diff --git a/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterTwigExtensionsPass.php b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterTwigExtensionsPass.php
index 0f1a88c..66fbb86 100644
--- a/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterTwigExtensionsPass.php
+++ b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterTwigExtensionsPass.php
@@ -15,12 +15,12 @@
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 
 /**
- * Adds services tagged 'twig.extension' to the twig service.
+ * Register additional Twig extensions to the Twig service container.
  */
 class RegisterTwigExtensionsPass implements CompilerPassInterface {
 
   /**
-   * Adds services tagged 'twig.extension' to the twig service.
+   * Adds services tagged 'twig.extension' to the Twig service container.
    *
    * @param \Symfony\Component\DependencyInjection\ContainerBuilder $container
    *   The container to process.
@@ -45,4 +45,5 @@ public function process(ContainerBuilder $container) {
       $definition->addMethodCall('addExtension', array(new Reference($id)));
     }
   }
+
 }
diff --git a/core/modules/system/tests/modules/twig_extension_test/lib/Drupal/twig_extension_test/TwigExtension/TestExtension.php b/core/modules/system/tests/modules/twig_extension_test/lib/Drupal/twig_extension_test/TwigExtension/TestExtension.php
index adc0556..bda959f 100644
--- a/core/modules/system/tests/modules/twig_extension_test/lib/Drupal/twig_extension_test/TwigExtension/TestExtension.php
+++ b/core/modules/system/tests/modules/twig_extension_test/lib/Drupal/twig_extension_test/TwigExtension/TestExtension.php
@@ -11,7 +11,7 @@
 use Drupal\Core\Template\TwigReferenceFunction;
 
 /**
- * A test Twig extension that adds a few simple tags.
+ * A test Twig extension that adds a custom function and a custom filter.
  */
 class TestExtension extends TwigExtension {
 
@@ -19,11 +19,13 @@ class TestExtension extends TwigExtension {
    * Generates a list of all Twig functions that this extension defines.
    *
    * @return array
-   *   A key/value array that defines custom Twig functions.
-   *   The key denotes the function name used in the tag.
-   *   eg. {{ testfunc() }}.
-   *   The value is a standard PHP callback that defines what the function
-   *   does.
+   *   A key/value array that defines custom Twig functions. The key denotes the
+   *   function name used in the tag, e.g.:
+   *   @code
+   *   {{ testfunc() }}
+   *   @endcode
+   *
+   *   The value is a standard PHP callback that defines what the function does.
    */
   public function getFunctions() {
     return array(
@@ -37,9 +39,12 @@ public function getFunctions() {
    * Generates a list of all Twig filters that this extension defines.
    *
    * @return array
-   *   A key/value array that defines custom Twig filters.
-   *   The key denotes the filter name used in the tag.
-   *   eg. {{ foo|testfilter }}.
+   *   A key/value array that defines custom Twig filters. The key denotes the
+   *   filter name used in the tag, e.g.:
+   *   @code
+   *   {{ foo|testfilter }}
+   *   @endcode
+   *
    *   The value is a standard PHP callback that defines what the filter does.
    */
   public function getFilters() {
@@ -61,35 +66,22 @@ public function getName() {
   }
 
   /**
-   * A Twig filter designed for testing, which replaces all instances of
-   * "animal" in a string with "plant".
-   * This is tested for in the class
-   * \Drupal\system\Tests\Theme\TwigExtensionTest.
+   * Outputs either an uppercase or lowercase test phrase.
    *
-   * @param string $string
-   *   The string to be filtered.
-   * @return string
-   *   The filtered string.
-   */
-  public static function testFilter ($string) {
-    return str_replace(array('animal'), array('plant'), $string);
-  }
-
-  /**
-   * A Twig function designed for testing, which generates either an uppercase
-   * or lowercase version of the phrase "The quick brown fox jumps over the
-   * lazy dog 123.", depending on whether or not the provided $upperCase
-   * parameter is truthy. If it is truthy, the result will be uppercase, and
-   * if not, the result will be lowercase.
-   * This is tested for in the class
-   * \Drupal\system\Tests\Theme\TwigExtensionTest.
+   * The function generates either an uppercase or lowercase version of the
+   * phrase "The quick brown fox jumps over the lazy dog 123.", depending on
+   * whether or not the $upperCase parameter evaluates to TRUE. If $upperCase
+   * evaluates to TRUE, the result will be uppercase, and if it evaluates to
+   * FALSE, the result will be lowercase.
    *
-   * @param boolean $upperCase
+   * @param bool $upperCase
    *   (optional) Whether the result is uppercase (true) or lowercase (false).
    * @return string
    *   The generated string.
+   *
+   * @see \Drupal\system\Tests\Theme\TwigExtensionTest::testTwigExtensionFunction()
    */
-  public static function testFunction ($upperCase = FALSE) {
+  public static function testFunction($upperCase = FALSE) {
     $string = "The quick brown box jumps over the lazy dog 123.";
     if ($upperCase == TRUE) {
       return strtoupper($string);
@@ -98,5 +90,19 @@ public static function testFunction ($upperCase = FALSE) {
       return strtolower($string);
     }
   }
-}
 
+  /**
+   * Replaces all instances of "animal" in a string with "plant".
+   *
+   * @param string $string
+   *   The string to be filtered.
+   * @return string
+   *   The filtered string.
+   *
+   * @see \Drupal\system\Tests\Theme\TwigExtensionTest::testTwigExtensionFilter()
+   */
+  public static function testFilter($string) {
+    return str_replace(array('animal'), array('plant'), $string);
+  }
+
+}