From 311ac0f533bf5a308200a51b861a9728b9223276 Mon Sep 17 00:00:00 2001
From: Armin Ronacher <armin.ronacher@active-4.com>
Date: Thu, 25 Aug 2011 15:33:03 +0100
Subject: [PATCH] Ensure that nobody can nest test client invocations

---
 flask/testing.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/flask/testing.py b/flask/testing.py
index c1844c00..dfdaff57 100644
--- a/flask/testing.py
+++ b/flask/testing.py
@@ -108,6 +108,8 @@ class FlaskClient(Client):
             self.context_preserved = _request_ctx_stack.top is not old
 
     def __enter__(self):
+        if self.preserve_context:
+            raise RuntimeError('Cannot nest client invocations')
         self.preserve_context = True
         return self