diff --git a/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php b/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
index cf2df4afaf4..8b6327cadb7 100644
--- a/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
+++ b/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
@@ -205,7 +205,7 @@ class BigPipeTest extends BrowserTestBase {
     $this->assertNoRaw(BigPipe::STOP_SIGNAL, 'BigPipe stop signal absent: error occurred before then.');
     $this->assertNoRaw('</body>', 'Closing body tag absent: error occurred before then.');
     // The exception is expected. Do not interpret it as a test failure.
-    unlink(\Drupal::root() . '/' . $this->siteDirectory . '/error.log');
+    unlink($this->root . '/' . $this->siteDirectory . '/error.log');
   }
 
   /**
@@ -273,7 +273,7 @@ class BigPipeTest extends BrowserTestBase {
     $this->assertRaw('You are not allowed to say llamas are not cool!');
     $this->assertNoRaw('</body>', 'Closing body tag absent: error occurred before then.');
     // The exception is expected. Do not interpret it as a test failure.
-    unlink(\Drupal::root() . '/' . $this->siteDirectory . '/error.log');
+    unlink($this->root . '/' . $this->siteDirectory . '/error.log');
   }
 
   /**
diff --git a/core/modules/field/tests/src/Kernel/FieldTypePluginManagerTest.php b/core/modules/field/tests/src/Kernel/FieldTypePluginManagerTest.php
index 34c241f3951..c40229fe7a9 100644
--- a/core/modules/field/tests/src/Kernel/FieldTypePluginManagerTest.php
+++ b/core/modules/field/tests/src/Kernel/FieldTypePluginManagerTest.php
@@ -112,7 +112,7 @@ class FieldTypePluginManagerTest extends FieldKernelTestBase {
    * Enable all core modules.
    */
   protected function enableAllCoreModules() {
-    $listing = new ExtensionDiscovery(\Drupal::root());
+    $listing = new ExtensionDiscovery($this->root);
     $module_list = $listing->scan('module', FALSE);
     /** @var \Drupal\Core\Extension\ModuleHandlerInterface $module_handler */
     $module_handler = $this->container->get('module_handler');
diff --git a/core/modules/file/tests/src/Kernel/Migrate/d6/FileMigrationTestTrait.php b/core/modules/file/tests/src/Kernel/Migrate/d6/FileMigrationTestTrait.php
index 0aa4e194eec..1fc8a52be0e 100644
--- a/core/modules/file/tests/src/Kernel/Migrate/d6/FileMigrationTestTrait.php
+++ b/core/modules/file/tests/src/Kernel/Migrate/d6/FileMigrationTestTrait.php
@@ -30,7 +30,7 @@ trait FileMigrationTestTrait {
       // Make sure we have a single trailing slash.
       $source = $migration->getSourceConfiguration();
       $source['site_path'] = 'core/modules/simpletest';
-      $source['constants']['source_base_path'] = \Drupal::root() . '/';
+      $source['constants']['source_base_path'] = $this->root . '/';
       $migration->set('source', $source);
     }
   }
diff --git a/core/modules/image/tests/src/Kernel/ImageItemTest.php b/core/modules/image/tests/src/Kernel/ImageItemTest.php
index 45d9d0378a2..9621423823d 100644
--- a/core/modules/image/tests/src/Kernel/ImageItemTest.php
+++ b/core/modules/image/tests/src/Kernel/ImageItemTest.php
@@ -67,7 +67,7 @@ class ImageItemTest extends FieldKernelTestBase {
         'file_extensions' => 'jpg',
       ],
     ])->save();
-    file_unmanaged_copy(\Drupal::root() . '/core/misc/druplicon.png', 'public://example.jpg');
+    file_unmanaged_copy($this->root . '/core/misc/druplicon.png', 'public://example.jpg');
     $this->image = File::create([
       'uri' => 'public://example.jpg',
     ]);
@@ -100,7 +100,7 @@ class ImageItemTest extends FieldKernelTestBase {
     $this->assertEqual($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/druplicon.png', 'public://example-2.jpg');
+    file_unmanaged_copy($this->root . '/core/misc/druplicon.png', 'public://example-2.jpg');
     $image2 = File::create([
       'uri' => 'public://example-2.jpg',
     ]);
diff --git a/core/modules/image/tests/src/Kernel/ImageThemeFunctionTest.php b/core/modules/image/tests/src/Kernel/ImageThemeFunctionTest.php
index 0e6e3f2815b..bffd6545f6d 100644
--- a/core/modules/image/tests/src/Kernel/ImageThemeFunctionTest.php
+++ b/core/modules/image/tests/src/Kernel/ImageThemeFunctionTest.php
@@ -62,7 +62,7 @@ class ImageThemeFunctionTest extends KernelTestBase {
       'field_name' => 'image_test',
       'bundle' => 'entity_test',
     ])->save();
-    file_unmanaged_copy(\Drupal::root() . '/core/misc/druplicon.png', 'public://example.jpg');
+    file_unmanaged_copy($this->root . '/core/misc/druplicon.png', 'public://example.jpg');
     $this->image = File::create([
       'uri' => 'public://example.jpg',
     ]);
diff --git a/core/modules/media/tests/src/Functional/MediaRevisionTest.php b/core/modules/media/tests/src/Functional/MediaRevisionTest.php
index 001d59b07c9..1747d5dd787 100644
--- a/core/modules/media/tests/src/Functional/MediaRevisionTest.php
+++ b/core/modules/media/tests/src/Functional/MediaRevisionTest.php
@@ -135,7 +135,7 @@ class MediaRevisionTest extends MediaFunctionalTestBase {
     $this->drupalGet('/media/add/image');
     $page = $this->getSession()->getPage();
     $page->fillField('Name', 'Foobar');
-    $page->attachFileToField('Image', \Drupal::root() . '/core/modules/media/tests/fixtures/example_1.jpeg');
+    $page->attachFileToField('Image', $this->root . '/core/modules/media/tests/fixtures/example_1.jpeg');
     $page->pressButton('Save');
     $assert->addressMatches('/^\/media\/[0-9]+$/');
 
