commit 7d639cf7ba5167c42ae5a1f58107ac09514bb9a2
Author: Dom <dom.clause@gmail.com>
Date:   Fri Oct 30 01:46:38 2015 +0100

    new patch 17

diff --git a/core/tests/Drupal/KernelTests/Core/Common/DrupalSetMessageLoadsCssTest.php b/core/tests/Drupal/KernelTests/Core/Common/DrupalSetMessageLoadsCssTest.php
index 587fc68..d3e0f0c 100644
--- a/core/tests/Drupal/KernelTests/Core/Common/DrupalSetMessageLoadsCssTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Common/DrupalSetMessageLoadsCssTest.php
@@ -28,18 +28,20 @@ public function testDrupalSetMessage() {
 
+    // Test with aggregated CSS turned off.
+    $config = $this->config('system.performance');
+    $config->set('css.preprocess', 0);
+    $config->save();
+
     // Get the frontpage.
     $this->drupalGet("<front>");
-    // Check that message assets are loaded.
-    $this->assertRaw("core/themes/classy/css/components/messages.css", "Message CSS assets should be loaded.");
+    // Check that no message appears.
+    $this->assertNoRaw("messages--", "No message should be displayed on page.");
+    // Thus, check that no message asset is loaded uselessly.
+    $this->assertNoRaw("core/themes/classy/css/components/messages.css", "Message CSS assets should not be loaded when not needed.");
 
     // Display a message.
-    drupal_set_message(t('A message: @foo', ['@foo' => 'bar']));
+    drupal_set_message(t('A status message.'));
 
     // Get the frontpage.
     $this->drupalGet("<front>");
     // Check that messages are display.
-    $this->assertRaw("A message:", "The Drupal message should be displayed.");
+    $this->assertRaw("messages--", "The message should appear on page");
- 
-    // Check that message assets are not loaded.
-    $this->assertNoRaw("core/themes/classy/css/components/messages.css", "Message CSS assets should not be loaded.");
+    // Thus, check that message assets are loaded when required.
+    $this->assertRaw("core/themes/classy/css/components/messages.css", "Message CSS assets should be loaded when needed.");
   }
 }