Merge branch '5.4' into 6.0

* 5.4:
  add break lines and remove useless line
  Update testing.rst
  Update testing.rst
  Update testing.rst
  Add caution message about reset container on each request

Author: OskarStark

testing.rst

@@ -616,6 +616,15 @@ This allows you to create all types of requests you can think of:
     :ref:`framework.test <reference-framework-test>` option is enabled).
     This means you can override the service entirely if you need to.
 
+.. caution::
+
+    Before each request, the client reboots the kernel, recreating
+    the container from scratch.
+    This ensures that every requests are "isolated" using "new" service objects.
+    Also, it means that entities loaded by Doctrine repositories will
+    be "detached", so they will need to be refreshed by the manager or
+    queried again from a repository.
+
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