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php
index fd508cf0fd5..48b42916aa7 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php
@@ -68,7 +68,7 @@ class MediaDisplayTest extends MediaJavascriptTestBase {
     $this->drupalGet('media/add/image');
     $image_media_name = 'Fantastic image asset!';
     $page->fillField('name[0][value]', $image_media_name);
-    $page->attachFileToField('files[field_media_image_0]', \Drupal::root() . '/core/modules/media/tests/fixtures/example_1.jpeg');
+    $page->attachFileToField('files[field_media_image_0]', $this->root . '/core/modules/media/tests/fixtures/example_1.jpeg');
     $result = $assert_session->waitForButton('Remove');
     $this->assertNotEmpty($result);
     $page->fillField('field_media_image[0][alt]', 'Image Alt Text 1');
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceImageTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceImageTest.php
index 708cec0bd40..2be4321bbb1 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceImageTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceImageTest.php
@@ -46,7 +46,7 @@ class MediaSourceImageTest extends MediaSourceTestBase {
 
     // Create a media item.
     $this->drupalGet("media/add/{$media_type_id}");
-    $page->attachFileToField("files[{$source_field_id}_0]", \Drupal::root() . '/core/modules/media/tests/fixtures/example_1.jpeg');
+    $page->attachFileToField("files[{$source_field_id}_0]", $this->root . '/core/modules/media/tests/fixtures/example_1.jpeg');
     $result = $assert_session->waitForButton('Remove');
     $this->assertNotEmpty($result);
     $page->fillField("{$source_field_id}[0][alt]", 'Image Alt Text 1');
diff --git a/core/modules/rdf/tests/src/Functional/StandardProfileTest.php b/core/modules/rdf/tests/src/Functional/StandardProfileTest.php
index 8662b9daca5..6d953117406 100644
--- a/core/modules/rdf/tests/src/Functional/StandardProfileTest.php
+++ b/core/modules/rdf/tests/src/Functional/StandardProfileTest.php
@@ -136,7 +136,7 @@ class StandardProfileTest extends BrowserTestBase {
     $this->term->save();
 
     // Create image.
-    file_unmanaged_copy(\Drupal::root() . '/core/misc/druplicon.png', 'public://example.jpg');
+    file_unmanaged_copy($this->root . '/core/misc/druplicon.png', 'public://example.jpg');
     $this->image = File::create(['uri' => 'public://example.jpg']);
     $this->image->save();
 
diff --git a/core/modules/search/tests/src/Functional/SearchSimplifyTest.php b/core/modules/search/tests/src/Functional/SearchSimplifyTest.php
index 399f4ba0d85..11220e25fdf 100644
--- a/core/modules/search/tests/src/Functional/SearchSimplifyTest.php
+++ b/core/modules/search/tests/src/Functional/SearchSimplifyTest.php
@@ -20,7 +20,7 @@ class SearchSimplifyTest extends SearchTestBase {
     // 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');
+    $input = file_get_contents($this->root . '/core/modules/search/tests/UnicodeTest.txt');
     $basestrings = explode(chr(10), $input);
     $strings = [];
     foreach ($basestrings as $key => $string) {
diff --git a/core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php b/core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php
index 451cef911f7..9d6c0af5d10 100644
--- a/core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php
+++ b/core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php
@@ -104,7 +104,7 @@ class EarlyRenderingControllerTest extends BrowserTestBase {
 
     // 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() . '/' . $this->siteDirectory . '/error.log');
+    unlink($this->root . '/' . $this->siteDirectory . '/error.log');
   }
 
 }
diff --git a/core/modules/system/tests/src/Functional/FileTransfer/FileTransferTest.php b/core/modules/system/tests/src/Functional/FileTransfer/FileTransferTest.php
index a4fbb667bad..a15a92a6dbb 100644
--- a/core/modules/system/tests/src/Functional/FileTransfer/FileTransferTest.php
+++ b/core/modules/system/tests/src/Functional/FileTransfer/FileTransferTest.php
@@ -20,7 +20,7 @@ class FileTransferTest extends BrowserTestBase {
 
   protected function setUp() {
     parent::setUp();
-    $this->testConnection = TestFileTransfer::factory(\Drupal::root(), ['hostname' => $this->hostname, 'username' => $this->username, 'password' => $this->password, 'port' => $this->port]);
+    $this->testConnection = TestFileTransfer::factory($this->root, ['hostname' => $this->hostname, 'username' => $this->username, 'password' => $this->password, 'port' => $this->port]);
   }
 
   public function _getFakeModuleFiles() {
@@ -82,7 +82,7 @@ class FileTransferTest extends BrowserTestBase {
 
     $gotit = TRUE;
     try {
-      $this->testConnection->copyDirectory($source, \Drupal::root() . '/' . PublicStream::basePath());
+      $this->testConnection->copyDirectory($source, $this->root . '/' . PublicStream::basePath());
     }
     catch (FileTransferException $e) {
       $gotit = FALSE;
diff --git a/core/modules/system/tests/src/Functional/Update/DependencyHookInvocationTest.php b/core/modules/system/tests/src/Functional/Update/DependencyHookInvocationTest.php
index 8ff7b883db5..203d89ef2a7 100644
--- a/core/modules/system/tests/src/Functional/Update/DependencyHookInvocationTest.php
+++ b/core/modules/system/tests/src/Functional/Update/DependencyHookInvocationTest.php
@@ -21,7 +21,7 @@ class DependencyHookInvocationTest extends BrowserTestBase {
 
   protected function setUp() {
     parent::setUp();
-    require_once \Drupal::root() . '/core/includes/update.inc';
+    require_once $this->root . '/core/includes/update.inc';
   }
 
