--- /dev/null
+<?php
+
+namespace Drupal\Tests\system\Functional\Common;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests the format_date() function.
+ *
+ * @group Common
+ */
+class FormatDateTest extends BrowserTestBase {
+
+ /**
+ * Tests admin-defined formats in format_date().
+ */
+ public function testAdminDefinedFormatDate() {
+ // Create and log in an admin user.
+ $this->drupalLogin($this->drupalCreateUser(['administer site configuration']));
+
+ // Add new date format.
+ $edit = [
+ 'id' => 'example_style',
+ 'label' => 'Example Style',
+ 'date_format_pattern' => 'j M y',
+ ];
+ $this->drupalPostForm('admin/config/regional/date-time/formats/add', $edit, t('Add format'));
+
+ // Add a second date format with a different case than the first.
+ $edit = [
+ 'id' => 'example_style_uppercase',
+ 'label' => 'Example Style Uppercase',
+ 'date_format_pattern' => 'j M Y',
+ ];
+ $this->drupalPostForm('admin/config/regional/date-time/formats/add', $edit, t('Add format'));
+ $this->assertText(t('Custom date format added.'));
+
+ $timestamp = strtotime('2007-03-10T00:00:00+00:00');
+ $this->assertIdentical(format_date($timestamp, 'example_style', '', 'America/Los_Angeles'), '9 Mar 07');
+ $this->assertIdentical(format_date($timestamp, 'example_style_uppercase', '', 'America/Los_Angeles'), '9 Mar 2007');
+ $this->assertIdentical(format_date($timestamp, 'undefined_style'), format_date($timestamp, 'fallback'), 'Test format_date() defaulting to `fallback` when $type not found.');
+ }
+
+}