commit 681f39f4516bc9e3635ce47b38135a430f28cbd1
Author: Bart Feenstra <bart@mynameisbart.com>
Date:   Sat Jun 7 16:37:13 2014 -0500

    Comment #7

diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 805f7b5..3e539e1 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -1158,7 +1158,7 @@ function watchdog($type, $message, array $variables = array(), $severity = WATCH
  *
  * @param string $message
  *   (optional) The translated message to be displayed to the user. For
- *   consistency with other messages, it should begin with a capital letter and
+ *   consistency with other messages it should begin with a capital letter and
  *   end with a period.
  * @param string $type
  *   (optional) The message's type. Defaults to 'status'. These values are
@@ -1179,13 +1179,13 @@ function watchdog($type, $message, array $variables = array(), $severity = WATCH
  * @see theme_status_messages()
  *
  * @deprecated Deprecated as of Drupal 8.0.
- *   Use \Drupal::service('messenger')->setMessage() instead.
+ *   Use \Drupal::service('messenger')->addMessage() instead.
  */
 function drupal_set_message($message = NULL, $type = 'status', $repeat = FALSE) {
   /** @var \Drupal\Core\Messenger\MessengerInterface $messenger */
   $messenger = \Drupal::service('messenger');
 
-  $messenger->setMessage($messenger, $type, $repeat);
+  $messenger->addMessage($message, $type, $repeat);
 
   return $messenger->getMessages();
 }
diff --git a/core/lib/Drupal/Core/Messenger/Messenger.php b/core/lib/Drupal/Core/Messenger/Messenger.php
index 436f0a9..073ebc4 100644
--- a/core/lib/Drupal/Core/Messenger/Messenger.php
+++ b/core/lib/Drupal/Core/Messenger/Messenger.php
@@ -7,18 +7,22 @@
 
 namespace Drupal\Core\Messenger;
 
+/**
+ * Provides a session-based messenger.
+ *
+ * @todo Use Symfony's session components once http://drupal.org/node/1858196
+ *   has been fixed.
+ */
 class Messenger implements MessengerInterface {
 
   /**
    * {@inheritdoc}
    */
-  public function setMessage($message, $type = self::STATUS, $repeat = FALSE) {
+  public function addMessage($message, $type = self::STATUS, $repeat = FALSE) {
     if ($repeat || !array_key_exists('messages', $_SESSION) || !array_key_exists($type, $_SESSION['messages']) || !in_array($message, $_SESSION['messages'][$type])) {
       $_SESSION['messages'][$type][] = $message;
-      drupal_page_is_cacheable(FALSE);
     }
 
-
     return $this;
   }
 
diff --git a/core/lib/Drupal/Core/Messenger/MessengerInterface.php b/core/lib/Drupal/Core/Messenger/MessengerInterface.php
index 2c90c8d..4b0a794 100644
--- a/core/lib/Drupal/Core/Messenger/MessengerInterface.php
+++ b/core/lib/Drupal/Core/Messenger/MessengerInterface.php
@@ -25,7 +25,7 @@
   const ERROR = 'error';
 
   /**
-   * Sets a new message.
+   * Adds a new message to the queue.
    *
    * @param string $message
    *   (optional) The translated message to be displayed to the user. For
@@ -40,7 +40,7 @@
    *
    * @return $this
    */
-  public function setMessage($message, $type = self::STATUS, $repeat = FALSE);
+  public function addMessage($message, $type = self::STATUS, $repeat = FALSE);
 
   /**
    * Gets all messages.
diff --git a/core/modules/system/src/Tests/MessengerTest.php b/core/modules/system/src/Tests/MessengerTest.php
new file mode 100644
index 0000000..4d3c2a5
--- /dev/null
+++ b/core/modules/system/src/Tests/MessengerTest.php
@@ -0,0 +1,79 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\Core\Messenger\MessengerTest.
+ */
+
+namespace Drupal\system\Tests;
+
+use Drupal\Core\Messenger\Messenger;
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Tests \Drupal\Core\Messenger\Messenger.
+ */
+class MessengerTest extends KernelTestBase {
+
+  /**
+   * The messenger under test.
+   *
+   * @var \Drupal\Core\Messenger\Messenger
+   */
+  protected $messenger;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getInfo() {
+    return array(
+      'description' => '',
+      'name' => '\Drupal\Core\Messenger\Messenger unit test',
+      'group' => 'Messenger',
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    $this->messenger = new Messenger();
+  }
+
+  /**
+   * Tests the messenger.
+   */
+  public function testMessenger() {
+    $message_a = $this->randomName();
+    $type_a = $this->randomName();
+    $message_b = $this->randomName();
+    $type_b = $this->randomName();
+
+    // Test that if there are no messages, the default is an empty array.
+    $this->assertEqual($this->messenger->getMessages(), array());
+
+    // Test that adding a message returns the messenger and that the message can
+    // be retrieved.
+    $this->assertEqual($this->messenger->addMessage($message_a, $type_a), $this->messenger);
+    $this->messenger->addMessage($message_a, $type_a);
+    $this->messenger->addMessage($message_a, $type_a, TRUE);
+    $this->messenger->addMessage($message_b, $type_b, TRUE);
+    $this->assertEqual($this->messenger->getMessages(), array(
+      $type_a => array($message_a, $message_a),
+      $type_b => array($message_b),
+    ));
+
+    // Test deleting messages of a certain type.
+    $this->assertEqual($this->messenger->deleteMessagesByType($type_a), $this->messenger);
+    $this->assertEqual($this->messenger->getMessages(), array(
+      $type_b => array($message_b),
+    ));
+
+    // Test deleting all messages.
+    $this->assertEqual($this->messenger->deleteMessages(), $this->messenger);
+    $this->assertEqual($this->messenger->getMessages(), array());
+
+
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/Messenger/MessengerTest.php b/core/tests/Drupal/Tests/Core/Messenger/MessengerTest.php
deleted file mode 100644
index bc5d12c..0000000
--- a/core/tests/Drupal/Tests/Core/Messenger/MessengerTest.php
+++ /dev/null
@@ -1,58 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Tests\Core\Messenger\MessengerTest.
- */
-
-namespace Drupal\Tests\Core\Messenger;
-
-use Drupal\Core\Messenger\Messenger;
-use Drupal\Tests\UnitTestCase;
-
-/**
- * @coversDefaultClass \Drupal\Core\Messenger\Messenger
- */
-class MessengerTest extends UnitTestCase {
-
-  /**
-   * The messenger under test.
-   *
-   * @var \Drupal\Core\Messenger\Messenger
-   */
-  protected $messenger;
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function getInfo() {
-    return array(
-      'description' => '',
-      'name' => '\Drupal\Core\Messenger\Messenger unit test',
-      'group' => 'Messenger',
-    );
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function setUp() {
-    $this->messenger = new Messenger();
-  }
-
-  /**
-   * @covers ::setMessage
-   * @covers ::getMessages
-   */
-  public function testSetMessage() {
-    session_start();
-
-    $message = $this->randomName();
-
-    $this->assertSame(array(), $this->messenger->getMessages());
-    $this->assertSame($this->messenger, $this->messenger->setMessage($message));
-
-    session_destroy();
-  }
-
-}