   /**
diff --git a/core/modules/system/tests/src/Functional/Update/DependencyMissingTest.php b/core/modules/system/tests/src/Functional/Update/DependencyMissingTest.php
index 6ae4dc40c8f..e11999a46c2 100644
--- a/core/modules/system/tests/src/Functional/Update/DependencyMissingTest.php
+++ b/core/modules/system/tests/src/Functional/Update/DependencyMissingTest.php
@@ -22,7 +22,7 @@ class DependencyMissingTest extends BrowserTestBase {
     // 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 $this->root . '/core/includes/update.inc';
   }
 
   public function testMissingUpdate() {
diff --git a/core/modules/system/tests/src/Functional/Update/DependencyOrderingTest.php b/core/modules/system/tests/src/Functional/Update/DependencyOrderingTest.php
index 8cafaaddba3..0f168aa78f5 100644
--- a/core/modules/system/tests/src/Functional/Update/DependencyOrderingTest.php
+++ b/core/modules/system/tests/src/Functional/Update/DependencyOrderingTest.php
@@ -20,7 +20,7 @@ class DependencyOrderingTest extends BrowserTestBase {
 
   protected function setUp() {
     parent::setUp();
-    require_once \Drupal::root() . '/core/includes/update.inc';
+    require_once $this->root . '/core/includes/update.inc';
   }
 
   /**
diff --git a/core/modules/system/tests/src/Functional/Update/InvalidUpdateHookTest.php b/core/modules/system/tests/src/Functional/Update/InvalidUpdateHookTest.php
index 44d4832dd2c..85d041e2a48 100644
--- a/core/modules/system/tests/src/Functional/Update/InvalidUpdateHookTest.php
+++ b/core/modules/system/tests/src/Functional/Update/InvalidUpdateHookTest.php
@@ -35,7 +35,7 @@ class InvalidUpdateHookTest extends BrowserTestBase {
 
   protected function setUp() {
     parent::setUp();
-    require_once \Drupal::root() . '/core/includes/update.inc';
+    require_once $this->root . '/core/includes/update.inc';
 
     $this->updateUrl = $GLOBALS['base_url'] . '/update.php';
     $this->updateUser = $this->drupalCreateUser(['administer software updates']);
diff --git a/core/modules/system/tests/src/Functional/Update/UpdateSchemaTest.php b/core/modules/system/tests/src/Functional/Update/UpdateSchemaTest.php
index a42cbcb3c2a..1c2edee065d 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdateSchemaTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdateSchemaTest.php
@@ -35,7 +35,7 @@ class UpdateSchemaTest extends BrowserTestBase {
   protected function setUp() {
     parent::setUp();
 
-    require_once \Drupal::root() . '/core/includes/update.inc';
+    require_once $this->root . '/core/includes/update.inc';
     $this->user = $this->drupalCreateUser(['administer software updates', 'access site in maintenance mode']);
     $this->updateUrl = Url::fromRoute('system.db_update');
   }
diff --git a/core/modules/system/tests/src/Functional/Update/UpdatesWith7xTest.php b/core/modules/system/tests/src/Functional/Update/UpdatesWith7xTest.php
index 2452264e37a..4f536ea5aa4 100644
--- a/core/modules/system/tests/src/Functional/Update/UpdatesWith7xTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatesWith7xTest.php
@@ -31,7 +31,7 @@ class UpdatesWith7xTest extends BrowserTestBase {
 
   protected function setUp() {
     parent::setUp();
-    require_once \Drupal::root() . '/core/includes/update.inc';
+    require_once $this->root . '/core/includes/update.inc';
     $this->updateUrl = $GLOBALS['base_url'] . '/update.php';
     $this->updateUser = $this->drupalCreateUser(['administer software updates']);
   }
diff --git a/core/modules/system/tests/src/Kernel/Common/SystemListingTest.php b/core/modules/system/tests/src/Kernel/Common/SystemListingTest.php
index 221daeeaeb8..1a3f373f34a 100644
--- a/core/modules/system/tests/src/Kernel/Common/SystemListingTest.php
+++ b/core/modules/system/tests/src/Kernel/Common/SystemListingTest.php
@@ -33,13 +33,13 @@ class SystemListingTest extends KernelTestBase {
     foreach ($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.', ['@filename' => $filename]));
+        $this->assertTrue(file_exists($this->root . '/' . $filename), format_string('@filename exists.', ['@filename' => $filename]));
       }
     }
 
     // Now scan the directories and check that the files take precedence as
     // expected.
-    $listing = new ExtensionDiscovery(\Drupal::root());
+    $listing = new ExtensionDiscovery($this->root);
     $listing->setProfileDirectories(['core/profiles/testing']);
     $files = $listing->scan('module');
     foreach ($expected_directories as $module => $directories) {
@@ -56,7 +56,7 @@ class SystemListingTest extends KernelTestBase {
    * Tests that directories matching file_scan_ignore_directories are ignored
    */
   public function testFileScanIgnoreDirectory() {
-    $listing = new ExtensionDiscovery(\Drupal::root(), FALSE);
+    $listing = new ExtensionDiscovery($this->root, FALSE);
     $listing->setProfileDirectories(['core/profiles/testing']);
     $files = $listing->scan('module');
     $this->assertArrayHasKey('drupal_system_listing_compatible_test', $files);
@@ -68,7 +68,7 @@ class SystemListingTest extends KernelTestBase {
     $reflected_property->setValue($reflected_class, []);
 
