diff --git a/core/lib/Drupal/Core/Controller/ControllerBase.php b/core/lib/Drupal/Core/Controller/ControllerBase.php
index fae15e9..fb0f1d4 100644
--- a/core/lib/Drupal/Core/Controller/ControllerBase.php
+++ b/core/lib/Drupal/Core/Controller/ControllerBase.php
@@ -8,12 +8,26 @@
 namespace Drupal\Core\Controller;
 
 use Symfony\Component\DependencyInjection\ContainerAware;
+use Symfony\Component\HttpFoundation\RedirectResponse;
 
 /**
- * Defines a base class for 'thin' route controllers that don't need injected
- * dependencies.
+ * Utility base class for thin controllers.
  *
- * @todo Clarify the definition of 'thin' :)
+ * Controllers that use this base class have access to a number of utility
+ * methods and to the Container, which can greatly reduce boilerplate dependency
+ * handling code.  However, it also renders the class impossible to unit test.
+ * Therefore this base class should only be used by controller classes that
+ * contain only trivial glue code.  Controllers that contain sufficiently
+ * complex logic that it's worth testing should not use this base class but
+ * use ControllerInterface instead, or even better be refactored to be trivial
+ * glue code.
+ *
+ * The services exposed here are those that it is reasonable for a well-behaved
+ * controller to leverage. A controller that needs other other services may
+ * need to be refactored into a thin controller and a dependent unit-testable
+ * service.
+ *
+ * @see \Drupal\Core\Controller\ControllerInterface
  */
 abstract class ControllerBase extends ContainerAware {
 
@@ -58,7 +72,7 @@ protected function keyValueExpirable($collection) {
    * Retrieves a configuration object.
    *
    * This is the main entry point to the configuration API. Calling
-   * @code Drupal::config('book.admin') @endcode will return a configuration
+   * @code $this->config('book.admin') @endcode will return a configuration
    * object in which the book module can store its administrative settings.
    *
    * @param string $name
@@ -152,4 +166,20 @@ protected function languageManager() {
     return $this->container->get('language_manager');
   }
 
+  /**
+   * Returns a redirect response object for the specified
+   *
+   * @param string $route_name
+   *   The name of the route to which to redirect.
+   * @param array $parameters
+   *   Parameters for the route.
+   * @param int $status
+   *   The HTTP redirect status code for the redirect. The default is 302 Found.
+   * @return \Symfony\Component\HttpFoundation\RedirectResponse
+   *   A redirect response object that may be returned by the controller.
+   */
+  public function redirect($route_name, array $parameters = array(), $status = 302) {
+    $url = $this->container->get('url_generator')->generate($route_name, $parameters, TRUE);
+    return new RedirectResponse($url, $status);
+  }
 }
diff --git a/core/lib/Drupal/Core/Controller/ControllerInterface.php b/core/lib/Drupal/Core/Controller/ControllerInterface.php
index f87ae12..c490f9c 100644
--- a/core/lib/Drupal/Core/Controller/ControllerInterface.php
+++ b/core/lib/Drupal/Core/Controller/ControllerInterface.php
@@ -11,6 +11,14 @@
 
 /**
  * Defines a common interface for route controllers.
+ *
+ * This interface gives controller classes a factory method for instantiation
+ * rather than relying on a services.yml entry. However, it may result in
+ * a lot of boilerplate code in the class. As an alternative, controllers that
+ * contain only limited glue code ("thin" controllers) should instead extend
+ * ControllerBase as that allows direct access to the container. That renders
+ * the controller un-unit-testable so should only be used for controllers that
+ * are trivial in complexity.
  */
 interface ControllerInterface {