diff --cc core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
index d6bad4a,0171820..0000000
--- a/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
@@@ -167,39 -175,16 +175,39 @@@ class ThemeHandlerTest extends UnitTest
      // Ensure that the css paths are set with the proper prefix.
      $this->assertEquals(array(
        'screen' => array(
-         'css/base/elements.css' => DRUPAL_ROOT . '/core/themes/seven/css/base/elements.css',
-         'css/components/admin-list.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/admin-list.css',
-         'css/components/admin-options.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/admin-options.css',
-         'css/components/admin-panel.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/admin-panel.css',
-         'css/components/block-recent-content.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/block-recent-content.css',
-         'css/components/branding.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/branding.css',
-         'css/components/breadcrumb.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/breadcrumb.css',
-         'css/components/buttons.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/buttons.css',
-         'css/components/buttons.theme.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/buttons.theme.css',
-         'css/components/comments.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/comments.css',
-         'css/components/console.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/console.css',
-         'css/components/dropbutton.component.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/dropbutton.component.css',
-         'css/components/entity-meta.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/entity-meta.css',
-         'css/components/field-ui.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/field-ui.css',
-         'css/components/form.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/form.css',
-         'css/components/help.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/help.css',
-         'css/components/menus-and-lists.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/menus-and-lists.css',
-         'css/components/modules-page.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/modules-page.css',
-         'css/components/node.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/node.css',
-         'css/components/page-title.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/page-title.css',
-         'css/components/pager.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/pager.css',
-         'css/components/skip-link.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/skip-link.css',
-         'css/components/tables.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/tables.css',
-         'css/components/tabs.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/tabs.css',
-         'css/components/tour.theme.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/tour.theme.css',
-         'css/components/update-status.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/update-status.css',
-         'css/components/views-ui.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/views-ui.css',
-         'css/layout/layout.css' => DRUPAL_ROOT . '/core/themes/seven/css/layout/layout.css',
-         'css/layout/node-add.css' => DRUPAL_ROOT . '/core/themes/seven/css/layout/node-add.css',
-         'css/theme/appearance-page.css' => DRUPAL_ROOT . '/core/themes/seven/css/theme/appearance-page.css',
 -        'css/seven.base.css' => $this->root . '/core/themes/seven/css/seven.base.css',
 -        'css/style.css' => $this->root . '/core/themes/seven/css/style.css',
 -        'css/layout.css' => $this->root . '/core/themes/seven/css/layout.css',
++        'css/base/elements.css' => $this->root . '/core/themes/seven/css/base/elements.css',
++        'css/components/admin-list.css' => $this->root . '/core/themes/seven/css/components/admin-list.css',
++        'css/components/admin-options.css' => $this->root . '/core/themes/seven/css/components/admin-options.css',
++        'css/components/admin-panel.css' => $this->root . '/core/themes/seven/css/components/admin-panel.css',
++        'css/components/block-recent-content.css' => $this->root . '/core/themes/seven/css/components/block-recent-content.css',
++        'css/components/branding.css' => $this->root . '/core/themes/seven/css/components/branding.css',
++        'css/components/breadcrumb.css' => $this->root . '/core/themes/seven/css/components/breadcrumb.css',
+         'css/components/buttons.css' => $this->root . '/core/themes/seven/css/components/buttons.css',
+         'css/components/buttons.theme.css' => $this->root . '/core/themes/seven/css/components/buttons.theme.css',
++        'css/components/comments.css' => $this->root . '/core/themes/seven/css/components/comments.css',
++        'css/components/console.css' => $this->root . '/core/themes/seven/css/components/console.css',
+         'css/components/dropbutton.component.css' => $this->root . '/core/themes/seven/css/components/dropbutton.component.css',
++        'css/components/entity-meta.css' => $this->root . '/core/themes/seven/css/components/entity-meta.css',
++        'css/components/field-ui.css' => $this->root . '/core/themes/seven/css/components/field-ui.css',
++        'css/components/form.css' => $this->root . '/core/themes/seven/css/components/form.css',
++        'css/components/help.css' => $this->root . '/core/themes/seven/css/components/help.css',
++        'css/components/menus-and-lists.css' => $this->root . '/core/themes/seven/css/components/menus-and-lists.css',
++        'css/components/modules-page.css' => $this->root . '/core/themes/seven/css/components/modules-page.css',
++        'css/components/node.css' => $this->root . '/core/themes/seven/css/components/node.css',
++        'css/components/page-title.css' => $this->root . '/core/themes/seven/css/components/page-title.css',
++        'css/components/pager.css' => $this->root . '/core/themes/seven/css/components/pager.css',
++        'css/components/skip-link.css' => $this->root . '/core/themes/seven/css/components/skip-link.css',
++        'css/components/tables.css' => $this->root . '/core/themes/seven/css/components/tables.css',
++        'css/components/tabs.css' => $this->root . '/core/themes/seven/css/components/tabs.css',
+         'css/components/tour.theme.css' => $this->root . '/core/themes/seven/css/components/tour.theme.css',
++        'css/components/update-status.css' => $this->root . '/core/themes/seven/css/components/update-status.css',
++        'css/components/views-ui.css' => $this->root . '/core/themes/seven/css/components/views-ui.css',
++        'css/layout/layout.css' => $this->root . '/core/themes/seven/css/layout/layout.css',
++        'css/layout/node-add.css' => $this->root . '/core/themes/seven/css/layout/node-add.css',
++        'css/theme/appearance-page.css' => $this->root . '/core/themes/seven/css/theme/appearance-page.css',
        ),
      ), $info->info['stylesheets']);
-     $this->assertEquals(DRUPAL_ROOT . '/core/themes/seven/screenshot.png', $info->info['screenshot']);
+     $this->assertEquals($this->root . '/core/themes/seven/screenshot.png', $info->info['screenshot']);
    }
  
    /**
diff --git a/core/lib/Drupal.php b/core/lib/Drupal.php
index 19797d9..9810aea 100644
--- a/core/lib/Drupal.php
+++ b/core/lib/Drupal.php
@@ -157,7 +157,7 @@ public static function hasService($id) {
    * @return string
    */
   public static function root() {
-    return static::$container->get('app.root');
+    return static::$container->getParameter('app.root');
   }
 
   /**
diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index 5e8384b..f306305 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -179,6 +179,13 @@ class DrupalKernel implements DrupalKernelInterface, TerminableInterface {
   protected $sitePath;
 
   /**
+   * The app root.
+   *
+   * @var string
+   */
+  protected $root;
+
+  /**
    * Create a DrupalKernel object from a request.
    *
    * @param \Symfony\Component\HttpFoundation\Request $request
@@ -238,6 +245,7 @@ public function __construct($environment, $class_loader, $allow_dumping = TRUE)
     $this->environment = $environment;
     $this->classLoader = $class_loader;
     $this->allowDumping = $allow_dumping;
+    $this->root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
   }
 
   /**
@@ -351,22 +359,22 @@ public function boot() {
     Timer::start('page');
 