     $this->setSetting('file_scan_ignore_directories', ['drupal_system_listing_compatible_test']);
-    $listing = new ExtensionDiscovery(\Drupal::root(), FALSE);
+    $listing = new ExtensionDiscovery($this->root, FALSE);
     $listing->setProfileDirectories(['core/profiles/testing']);
     $files = $listing->scan('module');
     $this->assertArrayNotHasKey('drupal_system_listing_compatible_test', $files);
diff --git a/core/modules/taxonomy/tests/src/Functional/VocabularyCrudTest.php b/core/modules/taxonomy/tests/src/Functional/VocabularyCrudTest.php
index 7803f3966e7..1fb01630bf6 100644
--- a/core/modules/taxonomy/tests/src/Functional/VocabularyCrudTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/VocabularyCrudTest.php
@@ -164,7 +164,7 @@ class VocabularyCrudTest extends TaxonomyTestBase {
     // installed for testing below.
     $this->vocabulary->unsetThirdPartySetting('taxonomy_crud', 'foo');
 
-    require_once \Drupal::root() . '/core/includes/install.inc';
+    require_once $this->root . '/core/includes/install.inc';
     $this->container->get('module_installer')->uninstall(['taxonomy']);
     $this->container->get('module_installer')->install(['taxonomy']);
 
diff --git a/core/modules/update/tests/src/Functional/UpdateUploadTest.php b/core/modules/update/tests/src/Functional/UpdateUploadTest.php
index 60966200629..e86dff54981 100644
--- a/core/modules/update/tests/src/Functional/UpdateUploadTest.php
+++ b/core/modules/update/tests/src/Functional/UpdateUploadTest.php
@@ -190,10 +190,10 @@ class UpdateUploadTest extends UpdateTestBase {
    * Tests only an *.info.yml file are detected without supporting files.
    */
   public function testUpdateDirectory() {
-    $type = Updater::getUpdaterFromDirectory(\Drupal::root() . '/core/modules/update/tests/modules/aaa_update_test');
+    $type = Updater::getUpdaterFromDirectory($this->root . '/core/modules/update/tests/modules/aaa_update_test');
     $this->assertEqual($type, 'Drupal\\Core\\Updater\\Module', 'Detected a Module');
 
-    $type = Updater::getUpdaterFromDirectory(\Drupal::root() . '/core/modules/update/tests/themes/update_test_basetheme');
+    $type = Updater::getUpdaterFromDirectory($this->root . '/core/modules/update/tests/themes/update_test_basetheme');
     $this->assertEqual($type, 'Drupal\\Core\\Updater\\Theme', 'Detected a Theme.');
   }
 
diff --git a/core/modules/user/tests/src/Kernel/UserAccountFormFieldsTest.php b/core/modules/user/tests/src/Kernel/UserAccountFormFieldsTest.php
index 643302192c7..fe967b2d9f6 100644
--- a/core/modules/user/tests/src/Kernel/UserAccountFormFieldsTest.php
+++ b/core/modules/user/tests/src/Kernel/UserAccountFormFieldsTest.php
@@ -24,8 +24,8 @@ class UserAccountFormFieldsTest extends KernelTestBase {
    * Tests the root user account form section in the "Configure site" form.
    */
   public function testInstallConfigureForm() {
-    require_once \Drupal::root() . '/core/includes/install.core.inc';
-    require_once \Drupal::root() . '/core/includes/install.inc';
+    require_once $this->root . '/core/includes/install.core.inc';
+    require_once $this->root . '/core/includes/install.inc';
     $install_state = install_state_defaults();
     $form_state = new FormState();
     $form_state->addBuildInfo('args', [&$install_state]);
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguageDirectionTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguageDirectionTest.php
index da63ec9b308..ac2c46297f0 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguageDirectionTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguageDirectionTest.php
@@ -21,8 +21,8 @@ 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() . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.ar.po', "msgid \"\"\nmsgstr \"\"\nmsgid \"Save and continue\"\nmsgstr \"Save and continue Arabic\"");
+    mkdir($this->root . '/' . $this->siteDirectory . '/files/translations', 0777, TRUE);
+    file_put_contents($this->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/tests/Drupal/FunctionalTests/Installer/InstallerLanguagePageTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguagePageTest.php
index a040da965ca..5ea9692f341 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguagePageTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerLanguagePageTest.php
@@ -16,8 +16,8 @@ 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() . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.xoxo.po');
+    mkdir($this->root . '/' . $this->siteDirectory . '/files/translations', 0777, TRUE);
+    touch($this->root . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.xoxo.po');
 
     // Check that all predefined languages show up with their native names.
     $this->visitInstaller();
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerTest.php
index 974318b08d3..2f6deba4dee 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerTest.php
@@ -19,7 +19,7 @@ class InstallerTest extends InstallerTestBase {
     $this->assertText($this->rootUser->getUsername());
 
     // Verify that the confirmation message appears.
-    require_once \Drupal::root() . '/core/includes/install.inc';
+    require_once $this->root . '/core/includes/install.inc';
     $this->assertRaw(t('Congratulations, you installed @drupal!', [
       '@drupal' => drupal_install_profile_distribution_name(),
     ]));
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationQueryTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationQueryTest.php
index 8a6cc1e8c39..152713b2732 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationQueryTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationQueryTest.php
@@ -23,8 +23,8 @@ class InstallerTranslationQueryTest extends InstallerTestBase {
    */
   protected function visitInstaller() {
     // 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', $this->getPo('de'));
+    mkdir($this->root . '/' . $this->siteDirectory . '/files/translations', 0777, TRUE);
+    file_put_contents($this->root . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.de.po', $this->getPo('de'));
 
     // The unrouted URL assembler does not exist at this point, so we build the
     // URL ourselves.
diff --git a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationTest.php b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationTest.php
index 974d2825883..ecf7d8867a1 100644
--- a/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationTest.php
+++ b/core/tests/Drupal/FunctionalTests/Installer/InstallerTranslationTest.php
@@ -24,8 +24,8 @@ 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', $this->getPo('de'));
+    mkdir($this->root . '/' . $this->siteDirectory . '/files/translations', 0777, TRUE);
+    file_put_contents($this->root . '/' . $this->siteDirectory . '/files/translations/drupal-8.0.0.de.po', $this->getPo('de'));
 
     parent::setUpLanguage();
 
diff --git a/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php b/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php
index 8e192d4c541..34b4cc4dbef 100644
--- a/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php
+++ b/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php
@@ -193,7 +193,7 @@ abstract class UpdatePathTestBase extends BrowserTestBase {
 
