From f318f352227b1b4fa7d214202525e4226a518501 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ren=C3=A9=20H?= <rene.hoehle@gmail.com>
Date: Sat, 6 Jan 2018 23:01:55 +0100
Subject: [PATCH] Add tip for headers already send error.

Change for the problem PHPUnit headers already send.

https://github.com/symfony/symfony/issues/25615
---
 testing/http_authentication.rst | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/testing/http_authentication.rst b/testing/http_authentication.rst
index ff1f0d49a90..e35e1c20a63 100644
--- a/testing/http_authentication.rst
+++ b/testing/http_authentication.rst
@@ -71,6 +71,20 @@ The username and password can also be passed on a per request basis::
         'PHP_AUTH_PW'   => 'pa$$word',
     ));
 
+.. tip::
+
+    In Symfony 3.4 and 4.0 you have to change the session handler for PHPUnit tests otherwise you get an error 
+    ``PHPUnit Test header already send by...``.
+
+    .. code-block:: yaml
+
+        # config/packages/test/framework.yaml
+        framework:
+            test: ~
+            session:
+                storage_id: session.storage.mock_file
+
+
 Creating the Authentication Token
 ---------------------------------