diff --git a/contributing/code/bc.rst b/contributing/code/bc.rst
index 596967a719f..677109cb674 100644
--- a/contributing/code/bc.rst
+++ b/contributing/code/bc.rst
@@ -150,6 +150,13 @@ Classes, properties and class methods tagged with ``@deprecated`` will be
 removed in a future Symfony version. You should never use nor extend them.
 
 
+Test Classes
+............
+
+All classes located in the various ``*\\Tests\\`` namespaces are meant for
+internal use only. You should never create, extend or call them directly.
+
+
 Safe Operations
 ...............