     $this->replaceUser1();
 
-    require_once \Drupal::root() . '/core/includes/update.inc';
+    require_once $this->root . '/core/includes/update.inc';
 
     // Setup Mink.
     $session = $this->initMink();
diff --git a/core/tests/Drupal/KernelTests/Core/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php b/core/tests/Drupal/KernelTests/Core/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
index 2131a35ad0f..bbb3d6a5a02 100644
--- a/core/tests/Drupal/KernelTests/Core/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
@@ -149,7 +149,6 @@ class ResolvedLibraryDefinitionsFilesMatchTest extends KernelTestBase {
    *   so on.
    */
   protected function verifyLibraryFilesExist($library_definitions) {
-    $root = \Drupal::root();
     foreach ($library_definitions as $extension => $libraries) {
       foreach ($libraries as $library_name => $library) {
         if (in_array("$extension/$library_name", $this->librariesToSkip)) {
@@ -160,7 +159,7 @@ class ResolvedLibraryDefinitionsFilesMatchTest extends KernelTestBase {
         foreach (['css', 'js'] as $asset_type) {
           foreach ($library[$asset_type] as $asset) {
             $file = $asset['data'];
-            $path = $root . '/' . $file;
+            $path = $this->root . '/' . $file;
             // Only check and assert each file path once.
             if (!isset($this->pathsChecked[$path])) {
               $this->assertTrue(is_file($path), "$file file referenced from the $extension/$library_name library exists.");
@@ -192,10 +191,9 @@ class ResolvedLibraryDefinitionsFilesMatchTest extends KernelTestBase {
 
     $libraries['core'] = $this->libraryDiscovery->getLibrariesByExtension('core');
 
-    $root = \Drupal::root();
     foreach ($extensions as $extension_name => $extension) {
       $library_file = $extension->getPath() . '/' . $extension_name . '.libraries.yml';
-      if (is_file($root . '/' . $library_file)) {
+      if (is_file($this->root . '/' . $library_file)) {
         $libraries[$extension_name] = $this->libraryDiscovery->getLibrariesByExtension($extension_name);
       }
     }
diff --git a/core/tests/Drupal/KernelTests/Core/EventSubscriber/IgnoreReplicaSubscriberTest.php b/core/tests/Drupal/KernelTests/Core/EventSubscriber/IgnoreReplicaSubscriberTest.php
index 7ce994a9447..237edb63c31 100644
--- a/core/tests/Drupal/KernelTests/Core/EventSubscriber/IgnoreReplicaSubscriberTest.php
+++ b/core/tests/Drupal/KernelTests/Core/EventSubscriber/IgnoreReplicaSubscriberTest.php
@@ -28,7 +28,7 @@ class IgnoreReplicaSubscriberTest extends KernelTestBase {
     Database::addConnectionInfo('default', 'replica', $connection_info['default']);
 
     db_ignore_replica();
-    $class_loader = require \Drupal::root() . '/autoload.php';
+    $class_loader = require $this->root . '/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/tests/Drupal/KernelTests/Core/Plugin/Discovery/AnnotatedClassDiscoveryTest.php b/core/tests/Drupal/KernelTests/Core/Plugin/Discovery/AnnotatedClassDiscoveryTest.php
index 9003713f532..34168dab50a 100644
--- a/core/tests/Drupal/KernelTests/Core/Plugin/Discovery/AnnotatedClassDiscoveryTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Plugin/Discovery/AnnotatedClassDiscoveryTest.php
@@ -73,8 +73,8 @@ class AnnotatedClassDiscoveryTest extends DiscoveryTestBase {
       ],
     ];
 
-    $base_directory = \Drupal::root() . '/core/modules/system/tests/modules/plugin_test/src';
-    $base_directory2 = \Drupal::root() . '/core/modules/system/tests/modules/plugin_test_extended/src';
+    $base_directory = $this->root . '/core/modules/system/tests/modules/plugin_test/src';
+    $base_directory2 = $this->root . '/core/modules/system/tests/modules/plugin_test_extended/src';
     $namespaces = new \ArrayObject(['Drupal\plugin_test' => $base_directory, 'Drupal\plugin_test_extended' => $base_directory2]);
 
     $annotation_namespaces = ['Drupal\plugin_test\Plugin\Annotation', 'Drupal\plugin_test_extended\Plugin\Annotation'];
diff --git a/core/tests/Drupal/KernelTests/Core/Plugin/Discovery/CustomAnnotationClassDiscoveryTest.php b/core/tests/Drupal/KernelTests/Core/Plugin/Discovery/CustomAnnotationClassDiscoveryTest.php
index 3ae576cfdfb..c6e32b7124f 100644
--- a/core/tests/Drupal/KernelTests/Core/Plugin/Discovery/CustomAnnotationClassDiscoveryTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Plugin/Discovery/CustomAnnotationClassDiscoveryTest.php
@@ -30,7 +30,7 @@ class CustomAnnotationClassDiscoveryTest extends DiscoveryTestBase {
       ],
     ];
 
