectionInfoAsUrl($key = 'default') {
     $db_info = static::getConnectionInfo($key);
     if ($db_info['default']['driver'] == 'sqlite') {
-      $db_url = $db_info['default']['driver'] . '://localhost/' . $db_info['default']['database'];
+      $db_url = 'sqlite://localhost/' . $db_info['default']['database'];
     }
     else {
       $user = '';
diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index 327ff51..3b46028 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -238,8 +238,8 @@ function simpletest_phpunit_configuration_filepath() {
  *  The results as returned by exec().
  */
 function simpletest_phpunit_run_command(array $unescaped_test_classnames, $phpunit_file) {
-  // Set the up an environment variable containing the database connection so
-  // that functional tests can connect to the database.
+  // Setup an environment variable containing the database connection so that
+  // functional tests can connect to the database.
   putenv('SIMPLETEST_DB=' . Database::getConnectionInfoAsUrl());
   $phpunit_bin = simpletest_phpunit_command();
 
diff --git a/core/modules/simpletest/src/BrowserTestBase.php b/core/modules/simpletest/src/BrowserTestBase.php
index d4d3168..ac7845f 100644
--- a/core/modules/simpletest/src/BrowserTestBase.php
+++ b/core/modules/simpletest/src/BrowserTestBase.php
@@ -26,10 +26,11 @@
 use Drupal\Core\Site\Settings;
 use Drupal\Core\StreamWrapper\StreamWrapperInterface;
 use Drupal\Core\Test\TestRunnerKernel;
+use Drupal\user\UserInterface;
 use Symfony\Component\HttpFoundation\Request;
 
 /**
- * Test case for typical Drupal tests.
+ * Test case for functional Drupal tests.
  *
  * @ingroup testing
  *
@@ -68,6 +69,8 @@
 
   /**
    * Time limit in seconds for the test.
+   *
+   * @var int
    */
   protected $timeLimit = 500;
 
@@ -150,7 +153,7 @@
   protected $sessionName;
 
   /**
-   * The current user logged in using the internal browser.
+   * The current user logged in using the Mink controled browser.
    *
    * @var bool
    */
@@ -159,12 +162,14 @@
   /**
    * The root user.
    *
-   * @var UserSession
+   * @var \Drupal\Core\Session\UserSession
    */
   protected $rootUser;
 
   /**
    * The config directories used in this test.
+   *
+   * @var array
    */
   protected $configDirectories = array();
 
@@ -178,7 +183,7 @@
   /**
    * Mink session manager.
    *
-   * @var Mink
+   * @var \Behat\Mink\Mink
    */
   protected $mink;
 
@@ -228,10 +233,8 @@ protected function setUp() {
     $parsed_url = parse_url($base_url);
     $host = $parsed_url['host'] . (isset($parsed_url['port']) ? ':' . $parsed_url['port'] : '');
     $path = isset($parsed_url['path']) ? rtrim(rtrim($parsed_url['path']), '/') : '';
-    $port = (isset($parsed_url['port']) ? $parsed_url['port'] : 80);
-    if ($path == '/') {
-      $path = '';
-    }
+    $port = isset($parsed_url['port']) ? $parsed_url['port'] : 80;
+
     // If the passed URL schema is 'https' then setup the $_SERVER variables
     // properly so that testing will run under HTTPS.
     if ($parsed_url['scheme'] === 'https') {
@@ -277,8 +280,8 @@ protected function setUp() {
       foreach ($pairs as $pair) {
         list($key, $value) = explode('=', $pair);
         // Account for key-value pairs being separated by multiple spaces.
-        if (trim($key, ' ') == 'idekey') {
-          $session->setCookie('XDEBUG_SESSION', trim($value, ' '));
+        if (trim($key) == 'idekey') {
+          $session->setCookie('XDEBUG_SESSION', trim($value));
         }
       }
     }
@@ -344,8 +347,8 @@ protected function tearDown() {
   /**
    * Returns Mink session.
    *
-   * @param string|null $name
-   *   (optional) Name of the session OR active session will be used.
+   * @param string $name
+   *   (optional) Name of the session. Defaults to the active session.
    *
    * @return \Behat\Mink\Session
    *   The active mink session object.
@@ -355,9 +358,9 @@ public function getSession($name = NULL) {
   }
 
