diff -u b/core/modules/action/lib/Drupal/action/Tests/ActionUninstallTest.php b/core/modules/action/lib/Drupal/action/Tests/ActionUninstallTest.php
--- b/core/modules/action/lib/Drupal/action/Tests/ActionUninstallTest.php
+++ b/core/modules/action/lib/Drupal/action/Tests/ActionUninstallTest.php
@@ -38,7 +38,7 @@
     \Drupal::moduleHandler()->disable(array('action'));
     \Drupal::moduleHandler()->uninstall(array('action'));
 
-    $this->assertTrue(entity_load('action', 'user_block_user_action', TRUE));
+    $this->assertTrue(entity_load('action', 'user_block_user_action', TRUE), 'Configuration entity \'user_block_user_action\' still exists after uninstalling action module.' );
 
     $admin_user = $this->drupalCreateUser(array('administer users'));
     $this->drupalLogin($admin_user);