-    $base_directory = \Drupal::root() . '/core/modules/system/tests/modules/plugin_test/src';
+    $base_directory = $this->root . '/core/modules/system/tests/modules/plugin_test/src';
     $root_namespaces = new \ArrayObject(['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/tests/Drupal/KernelTests/Core/Plugin/Discovery/CustomDirectoryAnnotatedClassDiscoveryTest.php b/core/tests/Drupal/KernelTests/Core/Plugin/Discovery/CustomDirectoryAnnotatedClassDiscoveryTest.php
index a6ae259bc2f..1074eb1ba52 100644
--- a/core/tests/Drupal/KernelTests/Core/Plugin/Discovery/CustomDirectoryAnnotatedClassDiscoveryTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Plugin/Discovery/CustomDirectoryAnnotatedClassDiscoveryTest.php
@@ -80,7 +80,7 @@ class CustomDirectoryAnnotatedClassDiscoveryTest extends DiscoveryTestBase {
       ],
     ];
 
-    $base_directory = \Drupal::root() . '/core/modules/system/tests/modules/plugin_test/src';
+    $base_directory = $this->root . '/core/modules/system/tests/modules/plugin_test/src';
     $namespaces = new \ArrayObject(['Drupal\plugin_test' => $base_directory]);
 
     $this->discovery = new AnnotatedClassDiscovery('', $namespaces);
diff --git a/core/tests/Drupal/KernelTests/Core/Plugin/PluginTestBase.php b/core/tests/Drupal/KernelTests/Core/Plugin/PluginTestBase.php
index ccc82369a0e..fac49b214ab 100644
--- a/core/tests/Drupal/KernelTests/Core/Plugin/PluginTestBase.php
+++ b/core/tests/Drupal/KernelTests/Core/Plugin/PluginTestBase.php
@@ -42,7 +42,7 @@ abstract class PluginTestBase extends KernelTestBase {
     //   as derivatives and ReflectionFactory.
     $this->testPluginManager = new TestPluginManager();
     $this->mockBlockManager = new MockBlockManager();
-    $module_handler = new ModuleHandler(\Drupal::root(), [], new MemoryBackend(), $this->container->get('event_dispatcher'));
+    $module_handler = new ModuleHandler($this->root, [], new MemoryBackend(), $this->container->get('event_dispatcher'));
     $this->defaultsTestPluginManager = new DefaultsTestPluginManager($module_handler);
 
     // The expected plugin definitions within each manager. Several tests assert
diff --git a/core/tests/Drupal/KernelTests/Core/RouteProcessor/RouteNoneTest.php b/core/tests/Drupal/KernelTests/Core/RouteProcessor/RouteNoneTest.php
index 2b599339294..6d26891fdbc 100644
--- a/core/tests/Drupal/KernelTests/Core/RouteProcessor/RouteNoneTest.php
+++ b/core/tests/Drupal/KernelTests/Core/RouteProcessor/RouteNoneTest.php
@@ -53,7 +53,7 @@ class RouteNoneTest extends KernelTestBase {
     // Test request with subdir on homepage.
     $server = [
       'SCRIPT_NAME' => '/subdir/index.php',
-      'SCRIPT_FILENAME' => \Drupal::root() . '/index.php',
+      'SCRIPT_FILENAME' => $this->root . '/index.php',
       'SERVER_NAME' => 'http://www.example.com',
     ];
     $request = Request::create('/subdir', 'GET', [], [], [], $server);
@@ -70,7 +70,7 @@ class RouteNoneTest extends KernelTestBase {
     // Test request with subdir on other page.
     $server = [
       'SCRIPT_NAME' => '/subdir/index.php',
-      'SCRIPT_FILENAME' => \Drupal::root() . '/index.php',
+      'SCRIPT_FILENAME' => $this->root . '/index.php',
       'SERVER_NAME' => 'http://www.example.com',
     ];
     $request = Request::create('/subdir/node/add', 'GET', [], [], [], $server);
@@ -87,7 +87,7 @@ class RouteNoneTest extends KernelTestBase {
     // Test request without subdir on the homepage.
     $server = [
       'SCRIPT_NAME' => '/index.php',
-      'SCRIPT_FILENAME' => \Drupal::root() . '/index.php',
+      'SCRIPT_FILENAME' => $this->root . '/index.php',
       'SERVER_NAME' => 'http://www.example.com',
     ];
     $request = Request::create('/', 'GET', [], [], [], $server);
@@ -104,7 +104,7 @@ class RouteNoneTest extends KernelTestBase {
     // Test request without subdir on other page.
     $server = [
       'SCRIPT_NAME' => '/index.php',
-      'SCRIPT_FILENAME' => \Drupal::root() . '/index.php',
+      'SCRIPT_FILENAME' => $this->root . '/index.php',
       'SERVER_NAME' => 'http://www.example.com',
     ];
     $request = Request::create('/node/add', 'GET', [], [], [], $server);
diff --git a/core/tests/Drupal/KernelTests/Core/RouteProcessor/RouteProcessorCurrentIntegrationTest.php b/core/tests/Drupal/KernelTests/Core/RouteProcessor/RouteProcessorCurrentIntegrationTest.php
index ea6a9c25380..4e42271aa58 100644
--- a/core/tests/Drupal/KernelTests/Core/RouteProcessor/RouteProcessorCurrentIntegrationTest.php
+++ b/core/tests/Drupal/KernelTests/Core/RouteProcessor/RouteProcessorCurrentIntegrationTest.php
@@ -54,7 +54,7 @@ class RouteProcessorCurrentIntegrationTest extends KernelTestBase {
     // Test request with subdir on homepage.
     $server = [
       'SCRIPT_NAME' => '/subdir/index.php',
-      'SCRIPT_FILENAME' => \Drupal::root() . '/index.php',
+      'SCRIPT_FILENAME' => $this->root . '/index.php',
       'SERVER_NAME' => 'http://www.example.com',
     ];
     $request = Request::create('/subdir/', 'GET', [], [], [], $server);
@@ -69,7 +69,7 @@ class RouteProcessorCurrentIntegrationTest extends KernelTestBase {
     // Test request with subdir on other page.
     $server = [
       'SCRIPT_NAME' => '/subdir/index.php',
-      'SCRIPT_FILENAME' => \Drupal::root() . '/index.php',
+      'SCRIPT_FILENAME' => $this->root . '/index.php',
       'SERVER_NAME' => 'http://www.example.com',
     ];
     $request = Request::create('/subdir/node/add', 'GET', [], [], [], $server);
@@ -84,7 +84,7 @@ class RouteProcessorCurrentIntegrationTest extends KernelTestBase {
     // Test request without subdir on the homepage.
     $server = [
       'SCRIPT_NAME' => '/index.php',
-      'SCRIPT_FILENAME' => \Drupal::root() . '/index.php',
+      'SCRIPT_FILENAME' => $this->root . '/index.php',
       'SERVER_NAME' => 'http://www.example.com',
     ];
     $request = Request::create('/', 'GET', [], [], [], $server);
@@ -99,7 +99,7 @@ class RouteProcessorCurrentIntegrationTest extends KernelTestBase {
     // Test request without subdir on other page.
     $server = [
       'SCRIPT_NAME' => '/index.php',
-      'SCRIPT_FILENAME' => \Drupal::root() . '/index.php',
+      'SCRIPT_FILENAME' => $this->root . '/index.php',
       'SERVER_NAME' => 'http://www.example.com',
     ];
     $request = Request::create('/node/add', 'GET', [], [], [], $server);
@@ -115,7 +115,7 @@ class RouteProcessorCurrentIntegrationTest extends KernelTestBase {
     // not found exception page.
     $server = [
       'SCRIPT_NAME' => '/index.php',
-      'SCRIPT_FILENAME' => \Drupal::root() . '/index.php',
+      'SCRIPT_FILENAME' => $this->root . '/index.php',
       'SERVER_NAME' => 'http://www.example.com',
     ];
     $request = Request::create('/invalid-path', 'GET', [], [], [], $server);
diff --git a/core/tests/Drupal/KernelTests/Core/Site/SettingsRewriteTest.php b/core/tests/Drupal/KernelTests/Core/Site/SettingsRewriteTest.php
index 40a8a743dd3..05078711244 100644
--- a/core/tests/Drupal/KernelTests/Core/Site/SettingsRewriteTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Site/SettingsRewriteTest.php
@@ -16,7 +16,7 @@ class SettingsRewriteTest extends KernelTestBase {
    * Tests the drupal_rewrite_settings() function.
    */
   public function testDrupalRewriteSettings() {
-    include_once \Drupal::root() . '/core/includes/install.inc';
+    include_once $this->root . '/core/includes/install.inc';
     $site_path = $this->container->get('site.path');
     $tests = [
       [
diff --git a/core/tests/Drupal/KernelTests/Core/Theme/RegistryTest.php b/core/tests/Drupal/KernelTests/Core/Theme/RegistryTest.php
index 169da31925d..320e92f46a1 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/RegistryTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/RegistryTest.php
@@ -69,11 +69,11 @@ class RegistryTest extends KernelTestBase {
     $theme_handler = \Drupal::service('theme_handler');
     $theme_handler->install(['test_basetheme', 'test_subtheme', 'test_subsubtheme']);
 