     // Load legacy and other functional code.
-    require_once DRUPAL_ROOT . '/core/includes/common.inc';
-    require_once DRUPAL_ROOT . '/core/includes/database.inc';
-    require_once DRUPAL_ROOT . '/' . Settings::get('path_inc', 'core/includes/path.inc');
-    require_once DRUPAL_ROOT . '/core/includes/module.inc';
-    require_once DRUPAL_ROOT . '/core/includes/theme.inc';
-    require_once DRUPAL_ROOT . '/core/includes/pager.inc';
-    require_once DRUPAL_ROOT . '/' . Settings::get('menu_inc', 'core/includes/menu.inc');
-    require_once DRUPAL_ROOT . '/core/includes/tablesort.inc';
-    require_once DRUPAL_ROOT . '/core/includes/file.inc';
-    require_once DRUPAL_ROOT . '/core/includes/unicode.inc';
-    require_once DRUPAL_ROOT . '/core/includes/form.inc';
-    require_once DRUPAL_ROOT . '/core/includes/mail.inc';
-    require_once DRUPAL_ROOT . '/core/includes/ajax.inc';
-    require_once DRUPAL_ROOT . '/core/includes/errors.inc';
-    require_once DRUPAL_ROOT . '/core/includes/schema.inc';
-    require_once DRUPAL_ROOT . '/core/includes/entity.inc';
+    require_once $this->root . '/core/includes/common.inc';
+    require_once $this->root . '/core/includes/database.inc';
+    require_once $this->root . '/' . Settings::get('path_inc', 'core/includes/path.inc');
+    require_once $this->root . '/core/includes/module.inc';
+    require_once $this->root . '/core/includes/theme.inc';
+    require_once $this->root . '/core/includes/pager.inc';
+    require_once $this->root . '/' . Settings::get('menu_inc', 'core/includes/menu.inc');
+    require_once $this->root . '/core/includes/tablesort.inc';
+    require_once $this->root . '/core/includes/file.inc';
+    require_once $this->root . '/core/includes/unicode.inc';
+    require_once $this->root . '/core/includes/form.inc';
+    require_once $this->root . '/core/includes/mail.inc';
+    require_once $this->root . '/core/includes/ajax.inc';
+    require_once $this->root . '/core/includes/errors.inc';
+    require_once $this->root . '/core/includes/schema.inc';
+    require_once $this->root . '/core/includes/entity.inc';
 
     // Ensure that findSitePath is set.
     if (!$this->sitePath) {
@@ -584,7 +592,7 @@ public function prepareLegacyRequest(Request $request) {
   protected function moduleData($module) {
     if (!$this->moduleData) {
       // First, find profiles.
-      $listing = new ExtensionDiscovery(DRUPAL_ROOT);
+      $listing = new ExtensionDiscovery($this->root);
       $listing->setProfileDirectories(array());
       $all_profiles = $listing->scan('profile');
       $profiles = array_intersect_key($all_profiles, $this->moduleList);
@@ -985,7 +993,7 @@ protected function attachSynthetic(ContainerInterface $container) {
     // Set the class loader which was registered as a synthetic service.
     $container->set('class_loader', $this->classLoader);
 
-    $container->set('app.root', DRUPAL_ROOT);
+    $container->set('app.root', $this->root);
     return $container;
   }
 
@@ -1012,7 +1020,7 @@ protected function compileContainer() {
     // Add all components in \Drupal\Core and \Drupal\Component that have a
     // Plugin directory.
     foreach (array('Core', 'Component') as $parent_directory) {
-      $path = DRUPAL_ROOT . '/core/lib/Drupal/' . $parent_directory;
+      $path = $this->root . '/core/lib/Drupal/' . $parent_directory;
       $parent_namespace = 'Drupal\\' . $parent_directory;
       foreach (new \DirectoryIterator($path) as $component) {
         if (!$component->isDot() && $component->isDir() && is_dir($component->getPathname() . '/Plugin')) {
@@ -1219,7 +1227,7 @@ protected function getModuleFileNames() {
   protected function getModuleNamespacesPsr4($module_file_names) {
     $namespaces = array();
     foreach ($module_file_names as $module => $filename) {
-      $namespaces["Drupal\\$module"] = DRUPAL_ROOT . '/' . dirname($filename) . '/src';
+      $namespaces["Drupal\\$module"] = $this->root . '/' . dirname($filename) . '/src';
     }
     return $namespaces;
   }
diff --git a/core/modules/ckeditor/src/Plugin/Editor/CKEditor.php b/core/modules/ckeditor/src/Plugin/Editor/CKEditor.php
index 6d92f98..4f59e1f 100644
--- a/core/modules/ckeditor/src/Plugin/Editor/CKEditor.php
+++ b/core/modules/ckeditor/src/Plugin/Editor/CKEditor.php
@@ -323,7 +323,7 @@ public function getLangcodes() {
     if (empty($langcodes)) {
       $langcodes = array();
       // Collect languages included with CKEditor based on file listing.
-      $ckeditor_languages = new \GlobIterator(DRUPAL_ROOT . '/core/assets/vendor/ckeditor/lang/*.js');
+      $ckeditor_languages = new \GlobIterator(\Drupal::root() . '/core/assets/vendor/ckeditor/lang/*.js');
       foreach ($ckeditor_languages as $language_file) {
         $langcode = $language_file->getBasename('.js');
         $langcodes[$langcode] = $langcode;
diff --git a/core/modules/color/color.module b/core/modules/color/color.module
index 7010ddf..aa9ff40 100644
--- a/core/modules/color/color.module
+++ b/core/modules/color/color.module
@@ -118,7 +118,7 @@ function color_get_info($theme) {
   }
 
   $path = drupal_get_path('theme', $theme);
-  $file = DRUPAL_ROOT . '/' . $path . '/color/color.inc';
+  $file = \Drupal::root() . '/' . $path . '/color/color.inc';
   if ($path && file_exists($file)) {
     include $file;
     // Add in default values.
diff --git a/core/modules/config/tests/config_test/src/TestInstallStorage.php b/core/modules/config/tests/config_test/src/TestInstallStorage.php
index a689efc..e4b3864 100644
--- a/core/modules/config/tests/config_test/src/TestInstallStorage.php
+++ b/core/modules/config/tests/config_test/src/TestInstallStorage.php
@@ -25,7 +25,7 @@ protected function getAllFolders() {
     if (!isset($this->folders)) {
       $this->folders = $this->getComponentNames('core', array('core'));
       // @todo Refactor getComponentNames() to use the extension list directly.
-      $listing = new ExtensionDiscovery(DRUPAL_ROOT);
+      $listing = new ExtensionDiscovery(\Drupal::root());
       $listing->setProfileDirectories(array());
       $this->folders += $this->getComponentNames('profile', array_keys($listing->scan('profile')));
       $this->folders += $this->getComponentNames('module', array_keys($listing->scan('module')));
diff --git a/core/modules/filter/filter.module b/core/modules/filter/filter.module
index 3fa834b..3d7c059 100644
--- a/core/modules/filter/filter.module
+++ b/core/modules/filter/filter.module
@@ -1160,7 +1160,7 @@ function _filter_html_image_secure_process($text) {
   $base_path_length = drupal_strlen($base_path);
 
   // Find the directory on the server where index.php resides.
-  $local_dir = DRUPAL_ROOT . '/';
+  $local_dir = \Drupal::root() . '/';
 
   $html_dom = Html::load($text);
   $images = $html_dom->getElementsByTagName('img');
diff --git a/core/modules/image/src/Tests/ImageItemTest.php b/core/modules/image/src/Tests/ImageItemTest.php
index d758615..717576a 100644
--- a/core/modules/image/src/Tests/ImageItemTest.php
+++ b/core/modules/image/src/Tests/ImageItemTest.php
@@ -55,7 +55,7 @@ protected function setUp() {
       'field_name' => 'image_test',
       'bundle' => 'entity_test',
     ))->save();
-    file_unmanaged_copy(DRUPAL_ROOT . '/core/misc/druplicon.png', 'public://example.jpg');
+    file_unmanaged_copy(\Drupal::root() . '/core/misc/druplicon.png', 'public://example.jpg');
     $this->image = entity_create('file', array(
       'uri' => 'public://example.jpg',
     ));
@@ -88,7 +88,7 @@ public function testImageItem() {
     $this->assertEqual($entity->image_test->entity->uuid(), $this->image->uuid());
 
