--- a/tests/test-extension.t	Mon Nov 30 20:44:22 2015 +0000
+++ b/tests/test-extension.t	Mon Nov 30 20:45:07 2015 +0000
@@ -367,6 +367,15 @@
 
   $ echo 'debugextension = !' >> $HGRCPATH
 
+Asking for help about a deprecated extension should do something useful:
+
+  $ hg help glog
+  'glog' is provided by the following extension:
+  
+      graphlog      command to view revision graphs from a shell (DEPRECATED)
+  
+  (use "hg help extensions" for information on enabling extensions)
+
 Extension module help vs command help:
 
   $ echo 'extdiff =' >> $HGRCPATH