   /**
-   * Returns Mink assert session.
+   * Returns WebAssert object.
    *
-   * @param string|null $name
+   * @param string $name
    *   (optional) Name of the session. Defaults to the active session.
    *
    * @return \Drupal\simpletest\WebAssert
@@ -384,7 +387,7 @@ protected function prepareRequest() {
    * Retrieves a Drupal path or an absolute path.
    *
    * @param string $path
-   *   Drupal path or URL to load into internal browser
+   *   Drupal path or URL to load into Mink controled browser.
    * @param array $options
    *   (optional) Options to be forwarded to the url generator.
    *
@@ -418,7 +421,7 @@ protected function drupalGet($path, array $options = array()) {
    * Takes a path and returns an absolute path.
    *
    * @param string $path
-   *   A path from the internal browser content.
+   *   A path from the Mink controled browser content.
    *
    * @return string
    *   The $path with $base_url prepended, if necessary.
@@ -553,9 +556,21 @@ protected function drupalCreateRole(array $permissions, $rid = NULL, $name = NUL
       }
       return $role->id();
     }
-    else {
-      return FALSE;
+
+    return FALSE;
+  }
+
+  /**
+   * Gets the random generator for the utility methods.
+   *
+   * @return \Drupal\Component\Utility\Random
+   *   The random generator
+   */
+  protected function getRandomGenerator() {
+    if (!is_object($this->randomGenerator)) {
+      $this->randomGenerator = new Random();
     }
+    return $this->randomGenerator;
   }
 
   /**
@@ -630,7 +645,7 @@ protected function checkPermissions(array $permissions) {
   }
 
   /**
-   * Logs in a user using the mink browser.
+   * Logs in a user using the mink controled browser.
    *
    * If a user is already logged in, then the current user is logged out before
    * logging in the specified user.
@@ -677,7 +692,7 @@ protected function drupalLogin(AccountInterface $account) {
   }
 
   /**
-   * Logs a user out of the internal browser and confirms.
+   * Logs a user out of the Mink controled browser and confirms.
    *
    * Confirms logout by checking the login page.
    */
@@ -725,7 +740,7 @@ protected function submitForm($edit, $submit, $form_html_id = NULL) {
 
     // Get the form.
     if (isset($form_html_id)) {
-      $form = $assert_session->elementExists('xpath', "//form[@id='" . $form_html_id . "']");
+      $form = $assert_session->elementExists('xpath', "//form[@id='$form_html_id']");
       $submit_button = $assert_session->buttonExists($submit, $form);
     }
     else {
@@ -750,9 +765,9 @@ protected function submitForm($edit, $submit, $form_html_id = NULL) {
   /**
    * Helper function to get the options of select field.
    *
-   * @param NodeElement|string $select
+   * @param \Behat\Mink\Element\NodeElement|string $select
    *   Name, ID, or Label of select field to assert.
-   * @param Element $container
+   * @param \Behat\Mink\Element\Element $container
    *   (optional) Container element to check against. Defaults to current page.
    *
    * @return array
@@ -773,18 +788,6 @@ protected function getOptions($select, Element $container = NULL) {
   }
 
   /**
-   * {@inheritdoc}
-   */
-  public function run(\PHPUnit_Framework_TestResult $result = NULL) {
-    if ($result === NULL) {
-      $result = $this->createResult();
-    }
-
-    parent::run($result);
-    return $result;
-  }
-
-  /**
    * Override to use Mink exceptions.
    *
    * @return mixed
@@ -802,37 +805,6 @@ protected function runTest() {
   }
 
   /**
-   * Generates a unique random string containing letters and numbers.
-   *
-   * Do not use this method when testing unvalidated user input. Instead, use
-   * \Drupal\simpletest\TestBase::randomString().
-   *
-   * @param int $length
-   *   (optional) Length of random string to generate.
-   *
-   * @return string
-   *   Randomly generated unique string.
-   *
-   * @see \Drupal\Component\Utility\Random::name()
-   */
-  public function randomName($length = 8) {
-    return $this->getRandomGenerator()->name($length, TRUE);
-  }
-
-  /**
-   * Gets the random generator for the utility methods.
-   *
-   * @return \Drupal\Component\Utility\Random
-   *   The random generator
-   */
-  protected function getRandomGenerator() {
-    if (!is_object($this->randomGenerator)) {
-      $this->randomGenerator = new Random();
-    }
-    return $this->randomGenerator;
-  }
-
-  /**
    * Installs drupal into the simpletest site.
    */
   public function installDrupal() {
@@ -841,7 +813,7 @@ public function installDrupal() {
       'uid' => 1,
       'name' => 'admin',
       'mail' => 'admin@example.com',
-      'passRaw' => $this->randomName(),
+      'passRaw' => $this->randomMachineName(),
     ));
 