-    $registry_subsub_theme = new Registry(\Drupal::root(), \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_subsubtheme');
+    $registry_subsub_theme = new Registry($this->root, \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_subsubtheme');
     $registry_subsub_theme->setThemeManager(\Drupal::theme());
-    $registry_sub_theme = new Registry(\Drupal::root(), \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_subtheme');
+    $registry_sub_theme = new Registry($this->root, \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_subtheme');
     $registry_sub_theme->setThemeManager(\Drupal::theme());
-    $registry_base_theme = new Registry(\Drupal::root(), \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_basetheme');
+    $registry_base_theme = new Registry($this->root, \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_basetheme');
     $registry_base_theme->setThemeManager(\Drupal::theme());
 
     $preprocess_functions = $registry_subsub_theme->get()['theme_test_template_test']['preprocess functions'];
@@ -111,7 +111,7 @@ class RegistryTest extends KernelTestBase {
     $theme_handler = \Drupal::service('theme_handler');
     $theme_handler->install(['test_theme']);
 
-    $registry_theme = new Registry(\Drupal::root(), \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_theme');
+    $registry_theme = new Registry($this->root, \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_theme');
     $registry_theme->setThemeManager(\Drupal::theme());
 
     $suggestions = ['__kitten', '__flamingo'];
@@ -154,7 +154,7 @@ class RegistryTest extends KernelTestBase {
     $theme_handler->install(['test_theme']);
     $this->config('system.theme')->set('default', 'test_theme')->save();
 
-    $registry = new Registry(\Drupal::root(), \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_theme');
+    $registry = new Registry($this->root, \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_theme');
     $registry->setThemeManager(\Drupal::theme());
     $this->assertEqual('value', $registry->get()['theme_test_template_test']['variables']['additional']);
   }
@@ -199,7 +199,7 @@ class RegistryTest extends KernelTestBase {
     $theme_handler = \Drupal::service('theme_handler');
     $theme_handler->install(['test_theme']);
 
-    $registry_theme = new Registry(\Drupal::root(), \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_theme');
+    $registry_theme = new Registry($this->root, \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $theme_handler, \Drupal::service('theme.initialization'), 'test_theme');
     $registry_theme->setThemeManager(\Drupal::theme());
 
     $expected = [
diff --git a/core/tests/Drupal/KernelTests/Core/Theme/StableLibraryOverrideTest.php b/core/tests/Drupal/KernelTests/Core/Theme/StableLibraryOverrideTest.php
index a71c3fe6422..1976b2684c2 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/StableLibraryOverrideTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/StableLibraryOverrideTest.php
@@ -94,7 +94,6 @@ class StableLibraryOverrideTest extends KernelTestBase {
     $libraries_after = $this->getAllLibraries();
     $libraries_after = $this->removeVendorAssets($libraries_after);
 