     // Make sure the computed entity reflects updates to the referenced file.
-    file_unmanaged_copy(DRUPAL_ROOT . '/core/misc/feed.png', 'public://example-2.jpg');
+    file_unmanaged_copy(\Drupal::root() . '/core/misc/feed.png', 'public://example-2.jpg');
     $image2 = entity_create('file', array(
       'uri' => 'public://example-2.jpg',
     ));
diff --git a/core/modules/image/src/Tests/ImageThemeFunctionTest.php b/core/modules/image/src/Tests/ImageThemeFunctionTest.php
index 97c5a2b..9192e2b 100644
--- a/core/modules/image/src/Tests/ImageThemeFunctionTest.php
+++ b/core/modules/image/src/Tests/ImageThemeFunctionTest.php
@@ -50,7 +50,7 @@ protected function setUp() {
       'field_name' => 'image_test',
       'bundle' => 'entity_test',
     ))->save();
-    file_unmanaged_copy(DRUPAL_ROOT . '/core/misc/druplicon.png', 'public://example.jpg');
+    file_unmanaged_copy(\Drupal::root() . '/core/misc/druplicon.png', 'public://example.jpg');
     $this->image = entity_create('file', array(
       'uri' => 'public://example.jpg',
     ));
diff --git a/core/modules/rdf/src/Tests/StandardProfileTest.php b/core/modules/rdf/src/Tests/StandardProfileTest.php
index 2b297a4..911fb03 100644
--- a/core/modules/rdf/src/Tests/StandardProfileTest.php
+++ b/core/modules/rdf/src/Tests/StandardProfileTest.php
@@ -131,7 +131,7 @@ protected function setUp() {
     $this->term->save();
 
     // Create image.
-    file_unmanaged_copy(DRUPAL_ROOT . '/core/misc/druplicon.png', 'public://example.jpg');
+    file_unmanaged_copy(\Drupal::root() . '/core/misc/druplicon.png', 'public://example.jpg');
     $this->image = entity_create('file', array('uri' => 'public://example.jpg'));
     $this->image->save();
 
diff --git a/core/modules/search/src/Tests/SearchSimplifyTest.php b/core/modules/search/src/Tests/SearchSimplifyTest.php
index a850750..c3f7123 100644
--- a/core/modules/search/src/Tests/SearchSimplifyTest.php
+++ b/core/modules/search/src/Tests/SearchSimplifyTest.php
@@ -24,7 +24,7 @@ function testSearchSimplifyUnicode() {
     // their own lines).  So the even-numbered lines should simplify to nothing,
     // and the odd-numbered lines we need to split into shorter chunks and
     // verify that simplification doesn't lose any characters.
-    $input = file_get_contents(DRUPAL_ROOT . '/core/modules/search/tests/UnicodeTest.txt');
+    $input = file_get_contents(\Drupal::root() . '/core/modules/search/tests/UnicodeTest.txt');
     $basestrings = explode(chr(10), $input);
     $strings = array();
     foreach ($basestrings as $key => $string) {
diff --git a/core/modules/simpletest/simpletest.install b/core/modules/simpletest/simpletest.install
index 0094e53..147f4da 100644
--- a/core/modules/simpletest/simpletest.install
+++ b/core/modules/simpletest/simpletest.install
@@ -66,17 +66,17 @@ function simpletest_requirements($phase) {
   }
 
   $site_directory = 'sites/simpletest';
-  if (!drupal_verify_install_file(DRUPAL_ROOT . '/' . $site_directory, FILE_EXIST|FILE_READABLE|FILE_WRITABLE|FILE_EXECUTABLE, 'dir')) {
+  if (!drupal_verify_install_file(\Drupal::root() . '/' . $site_directory, FILE_EXIST|FILE_READABLE|FILE_WRITABLE|FILE_EXECUTABLE, 'dir')) {
     $requirements['simpletest_site_directory'] = array(
       'title' => t('Simpletest site directory'),
-      'value' => is_dir(DRUPAL_ROOT . '/' . $site_directory) ? t('Not writable') : t('Missing'),
+      'value' => is_dir(\Drupal::root() . '/' . $site_directory) ? t('Not writable') : t('Missing'),
       'severity' => REQUIREMENT_ERROR,
       'description' => t('The testing framework requires the !sites-simpletest directory to exist and be writable in order to run tests.', array(
         '!sites-simpletest' => '<code>./' . String::checkPlain($site_directory) . '</code>',
       )),
     );
   }
-  elseif (!file_save_htaccess(DRUPAL_ROOT . '/' . $site_directory, FALSE)) {
+  elseif (!file_save_htaccess(\Drupal::root() . '/' . $site_directory, FALSE)) {
     $requirements['simpletest_site_directory'] = array(
       'title' => t('Simpletest site directory'),
       'value' => t('Not protected'),
diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index 24665c7..01eab47 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -235,7 +235,7 @@ function simpletest_phpunit_xml_filepath($test_id) {
  *   The path to core's phpunit.xml.dist configuration file.
  */
 function simpletest_phpunit_configuration_filepath() {
-  return DRUPAL_ROOT . '/core/phpunit.xml.dist';
+  return \Drupal::root() . '/core/phpunit.xml.dist';
 }
 
 /**
@@ -280,7 +280,7 @@ function simpletest_phpunit_run_command(array $unescaped_test_classnames, $phpun
   // Need to change directories before running the command so that we can use
   // relative paths in the configuration file's exclusions.
   $old_cwd = getcwd();
-  chdir(DRUPAL_ROOT . "/core");
+  chdir(\Drupal::root() . "/core");
 
   // exec in a subshell so that the environment is isolated when running tests
   // via the simpletest UI.
@@ -301,10 +301,10 @@ function simpletest_phpunit_command() {
   if (substr(PHP_OS, 0, 3) == 'WIN') {
     $php_executable_finder = new PhpExecutableFinder();
     $php = $php_executable_finder->find();
-    $phpunit_bin = escapeshellarg($php) . " -f " . escapeshellarg(DRUPAL_ROOT . "/core/vendor/phpunit/phpunit/composer/bin/phpunit") . " --";
+    $phpunit_bin = escapeshellarg($php) . " -f " . escapeshellarg(\Drupal::root() . "/core/vendor/phpunit/phpunit/composer/bin/phpunit") . " --";
   }
   else {
-    $phpunit_bin = DRUPAL_ROOT . "/core/vendor/bin/phpunit";
+    $phpunit_bin = \Drupal::root() . "/core/vendor/bin/phpunit";
   }
   return $phpunit_bin;
 }
diff --git a/core/modules/system/src/Tests/Ajax/FormValuesTest.php b/core/modules/system/src/Tests/Ajax/FormValuesTest.php
index c4f1a7c..17e74f6 100644
--- a/core/modules/system/src/Tests/Ajax/FormValuesTest.php
+++ b/core/modules/system/src/Tests/Ajax/FormValuesTest.php
@@ -59,6 +59,6 @@ function testSimpleAjaxFormValue() {
     }
     // The exceptions are expected. Do not interpret them as a test failure.
     // Not using File API; a potential error must trigger a PHP warning.
-    unlink(DRUPAL_ROOT . '/' . $this->siteDirectory . '/error.log');
+    unlink(\Drupal::root() . '/' . $this->siteDirectory . '/error.log');
   }
 }
diff --git a/core/modules/system/src/Tests/Common/SystemListingTest.php b/core/modules/system/src/Tests/Common/SystemListingTest.php
index de6a941..6b2e1bb 100644
--- a/core/modules/system/src/Tests/Common/SystemListingTest.php
+++ b/core/modules/system/src/Tests/Common/SystemListingTest.php
@@ -37,7 +37,7 @@ function testDirectoryPrecedence() {
     foreach ($expected_directories as $module => $directories) {
       foreach ($directories as $directory) {
         $filename = "$directory/$module/$module.info.yml";
-        $this->assertTrue(file_exists(DRUPAL_ROOT . '/' . $filename), format_string('@filename exists.', array('@filename' => $filename)));
+        $this->assertTrue(file_exists(\Drupal::root() . '/' . $filename), format_string('@filename exists.', array('@filename' => $filename)));
       }
     }
 