     // Some tests (SessionTest and SessionHttpsTest) need to examine whether the
@@ -1033,9 +1005,9 @@ protected function installParameters() {
    *
    * The generated database table prefix is used for the Drupal installation
    * being performed for the test. It is also used by the cookie value of
-   * SIMPLETEST_USER_AGENT by the mink browser. During early Drupal bootstrap,
-   * the cookie is parsed, and if it matches, all database queries use
-   * the database table prefix that has been generated here.
+   * SIMPLETEST_USER_AGENT by the mink controled browser. During early Drupal
+   * bootstrap, the cookie is parsed, and if it matches, all database queries
+   * use the database table prefix that has been generated here.
    *
    * @see drupal_valid_test_ua()
    * @see BrowserTestBase::prepareEnvironment()
@@ -1202,8 +1174,6 @@ protected function writeSettings(array $settings) {
     include_once DRUPAL_ROOT . '/core/includes/install.inc';
     $filename = $this->siteDirectory . '/settings.php';
 
-    error_log($filename);
-
     // system_requirements() removes write permissions from settings.php
     // whenever it is invoked.
     // Not using File API; a potential error must trigger a PHP warning.
@@ -1215,9 +1185,9 @@ protected function writeSettings(array $settings) {
    * Rebuilds \Drupal::getContainer().
    *
    * Use this to build a new kernel and service container. For example, when the
-   * list of enabled modules is changed via the internal browser, in which case
-   * the test process still contains an old kernel and service container with an
-   * old module list.
+   * list of enabled modules is changed via the Mink controled browser, in which
+   * case the test process still contains an old kernel and service container
+   * with an old module list.
    *
    * @see BrowserTestBase::prepareEnvironment()
    * @see BrowserTestBase::restoreEnvironment()
@@ -1290,7 +1260,7 @@ protected function prepareRequestForGenerator($clean_urls = TRUE, $override_serv
   /**
    * Resets all data structures after having enabled new modules.
    *
-   * This method is called by \Drupal\simpletest\WebTestBase::setUp() after
+   * This method is called by \Drupal\simpletest\BrowserTestBase::setUp() after
    * enabling the requested modules. It must be called again when additional
    * modules are enabled later.
    */
@@ -1309,7 +1279,7 @@ protected function resetAll() {
    * Useful after a page request is made that changes configuration or state in
    * a different thread.
    *
-   * In other words calling a settings page with $this->drupalPostForm() with a
+   * In other words calling a settings page with $this->submitForm() with a
    * changed value would update configuration to reflect that change, but in the
    * thread that made the call (thread running the test) the changed values
    * would not be picked up.
@@ -1343,7 +1313,7 @@ protected function refreshVariables() {
    * @return bool
    *   Return TRUE if the user is logged in, FALSE otherwise.
    */
-  protected function drupalUserIsLoggedIn($account) {
+  protected function drupalUserIsLoggedIn(UserInterface $account) {
     if (!isset($account->sessionId)) {
       return FALSE;
     }
diff --git a/core/modules/simpletest/src/TestDiscovery.php b/core/modules/simpletest/src/TestDiscovery.php
index f3a0449..60ef6ce 100644
--- a/core/modules/simpletest/src/TestDiscovery.php
+++ b/core/modules/simpletest/src/TestDiscovery.php
@@ -426,8 +426,8 @@ public static function isUnitTest($classname) {
         // A core unit test.
         return TRUE;
       }
-      else if ($namespace[3] == 'Unit') {
-        // A module unit test
+      elseif ($namespace[3] == 'Unit') {
+        // A module unit test.
         return TRUE;
       }
     }
diff --git a/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php b/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php
index c86933d..adf8326 100644
--- a/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php
+++ b/core/modules/simpletest/src/Tests/SimpleTestBrowserTest.php
@@ -128,29 +128,23 @@ public function testTestingThroughUI() {
     // to be created. However this scenario is covered by the testception of
     // \Drupal\simpletest\Tests\SimpleTestTest.
 
