diff --git a/core/lib/Drupal/Core/Test/TestDatabase.php b/core/lib/Drupal/Core/Test/TestDatabase.php
new file mode 100644
index 0000000000000000000000000000000000000000..a0121dc22603114328a198d0cb91e14c081038e9
--- /dev/null
+++ b/core/lib/Drupal/Core/Test/TestDatabase.php
@@ -0,0 +1,44 @@
+<?php
+
+namespace Drupal\Core\Test;
+
+use Drupal\Core\Database\ConnectionNotDefinedException;
+use Drupal\Core\Database\Database;
+
+/**
+ * Provides helper methods for interacting with the Simpletest database.
+ */
+class TestDatabase {
+
+  /**
+   * Returns the database connection to the site running Simpletest.
+   *
+   * @return \Drupal\Core\Database\Connection
+   *   The database connection to use for inserting assertions.
+   *
+   * @see \Drupal\simpletest\TestBase::prepareEnvironment()
+   */
+  public static function getConnection() {
+    // Check whether there is a test runner connection.
+    // @see run-tests.sh
+    // @todo Convert Simpletest UI runner to create + use this connection, too.
+    try {
+      $connection = Database::getConnection('default', 'test-runner');
+    }
+    catch (ConnectionNotDefinedException $e) {
+      // Check whether there is a backup of the original default connection.
+      // @see TestBase::prepareEnvironment()
+      try {
+        $connection = Database::getConnection('default', 'simpletest_original_default');
+      }
+      catch (ConnectionNotDefinedException $e) {
+        // If TestBase::prepareEnvironment() or TestBase::restoreEnvironment()
+        // failed, the test-specific database connection does not exist
+        // yet/anymore, so fall back to the default of the (UI) test runner.
+        $connection = Database::getConnection('default', 'default');
+      }
+    }
+    return $connection;
+  }
+
+}
diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index 58ede7c1d5678102a53a66fd42de61cc4506f8f5..d8b653e87e362a7a658c07abe163ca4702d32b14 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -10,6 +10,7 @@
 use Drupal\Core\Render\Element;
 use Drupal\Core\Routing\RouteMatchInterface;
 use Drupal\simpletest\TestBase;
+use Drupal\Core\Test\TestDatabase;
 use Drupal\simpletest\TestDiscovery;
 use Symfony\Component\Process\PhpExecutableFinder;
 
@@ -212,7 +213,7 @@ function simpletest_process_phpunit_results($phpunit_results) {
   // Insert the results of the PHPUnit test run into the database so the results
   // are displayed along with Simpletest's results.
   if (!empty($phpunit_results)) {
-    $query = TestBase::getDatabaseConnection()
+    $query = TestDatabase::getConnection()
       ->insert('simpletest')
       ->fields(array_keys($phpunit_results[0]));
     foreach ($phpunit_results as $result) {
@@ -428,12 +429,12 @@ function _simpletest_batch_finished($success, $results, $operations, $elapsed) {
  *   that ran.
  */
 function simpletest_last_test_get($test_id) {
-  $last_prefix = TestBase::getDatabaseConnection()
+  $last_prefix = TestDatabase::getConnection()
     ->queryRange('SELECT last_prefix FROM {simpletest_test_id} WHERE test_id = :test_id', 0, 1, array(
       ':test_id' => $test_id,
     ))
     ->fetchField();
-  $last_test_class = TestBase::getDatabaseConnection()
+  $last_test_class = TestDatabase::getConnection()
     ->queryRange('SELECT test_class FROM {simpletest} WHERE test_id = :test_id ORDER BY message_id DESC', 0, 1, array(
       ':test_id' => $test_id,
     ))
@@ -643,7 +644,7 @@ function simpletest_clean_temporary_directories() {
  */
 function simpletest_clean_results_table($test_id = NULL) {
   if (\Drupal::config('simpletest.settings')->get('clear_results')) {
-    $connection = TestBase::getDatabaseConnection();
+    $connection = TestDatabase::getConnection();
     if ($test_id) {
       $count = $connection->query('SELECT COUNT(test_id) FROM {simpletest_test_id} WHERE test_id = :test_id', array(':test_id' => $test_id))->fetchField();
 
diff --git a/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
index 9bc2c5bed771da5bf1618eb427decccc5b4a30a4..6bb84fda7c058d5199a2ef97493743e60b52ed14 100644
--- a/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -9,10 +9,10 @@
 use Drupal\Core\Database\Database;
 use Drupal\Core\Config\ConfigImporter;
 use Drupal\Core\Config\StorageComparer;
-use Drupal\Core\Database\ConnectionNotDefinedException;
 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\RandomGeneratorTrait;
 use Drupal\Tests\SessionTestTrait;
@@ -510,26 +510,7 @@ public static function deleteAssert($message_id) {
    *   The database connection to use for inserting assertions.
    */
   public static function getDatabaseConnection() {
-    // Check whether there is a test runner connection.
-    // @see run-tests.sh
-    // @todo Convert Simpletest UI runner to create + use this connection, too.
-    try {
-      $connection = Database::getConnection('default', 'test-runner');
-    }
-    catch (ConnectionNotDefinedException $e) {
-      // Check whether there is a backup of the original default connection.
-      // @see TestBase::prepareEnvironment()
-      try {
-        $connection = Database::getConnection('default', 'simpletest_original_default');
-      }
-      catch (ConnectionNotDefinedException $e) {
-        // If TestBase::prepareEnvironment() or TestBase::restoreEnvironment()
-        // failed, the test-specific database connection does not exist
-        // yet/anymore, so fall back to the default of the (UI) test runner.
-        $connection = Database::getConnection('default', 'default');
-      }
-    }
-    return $connection;
+    return TestDatabase::getConnection();
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index aa71fc128132e4587111bf9531edc40553d7736e..8f2e671036968d14477500eccb8f481484e0a386 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -10,7 +10,6 @@
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Cache\Cache;
-use Drupal\Core\Database\ConnectionNotDefinedException;
 use Drupal\Core\Database\Database;
 use Drupal\Core\DrupalKernel;
 use Drupal\Core\Session\AccountInterface;
@@ -20,6 +19,7 @@
 use Drupal\Core\StreamWrapper\StreamWrapperInterface;
 use Drupal\Core\Test\TestRunnerKernel;
 use Drupal\Core\Url;
+use Drupal\Core\Test\TestDatabase;
 use Drupal\user\Entity\Role;
 use Drupal\user\Entity\User;
 use Drupal\user\UserInterface;
@@ -1250,26 +1250,7 @@ protected function prepareEnvironment() {
    *   The database connection to use for inserting assertions.
    */
   public static function getDatabaseConnection() {
-    // Check whether there is a test runner connection.
-    // @see run-tests.sh
-    try {
-      $connection = Database::getConnection('default', 'test-runner');
-    }
-    catch (ConnectionNotDefinedException $e) {
-      // Check whether there is a backup of the original default connection.
-      // @see BrowserTestBase::prepareEnvironment()
-      try {
-        $connection = Database::getConnection('default', 'simpletest_original_default');
-      }
-      catch (ConnectionNotDefinedException $e) {
-        // If BrowserTestBase::prepareEnvironment() or
-        // BrowserTestBase::restoreEnvironment() failed, the test-specific
-        // database connection does not exist yet/anymore, so fall back to the
-        // default of the (UI) test runner.
-        $connection = Database::getConnection('default', 'default');
-      }
-    }
-    return $connection;
+    return TestDatabase::getConnection();
   }
 
   /**