diff --git a/core/tests/Drupal/FunctionalTests/Theme/ClaroTest.php b/core/tests/Drupal/FunctionalTests/Theme/ClaroTest.php
index 4df39abb7a..1001022705 100644
--- a/core/tests/Drupal/FunctionalTests/Theme/ClaroTest.php
+++ b/core/tests/Drupal/FunctionalTests/Theme/ClaroTest.php
@@ -43,6 +43,8 @@ public function setUp() {
   public function testRegressionMissingElementsCss() {
     $this->drupalGet('');
     $this->assertSession()->statusCodeEquals(200);
+    // Testing that the global library is attached.
+    // The 'elements.css' file is the first asset of the global library.
     $this->assertSession()->responseContains('claro/css/base/elements.css');
 
     $this->drupalLogin($this->rootUser);