diff --git a/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
index 6fa40a3..4258f80 100644
--- a/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -7,13 +7,11 @@
 use Drupal\Component\Utility\Crypt;
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Database\Database;
-use Drupal\Core\Config\ConfigImporter;
-use Drupal\Core\Config\StorageComparer;
-use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\Site\Settings;
 use Drupal\Core\StreamWrapper\PublicStream;
 use Drupal\Core\Test\TestDatabase;
 use Drupal\Core\Utility\Error;
+use Drupal\Tests\ConfigTestTrait;
 use Drupal\Tests\RandomGeneratorTrait;
 use Drupal\Tests\SessionTestTrait;
 
@@ -27,6 +25,11 @@
   use SessionTestTrait;
   use RandomGeneratorTrait;
   use AssertHelperTrait;
+  // For backwards compatibility switch the visbility of the methods to public.
+  use ConfigTestTrait {
+    configImporter as public;
+    copyConfig as public;
+  }
 
   /**
    * The test run ID.
@@ -1538,51 +1541,6 @@ public static function filePreDeleteCallback($path) {
   }
 
   /**
-   * Returns a ConfigImporter object to import test importing of configuration.
-   *
-   * @return \Drupal\Core\Config\ConfigImporter
-   *   The ConfigImporter object.
-   */
-  public function configImporter() {
-    if (!$this->configImporter) {
-      // Set up the ConfigImporter object for testing.
-      $storage_comparer = new StorageComparer(
-        $this->container->get('config.storage.sync'),
-        $this->container->get('config.storage'),
-        $this->container->get('config.manager')
-      );
-      $this->configImporter = new ConfigImporter(
-        $storage_comparer,
-        $this->container->get('event_dispatcher'),
-        $this->container->get('config.manager'),
-        $this->container->get('lock'),
-        $this->container->get('config.typed'),
-        $this->container->get('module_handler'),
-        $this->container->get('module_installer'),
-        $this->container->get('theme_handler'),
-        $this->container->get('string_translation')
-      );
-    }
-    // Always recalculate the changelist when called.
-    return $this->configImporter->reset();
-  }
-
-  /**
-   * Copies configuration objects from source storage to target storage.
-   *
-   * @param \Drupal\Core\Config\StorageInterface $source_storage
-   *   The source config storage service.
-   * @param \Drupal\Core\Config\StorageInterface $target_storage
-   *   The target config storage service.
-   */
-  public function copyConfig(StorageInterface $source_storage, StorageInterface $target_storage) {
-    $target_storage->deleteAll();
-    foreach ($source_storage->listAll() as $name) {
-      $target_storage->write($name, $source_storage->read($name));
-    }
-  }
-
-  /**
    * Configuration accessor for tests. Returns non-overridden configuration.
    *
    * @param $name
diff --git a/core/tests/Drupal/KernelTests/KernelTestBase.php b/core/tests/Drupal/KernelTests/KernelTestBase.php
index ed3875d..8807cb5 100644
--- a/core/tests/Drupal/KernelTests/KernelTestBase.php
+++ b/core/tests/Drupal/KernelTests/KernelTestBase.php
@@ -7,9 +7,6 @@
 use Drupal\Component\FileCache\FileCacheFactory;
 use Drupal\Component\Utility\Html;
 use Drupal\Component\Utility\SafeMarkup;
-use Drupal\Core\Config\ConfigImporter;
-use Drupal\Core\Config\StorageComparer;
-use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\Database\Database;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Core\DependencyInjection\ServiceProviderInterface;
@@ -20,6 +17,7 @@
 use Drupal\Core\Site\Settings;
 use Drupal\simpletest\AssertContentTrait;
 use Drupal\simpletest\AssertHelperTrait;
+use Drupal\Tests\ConfigTestTrait;
 use Drupal\Tests\RandomGeneratorTrait;
 use Drupal\simpletest\TestServiceProvider;
 use Symfony\Component\DependencyInjection\Reference;
@@ -55,6 +53,7 @@
   use AssertContentTrait;
   use AssertHelperTrait;
   use RandomGeneratorTrait;
+  use ConfigTestTrait;
 
   /**
    * {@inheritdoc}
@@ -1016,54 +1015,6 @@ protected function setSetting($name, $value) {
   }
 
