diff --git a/tests/AppTest.php b/tests/AppTest.php
index 70032658d..79d453037 100644
--- a/tests/AppTest.php
+++ b/tests/AppTest.php
@@ -26,7 +26,7 @@
 use Slim\Http\Response;
 use Slim\Http\Uri;
 use Slim\Router;
-use Slim\HeaderStackTestAsset;
+use Slim\Tests\Assets\HeaderStack;
 use Slim\Tests\Mocks\MockAction;
 
 /**
@@ -43,12 +43,12 @@ class AppTest extends \PHPUnit_Framework_TestCase
 {
     public function setUp()
     {
-        HeaderStackTestAsset::reset();
+        HeaderStack::reset();
     }
 
     public function tearDown()
     {
-        HeaderStackTestAsset::reset();
+        HeaderStack::reset();
     }
 
     public static function setupBeforeClass()
@@ -1797,7 +1797,7 @@ public function testResponseReplacesPreviouslySetHeaders()
             ['header' => 'HTTP/1.1 200 OK', 'replace' => true, 'status_code' => 200],
         ];
 
-        $this->assertSame($expectedStack, HeaderStackTestAsset::stack());
+        $this->assertSame($expectedStack, HeaderStack::stack());
     }
 
     public function testResponseDoesNotReplacePreviouslySetSetCookieHeaders()
@@ -1834,7 +1834,7 @@ public function testResponseDoesNotReplacePreviouslySetSetCookieHeaders()
             ['header' => 'HTTP/1.1 200 OK', 'replace' => true, 'status_code' => 200],
         ];
 
-        $this->assertSame($expectedStack, HeaderStackTestAsset::stack());
+        $this->assertSame($expectedStack, HeaderStack::stack());
     }
 
     public function testExceptionErrorHandlerDoesNotDisplayErrorDetails()
diff --git a/tests/Assets/HeaderFunctions.php b/tests/Assets/HeaderFunctions.php
index 99e9218bd..e7327d042 100644
--- a/tests/Assets/HeaderFunctions.php
+++ b/tests/Assets/HeaderFunctions.php
@@ -8,6 +8,8 @@
  */
 namespace Slim;
 
+use Slim\Tests\Assets\HeaderStack;
+
 /**
  * Zend Framework (http://framework.zend.com/)
  *
@@ -28,63 +30,6 @@
  * @license   https://github.com/zendframework/zend-diactoros/blob/master/LICENSE.md New BSD License
  */
 
-/**
- * Store output artifacts
- */
-class HeaderStackTestAsset
-{
-    /**
-     * @var string[][]
-     */
-    private static $data = [];
-
-    /**
-     * Reset state
-     */
-    public static function reset()
-    {
-        self::$data = [];
-    }
-
-    /**
-     * Push a header on the stack
-     *
-     * @param string[] $header
-     */
-    public static function push(array $header)
-    {
-        self::$data[] = $header;
-    }
-
-    /**
-     * Return the current header stack
-     *
-     * @return string[][]
-     */
-    public static function stack()
-    {
-        return self::$data;
-    }
-
-    /**
-     * Verify if there's a header line on the stack
-     *
-     * @param string $header
-     *
-     * @return bool
-     */
-    public static function has($header)
-    {
-        foreach (self::$data as $item) {
-            if ($item['header'] === $header) {
-                return true;
-            }
-        }
-
-        return false;
-    }
-}
-
 /**
  * Have headers been sent?
  *
@@ -104,7 +49,7 @@ function headers_sent()
  */
 function header($string, $replace = true, $statusCode = null)
 {
-    HeaderStackTestAsset::push(
+    HeaderStack::push(
         [
             'header'      => $string,
             'replace'     => $replace,
diff --git a/tests/Assets/HeaderStack.php b/tests/Assets/HeaderStack.php
new file mode 100644
index 000000000..188e278a8
--- /dev/null
+++ b/tests/Assets/HeaderStack.php
@@ -0,0 +1,84 @@
+<?php
+/**
+ * This is a direct copy of zend-diactoros/test/TestAsset/Functions.php and is used to override
+ * header() and headers_sent() so we can test that they do the right thing.
+ *
+ */
+namespace Slim\Tests\Assets;
+
+/**
+ * Zend Framework (http://framework.zend.com/)
+ *
+ * This file exists to allow overriding the various output-related functions
+ * in order to test what happens during the `Server::listen()` cycle.
+ *
+ * These functions include:
+ *
+ * - headers_sent(): we want to always return false so that headers will be
+ *   emitted, and we can test to see their values.
+ * - header(): we want to aggregate calls to this function.
+ *
+ * The HeaderStack class then aggregates that information for us, and the test
+ * harness resets the values pre and post test.
+ *
+ * @see       http://github.com/zendframework/zend-diactoros for the canonical source repository
+ * @copyright Copyright (c) 2015-2016 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license   https://github.com/zendframework/zend-diactoros/blob/master/LICENSE.md New BSD License
+ */
+
+/**
+ * Store output artifacts
+ */
+class HeaderStack
+{
+    /**
+     * @var string[][]
+     */
+    private static $data = [];
+
+    /**
+     * Reset state
+     */
+    public static function reset()
+    {
+        self::$data = [];
+    }
+
+    /**
+     * Push a header on the stack
+     *
+     * @param string[] $header
+     */
+    public static function push(array $header)
+    {
+        self::$data[] = $header;
+    }
+
+    /**
+     * Return the current header stack
+     *
+     * @return string[][]
+     */
+    public static function stack()
+    {
+        return self::$data;
+    }
+
+    /**
+     * Verify if there's a header line on the stack
+     *
+     * @param string $header
+     *
+     * @return bool
+     */
+    public static function has($header)
+    {
+        foreach (self::$data as $item) {
+            if ($item['header'] === $header) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}