-    $this->drupalGet('admin/config/development/testing');
-    $edit = array(
+    $tests = array(
       // A KernalTestBase test.
-      'tests[Drupal\field\Tests\String\StringFormatterTest]' => TRUE,
-    );
-    $this->drupalPostForm(NULL, $edit, t('Run tests'));
-    $this->assertText('0 fails, 0 exceptions');
-
-    $this->drupalGet('admin/config/development/testing');
-    $edit = array(
+      'Drupal\field\Tests\String\StringFormatterTest',
       // A PHPUnit unit test.
-      'tests[Drupal\Tests\action\Unit\Menu\ActionLocalTasksTest]' => TRUE,
-    );
-    $this->drupalPostForm(NULL, $edit, t('Run tests'));
-    $this->assertText('0 fails, 0 exceptions');
-
-    $this->drupalGet('admin/config/development/testing');
-    $edit = array(
+      'Drupal\Tests\action\Unit\Menu\ActionLocalTasksTest',
       // A PHPUnit functional test.
-      'tests[Drupal\Tests\simpletest\Functional\BrowserTestBaseTest]' => TRUE,
+      'Drupal\Tests\simpletest\Functional\BrowserTestBaseTest',
     );
-    $this->drupalPostForm(NULL, $edit, t('Run tests'));
-    $this->assertText('0 fails, 0 exceptions');
+
+    foreach($tests as $test) {
+      $this->drupalGet('admin/config/development/testing');
+      $edit = array(
+        "tests[$test]" => TRUE,
+      );
+      $this->drupalPostForm(NULL, $edit, t('Run tests'));
+      $this->assertText('0 fails, 0 exceptions');
+    }
   }
 
 }
diff --git a/core/modules/simpletest/src/WebAssert.php b/core/modules/simpletest/src/WebAssert.php
index daea904..9f96260 100644
--- a/core/modules/simpletest/src/WebAssert.php
+++ b/core/modules/simpletest/src/WebAssert.php
@@ -22,7 +22,7 @@ class WebAssert extends MinkWebAssert {
    * @param string $button
    *   One of id|name|label|value for the button.
    * @param \Behat\Mink\Element\TraversableElement $container
-   *   The document to check against.
+   *   (optional) The document to check against. Defaults to the current page.
    *
    * @return \Behat\Mink\Element\NodeElement
    *   The matching element.
@@ -34,7 +34,7 @@ public function buttonExists($button, TraversableElement $container = NULL) {
     $container = $container ?: $this->session->getPage();
     $node = $container->findButton($button);
 
-    if (NULL === $node) {
+    if ($node === NULL) {
       throw new ElementNotFoundException($this->session, 'button', 'id|name|label|value', $button);
     }
 
@@ -47,7 +47,7 @@ public function buttonExists($button, TraversableElement $container = NULL) {
    * @param string $select
    *   One of id|name|label|value for the select field.
    * @param \Behat\Mink\Element\TraversableElement $container
-   *   The document to check against.
+   *   (optional) The document to check against. Defaults to the current page.
    *
    * @return \Behat\Mink\Element\NodeElement
    *   The matching element
@@ -62,7 +62,7 @@ public function selectExists($select, TraversableElement $container = NULL) {
       $this->session->getSelectorsHandler()->xpathLiteral($select),
     ));
 
-    if (NULL === $node) {
+    if ($node === NULL) {
       throw new ElementNotFoundException($this->session, 'select', 'id|name|label|value', $select);
     }
 
diff --git a/core/modules/simpletest/tests/src/Functional/BrowserTestBaseTest.php b/core/modules/simpletest/tests/src/Functional/BrowserTestBaseTest.php
index 99194c5..4dc5f11 100644
--- a/core/modules/simpletest/tests/src/Functional/BrowserTestBaseTest.php
+++ b/core/modules/simpletest/tests/src/Functional/BrowserTestBaseTest.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of \Drupal\Tests\simpletest\Functional\BrowserTestBaseTest.
+ * Contains \Drupal\Tests\simpletest\Functional\BrowserTestBaseTest.
  */
 
 namespace Drupal\Tests\simpletest\Functional;
@@ -13,7 +13,6 @@
  * Tests BrowserTestBase functionality.
  *
  * @group simpletest
- * @group modern
  *
  * @runTestsInSeparateProcesses
  */