only in patch2:
unchanged:
--- a/core/tests/Drupal/KernelTests/KernelTestBase.php
+++ b/core/tests/Drupal/KernelTests/KernelTestBase.php
@@ -336,6 +336,20 @@ private function bootKernel() {
 
     $modules = self::getModulesToEnable(static::class);
 
+    // When a module is providing the database driver, then enable that module.
+    $connection_info = Database::getConnectionInfo();
+    $driver = $connection_info['default']['driver'];
+    $namespace = $connection_info['default']['namespace'] ?? NULL;
+    $autoload = $connection_info['default']['autoload'] ?? NULL;
+    if (strpos($autoload, 'src/Driver/Database/') !== FALSE) {
+      [$first, $second] = explode('\\', $namespace, 3);
+      if ($first === 'Drupal' && strtolower($second) === $second) {
+        // Add the module that provides the database driver to the list of
+        // modules as the first to be enabled.
+        array_unshift($modules, $second);
+      }
+    }
+
     // Bootstrap the kernel. Do not use createFromRequest() to retain Settings.
     $kernel = new DrupalKernel('testing', $this->classLoader, FALSE);
     $kernel->setSitePath($this->siteDirectory);
@@ -357,9 +371,6 @@ private function bootKernel() {
 
     // Ensure database tasks have been run.
     require_once __DIR__ . '/../../../includes/install.inc';
-    $connection_info = Database::getConnectionInfo();
-    $driver = $connection_info['default']['driver'];
-    $namespace = $connection_info['default']['namespace'] ?? NULL;
     $errors = db_installer_object($driver, $namespace)->runTasks();
     if (!empty($errors)) {
       $this->fail('Failed to run installer database tasks: ' . implode(', ', $errors));
only in patch2:
unchanged:
--- /dev/null
+++ b/core/tests/Drupal/KernelTests/KernelTestBaseDatabaseDriverModuleTest.php
@@ -0,0 +1,66 @@
+<?php
+
+namespace Drupal\KernelTests;
+
+use Drupal\Core\Database\Database;
+
+/**
+ * @coversDefaultClass \Drupal\KernelTests\KernelTestBase
+ *
+ * @group PHPUnit
+ * @group Test
+ * @group KernelTests
+ */
+class KernelTestBaseDatabaseDriverModuleTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getDatabaseConnectionInfo() {
+    // If the test is run with argument dburl then use it.
+    $db_url = getenv('SIMPLETEST_DB');
+    if (empty($db_url)) {
+      throw new \Exception('There is no database connection so no tests can be run. You must provide a SIMPLETEST_DB environment variable to run PHPUnit based functional tests outside of run-tests.sh. See https://www.drupal.org/node/2116263#skipped-tests for more information.');
+    }
+    else {
+      $database = Database::convertDbUrlToConnectionInfo($db_url, $this->root);
+
+      // Change the used database driver to the one provided by the module
+      // "driver_test".
+      $driver = 'Drivertest' . ucfirst($database['driver']);
+      $database['driver'] = $driver;
+      $database['namespace'] = 'Drupal\\driver_test\\Driver\\Database\\' . $driver;
+      $database['autoload'] = "core/modules/system/tests/modules/driver_test/src/Driver/Database/$driver/";
+
+      Database::addConnectionInfo('default', 'default', $database);
+    }
+
+    // Clone the current connection and replace the current prefix.
+    $connection_info = Database::getConnectionInfo('default');
+    if (!empty($connection_info)) {
+      Database::renameConnection('default', 'simpletest_original_default');
+      foreach ($connection_info as $target => $value) {
+        // Replace the full table prefix definition to ensure that no table
+        // prefixes of the test runner leak into the test.
+        $connection_info[$target]['prefix'] = [
+          'default' => $this->databasePrefix,
+        ];
+      }
+    }
+    return $connection_info;
+  }
+
+  /**
+   * @covers ::bootEnvironment
+   */
+  public function testDatabaseDriverModuleEnabled() {
+    $driver = Database::getConnection()->driver();
+    if (!in_array($driver, ['DrivertestMysql', 'DrivertestPgsql'])) {
+      $this->markTestSkipped("This test does not support the {$driver} database driver.");
+    }
+
+    // Test that the module that is providing the database driver is enabled.
+    $this->assertSame(1, \Drupal::service('extension.list.module')->get('driver_test')->status);
+  }
+
+}