diff --git a/core/modules/system/src/Tests/Routing/RouteNormalizerTest.php b/core/modules/system/src/Tests/Routing/RouteNormalizerTest.php
new file mode 100644
index 0000000..2f70d72
--- /dev/null
+++ b/core/modules/system/src/Tests/Routing/RouteNormalizerTest.php
@@ -0,0 +1,104 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Routing\RouteNormalizerTest.
+ */
+
+namespace Drupal\system\Tests\Routing;
+
+use Drupal\Component\Utility\UrlHelper;
+use Drupal\Core\Url;
+use Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUrl;
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Tests the route normalizer functionality.
+ *
+ * @group Routing
+ *
+ * @see \Drupal\Core\EventSubscriber\RouteNormalizerRequestSubscriber
+ */
+class RouteNormalizerTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = ['language', 'path', 'menu_test'];
+
+  /**
+   * Tests redirects performed by the route normalizer.
+   *
+   * @see \Drupal\Core\EventSubscriber\RouteNormalizerRequestSubscriber::onKernelRequestRedirect()
+   */
+  public function testRedirects() {
+
+    // Test front page redirect.
+    $front_page_path = '/user/login';
+    $this->config('system.site')->set('page.front', $front_page_path)->save();
+    $this->drupalGet(Url::fromUri('base:' . $front_page_path));
+    $this->assertNotEqual($this->redirectCount, 0);
+    $this->assertUrl(Url::fromRoute('<front>'));
+
+    // Test path alias redirect.
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer url aliases',
+    ]));
+    $edit = [
+      'source' => '/user/password',
+      'alias' => '/my-cool/password/recovery/page',
+    ];
+    $this->drupalPostForm('admin/config/search/path/add', $edit, t('Save'));
+    $this->drupalGet(Url::fromUri('base:' . $edit['source']));
+    $this->assertNotEqual($this->redirectCount, 0);
+    $this->assertUrl(Url::fromUri('base:' . $edit['alias']));
+
+    // Test language redirect.
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer languages',
+    ]));
+    // We need more than one language to make the redirect work.
+    $edit = [
+      'predefined_langcode' => 'fr',
+    ];
+    $this->drupalPostForm('admin/config/regional/language/add', $edit, t('Add language'));
+    $edit = [
+      'language_interface[enabled][language-url]' => 1,
+    ];
+    $this->drupalPostForm('admin/config/regional/language/detection', $edit, t('Save settings'));
+    $edit = [
+      'language_negotiation_url_part' => LanguageNegotiationUrl::CONFIG_PATH_PREFIX,
+      'prefix[en]' => 'en',
+      'prefix[fr]' => 'fr',
+    ];
+    $this->drupalPostForm('admin/config/regional/language/detection/url', $edit, t('Save configuration'));
+    $this->rebuildContainer();
+    $url = Url::fromUri('base:/admin/config/regional/language')->setAbsolute()->toString();
+    $prefix_count = substr_count($url, '/en/');
+    $this->drupalGet($url);
+    $this->assertNotEqual($this->redirectCount, 0);
+    $this->assertTrue(substr_count($this->url, '/en/') == $prefix_count + 1, 'The default language path prefix was added to the final URL.');
+    $this->assertTrue(strpos($this->url, '/admin/config/regional/language') !== FALSE, 'Path preserved.');
+
+    // Test a redirect having special characters in source/destination paths.
+    /** @var \Drupal\Core\Menu\MenuLinkManagerInterface $menu_link_manager */
+    $menu_link_manager = $this->container->get('plugin.manager.menu.link');
+    /** @var \Drupal\Core\Menu\MenuLinkInterface $menu_link */
+    $menu_link = $menu_link_manager->createInstance('menu_test.exotic_path');
+    $exotic_path = rawurldecode($menu_link->getUrlObject()->getInternalPath());
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer url aliases',
+    ]));
+    $edit = [
+      'source' => '/' . $exotic_path,
+      'alias' => '/' . $exotic_path . rawurlencode(rawurlencode('#%&+/?')),
+    ];
+    $this->drupalPostForm('admin/config/search/path/add', $edit, t('Save'));
+    $this->drupalGet($exotic_path, ['alias' => TRUE]);
+    $this->assertNotEqual($this->redirectCount, 0);
+    $this->assertTrue(strpos($this->url, UrlHelper::encodePath($edit['alias'])) !== FALSE, 'Redirected to the alias.');
+  }
+
+}