diff --git a/core/modules/system/src/Tests/DrupalKernel/DrupalKernelTest.php b/core/modules/system/src/Tests/DrupalKernel/DrupalKernelTest.php
index a7ac85a..ae93539 100644
--- a/core/modules/system/src/Tests/DrupalKernel/DrupalKernelTest.php
+++ b/core/modules/system/src/Tests/DrupalKernel/DrupalKernelTest.php
@@ -30,7 +30,7 @@ protected function setUp() {
     $this->settingsSet('php_storage', array('service_container' => array(
       'bin' => 'service_container',
       'class' => 'Drupal\Component\PhpStorage\MTimeProtectedFileStorage',
-      'directory' => DRUPAL_ROOT . '/' . $this->public_files_directory . '/php',
+      'directory' => \Drupal::root() . '/' . $this->public_files_directory . '/php',
       'secret' => Settings::getHashSalt(),
     )));
   }
@@ -52,7 +52,7 @@ protected function setUp() {
    */
   protected function getTestKernel(Request $request, array $modules_enabled = NULL, $read_only = FALSE) {
     // Manually create kernel to avoid replacing settings.
-    $class_loader = require DRUPAL_ROOT . '/core/vendor/autoload.php';
+    $class_loader = require \Drupal::root() . '/core/vendor/autoload.php';
     $kernel = DrupalKernel::createFromRequest($request, $class_loader, 'testing');
     $this->settingsSet('hash_salt', $this->databasePrefix);
     if (isset($modules_enabled)) {
diff --git a/core/modules/system/src/Tests/FileTransfer/FileTransferTest.php b/core/modules/system/src/Tests/FileTransfer/FileTransferTest.php
index ef7a43a..07ce6ad 100644
--- a/core/modules/system/src/Tests/FileTransfer/FileTransferTest.php
+++ b/core/modules/system/src/Tests/FileTransfer/FileTransferTest.php
@@ -25,7 +25,7 @@ class FileTransferTest extends WebTestBase {
 
   protected function setUp() {
     parent::setUp();
-    $this->testConnection = TestFileTransfer::factory(DRUPAL_ROOT, array('hostname' => $this->hostname, 'username' => $this->username, 'password' => $this->password, 'port' => $this->port));
+    $this->testConnection = TestFileTransfer::factory(\Drupal::root(), array('hostname' => $this->hostname, 'username' => $this->username, 'password' => $this->password, 'port' => $this->port));
   }
 
   function _getFakeModuleFiles() {
@@ -87,7 +87,7 @@ function testJail() {
 
     $gotit = TRUE;
     try {
-      $this->testConnection->copyDirectory($source, DRUPAL_ROOT . '/' . PublicStream::basePath());
+      $this->testConnection->copyDirectory($source, \Drupal::root() . '/' . PublicStream::basePath());
     }
     catch (FileTransferException $e) {
       $gotit = FALSE;
diff --git a/core/modules/system/src/Tests/Installer/InstallerLanguageDirectionTest.php b/core/modules/system/src/Tests/Installer/InstallerLanguageDirectionTest.php
index cd7bce5..0c183d8 100644
--- a/core/modules/system/src/Tests/Installer/InstallerLanguageDirectionTest.php
+++ b/core/modules/system/src/Tests/Installer/InstallerLanguageDirectionTest.php
@@ -28,8 +28,8 @@ class InstallerLanguageDirectionTest extends InstallerTestBase {
    */
   protected function setUpLanguage() {
     // Place a custom local translation in the translations directory.
-    mkdir(DRUPAL_ROOT . '/' . $this->siteDirectory . '/files/translations', 0777, TRUE);
-    file_put_contents(DRUPAL_ROOT . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.ar.po', "msgid \"\"\nmsgstr \"\"\nmsgid \"Save and continue\"\nmsgstr \"Save and continue Arabic\"");
+    mkdir(\Drupal::root() . '/' . $this->siteDirectory . '/files/translations', 0777, TRUE);
+    file_put_contents(\Drupal::root() . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.ar.po', "msgid \"\"\nmsgstr \"\"\nmsgid \"Save and continue\"\nmsgstr \"Save and continue Arabic\"");
 
     parent::setUpLanguage();
     // After selecting a different language than English, all following screens
diff --git a/core/modules/system/src/Tests/Installer/InstallerLanguagePageTest.php b/core/modules/system/src/Tests/Installer/InstallerLanguagePageTest.php
index 4c74ddc..ce573ba 100644
--- a/core/modules/system/src/Tests/Installer/InstallerLanguagePageTest.php
+++ b/core/modules/system/src/Tests/Installer/InstallerLanguagePageTest.php
@@ -21,8 +21,8 @@ class InstallerLanguagePageTest extends InstallerTestBase {
    */
   protected function setUpLanguage() {
     // Place a custom local translation in the translations directory.
-    mkdir(DRUPAL_ROOT . '/' . $this->siteDirectory . '/files/translations', 0777, TRUE);
-    touch(DRUPAL_ROOT . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.xoxo.po');
+    mkdir(\Drupal::root() . '/' . $this->siteDirectory . '/files/translations', 0777, TRUE);
+    touch(\Drupal::root() . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.xoxo.po');
 
     // Check that all predefined languages show up with their native names.
     $this->drupalGet($GLOBALS['base_url'] . '/core/install.php');
diff --git a/core/modules/system/src/Tests/Installer/InstallerTest.php b/core/modules/system/src/Tests/Installer/InstallerTest.php
index 760a942..6d48123 100644
--- a/core/modules/system/src/Tests/Installer/InstallerTest.php
+++ b/core/modules/system/src/Tests/Installer/InstallerTest.php
@@ -26,7 +26,7 @@ public function testInstaller() {
     $this->assertText($this->root_user->getUsername());
 
