diff -u b/core/modules/simpletest/tests/src/Functional/BrowserWithJavascriptTest.php b/core/modules/simpletest/tests/src/Functional/BrowserWithJavascriptTest.php
--- b/core/modules/simpletest/tests/src/Functional/BrowserWithJavascriptTest.php
+++ b/core/modules/simpletest/tests/src/Functional/BrowserWithJavascriptTest.php
@@ -37,7 +37,6 @@
     }());
 JS;
     $pageSize = $session->evaluateScript($javascript);
-    print_r($pageSize);
     $this->assertEquals(400, $pageSize["width"]);
     $this->assertEquals(300, $pageSize["height"]);
   }