--- /dev/null
+<?php
+
+namespace Drupal\Tests\system\Functional\System;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests the locked functionality of date formats.
+ *
+ * @group system
+ */
+class DateFormatsLockedTest extends BrowserTestBase {
+
+ /**
+ * Tests attempts at listing, editing, and deleting locked date formats.
+ */
+ public function testDateLocking() {
+ $this->drupalLogin($this->rootUser);
+
+ // Locked date formats are not linked on the listing page, locked date
+ // formats are clearly marked as such; unlocked formats are not marked as
+ // "locked".
+ $this->drupalGet('admin/config/regional/date-time');
+ $this->assertLinkByHref('admin/config/regional/date-time/formats/manage/short');
+ $this->assertNoLinkByHref('admin/config/regional/date-time/formats/manage/html_date');
+ $this->assertText('Fallback date format');
+ $this->assertNoText('short (locked)');
+
+ // Locked date formats are not editable.
+ $this->drupalGet('admin/config/regional/date-time/formats/manage/short');
+ $this->assertResponse(200);
+ $this->drupalGet('admin/config/regional/date-time/formats/manage/html_date');
+ $this->assertResponse(403);
+
+ // Locked date formats are not deletable.
+ $this->drupalGet('admin/config/regional/date-time/formats/manage/short/delete');
+ $this->assertResponse(200);
+ $this->drupalGet('admin/config/regional/date-time/formats/manage/html_date/delete');
+ $this->assertResponse(403);
+ }
+
+}