diff --git a/core/includes/update.inc b/core/includes/update.inc
index 18ce171..547a567 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -880,8 +880,8 @@ function update_retrieve_dependencies() {
  *
  * @param $config_name
  *   The name of the configuration object to retrieve. The name corresponds to
- *   an XML configuration file. For example, passing "book.admin" will return
- *   the config object containing the contents of book.admin.xml.
+ *   a YAML configuration file. For example, passing "book.admin" will return
+ *   the config object containing the contents of book.admin.yml.
  * @param $variable_map
  *   An array to map new to old configuration naming conventions. Example:
  *   @code
diff --git a/core/modules/config/config.test b/core/modules/config/config.test
index 257ab0f..cdd05e8 100644
--- a/core/modules/config/config.test
+++ b/core/modules/config/config.test
@@ -251,6 +251,7 @@ class ConfigFileContentTestCase extends WebTestBase {
         // Unicode in keys and values.
         'ΑΒΓΔΕΖΗΘΙΚΛΜΝΞΟΣὨ' => 'αβγδεζηθικλμνξοσὠ',
       ),
+      @todo: Update this for YAML.
       'invalid xml' => '</title><script type="text/javascript">alert("Title XSS!");</script> & < > " \' ',
     );
 
diff --git a/core/modules/system/system.test b/core/modules/system/system.test
index 40f590e..c2000f0 100644
--- a/core/modules/system/system.test
+++ b/core/modules/system/system.test
@@ -90,7 +90,7 @@ class ModuleTestCase extends WebTestBase {
     // Get the path to the module's config dir.
     $module_config_dir = drupal_get_path('module', $module) . '/config';
     if (is_dir($module_config_dir)) {
-      $files = glob($module_config_dir . '/' . '*.xml');
+      $files = glob($module_config_dir . '/' . '*.yml');
       $config_dir = config_get_config_directory();
       // Get the filename of each config file.
       foreach ($files as $file) {
@@ -120,7 +120,7 @@ class ModuleTestCase extends WebTestBase {
     // Get the path to the module's config dir.
     $module_config_dir = drupal_get_path('module', $module) . '/config';
     if (is_dir($module_config_dir)) {
-      $files = glob($module_config_dir . '/' . '*.xml');
+      $files = glob($module_config_dir . '/' . '*.yml');
       $config_dir = config_get_config_directory();
       // Get the filename of each config file.
       foreach ($files as $file) {