core/modules/simpletest/src/KernelTestBase.php | 1 -
 1 file changed, 1 deletion(-)

diff --git a/core/modules/simpletest/src/KernelTestBase.php b/core/modules/simpletest/src/KernelTestBase.php
index 309bb2b..0e2bf5c 100644
--- a/core/modules/simpletest/src/KernelTestBase.php
+++ b/core/modules/simpletest/src/KernelTestBase.php
@@ -586,7 +586,6 @@ protected function registerStreamWrapper($scheme, $class, $type = StreamWrapperI
    */
   protected function render(array &$elements) {
     $content = $this->container->get('renderer')->renderRoot($elements);
-    drupal_process_attached($elements);
     $this->setRawContent($content);
     $this->verbose('<pre style="white-space: pre-wrap">' . Html::escape($content));
     return $content;