     // Verify that the confirmation message appears.
-    require_once DRUPAL_ROOT . '/core/includes/install.inc';
+    require_once \Drupal::root() . '/core/includes/install.inc';
     $this->assertRaw(t('Congratulations, you installed @drupal!', array(
       '@drupal' => drupal_install_profile_distribution_name(),
     )));
diff --git a/core/modules/system/src/Tests/Installer/InstallerTranslationTest.php b/core/modules/system/src/Tests/Installer/InstallerTranslationTest.php
index 1ab8e5a..3ce8361 100644
--- a/core/modules/system/src/Tests/Installer/InstallerTranslationTest.php
+++ b/core/modules/system/src/Tests/Installer/InstallerTranslationTest.php
@@ -29,8 +29,8 @@ class InstallerTranslationTest extends InstallerTestBase {
    */
   protected function setUpLanguage() {
     // Place a custom local translation in the translations directory.
-    mkdir(DRUPAL_ROOT . '/' . $this->siteDirectory . '/files/translations', 0777, TRUE);
-    file_put_contents(DRUPAL_ROOT . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.de.po', "msgid \"\"\nmsgstr \"\"\nmsgid \"Save and continue\"\nmsgstr \"Save and continue German\"");
+    mkdir(\Drupal::root() . '/' . $this->siteDirectory . '/files/translations', 0777, TRUE);
+    file_put_contents(\Drupal::root() . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.de.po', "msgid \"\"\nmsgstr \"\"\nmsgid \"Save and continue\"\nmsgstr \"Save and continue German\"");
 
     parent::setUpLanguage();
     // After selecting a different language than English, all following screens
diff --git a/core/modules/system/src/Tests/Installer/InstallerTranslationVersionUnitTest.php b/core/modules/system/src/Tests/Installer/InstallerTranslationVersionUnitTest.php
index 031a79d..844ff83 100644
--- a/core/modules/system/src/Tests/Installer/InstallerTranslationVersionUnitTest.php
+++ b/core/modules/system/src/Tests/Installer/InstallerTranslationVersionUnitTest.php
@@ -19,7 +19,7 @@ class InstallerTranslationVersionUnitTest extends DrupalUnitTestBase {
 
   protected function setUp() {
     parent::setUp();
-    require_once DRUPAL_ROOT . '/core/includes/install.core.inc';
+    require_once \Drupal::root() . '/core/includes/install.core.inc';
   }
 
   /**
diff --git a/core/modules/system/src/Tests/PhpStorage/PhpStorageFactoryTest.php b/core/modules/system/src/Tests/PhpStorage/PhpStorageFactoryTest.php
index 166f3ff..bad4c2f 100644
--- a/core/modules/system/src/Tests/PhpStorage/PhpStorageFactoryTest.php
+++ b/core/modules/system/src/Tests/PhpStorage/PhpStorageFactoryTest.php
@@ -59,7 +59,7 @@ public function testGetOverride() {
     $this->setSettings('test', array('directory' => NULL));
     $php = PhpStorageFactory::get('test');
     $this->assertTrue($php instanceof MockPhpStorage, 'An MockPhpStorage instance was returned from overridden settings.');
-    $this->assertIdentical(DRUPAL_ROOT . '/' . PublicStream::basePath() . '/php', $php->getConfigurationValue('directory'), 'Default file directory was used.');
+    $this->assertIdentical(\Drupal::root() . '/' . PublicStream::basePath() . '/php', $php->getConfigurationValue('directory'), 'Default file directory was used.');
 
     // Test that a default storage class is set if it's empty.
     $this->setSettings('test', array('class' => NULL));
diff --git a/core/modules/system/src/Tests/Plugin/Discovery/AnnotatedClassDiscoveryTest.php b/core/modules/system/src/Tests/Plugin/Discovery/AnnotatedClassDiscoveryTest.php
index 941a93a..05d5a43 100644
--- a/core/modules/system/src/Tests/Plugin/Discovery/AnnotatedClassDiscoveryTest.php
+++ b/core/modules/system/src/Tests/Plugin/Discovery/AnnotatedClassDiscoveryTest.php
@@ -52,7 +52,7 @@ protected function setUp() {
       ),
     );
 
-    $base_directory = DRUPAL_ROOT . '/core/modules/system/tests/modules/plugin_test/src';
+    $base_directory = \Drupal::root() . '/core/modules/system/tests/modules/plugin_test/src';
     $namespaces = new \ArrayObject(array('Drupal\plugin_test' => $base_directory));
 
     $this->discovery = new AnnotatedClassDiscovery('Plugin/plugin_test/fruit', $namespaces);
diff --git a/core/modules/system/src/Tests/Plugin/Discovery/CustomAnnotationClassDiscoveryTest.php b/core/modules/system/src/Tests/Plugin/Discovery/CustomAnnotationClassDiscoveryTest.php
index eb5285e..890329c 100644
--- a/core/modules/system/src/Tests/Plugin/Discovery/CustomAnnotationClassDiscoveryTest.php
+++ b/core/modules/system/src/Tests/Plugin/Discovery/CustomAnnotationClassDiscoveryTest.php
@@ -35,7 +35,7 @@ protected function setUp() {
       ),
     );
 
-    $base_directory = DRUPAL_ROOT . '/core/modules/system/tests/modules/plugin_test/src';
+    $base_directory = \Drupal::root() . '/core/modules/system/tests/modules/plugin_test/src';
     $root_namespaces = new \ArrayObject(array('Drupal\plugin_test' => $base_directory));
 
     $this->discovery = new AnnotatedClassDiscovery('Plugin/plugin_test/custom_annotation', $root_namespaces, 'Drupal\plugin_test\Plugin\Annotation\PluginExample');
diff --git a/core/modules/system/src/Tests/Plugin/Discovery/CustomDirectoryAnnotatedClassDiscoveryTest.php b/core/modules/system/src/Tests/Plugin/Discovery/CustomDirectoryAnnotatedClassDiscoveryTest.php
index aa29a09..ad6f5e4 100644
--- a/core/modules/system/src/Tests/Plugin/Discovery/CustomDirectoryAnnotatedClassDiscoveryTest.php
+++ b/core/modules/system/src/Tests/Plugin/Discovery/CustomDirectoryAnnotatedClassDiscoveryTest.php
@@ -66,7 +66,7 @@ protected function setUp() {
       ),
     );
 
-    $base_directory = DRUPAL_ROOT . '/core/modules/system/tests/modules/plugin_test/src';
+    $base_directory = \Drupal::root() . '/core/modules/system/tests/modules/plugin_test/src';
     $namespaces = new \ArrayObject(array('Drupal\plugin_test' => $base_directory));
 
     $this->discovery = new AnnotatedClassDiscovery('', $namespaces);
diff --git a/core/modules/system/src/Tests/System/ErrorHandlerTest.php b/core/modules/system/src/Tests/System/ErrorHandlerTest.php
index 69f1760..30a77b8 100644
--- a/core/modules/system/src/Tests/System/ErrorHandlerTest.php
+++ b/core/modules/system/src/Tests/System/ErrorHandlerTest.php
@@ -121,7 +121,7 @@ function testExceptionHandler() {
 
     // The exceptions are expected. Do not interpret them as a test failure.
     // Not using File API; a potential error must trigger a PHP warning.
-    unlink(DRUPAL_ROOT . '/' . $this->siteDirectory . '/error.log');
+    unlink(\Drupal::root() . '/' . $this->siteDirectory . '/error.log');
   }
 
