diff --git a/core/tests/Drupal/KernelTests/Setup/Commands/SetupDrupalTestScriptTest.php b/core/tests/Drupal/KernelTests/Setup/Commands/SetupDrupalTestScriptTest.php
index b8236f9b3f..7af4c369bc 100644
--- a/core/tests/Drupal/KernelTests/Setup/Commands/SetupDrupalTestScriptTest.php
+++ b/core/tests/Drupal/KernelTests/Setup/Commands/SetupDrupalTestScriptTest.php
@@ -16,6 +16,11 @@
  *
  * @todo Move this to the \Drupal\KernelTests\Setup\Commands\ namespace after
  *   https://www.drupal.org/project/drupal/issues/2878269
+ *
+ * @see \Drupal\Setup\TestInstallationSetup
+ * @see \Drupal\Setup\Commands\TestInstallationSetupApplication
+ * @see \Drupal\Setup\Commands\TestInstallationSetupCommand
+ * @see \Drupal\Setup\Commands\TestTeardownCommand
  */
 class SetupDrupalTestScriptTest extends KernelTestBase {
 
@@ -91,18 +96,71 @@ public function testInstallScript() {
       ]
     );
 
+
+    $this->assertNotRegExp('/PHPUnit_Framework_Error_Warning/', $app_tester->getDisplay());
+    $this->assertNotRegExp('/AlreadyInstalledException/', $app_tester->getDisplay());
+
+    $result = json_decode($app_tester->getDisplay(), TRUE);
+    $db_prefix = substr($result['db_prefix'], 4);
+    $this->assertNotEmpty($db_prefix);
+    $this->assertStringStartsWith('simpletest' . $db_prefix . ':', $result['user_agent']);
+
+    $this->assertEqual(0, $app_tester->getStatusCode());
+
+    $http_client = new Client();
+    $request = (new Request('GET', getenv('SIMPLETEST_BASE_URL') . '/test-page'))
+      ->withHeader('User-Agent', trim($result['user_agent']));
+
+    $response = $http_client->send($request);
+    // Ensure the test_page_test module got installed.
+    $this->assertContains('Test page | Drupal', (string) $response->getBody());
+
+    // Now test the tear down process as well.
+    $app_tester->run(
+      [
+        'command' => 'teardown-drupal-test',
+        'db_prefix' => $this->databasePrefix,
+      ],
+      [
+        'interactive' => FALSE,
+      ]
+    );
+  }
+
+  /**
+   * @coversNothing
+   */
+  public function testInstallInDifferentLanguage() {
+    $autoloader = $this->root . '/autoload.php';
+    $app = new TestInstallationSetupApplication(require $autoloader);
+    $app->setAutoExit(FALSE);
+
+    $app_tester = new ApplicationTester($app);
+    $app_tester->run(
+      [
+        'command' => 'setup-drupal-test',
+        '--langcode' => 'fr',
+        '--setup_class' => SetupDrupalTestScript::class,
+      ],
+      [
+        'interactive' => FALSE,
+      ]
+    );
+
+
     $this->assertNotRegExp('/PHPUnit_Framework_Error_Warning/', $app_tester->getDisplay());
     $this->assertNotRegExp('/AlreadyInstalledException/', $app_tester->getDisplay());
-    $this->assertRegExp('/simpletest/', $app_tester->getDisplay());
     $this->assertEqual(0, $app_tester->getStatusCode());
 
+    $result = json_decode($app_tester->getDisplay(), TRUE);
     $http_client = new Client();
     $request = (new Request('GET', getenv('SIMPLETEST_BASE_URL') . '/test-page'))
-      ->withHeader('User-Agent', trim($app_tester->getDisplay()));
+      ->withHeader('User-Agent', trim($result['user_agent']));
 
     $response = $http_client->send($request);
     // Ensure the test_page_test module got installed.
     $this->assertContains('Test page | Drupal', (string) $response->getBody());
+    $this->assertContains('lang="fr"', (string) $response->getBody());
 
     // Now test the tear down process as well.
     $app_tester->run(
diff --git a/core/tests/Drupal/Setup/Commands/TestInstallationSetupCommand.php b/core/tests/Drupal/Setup/Commands/TestInstallationSetupCommand.php
index 325537db5e..f14bee5276 100644
--- a/core/tests/Drupal/Setup/Commands/TestInstallationSetupCommand.php
+++ b/core/tests/Drupal/Setup/Commands/TestInstallationSetupCommand.php
@@ -47,7 +47,9 @@ protected function configure() {
     $this->setName('setup-drupal-test')
       ->addOption('setup_class', NULL, InputOption::VALUE_OPTIONAL)
       ->addOption('db_url', NULL, InputOption::VALUE_OPTIONAL, 'URL for database or SIMPLETEST_DB', getenv('SIMPLETEST_DB'))
-      ->addOption('base_url', NULL, InputOption::VALUE_OPTIONAL, 'Base URL for site under test or SIMPLETEST_BASE_URL', getenv('SIMPLETEST_BASE_URL'));
+      ->addOption('base_url', NULL, InputOption::VALUE_OPTIONAL, 'Base URL for site under test or SIMPLETEST_BASE_URL', getenv('SIMPLETEST_BASE_URL'))
+      ->addOption('langcode', NULL, InputOption::VALUE_OPTIONAL, 'The language to install the site in.')
+    ;
   }
 
   /**
@@ -63,9 +65,12 @@ protected function execute(InputInterface $input, OutputInterface $output) {
 
     // Manage site fixture.
     $test = new TestInstallationSetup();
-    $test->setup('testing', $input->getOption('setup_class'));
+    $test->setup('testing', $input->getOption('setup_class'), $input->getOption('langcode'));
 
-    $output->writeln(drupal_generate_test_ua($test->getDatabasePrefix()));
+    $output->writeln(json_encode([
+      'db_prefix' => $test->getDatabasePrefix(),
+      'user_agent' => drupal_generate_test_ua($test->getDatabasePrefix()),
+    ]));
   }
 
   protected function bootstrapDrupal() {
diff --git a/core/tests/Drupal/Setup/TestInstallationSetup.php b/core/tests/Drupal/Setup/TestInstallationSetup.php
index 4e816c1c06..25d33d530d 100644
--- a/core/tests/Drupal/Setup/TestInstallationSetup.php
+++ b/core/tests/Drupal/Setup/TestInstallationSetup.php
@@ -42,6 +42,14 @@ class TestInstallationSetup {
    */
   protected $databasePrefix;
 
+
+  /**
+   * The language to install the site in.
+   *
+   * @var string
+   */
+  protected $langcode = 'en';
+
   /**
    * Creates a test drupal installation.
    *
@@ -50,9 +58,12 @@ class TestInstallationSetup {
    * @param string $setup_class
    *   (optional) Setup class. A PHP class to setup configuration used by the
    *   test.
+   * @param string $langcode
+   *   (optional) The language to install the site in.
    */
-  public function setup($profile = 'testing', $setup_class = NULL) {
+  public function setup($profile = 'testing', $setup_class = NULL, $langcode = 'en') {
     $this->profile = $profile;
+    $this->langcode = $langcode;
     $this->setupBaseUrl();
     $this->prepareEnvironment();
     $this->installDrupal();
@@ -161,7 +172,7 @@ protected function installParameters() {
       'interactive' => FALSE,
       'parameters' => [
         'profile' => $this->profile,
-        'langcode' => 'en',
+        'langcode' => $this->langcode,
       ],
       'forms' => [
         'install_settings_form' => [