diff --git a/core/modules/book/lib/Drupal/book/Tests/BookTest.php b/core/modules/book/lib/Drupal/book/Tests/BookTest.php
index 388c476..5ea8b8d 100644
--- a/core/modules/book/lib/Drupal/book/Tests/BookTest.php
+++ b/core/modules/book/lib/Drupal/book/Tests/BookTest.php
@@ -511,7 +511,7 @@ public function testBookOrdering() {
   }
 
   /**
-   * Test outline of a book.
+   * Tests outline of a book.
    */
   public function testBookOutline() {
     // Create new book.