diff --git a/core/tests/Drupal/Tests/Core/Datetime/DrupalDateTimeTest.php b/core/tests/Drupal/Tests/Core/Datetime/DrupalDateTimeTest.php
index eff9f77..666512d 100644
--- a/core/tests/Drupal/Tests/Core/Datetime/DrupalDateTimeTest.php
+++ b/core/tests/Drupal/Tests/Core/Datetime/DrupalDateTimeTest.php
@@ -156,4 +156,30 @@ public function providerTestInvalidDateDiff() {
     ];
   }
 
+  /**
+   * Tests that object methods are chainable.
+   */
+  public function testChainable() {
+    $date = new DrupalDateTime('now', NULL, ['langcode' => 'en']);
+
+    $date->setTimestamp(12345678);
+    $rendered = $date->render();
+    $this->assertEquals('1970-05-24 07:21:18 Australia/Sydney', $rendered);
+
+    $date->setTimestamp(23456789);
+    $rendered = $date->setTimezone(new \DateTimeZone('America/New_York'))->render();
+    $this->assertEquals('1970-09-29 07:46:29 America/New_York', $rendered);
+  }
+
+}
+
+namespace Drupal\Core\Datetime;
+
+/**
+ * Shadow drupal_get_user_timezone().
+ *
+ * @returns string
+ */
+function drupal_get_user_timezone() {
+  return date_default_timezone_get();
 }