refs #6661 added a test to make sure it works

core/Tracker.php

@@ -669,7 +669,8 @@ class Tracker
         $request = $_GET + $_POST;
 
         if (array_key_exists('send_image', $request) && $request['send_image'] === '0') {
-            Common::sendHeader("HTTP/1.1 204 No Response");
+            Common::sendResponseCode(204);
+
             return;
         }
 

tests/PHPUnit/Framework/Constraint/ResponseCode.php

@@ -9,6 +9,7 @@ namespace Piwik\Tests\Framework\Constraint;
 
 class ResponseCode extends \PHPUnit_Framework_Constraint
 {
+    private $actualCode;
 
     /**
      * @param integer $value Expected response code
@@ -41,7 +42,9 @@ class ResponseCode extends \PHPUnit_Framework_Constraint
         $responseCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
         curl_close($ch);
 
-        return $this->value === (int) $responseCode;
+        $this->actualCode = (int) $responseCode;
+
+        return $this->value === $this->actualCode;
     }
 
     /**
@@ -51,6 +54,6 @@ class ResponseCode extends \PHPUnit_Framework_Constraint
      */
     public function toString()
     {
-        return 'does not return response code ' . $this->exporter->export($this->value);
+        return 'does not return response code ' . $this->exporter->export($this->value) . ' it is ' . $this->actualCode;
     }
 }?>
\ No newline at end of file

tests/PHPUnit/System/TrackerTest.php

@@ -69,4 +69,12 @@ class TrackerTest extends SystemTestCase
         $this->assertResponseCode(204, $url);
     }
 
+    public function test_response_ShouldSend400ResponseCode_IfSiteIdIsInvalid()
+    {
+        $url = $this->tracker->getUrlTrackPageView('Test');
+        $url .= '&idsite=100';
+
+        $this->assertResponseCode(400, $url);
+    }
+
 }