   /**
diff --git a/core/modules/system/src/Tests/System/IgnoreReplicaSubscriberTest.php b/core/modules/system/src/Tests/System/IgnoreReplicaSubscriberTest.php
index f9ceb3a..3615c43 100644
--- a/core/modules/system/src/Tests/System/IgnoreReplicaSubscriberTest.php
+++ b/core/modules/system/src/Tests/System/IgnoreReplicaSubscriberTest.php
@@ -32,7 +32,7 @@ function testSystemInitIgnoresSecondaries() {
     Database::addConnectionInfo('default', 'replica', $connection_info['default']);
 
     db_ignore_replica();
-    $class_loader = require DRUPAL_ROOT . '/core/vendor/autoload.php';
+    $class_loader = require \Drupal::root() . '/core/vendor/autoload.php';
     $kernel = new DrupalKernel('testing', $class_loader, FALSE);
     $event = new GetResponseEvent($kernel, Request::create('http://example.com'), HttpKernelInterface::MASTER_REQUEST);
     $subscriber = new ReplicaDatabaseIgnoreSubscriber();
diff --git a/core/modules/system/src/Tests/System/SettingsRewriteTest.php b/core/modules/system/src/Tests/System/SettingsRewriteTest.php
index 741f92c..70b4043 100644
--- a/core/modules/system/src/Tests/System/SettingsRewriteTest.php
+++ b/core/modules/system/src/Tests/System/SettingsRewriteTest.php
@@ -20,7 +20,7 @@ class SettingsRewriteTest extends KernelTestBase {
    * Tests the drupal_rewrite_settings() function.
    */
   function testDrupalRewriteSettings() {
-    include_once DRUPAL_ROOT . '/core/includes/install.inc';
+    include_once \Drupal::root() . '/core/includes/install.inc';
     $tests = array(
       array(
         'original' => '$no_index_value_scalar = TRUE;',
@@ -100,9 +100,9 @@ function testDrupalRewriteSettings() {
     );
     foreach ($tests as $test) {
       $filename = Settings::get('file_public_path', conf_path() . '/files') . '/mock_settings.php';
-      file_put_contents(DRUPAL_ROOT . '/' . $filename, "<?php\n" . $test['original'] . "\n");
+      file_put_contents(\Drupal::root() . '/' . $filename, "<?php\n" . $test['original'] . "\n");
       drupal_rewrite_settings($test['settings'], $filename);
-      $this->assertEqual(file_get_contents(DRUPAL_ROOT . '/' . $filename), "<?php\n" . $test['expected'] . "\n");
+      $this->assertEqual(file_get_contents(\Drupal::root() . '/' . $filename), "<?php\n" . $test['expected'] . "\n");
     }
 
     // Test that <?php gets added to the start of an empty settings file.
@@ -118,12 +118,12 @@ function testDrupalRewriteSettings() {
     );
     // Make an empty file.
     $filename = Settings::get('file_public_path', conf_path() . '/files') . '/mock_settings.php';
-    file_put_contents(DRUPAL_ROOT . '/' . $filename, "");
+    file_put_contents(\Drupal::root() . '/' . $filename, "");
 
     // Write the setting to the file.
     drupal_rewrite_settings($test['settings'], $filename);
 
     // Check that the result is just the php opening tag and the settings.
-    $this->assertEqual(file_get_contents(DRUPAL_ROOT . '/' . $filename), "<?php\n" . $test['expected'] . "\n");
+    $this->assertEqual(file_get_contents(\Drupal::root() . '/' . $filename), "<?php\n" . $test['expected'] . "\n");
   }
 }
diff --git a/core/modules/system/src/Tests/System/ShutdownFunctionsTest.php b/core/modules/system/src/Tests/System/ShutdownFunctionsTest.php
index d32148c..b0d7265 100644
--- a/core/modules/system/src/Tests/System/ShutdownFunctionsTest.php
+++ b/core/modules/system/src/Tests/System/ShutdownFunctionsTest.php
@@ -27,7 +27,7 @@ protected function tearDown() {
     // This test intentionally throws an exception in a PHP shutdown function.
     // Prevent it from being interpreted as an actual test failure.
     // Not using File API; a potential error must trigger a PHP warning.
-    unlink(DRUPAL_ROOT . '/' . $this->siteDirectory . '/error.log');
+    unlink(\Drupal::root() . '/' . $this->siteDirectory . '/error.log');
     parent::tearDown();
   }
 
diff --git a/core/modules/system/src/Tests/TypedData/TypedDataTest.php b/core/modules/system/src/Tests/TypedData/TypedDataTest.php
index 4185c17..e1dcc4d 100644
--- a/core/modules/system/src/Tests/TypedData/TypedDataTest.php
+++ b/core/modules/system/src/Tests/TypedData/TypedDataTest.php
@@ -244,7 +244,7 @@ public function testGetAndSet() {
     $files = array();
     for ($i = 0; $i < 3; $i++){
       $path = "public://example_$i.png";
-      file_unmanaged_copy(DRUPAL_ROOT . '/core/misc/druplicon.png', $path);
+      file_unmanaged_copy(\Drupal::root() . '/core/misc/druplicon.png', $path);
       $image = entity_create('file', array('uri' => $path));
       $image->save();
       $files[] = $image;
diff --git a/core/modules/system/src/Tests/Update/DependencyHookInvocationTest.php b/core/modules/system/src/Tests/Update/DependencyHookInvocationTest.php
index f75190a..1dd0bef 100644
--- a/core/modules/system/src/Tests/Update/DependencyHookInvocationTest.php
+++ b/core/modules/system/src/Tests/Update/DependencyHookInvocationTest.php
@@ -26,7 +26,7 @@ class DependencyHookInvocationTest extends WebTestBase {
 
   protected function setUp() {
     parent::setUp();
-    require_once DRUPAL_ROOT . '/core/includes/update.inc';
+    require_once \Drupal::root() . '/core/includes/update.inc';
   }
 
   /**
diff --git a/core/modules/system/src/Tests/Update/DependencyMissingTest.php b/core/modules/system/src/Tests/Update/DependencyMissingTest.php
index 7c31851..70cd56b 100644
--- a/core/modules/system/src/Tests/Update/DependencyMissingTest.php
+++ b/core/modules/system/src/Tests/Update/DependencyMissingTest.php
@@ -27,7 +27,7 @@ protected function setUp() {
     // Only install update_test_2.module, even though its updates have a
     // dependency on update_test_3.module.
     parent::setUp();
-    require_once DRUPAL_ROOT . '/core/includes/update.inc';
+    require_once \Drupal::root() . '/core/includes/update.inc';
   }
 
   function testMissingUpdate() {
diff --git a/core/modules/system/src/Tests/Update/DependencyOrderingTest.php b/core/modules/system/src/Tests/Update/DependencyOrderingTest.php
index 4bf270a..1360c6d 100644
--- a/core/modules/system/src/Tests/Update/DependencyOrderingTest.php
+++ b/core/modules/system/src/Tests/Update/DependencyOrderingTest.php
@@ -25,7 +25,7 @@ class DependencyOrderingTest extends WebTestBase {
 
   protected function setUp() {
     parent::setUp();
-    require_once DRUPAL_ROOT . '/core/includes/update.inc';
+    require_once \Drupal::root() . '/core/includes/update.inc';
   }
 
   /**
diff --git a/core/modules/system/src/Tests/Update/InvalidUpdateHookTest.php b/core/modules/system/src/Tests/Update/InvalidUpdateHookTest.php
index b5ea8fc..228d62c 100644
--- a/core/modules/system/src/Tests/Update/InvalidUpdateHookTest.php
+++ b/core/modules/system/src/Tests/Update/InvalidUpdateHookTest.php
@@ -41,7 +41,7 @@ class InvalidUpdateHookTest extends WebTestBase {
 
   protected function setUp() {
     parent::setUp();
-    require_once DRUPAL_ROOT . '/core/includes/update.inc';
+    require_once \Drupal::root() . '/core/includes/update.inc';
 
