diff -u b/core/modules/book/tests/src/Functional/BookTest.php b/core/modules/book/tests/src/Functional/BookTest.php
--- b/core/modules/book/tests/src/Functional/BookTest.php
+++ b/core/modules/book/tests/src/Functional/BookTest.php
@@ -304,9 +304,9 @@
     $this->drupalGet($nodes[0]->toUrl());
     $this->assertSession()->statusCodeEquals(403);
     $this->drupalGet($this->book->toUrl());
-    $this->assertSession()->responseNotContains($nodes[0]->getTitle(), 'Unpublished book page does not appear in the navigation for users without access.');
-    $this->assertSession()->responseNotContains($nodes[1]->getTitle(), 'Published child page does not appear below an unpublished parent.');
-    $this->assertSession()->responseNotContains($nodes[2]->getTitle(), 'Published child page does not appear below an unpublished parent.');
+    $this->assertSession()->responseNotContains($nodes[0]->getTitle());
+    $this->assertSession()->responseNotContains($nodes[1]->getTitle());
+    $this->assertSession()->responseNotContains($nodes[2]->getTitle());
   }
 
   /**
@@ -586,8 +586,8 @@
     $this->drupalGet('admin/structure/book/' . $this->book->id());
     $elements = $this->xpath('//table//ul[@class="dropbutton"]/li/a');
     $this->assertEquals(count($nodes), count($elements), 'All the book pages are displayed on the book outline page.');
-    $this->assertSession()->responseNotContains($new_title, 'The revision that is not the default revision does not appear.');
-    $this->assertSession()->responseContains($old_title, 'The default revision title appears.');
+    $this->assertSession()->responseNotContains($new_title);
+    $this->assertSession()->responseContains($old_title);
   }
 
   /**