-    $root = \Drupal::root();
     foreach ($libraries_before as $extension => $libraries) {
       foreach ($libraries as $library_name => $library) {
         // Allow skipping libraries.
@@ -173,10 +172,9 @@ class StableLibraryOverrideTest extends KernelTestBase {
 
     $libraries['core'] = $this->libraryDiscovery->getLibrariesByExtension('core');
 
-    $root = \Drupal::root();
     foreach ($modules as $module_name => $module) {
       $library_file = $module->getPath() . '/' . $module_name . '.libraries.yml';
-      if (is_file($root . '/' . $library_file)) {
+      if (is_file($this->root . '/' . $library_file)) {
         $libraries[$module_name] = $this->libraryDiscovery->getLibrariesByExtension($module_name);
       }
     }
diff --git a/core/tests/Drupal/KernelTests/Core/Theme/StableTemplateOverrideTest.php b/core/tests/Drupal/KernelTests/Core/Theme/StableTemplateOverrideTest.php
index edb66939c23..88bbde23a09 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/StableTemplateOverrideTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/StableTemplateOverrideTest.php
@@ -82,7 +82,7 @@ class StableTemplateOverrideTest extends KernelTestBase {
    * Ensures that Stable overrides all relevant core templates.
    */
   public function testStableTemplateOverrides() {
-    $registry = new Registry(\Drupal::root(), \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $this->themeHandler, \Drupal::service('theme.initialization'), 'stable');
+    $registry = new Registry($this->root, \Drupal::cache(), \Drupal::lock(), \Drupal::moduleHandler(), $this->themeHandler, \Drupal::service('theme.initialization'), 'stable');
     $registry->setThemeManager(\Drupal::theme());
 
     $registry_full = $registry->get();
diff --git a/core/tests/Drupal/KernelTests/Core/Theme/ThemeSettingsTest.php b/core/tests/Drupal/KernelTests/Core/Theme/ThemeSettingsTest.php
index 130df2baee5..cf0e7d2c212 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/ThemeSettingsTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/ThemeSettingsTest.php
@@ -33,7 +33,7 @@ class ThemeSettingsTest extends KernelTestBase {
     $this->installConfig(['system']);
 
     if (!isset($this->availableThemes)) {
-      $discovery = new ExtensionDiscovery(\Drupal::root());
+      $discovery = new ExtensionDiscovery($this->root);
       $this->availableThemes = $discovery->scan('theme');
     }
   }
diff --git a/core/tests/Drupal/KernelTests/Core/TypedData/TypedDataTest.php b/core/tests/Drupal/KernelTests/Core/TypedData/TypedDataTest.php
index 581960ed509..77714653073 100644
--- a/core/tests/Drupal/KernelTests/Core/TypedData/TypedDataTest.php
+++ b/core/tests/Drupal/KernelTests/Core/TypedData/TypedDataTest.php
@@ -250,7 +250,7 @@ class TypedDataTest extends KernelTestBase {
     $files = [];
     for ($i = 0; $i < 3; $i++) {
       $path = "public://example_$i.png";
-      file_unmanaged_copy(\Drupal::root() . '/core/misc/druplicon.png', $path);
+      file_unmanaged_copy($this->root . '/core/misc/druplicon.png', $path);
       $image = File::create(['uri' => $path]);
       $image->save();
       $files[] = $image;
diff --git a/core/tests/Drupal/KernelTests/Core/Update/CompatibilityFixTest.php b/core/tests/Drupal/KernelTests/Core/Update/CompatibilityFixTest.php
index a724623ec37..20a45cad5c1 100644
--- a/core/tests/Drupal/KernelTests/Core/Update/CompatibilityFixTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Update/CompatibilityFixTest.php
@@ -18,7 +18,7 @@ class CompatibilityFixTest extends KernelTestBase {
 
   protected function setUp() {
     parent::setUp();
-    require_once \Drupal::root() . '/core/includes/update.inc';
+    require_once $this->root . '/core/includes/update.inc';
   }
 
   public function testFixCompatibility() {
diff --git a/core/tests/Drupal/KernelTests/Core/Updater/UpdaterTest.php b/core/tests/Drupal/KernelTests/Core/Updater/UpdaterTest.php
index 9f26f4a454d..be6029fe673 100644
--- a/core/tests/Drupal/KernelTests/Core/Updater/UpdaterTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Updater/UpdaterTest.php
@@ -24,7 +24,7 @@ class UpdaterTest extends KernelTestBase {
   public function testGetProjectTitleWithChild() {
     // Get the project title from its directory. If it can't find the title
     // it will choose the first project title in the directory.
-    $directory = \Drupal::root() . '/core/modules/system/tests/modules/module_handler_test_multiple';
+    $directory = $this->root . '/core/modules/system/tests/modules/module_handler_test_multiple';
     $title = Updater::getProjectTitle($directory);
     $this->assertEqual('module handler test multiple', $title);
   }
diff --git a/core/tests/Drupal/KernelTests/KernelTestBase.php b/core/tests/Drupal/KernelTests/KernelTestBase.php
index 7f5e61c1214..71cb93f08b4 100644
--- a/core/tests/Drupal/KernelTests/KernelTestBase.php
+++ b/core/tests/Drupal/KernelTests/KernelTestBase.php
@@ -812,7 +812,7 @@ abstract class KernelTestBase extends TestCase implements ServiceProviderInterfa
     // profile that is not the current profile, and we don't yet have a cached
     // way to receive inactive profile information.
     // @todo Remove as part of https://www.drupal.org/node/2186491
-    $listing = new ExtensionDiscovery(\Drupal::root());
+    $listing = new ExtensionDiscovery($this->root);
     $module_list = $listing->scan('module');
     // In ModuleHandlerTest we pass in a profile as if it were a module.
     $module_list += $listing->scan('profile');