     $this->update_url = $GLOBALS['base_url'] . '/update.php';
     $this->update_user = $this->drupalCreateUser(array('administer software updates'));
diff --git a/core/modules/system/src/Tests/Update/UpdatesWith7xTest.php b/core/modules/system/src/Tests/Update/UpdatesWith7xTest.php
index b6c215d..09daad3 100644
--- a/core/modules/system/src/Tests/Update/UpdatesWith7xTest.php
+++ b/core/modules/system/src/Tests/Update/UpdatesWith7xTest.php
@@ -36,7 +36,7 @@ class UpdatesWith7xTest extends WebTestBase {
 
   protected function setUp() {
     parent::setUp();
-    require_once DRUPAL_ROOT . '/core/includes/update.inc';
+    require_once \Drupal::root() . '/core/includes/update.inc';
     $this->update_url = $GLOBALS['base_url'] . '/update.php';
     $this->update_user = $this->drupalCreateUser(array('administer software updates'));
   }
diff --git a/core/modules/system/tests/src/Unit/Menu/SystemLocalTasksTest.php b/core/modules/system/tests/src/Unit/Menu/SystemLocalTasksTest.php
index 6d98ebd..05c4709 100644
--- a/core/modules/system/tests/src/Unit/Menu/SystemLocalTasksTest.php
+++ b/core/modules/system/tests/src/Unit/Menu/SystemLocalTasksTest.php
@@ -36,7 +36,7 @@ protected function setUp() {
 
     $this->themeHandler = $this->getMock('Drupal\Core\Extension\ThemeHandlerInterface');
 
-    $theme = new Extension('theme', DRUPAL_ROOT . '/core/themes/bartik', 'bartik.info.yml');
+    $theme = new Extension(\Drupal::root(), 'theme', '/core/themes/bartik', 'bartik.info.yml');
     $theme->status = 1;
     $theme->info = array('name' => 'bartik');
     $this->themeHandler->expects($this->any())
diff --git a/core/modules/taxonomy/src/Tests/VocabularyCrudTest.php b/core/modules/taxonomy/src/Tests/VocabularyCrudTest.php
index 03201ab..bc70e63 100644
--- a/core/modules/taxonomy/src/Tests/VocabularyCrudTest.php
+++ b/core/modules/taxonomy/src/Tests/VocabularyCrudTest.php
@@ -189,7 +189,7 @@ function testUninstallReinstall() {
     );
     entity_create('field_instance_config', $instance_definition)->save();
 
-    require_once DRUPAL_ROOT . '/core/includes/install.inc';
+    require_once \Drupal::root() . '/core/includes/install.inc';
     $this->container->get('module_handler')->uninstall(array('taxonomy'));
     \Drupal::moduleHandler()->install(array('taxonomy'));
 
diff --git a/core/modules/update/src/Form/UpdateManagerInstall.php b/core/modules/update/src/Form/UpdateManagerInstall.php
index 3198a28..e65e730 100644
--- a/core/modules/update/src/Form/UpdateManagerInstall.php
+++ b/core/modules/update/src/Form/UpdateManagerInstall.php
@@ -207,7 +207,7 @@ public function submitForm(array &$form, FormStateInterface $form_state) {
     // update_authorize_run_install() directly.
     if (fileowner($project_real_location) == fileowner(conf_path())) {
       $this->moduleHandler->loadInclude('update', 'inc', 'update.authorize');
-      $filetransfer = new Local(DRUPAL_ROOT);
+      $filetransfer = new Local(\drupal::root());
       call_user_func_array('update_authorize_run_install', array_merge(array($filetransfer), $arguments));
     }
 
diff --git a/core/modules/update/src/Form/UpdateReady.php b/core/modules/update/src/Form/UpdateReady.php
index 66e94de..6c7c108 100644
--- a/core/modules/update/src/Form/UpdateReady.php
+++ b/core/modules/update/src/Form/UpdateReady.php
@@ -133,7 +133,7 @@ public function submitForm(array &$form, FormStateInterface $form_state) {
       // and invoke update_authorize_run_update() directly.
       if (fileowner($project_real_location) == fileowner(conf_path())) {
         $this->moduleHandler->loadInclude('update', 'inc', 'update.authorize');
-        $filetransfer = new Local(DRUPAL_ROOT);
+        $filetransfer = new Local(\Drupal::root());
         update_authorize_run_update($filetransfer, $updates);
       }
       // Otherwise, go through the regular workflow to prompt for FTP/SSH
diff --git a/core/modules/user/src/Tests/UserAccountFormFieldsTest.php b/core/modules/user/src/Tests/UserAccountFormFieldsTest.php
index 492218f..188da36 100644
--- a/core/modules/user/src/Tests/UserAccountFormFieldsTest.php
+++ b/core/modules/user/src/Tests/UserAccountFormFieldsTest.php
@@ -29,8 +29,8 @@ class UserAccountFormFieldsTest extends DrupalUnitTestBase {
    * Tests the root user account form section in the "Configure site" form.
    */
   function testInstallConfigureForm() {
-    require_once DRUPAL_ROOT . '/core/includes/install.core.inc';
-    require_once DRUPAL_ROOT . '/core/includes/install.inc';
+    require_once \Drupal::root() . '/core/includes/install.core.inc';
+    require_once \Drupal::root() . '/core/includes/install.inc';
     $install_state = install_state_defaults();
     $form_state = new FormState();
     $form_state['build_info']['args'][] = &$install_state;
diff --git a/core/modules/views/views.module b/core/modules/views/views.module
index b4da2d9..2b5c009 100644
--- a/core/modules/views/views.module
+++ b/core/modules/views/views.module
@@ -188,7 +188,7 @@ function views_theme($existing, $type, $theme, $path) {
       // Whenever we got a theme file, we include it directly so we can
       // auto-detect the theme function.
       if (isset($def['theme_file'])) {
-        $include = DRUPAL_ROOT . '/' . $module_dir. '/' . $def['theme_file'];
+        $include = \Drupal::root() . '/' . $module_dir. '/' . $def['theme_file'];
         if (is_file($include)) {
           require_once $include;
         }
diff --git a/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php b/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
index d4a9fe4..70bc427 100644
--- a/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php
@@ -31,6 +31,13 @@
 class LibraryDiscoveryParserTest extends UnitTestCase {
 
   /**
+   * The app root.
+   *
+   * @var string
+   */
+  protected $root;
+
+  /**
    * The tested library provider.
    *
    * @var \Drupal\Core\Asset\LibraryDiscoveryParser|\Drupal\Tests\Core\Asset\TestLibraryDiscoveryParser
@@ -63,8 +70,8 @@ class LibraryDiscoveryParserTest extends UnitTestCase {
    */
   protected function setUp() {
     $this->moduleHandler = $this->getMock('Drupal\Core\Extension\ModuleHandlerInterface');
-    $root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
-    $this->libraryDiscoveryParser = new TestLibraryDiscoveryParser($root, $this->moduleHandler);
+    $this->root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
+    $this->libraryDiscoveryParser = new TestLibraryDiscoveryParser($this->root, $this->moduleHandler);
   }
 
   /**
@@ -79,7 +86,7 @@ public function testBuildByExtensionSimple() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'example_module', $path);
 
     $libraries = $this->libraryDiscoveryParser->buildByExtension('example_module', 'example');
@@ -106,7 +113,7 @@ public function testBuildByExtensionWithTheme() {
       ->will($this->returnValue(FALSE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('theme', 'example_theme', $path);
 
     $libraries = $this->libraryDiscoveryParser->buildByExtension('example_theme');
@@ -130,7 +137,7 @@ public function testBuildByExtensionWithMissingLibraryFile() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files_not_existing';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'example_module', $path);
 