   /**
-   * Returns a ConfigImporter object to import test configuration.
-   *
-   * @return \Drupal\Core\Config\ConfigImporter
-   *
-   * @todo Move into Config-specific test base class.
-   */
-  protected function configImporter() {
-    if (!$this->configImporter) {
-      // Set up the ConfigImporter object for testing.
-      $storage_comparer = new StorageComparer(
-        $this->container->get('config.storage.sync'),
-        $this->container->get('config.storage'),
-        $this->container->get('config.manager')
-      );
-      $this->configImporter = new ConfigImporter(
-        $storage_comparer,
-        $this->container->get('event_dispatcher'),
-        $this->container->get('config.manager'),
-        $this->container->get('lock'),
-        $this->container->get('config.typed'),
-        $this->container->get('module_handler'),
-        $this->container->get('module_installer'),
-        $this->container->get('theme_handler'),
-        $this->container->get('string_translation')
-      );
-    }
-    // Always recalculate the changelist when called.
-    return $this->configImporter->reset();
-  }
-
-  /**
-   * Copies configuration objects from a source storage to a target storage.
-   *
-   * @param \Drupal\Core\Config\StorageInterface $source_storage
-   *   The source config storage.
-   * @param \Drupal\Core\Config\StorageInterface $target_storage
-   *   The target config storage.
-   *
-   * @todo Move into Config-specific test base class.
-   */
-  protected function copyConfig(StorageInterface $source_storage, StorageInterface $target_storage) {
-    $target_storage->deleteAll();
-    foreach ($source_storage->listAll() as $name) {
-      $target_storage->write($name, $source_storage->read($name));
-    }
-  }
-
-  /**
    * Stops test execution.
    */
   protected function stop() {
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index 3beb32f..a8560f0 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -56,6 +56,7 @@
   use ContentTypeCreationTrait {
     createContentType as drupalCreateContentType;
   }
+  use ConfigTestTrait;
 
   /**
    * Class loader.
diff --git a/core/tests/Drupal/Tests/ConfigTestTrait.php b/core/tests/Drupal/Tests/ConfigTestTrait.php
new file mode 100644
index 0000000..330ff47
--- /dev/null
+++ b/core/tests/Drupal/Tests/ConfigTestTrait.php
@@ -0,0 +1,59 @@
+<?php
+
+namespace Drupal\Tests;
+
+use Drupal\Core\Config\ConfigImporter;
+use Drupal\Core\Config\StorageComparer;
+use Drupal\Core\Config\StorageInterface;
+
+/**
+ * Provides helper methods to deal with config system objects in tests.
+ */
+trait ConfigTestTrait {
+
+  /**
+   * Returns a ConfigImporter object to import test configuration.
+   *
+   * @return \Drupal\Core\Config\ConfigImporter
+   *   The config importer object.
+   */
+  protected function configImporter() {
+    if (!$this->configImporter) {
+      // Set up the ConfigImporter object for testing.
+      $storage_comparer = new StorageComparer(
+        $this->container->get('config.storage.sync'),
+        $this->container->get('config.storage'),
+        $this->container->get('config.manager')
+      );
+      $this->configImporter = new ConfigImporter(
+        $storage_comparer,
+        $this->container->get('event_dispatcher'),
+        $this->container->get('config.manager'),
+        $this->container->get('lock'),
+        $this->container->get('config.typed'),
+        $this->container->get('module_handler'),
+        $this->container->get('module_installer'),
+        $this->container->get('theme_handler'),
+        $this->container->get('string_translation')
+      );
+    }
+    // Always recalculate the changelist when called.
+    return $this->configImporter->reset();
+  }
+
+  /**
+   * Copies configuration objects from source storage to target storage.
+   *
+   * @param \Drupal\Core\Config\StorageInterface $source_storage
+   *   The source config storage service.
+   * @param \Drupal\Core\Config\StorageInterface $target_storage
+   *   The target config storage service.
+   */
+  protected function copyConfig(StorageInterface $source_storage, StorageInterface $target_storage) {
+    $target_storage->deleteAll();
+    foreach ($source_storage->listAll() as $name) {
+      $target_storage->write($name, $source_storage->read($name));
+    }
+  }
+
+}