diff -u b/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php b/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
--- b/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
+++ b/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
@@ -42,6 +42,13 @@
   protected $configDirectories = [];
 
   /**
+   * The original container.
+   *
+   * @var \Symfony\Component\DependencyInjection\ContainerInterface
+   */
+  protected $originalContainer;
+
+  /**
    * Prepares site settings and services before installation.
    */
   protected function prepareSettings() {
@@ -603,6 +610,9 @@
     drupal_static_reset();
 
     // Ensure there is no service container.
+    if (empty($this->originalContainer)) {
+      $this->originalContainer = $this->initKernel(\Drupal::request());
+    }
     $this->container = NULL;
     \Drupal::unsetContainer();
 
@@ -641,2 +651,17 @@
 
+  /**
+   * Returns all supported database driver installer objects.
+   *
+   * This wraps drupal_get_database_types() for use without a current container.
+   *
+   * @return \Drupal\Core\Database\Install\Tasks[]
+   *   An array of available database driver installer objects.
+   */
+  protected function getDatabaseTypes() {
+    \Drupal::setContainer($this->originalContainer);
+    $database_types = drupal_get_database_types();
+    \Drupal::unsetContainer();
+    return $database_types;
+  }
+
 }
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
@@ -417,21 +417,6 @@
   }
 
   /**
-   * Returns all supported database driver installer objects.
-   *
-   * This wraps drupal_get_database_types() for use without a current container.
-   *
-   * @return \Drupal\Core\Database\Install\Tasks[]
-   *   An array of available database driver installer objects.
-   */
-  protected function getDatabaseTypes() {
-    \Drupal::setContainer($this->originalContainer);
-    $database_types = drupal_get_database_types();
-    \Drupal::unsetContainer();
-    return $database_types;
-  }
-
-  /**
    * Queues custom translations to be written to settings.php.
    *
    * Use WebTestBase::writeCustomTranslations() to apply and write the queued
reverted:
--- b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
+++ a/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
@@ -2314,7 +2314,6 @@
       $this->display['cache_metadata']['tags'] = $cache_metadata->getCacheTags();
     }
     else {
-      $a = 123;
       $cache_metadata = (new CacheableMetadata())
         ->setCacheMaxAge($this->display['cache_metadata']['max-age'])
         ->setCacheContexts($this->display['cache_metadata']['contexts'])
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
@@ -332,6 +332,7 @@
     $this->doSelectionTest();
     // Run the update hooks.
     $this->clickLink(t('Apply pending updates'));
+    $this->checkForMetaRefresh();
 
     // Ensure there are no failed updates.
     if ($this->checkFailedUpdates) {
diff -u b/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
--- b/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -28,7 +28,6 @@
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
 use Symfony\Component\CssSelector\CssSelectorConverter;
-use Symfony\Component\HttpFoundation\Request;
 
 /**
  * Provides a test case for functional Drupal tests.
@@ -1090,11 +1089,8 @@
    *   text. Defaults to 0.
    */
   protected function clickLink($label, $index = 0) {
-    static $i;
     $label = (string) $label;
     $links = $this->getSession()->getPage()->findAll('named', ['link', $label]);
-    $i++;
-    file_put_contents("/tmp/debug-$i.html", $this->getSession()->getPage()->getHtml());
     $links[$index]->click();
   }