     $this->assertSame($this->libraryDiscoveryParser->buildByExtension('example_module'), array());
@@ -150,7 +157,7 @@ public function testInvalidLibrariesFile() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'invalid_file', $path);
 
     $this->libraryDiscoveryParser->buildByExtension('invalid_file');
@@ -171,7 +178,7 @@ public function testBuildByExtensionWithMissingInformation() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'example_module_missing_information', $path);
 
     $this->libraryDiscoveryParser->buildByExtension('example_module_missing_information');
@@ -189,7 +196,7 @@ public function testExternalLibraries() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'external', $path);
 
     $libraries = $this->libraryDiscoveryParser->buildByExtension('external', 'example_external');
@@ -211,7 +218,7 @@ public function testDefaultCssWeights() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'css_weights', $path);
 
     $libraries = $this->libraryDiscoveryParser->buildByExtension('css_weights');
@@ -251,7 +258,7 @@ public function testJsWithPositiveWeight() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'js_positive_weight', $path);
 
     $this->libraryDiscoveryParser->buildByExtension('js_positive_weight');
@@ -269,7 +276,7 @@ public function testLibraryWithCssJsSetting() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'css_js_settings', $path);
 
     $libraries = $this->libraryDiscoveryParser->buildByExtension('css_js_settings');
@@ -300,7 +307,7 @@ public function testLibraryWithDependencies() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'dependencies', $path);
 
     $libraries = $this->libraryDiscoveryParser->buildByExtension('dependencies');
@@ -323,7 +330,7 @@ public function testLibraryWithDataTypes() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'data_types', $path);
 
     $this->libraryDiscoveryParser->setFileValidUri('public://test.css', TRUE);
@@ -355,7 +362,7 @@ public function testLibraryWithJavaScript() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'js', $path);
 
     $libraries = $this->libraryDiscoveryParser->buildByExtension('js');
@@ -380,7 +387,7 @@ public function testLibraryThirdPartyWithMissingLicense() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'licenses_missing_information', $path);
 
     $this->libraryDiscoveryParser->buildByExtension('licenses_missing_information');
@@ -398,7 +405,7 @@ public function testLibraryWithLicenses() {
       ->will($this->returnValue(TRUE));
 
     $path = __DIR__ . '/library_test_files';
-    $path = substr($path, strlen(DRUPAL_ROOT) + 1);
+    $path = substr($path, strlen($this->root) + 1);
     $this->libraryDiscoveryParser->setPaths('module', 'licenses', $path);
 
     $libraries = $this->libraryDiscoveryParser->buildByExtension('licenses');
diff --git a/core/tests/Drupal/Tests/Core/Extension/DefaultConfigTest.php b/core/tests/Drupal/Tests/Core/Extension/DefaultConfigTest.php
index b1c1c8b..666547b 100644
--- a/core/tests/Drupal/Tests/Core/Extension/DefaultConfigTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/DefaultConfigTest.php
@@ -28,7 +28,8 @@ class DefaultConfigTest extends UnitTestCase {
    * would not exist. Installation hooks would never be executed.
    */
   public function testConfigIsEmpty() {
-    $config = Yaml::parse(file_get_contents(DRUPAL_ROOT . '/core/config/install/core.extension.yml'));
+    $root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
+    $config = Yaml::parse(file_get_contents($root . '/core/config/install/core.extension.yml'));
     $expected = array(
       'module' => array(),
       'theme' => array(),
diff --git a/core/tests/Drupal/Tests/Core/Extension/ModuleHandlerTest.php b/core/tests/Drupal/Tests/Core/Extension/ModuleHandlerTest.php
index 73d81ab..2f0a67a 100644
--- a/core/tests/Drupal/Tests/Core/Extension/ModuleHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/ModuleHandlerTest.php
@@ -515,6 +515,7 @@ public function dependencyProvider() {
   public function testGetModuleDirectories() {
     $this->moduleHandler->setModuleList(array());
     $this->moduleHandler->addModule('module', 'place');
-    $this->assertEquals(array('module' => DRUPAL_ROOT . '/place'), $this->moduleHandler->getModuleDirectories());
+    $root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
+    $this->assertEquals(array('module' => $root . '/place'), $this->moduleHandler->getModuleDirectories());
   }
 }
diff --git a/core/tests/Drupal/Tests/Core/Menu/LocalTaskIntegrationTest.php b/core/tests/Drupal/Tests/Core/Menu/LocalTaskIntegrationTest.php
index 8470a6f..81f290b 100644
--- a/core/tests/Drupal/Tests/Core/Menu/LocalTaskIntegrationTest.php
+++ b/core/tests/Drupal/Tests/Core/Menu/LocalTaskIntegrationTest.php
@@ -50,6 +50,7 @@ protected function setUp() {
     $container = new ContainerBuilder();
     $config_factory = $this->getConfigFactoryStub(array());
     $container->set('config.factory', $config_factory);
+    $container->setParameter('app.root', dirname(dirname(dirname(dirname(dirname(dirname(__DIR__)))))));
     \Drupal::setContainer($container);
     $this->container = $container;
   }
@@ -142,7 +143,7 @@ protected function assertLocalTasks($route_name, $expected_tasks, $route_params
 
     $directory_list = array();
     foreach ($this->directoryList as $key => $value) {
-      $directory_list[$key] = DRUPAL_ROOT . '/' . $value;
+      $directory_list[$key] = \Drupal::root() . '/' . $value;
     }
 
     $manager = $this->getLocalTaskManager($directory_list, $route_name, $route_params);
diff --git a/core/tests/Drupal/Tests/Core/Plugin/DefaultPluginManagerTest.php b/core/tests/Drupal/Tests/Core/Plugin/DefaultPluginManagerTest.php
index 1eb0d26..34a890b 100644
--- a/core/tests/Drupal/Tests/Core/Plugin/DefaultPluginManagerTest.php
+++ b/core/tests/Drupal/Tests/Core/Plugin/DefaultPluginManagerTest.php
@@ -53,7 +53,8 @@ protected function setUp() {
     );
 
     $this->namespaces = new \ArrayObject();
-    $this->namespaces['Drupal\plugin_test'] = DRUPAL_ROOT . '/core/modules/system/tests/modules/plugin_test/src';
+    $root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
+    $this->namespaces['Drupal\plugin_test'] = $root . '/core/modules/system/tests/modules/plugin_test/src';
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php b/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
index c6c3576..00ec88d 100644
--- a/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
+++ b/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
@@ -73,7 +73,8 @@ public function testGetRegistryForModule() {
     $this->registry->setBaseThemes(array());
 
     // Include the module so that hook_theme can be called.
-    include_once DRUPAL_ROOT . '/core/modules/system/tests/modules/theme_test/theme_test.module';
+    $root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
+    include_once $root . '/core/modules/system/tests/modules/theme_test/theme_test.module';
     $this->moduleHandler->expects($this->once())
       ->method('getImplementations')
       ->with('theme')
diff --git a/core/themes/engines/phptemplate/phptemplate.engine b/core/themes/engines/phptemplate/phptemplate.engine
index 0521092..636da47 100644
--- a/core/themes/engines/phptemplate/phptemplate.engine
+++ b/core/themes/engines/phptemplate/phptemplate.engine
@@ -49,7 +49,7 @@ function phptemplate_render_template($template_file, $variables) {
   ob_start();
 
   // Include the template file
-  include DRUPAL_ROOT . '/' . $template_file;
+  include \Drupal::root() . '/' . $template_file;
 
   // End buffering and return its contents
   return ob_get_clean();