diff -r d5eb5269128a -r aa4db71a6224 tests/test-topic-stack.t
--- a/tests/test-topic-stack.t	Thu Jun 29 00:11:07 2017 +0530
+++ b/tests/test-topic-stack.t	Thu Jun 29 01:58:26 2017 +0530
@@ -216,6 +216,14 @@
   4 default {foo} draft c_e
   5 default {foo} draft c_f
 
+  $ hg log -r 'stack(foo)'
+  hg: parse error: stack() takes no argument, it works on current topic
+  [255]
+
+  $ hg log -r 'stack(foobar)'
+  hg: parse error: stack() takes no argument, it works on current topic
+  [255]
+
 Case with multiple heads on the topic
 -------------------------------------