diff --git a/core/modules/system/src/Tests/File/UrlRewritingTest.php b/core/modules/system/src/Tests/File/UrlRewritingTest.php
index 748e86d..c7fb40d 100644
--- a/core/modules/system/src/Tests/File/UrlRewritingTest.php
+++ b/core/modules/system/src/Tests/File/UrlRewritingTest.php
@@ -23,6 +23,15 @@ class UrlRewritingTest extends FileTestBase {
    */
   public static $modules = array('file_test');
 
+  public function setUp() {
+    parent::setUp();
+
+    // Populate the app object from request globals such that the base URL and
+    // path can be populated from a request containing valid SCRIPT_NAME and
+    // SCRIPT_FILENAME server values.
+    $this->container->get('app')->setRequest(Request::createFromGlobals());
+  }
+
   /**
    * Tests the rewriting of shipped file URLs by hook_file_url_alter().
    */
@@ -43,19 +52,19 @@ function testShippedFileURL()  {
     \Drupal::state()->set('file_test.hook_file_url_alter', 'root-relative');
     $filepath = 'core/assets/vendor/jquery/jquery.min.js';
     $url = file_create_url($filepath);
-    $this->assertEqual(base_path() . '/' . $filepath, $url, 'Correctly generated a root-relative URL for a shipped file.');
+    $this->assertEqual(base_path() . $filepath, $url, 'Correctly generated a root-relative URL for a shipped file.');
     $filepath = 'core/misc/favicon.ico';
     $url = file_create_url($filepath);
-    $this->assertEqual(base_path() . '/' . $filepath, $url, 'Correctly generated a root-relative URL for a shipped file.');
+    $this->assertEqual(base_path() . $filepath, $url, 'Correctly generated a root-relative URL for a shipped file.');
 
     // Test alteration of file URLs to use protocol-relative URLs.
     \Drupal::state()->set('file_test.hook_file_url_alter', 'protocol-relative');
     $filepath = 'core/assets/vendor/jquery/jquery.min.js';
     $url = file_create_url($filepath);
-    $this->assertEqual('/' . base_path() . '/' . $filepath, $url, 'Correctly generated a protocol-relative URL for a shipped file.');
+    $this->assertEqual('/' . base_path() . $filepath, $url, 'Correctly generated a protocol-relative URL for a shipped file.');
     $filepath = 'core/misc/favicon.ico';
     $url = file_create_url($filepath);
-    $this->assertEqual('/' . base_path() . '/' . $filepath, $url, 'Correctly generated a protocol-relative URL for a shipped file.');
+    $this->assertEqual('/' . base_path() . $filepath, $url, 'Correctly generated a protocol-relative URL for a shipped file.');
 
     // Test alteration of file URLs with query strings and/or fragment.
     \Drupal::state()->delete('file_test.hook_file_url_alter');
@@ -87,13 +96,13 @@ function testPublicManagedFileURL() {
     \Drupal::state()->set('file_test.hook_file_url_alter', 'root-relative');
     $uri = $this->createUri();
     $url = file_create_url($uri);
-    $this->assertEqual(base_path() . '/' . $public_directory_path . '/' . drupal_basename($uri), $url, 'Correctly generated a root-relative URL for a created file.');
+    $this->assertEqual(base_path() . $public_directory_path . '/' . drupal_basename($uri), $url, 'Correctly generated a root-relative URL for a created file.');
 
     // Test alteration of file URLs to use a protocol-relative URLs.
     \Drupal::state()->set('file_test.hook_file_url_alter', 'protocol-relative');
     $uri = $this->createUri();
     $url = file_create_url($uri);
-    $this->assertEqual('/' . base_path() . '/' . $public_directory_path . '/' . drupal_basename($uri), $url, 'Correctly generated a protocol-relative URL for a created file.');
+    $this->assertEqual('/' . base_path() . $public_directory_path . '/' . drupal_basename($uri), $url, 'Correctly generated a protocol-relative URL for a created file.');
   }
 
   /**