diff -u b/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
--- b/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -8,7 +8,6 @@
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Component\Utility\SafeMarkup;
-use Drupal\Core\Database\Database;
 use Drupal\Core\EventSubscriber\AjaxResponseSubscriber;
 use Drupal\Core\EventSubscriber\MainContentViewSubscriber;
 use Drupal\Core\Session\AccountInterface;
diff -u b/core/modules/system/tests/src/Functional/Update/DbUpdatesTrait.php b/core/modules/system/src/Tests/Update/DbUpdatesTrait.php
--- b/core/modules/system/tests/src/Functional/Update/DbUpdatesTrait.php
+++ b/core/modules/system/src/Tests/Update/DbUpdatesTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\Tests\system\Functional\Update;
+namespace Drupal\system\Tests\Update;
 
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\Core\Url;
@@ -9,7 +9,10 @@
  * Provides methods to conditionally enable db update functions and apply
  * pending db updates through the Update UI.
  *
- * This should be used only by classes extending \Drupal\Tests\BrowserTestBase.
+ * This should be used only by classes extending \Drupal\simpletest\WebTestBase.
+ *
+ * @deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0.
+ *   Use \Drupal\FunctionalTests\Update\DbUpdatesTrait.
  */
 trait DbUpdatesTrait {
 
diff -u b/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php b/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
--- b/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
+++ b/core/modules/system/tests/src/Functional/Update/UpdatePathTestBaseFilledTest.php
@@ -90,7 +90,7 @@
 
     // Log in as user 1.
     $account = User::load(1);
-    $account->pass_raw = 'drupal';
+    $account->passRaw = 'drupal';
     $this->drupalLogin($account);
 
     // Make sure we can see the access-restricted entity reference field
diff -u b/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php b/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php
--- b/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php
+++ b/core/tests/Drupal/FunctionalTests/Update/UpdatePathTestBase.php
@@ -7,7 +7,6 @@
 use Behat\Mink\Selector\SelectorsHandler;
 use Behat\Mink\Session;
 use Drupal\Component\Utility\Crypt;
-use Drupal\Core\DrupalKernel;
 use Drupal\Core\Test\TestRunnerKernel;
 use Drupal\Tests\BrowserTestBase;
 use Drupal\Tests\HiddenFieldSelector;
@@ -16,7 +15,6 @@
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Url;
-use Drupal\simpletest\WebTestBase;
 use Drupal\user\Entity\User;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\HttpFoundation\Request;